Studia Chiropterologica

Studia Chiropterologica Annals of the Chiropterological Information Center

Multifactor Analysis of Refugioclimate in Places of Hibernation of Chosen Bat Species Grzegorz Kłys

volume 8 (2013)

Publications of the Chiropterological Information Center Institute of Systematics and Evolution of Animals Polish Academy of Sciencies in Kraków

© Chiropterological Information Center Institute of Systematics and Evolution of Animals, Polish Academy of Sciences in Kraków Sławkowska 17, 31-016 Kraków, Poland Phone: (48) (prefix) (12) 422 64 10, 422 19 01; Fax: (48) (prefix) (12) 422 64 10, 422 42 94 E-mail: [email protected]

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Scientific Advisory Board

Bronisław W. Wołoszyn Tomasz Pasierbek Katarzyna Kozakiewicz Prof. Wiesław Bogdanowicz, Ph.D., D.Sc. (Poland) Prof. Zbigniew Głowaciński, Ph.D., D.Sc. (Poland) Prof. Dumitru Murariu, Ph.D., D.Sc. (Romania) Józef Omylak, M.Sc., Ing. (Poland) Krzysztof Piksa. Ph.D. (Poland) Zoltan Nagý, Ph.D. (Romania) Jordi Serra-Coba, Ph.D. (Spain) Andriy Taras-Baszta, Ph.D. (Ukraine)

Reviewers: Prof. Krzysztof Cena Ph.D., D.Sc. (Australia-Poland); Prof. Bronisław W. Wołoszyn Ph.D., D.Sc. (Poland), This issue was edited with financial support from the Babiogórski National Park. Materials published in Studia Chiropterologica may be reproducted only when the source publication is given. Example of literature citation: Kłys G., Hebda M. 2009. Efect of type of wood used to construct bat boxes. Studia Chiropterologica, 6: 123-132.

Studia Chiropterologica

Table of contents: Abstract 1. Introduction ........................................................................................................ 7 1.1. Purpose of the work ................................................................................... 9 1.2. Current state of research ............................................................................ 10 2. Ecology and biology of wintering of bats ......................................................... 15 2.1. The phenomenon of hibernation and its meaning ...................................... 15 2.2. The phenomenon of hibernation in bats ..................................................... 17 2.3. Choice of place of hibernation ................................................................... 19 2.3.1. Migration or hibernation? ................................................................ 19 2.3.2. Characteristic features of refuges .................................................... 19 3. The notion of ecoclimate – microclimate of an underground system and refugioclimate ................................................................................................... 23 4. Characteristics of physical elements which have influence on hibernation of bats ....................................................................................... 25 5. Material and methods ........................................................................................ 29 5.1. General Remarks ........................................................................................ 29 5.2. Places of research ....................................................................................... 30 5.3. General overview of devices and methodology of measurement of hibernation environment (refugioclimate) ............................................. 35 5.3. 1. Air temperature (T) ......................................................................... 35 5.3. 2. Substrate temperature ...................................................................... 38 5.3. 3. Air flow velocity (v) ........................................................................ 38 5.3. 4. Relative humidity of air (Rh) .......................................................... 41 5.3. 5. Thermal conduction of materials (λ) .............................................. 42 5.3. 6. Air pressure (p) ................................................................................ 44 5.3. 7. Level of cooling (Ka) ....................................................................... 44 6. Wintering strategies .......................................................................................... 47 7. Thermal comfort of a hibernating bat ................................................................ 51 7. 1. Conduction ................................................................................................ 55 7. 2. Radiation ................................................................................................... 55 7. 3. Convection ................................................................................................ 55 7. 4. Vaporization .............................................................................................. 56

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8. Choice of place of hibernation ........................................................................ 59 8. 1. Introduction ............................................................................................ 59 8. 2. Whether there is a relation of choosing by bats higher temperature at first rather than in later months of hibernation ................................... 60 8. 3. Joint or separate analysis of physical factors of refugioclimate ............ 61 8. 4. Comparison of physical factors (Ts; Rh; v; λ) of refugioclimate of chosen bat species .............................................................................. 64 8. 5. Analysis of particular species ................................................................. 68 8. 5. 1. Lesser Horseshoe Bat Rhinolophus hipposideros ...................... 68 8. 5. 2. Western Barbastelle Barbastella barbastellus .......................... 71 8. 5. 3. Daubenton’s Bat Myotis daubentonii ......................................... 81 8. 5. 4. Natterer’s Bat Myotis nattereri ................................................... 88 8. 5. 5. Greater Mouse-eared Bat Myotis myotis .................................... 94 8. 5. 6. Brown Long-eared Bat Plecotus auritus .................................... 100 9. Summary ......................................................................................................... 106 9. 1. Air temperature ...................................................................................... 106 9. 2. Relative humidity of air ......................................................................... 107 9. 3. Air flow velocity ..................................................................................... 108 9. 4. Thermal conduction ................................................................................ 109 9. 5. Air pressure ............................................................................................ 109 9. 6. Wintering strategies ................................................................................ 110 9. 7. Standard of conditions of measurement ................................................. 111 9. 8. Synthesis of chosen physical factors ...................................................... 111 9. 9. Theoretical and practical meaning ......................................................... 113 9. 10. What is new .......................................................................................... 113 10. Literature cited .............................................................................................. 115 Appendix ............................................................................................................. 130 List of acronyms and symbols used in the work ............................................... 161 Glossary .............................................................................................................. 163

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Abstract There is an enormous number of publications concerning ecology of wintering of bats, but complex research on the choice of place of wintering by bats was not performed so far. Few works from this scope deal with analyses of single parameters, rarely they concern larger number of parameters. It is generally known that rules of transferring heat are governed by laws of physics. There are four ways of transferring heat: conduction, convection, radiation and vaporization. The author in his research attempts to integrate particular abiotic factors in the immediate place of wintering of bats which is called refugioclimate. The following quantities were taken into consideration in the work: air flow velocity (v), air pressure (p), relative humidity (Rh), thermal conductivity of the substrate on which bats wintered (λ) and air temperature (Ta). Six most common in underground systems bat species were selected for the research: lesser horseshoe bat Rhinolophus hipposideros, greater mouse-eared bat Myotis myotis, Daubenton's bat Myotis daubentonii, Natterer's bat Myotis nattereri, brown long-eared bat Plecotus auritus and Western Barbastelle Barbastella barbastellus. Due to the fact that values of physical quantities are often relatively diversified in underground systems a methodology of measurement of physical factors which influence wintering of bats was established. Measurements were performed in the immediate proximity of a wintering bat. Six basic strategies of wintering of bats were proposed depending on their share in cooling a bat. The author of the current work made an attempt of a comprehensive evaluation of the influence of sum of chosen factors on the choice of hibernation place. Additionally, two basic questions were posed: are the chosen abiotic factors of refugioclimate: Ts, Rh, v, λ responsible for the choice of hibernation places? Do factors of refugioclimate differentiate species and strategies as far as places of their choice is concerned? It was assumed, that statistical analyses should facilitate evaluation and interpretation of obtained results. Therefore an attempt to answer the following questions was made: • Do bats choose higher air temperature at the beginning of hibernation? • Is there a relation in the choice of physical factors Ts; Rh; v? • Should each of the aforementioned factors be examined jointly or separately? • Are there any differences in choice of place of hibernation by 6 chosen bat species in relation to abiotic factors of physical parameters of refugioclimate (Ts; Rh; v)? In order to evaluate influence of the sum of these factors on the choice of hibernation place the author performed measurements of temperature (Ta - n=6389), relative humidity (Rh - n=6389), air flow (v - n=6389) and atmospheric air pressure (p - n=6389) of refugioclimate. Only part of results of physical values of refugioclimate of chosen six species of bats was used for the analysis. It produced in total 23352 items of data. 5


It has been proved that the choice of hibernation place of a given bat species and its strategy is dependant on physical conditions of refugioclimate such as Ts; Rh; v and thermal conductivity of substrate (λ) on which a bat hibernates. It has been demonstrated that each of the examined species possesses its own scope of physical quantities of a refuge which is optimal during hibernation, which quantities supplement one another and which differ one species from another. Wet Kata cooling power degrees were used in order to obtain single values of the analysed parameters such as Ts; Rh; v. For the first time empirical equations of three variables have been made which determine choice of hibernation places and strategies for analysed species. The obtained results and conclusions from the current paper allow to present two important theoretical and practical meanings in ecology and protection of bats in various ecosystems. They are: • Comparison of factors which condition choice of a hibernation place may have significant meaning in practice of protection of bats and their habitats. • There is a possibility of simulation of microclimate of an underground system and consequently a refugioclimate to the needs of hibernation of a given bat species.

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Introduction Bats are second after rodents group of mammals which is the most common around the world. Thanks to their ability of active flight they are able to carry out longdistance travels during seasonal migrations (Calisher et al., 2006). Flight ability of these animals requires intensive metabolism, high body temperature and significant level of oxygen consumption (Altringham, 1996). Thanks to the phenomenon of heterothermy bats are able to manage sparingly energy from reserves gathered during the period of activeness. Heterothermy allows to last long seasonal drop in external temperature and lack of food in the state of hibernation. In this period at values of body temperature close to ambient temperature metabolism of bats is reduced to minimal values (Hock, 1951; Dunbar and Tomasi, 2006; Boyles et al., 2008). The ability to hibernate is one of key aspects of settling high latitudes (both northern and southern) by bats. In unfavourable season bats in this climatic zone utilize possibility to shelter in various kinds of underground systems. They are used mainly for hibernation, because in winter period they provide sufficient set of physical conditions essential to survive this period without food. Research on bats is complicated due to methodological difficulties connected with their specific way of life, so collected information is often a result of accidental observations. The most intensive research on this group took place in the second half of the 20th century in Europe, North America and some tropical countries (Kunz et al., 1983; Altringham, 1996; Neuweiler, 2000; Evelyn, Stiles, 2003; Kunz, ter Hofstede Fenton, 2003; ter Hofstede, Fenton, 2005; Chaverri et al., 2007; Chaverri et al., 2007). Despite numerous research the knowledge of bats still includes lots of “blank pages”. So far, research focused mainly on measurements of temperature and humidity, very rarely on air flow (Kłys, 2004). Getting to know the most important factors of habitat which determine starting winter sleep (hibernation) by bats and getting to know relations between determinants of habitat and ecoclimate may have significant meaning both theoretical and practical one. Knowledge of these relations may allow to create artificial habitats for species of bats which are endangered and dying out; it also creates possibility to model conditions of refugioclimate for the needs of hibernation. Currently, attempts are made to protect and manage underground systems which take into account needs of bats (Mitchell-Jones et al., 2007). However, so far many of the conditions which determine settlement in underground systems and distribution of bats therein have not been defined. 7


Acknowledgments The author wishes to thank Prof. Jerzy Lis, Ph.D., D.Sc. for his support and help during work. I am grateful to the staff of the Faculty of Mining and Geology, Institute of Mining, at the Silesian University of Technology in Gliwice for scientific help: Paweł Wrona, Ph.D., Ing., Zenon Różański, Ph.D., Ing., Grzegorz Pach, Ph.D., Ing. I express my gratitude to Andrzej Sobolewski Ph.D., Ing. from Central Institute for Labour Protection – National Research Institute in Warsaw; Jacek Piasecki Ph.D. from the Department of Climatology and Atmosphere Protection, Department of Earth Sciences and Environment Shaping the University of Wroclaw; Grzegorz Wojtaszyn Ph.D. of the Polish Society for Nature Protection „Salamandra”; Magdalena Dziegielewska Ph.D. of Applied Entomology Department of the Agricultural University in Szczecin; Marek Bandrowski of the Association of Friends of Police "Treasure”; the staff of Moravský Kras Landscape Protection Park (Chráněná krajinná oblast – ChKO Moravský Kras) in the Czech Republic, in particular to Mr Miroslav Kovařik for enabling research of lesser horseshoe bat Rhinolophus hipposideros; the Ministry of Environment; Provincial Nature Conservation Authorities in Opole, Katowice, Wrocław, Gorzów Wielkopolski, Szczecin and Lublin. I also thank Mr Paweł Rutkowski from FLIR Systems Inc. for taking infrared pictures of wintering bats, as well as all other people who made this work possible. Thanks are also to Grzegorz Gurbała, who translated this paper into English.

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1.1. Purpose of the work The main purpose of this work is an attempt to determine and evaluate influence of abiotic factors on the choice of hibernation places by chosen species of bats in cave environment and in anthropogenic facilities taking as an example various underground systems. Earlier research did not take into consideration if the choice of hibernation place as well as the strategy of this choice are dependent on physical parameters of refugioclimate, and simultaneous influence of its three basic parameters (T, Rh, v) (see: List of acronyms and symbols used in the work) was not analysed, as well as influence of the substrate on which bats winter (λ degree of thermal conductivity). The author of the current work made an attempt of a comprehensive evaluation of the influence of sum of these factors on the choice of hibernation place. Additionally, two basic questions were put: • Are chosen abiotic factors of the refugioclimate: Ts, Rh, v, λ responsible for the choice of hibernation places? • Do factors of refugioclimate differentiate species and strategies as far as places of their choice is concerned? It was assumed, that statistical analyses should facilitate evaluation and interpretation of obtained results. Therefore an attempt to answer the following questions was made: • Do bats choose higher air temperature at the beginning of hibernation? • Is there a relation in the choice of physical factors Ts; Rh; v? • Should each of the aforementioned factors be examined jointly or separately? Are there any differences in choice of place of hibernation by 6 chosen bat species in relation to abiotic factors of physical parameters of refugioclimate (Ts; Rh; v)?

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1.2. Current state of research Only four out of eighteen currently known families of bats, namely Rhinolophidae, Vespertilionidae, Miniopteridae and Molossidae, possess ability to hibernate, which allowed them to settle in the temperate zone. Bats which inhabit temperate and northern climates, where seasonal changes of climatic conditions and lack of food appear, need specific morphological, physiological and behavioural adaptations. For a long time this problem have been arousing particular interest among scientists (Panugajewa, Slonim, 1953; Punt, van Nieuwenhoven, 1957; Kalabukhov, 1985; Tiunow, 1988; Ransome, 1990; Arnold, 1993; Koteja et al., 2001; Humphries et al., 2002; Dawydow, 2004; Geiser, 2004; Anufrijew, 2005; Anufrijew, Rewin, 2006). The ability to survive in low temperatures of various animal species is known since the 19th century. Professor A. Horvath (1878) observed drop in body temperature of striped ground squirrels to 0,2 °C. In 1912 benefit from decreasing body temperature was demonstrated experimentally by P.I. Bahmjetjeba (in: Kalabukhow, 1985). It was stated then that in the state of hypothermia body temperature may drop to -9 °C without creating ice in body fluids. Research conducted later showed that minimal temperatures to which an animal may be cooled without the danger of creating ice in tissues are different in various species and in general they are lower at slowed cooling (Kalabukhow, 1985). During recent years on the basis of experimental and field research basic knowledge of the phenomenon of “hibernation” in various groups of vertebrates and invertebrates was acquired (Kalabukhow, 1985; Pastuhow, 1986; Slonim, 1986; Hoczaczka, Somiero, 1988; Geiser, Ruf, 1995; Geiser, 2001, 2004а, b; Janicki, CyganSzczegielniak, 2006; Cooper, Geiser, 2008; Wojciechowski et al., 2011). These animals have a common feature: their organisms stop using up external supply of food after they enter the state of hibernation and at the same time in various, but always a controlled way, they reduce intensity of metabolism (Hoczaczka, Somiero, 1988). Hibernation allows to reduce the use of energy by 95% in comparison to the costs of keeping activeness during winter and preserving energy is correlated with temperature of hibernation (Geiser, 2004а). The process is not homogeneous, it is broken periodically by awakenings of the animals which constitutes a significant part of costs of energy of an organism in winter period (up to 84%, Boyles et al., 2008). For some species of bats calculations of the budget of time and energy in the state of hibernation were performed, in particular for a North American species of little brown 10


bat Myotis lucifugus (Thomas et al., 1990) and an Eurasian species of Daubenton’s bat Myotis daubentonii (Matveev et al., 2005). In Myotis lucifugus 15 days-long cycles of awakenings were observed. So during one cycle it uses up about 3.6 kJ which corresponds to energy contained in approximately 0.1 g of fat (Thomas, 1995). In this species there are on average from 10 to 13 such cycles. However, other research show that duration time of one cycle of “lethargy – readiness” of bats may differ significantly – from several days to several months (Strielkow, 1971b; Geiser, 2004а). Duration time of a cycle may depend on external factors (temperature in a winter refuge, humidity, change in atmospheric pressure), species, sex and individual features of a specimen (Strielkow, 1971b; Park et al., 2000). Since energy losses during awakenings constitute a significant part of wintering energy budget (Thomas et al., 1990), causes and functions of such “unnecessary” behaviour of bats aroused and still arouse interest. Hypotheses which try to explain this phenomenon (Park et al., 2000) may be divided into two groups. I. Awakenings caused by abiotic factors: • Searching for optimal temperature for hibernation (Boyles et al., 2006). • Compensation of lost moisture while breathing and evaporation through skin in refuges of insufficient humidity (Thomas, Cloutier, 1992; Thomas, Geiser, 1997). II. Awakenings caused by biotic factors: • Getting rid of by-products of metabolism (Park et al., 2000). • Reproduction (Boyles et al., 2006). • Acquiring food (important for areas with mild climate) (Avery, 1985; Brigham, 1987). Abiotic factors in a refuge not only may have on frequency of awakenings of the animals, but also determine risk of survival during hibernation. So far works have taken into consideration only temperature and humidity as factors which have influence on conditions of wintering (Nagel, Nagel, 1991; Visnovska et al., 2006;. Boyles et al., 2008; Boratyński et al., 2012). Optimal temperature for most bat species which winter in underground systems of the temperate zone equals from 0 to +10 °C (Webb et al., 1995; Humphries et al., 2002). Awakenings are connected with searching for optimal temperature in winter refuge in order to maximize saving energy (Speakman, Racey, 1989). 11


Research on energy expenses during hibernation of mammals often emphasise physiological aspects of thermoregulation, but do not take into account behaviour of mammals (Humphries et al., 2002). For instance, to form dense groups (aggregations) animals use euthermia in order to reduce heat loss, but it may also influence use of energy during hibernation of mammals. Aggregation is a phenomenon belonging to important physiological and ecological behaviours for hibernating animals (Boyles et al., 2008). Creating groups during hibernation is changeable within a species and between species. A tendency is observed to aggregate even in the same winter refuge. Some bat species form small, “thin” clusters, whereas other species create dense groups (Smirnow et al., 1999; Tomilienko, 2002) which contain up to a few thousands of specimens (Betke et al., 2008). During winter bats can move and change location, which leads sometimes to change in size and composition of aggregation in a hibernaculum (Orlowa et al., 1983; Tomilienko, 2002). It is believed that it is possible to form dense concentrations which allow to compensate loss of metabolic heat to the environment (Boyles et al., 2008). Body temperature of animals in the state of hibernation usually fluctuates around ambient temperature (Geiser, 2004a). However, research on the phenomenon of hibernation is usually limited to descriptive field observations (e.g. when and where mammals wintered) or physiological research in a laboratory (e.g. testing metabolism and internal secretion, functions of animals) which have no environmental context. Humidity of a wintering place has large influence on duration time of the “lethargy – readiness” cycle. Influence of this parameter is often more important than nutritional status of an animal (Thomas, Cloutier, 1992; Thomas, 1995). Even in conditions of high relative humidity (90-98%) the loss of moisture may be significant. The loss of moisture occurs through external surface of the animal’s body and through breathing. Loss of water from an organism that is too high stops normal course of metabolic processes and may lead to death. This is why in refuges of lower humidity bats often wake in order to replenish water in their organisms. Resilience to loss of water in various species is different (Ransome, 1990). Research conducted on Pipistrellus pipistrellus shows that animals wake up to replenish water in their organisms caused by vaporization (Speakman, Racey, 1989). By creating dense aggregations animals will reduce water loss and probably they will wake up less often, which will lead to a reduction of energy expenses in winter period (Ransome, 1990; Thomas, Cloutier, 1992; Thomas, 1995). Research conducted so far state that humidity and temperature may have influence on choice, duration time of the cycle of awakenings and formation of clusters of bats. It is obvious that an organism of a hibernating bat is influenced by a whole set of 12


factors (not always known). This is why data collected from hibernation places should concern above else cooling factors such as air flow velocity, temperature and thermal conductivity of the rock, air temperature, relative humidity and wintering strategy. The author stated that air flow velocity is one of the most important factors which condition bat hibernation (Kłys et al., 2002; Kłys, 2004, 2008). One of the issues in research on hibernation should be estimation of value of particular physical factors which complement each other. Equally important is methodology of measurement of these factors (Kłys et al., 2005). Many works concerning meteorological conditions in a place of occurrence of bats lack the description of methodology of measurement and devices used, which makes interpretation of such data impossible (Kłys et al., 2005). Influence of presence of the person performing measurements on their accuracy was also neglected (Kłys et al., 2005). Despite the fact of existence of an enormous number of publications concerning ecology of wintering of bats, complex research on the choice of place of wintering by bats was not performed. Few works from this scope deal with analyses of single parameters. Kłys, Wołoszyn, (2005) proposed a term of “refugioclimate” for description of the set of physical factors which have an effect directly in hibernation place of a bat. The author in his research attempts to connect particular abiotic factors in an immediate place of wintering called a refugioclimate.

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2. Ecology and biology of wintering of bats 2.1. The phenomenon of hibernation and its meaning In order to achieve high level of independence from restrictions imposed on them by environment, the endothermic organisms developed ability to create internal warmth to keep high and stable body temperature (Smith-Nilsen, 2008). However, this ability requires high energy costs. In many animals, especially small ones, costs connected with thermoregulation may exceed the amount of available energy. In order to solve the problem of shortage of energy, they enter a state of torpor. This strategy allows them to avoid energy-intensive, fast pace of metabolism necessary to maintain stable body temperature. It is a precisely regulated and controlled physiological state. Torpor is then an answer to unfavourable environmental conditions (shortage of food, water, cold, warmth) and is characterised with drastic drop in body temperature and other physiological functions. This state may last from several hours to several months Hoffman, 1964; Lyman (Hoffman, 1964; Lyman et al., 1982; Nelson, 1980; Wang, 1987; French, 1988; Storey and Storey, 1990; Geiser and Ruf, 1995). In contrast to ectothermic organisms (e.g. amphibians and reptiles), endothermic organisms are able to leave the state of torpor at any moment. With the use of thermogenesis they bring back normal body temperature. Representatives of many groups of mammals have an ability to enter the state of torpor. In the majority they are small animals, characterised with high metabolism, for which maintaining stable body temperature with shortage of food at the same time is to costly in terms of energy, for instance Tachyglossidae from Monotremata many Dasyuridae from Marsupialia, Xenarthra, Afrosoricida, Crocidurinae and Erinaceidae from Insectivora, many bat species of both suborders Megachiroptera and Microchiroptera, small Primates and various Rodentia: Cricetidae, Heteromyidae, Muridae, and Sciuridae, Carnivora: (Ursidae), and some Mustelidae, from Canidae Nyctereutes. Apart from numerous species of mammals there are only a few bird species known such as Phalaenoptilus nuttallii several species from the family of Trochilidae, Apodidae and mousebirds from Colius genus which enter the state of torpor (Lyman, 1982; Geiser, 2001; 2004a; Schmidt-Nielsen, 2008). Torpor in homoiothermal organisms may be characterized depending on duration time, depth of that state and as seasonal or non-seasonal. Seasonal torpor may be accomplished through estivation and hibernation; it is characterized with states of torpor which may last several hours, days, weeks or months within the period of one season. 15


There are two forms of torpor: a short one, called daily torpor, and a long one, called extended torpor or hibernation. Organisms which are able to enter into the state of hibernation are called hibernators. In reality seasonal torpor never encompasses entire season of hibernation, but it is broken by temporary awakenings and short periods of normothermia (French, 1985, 1988). There are many different kinds of torpor which differ in frequency of heartbeat, breath and body temperature. It results from a fact that torpor formed independently in various phyletic lineages of mammals and is caused by various ecological determinants, which in turn lead to enormous variety of patterns of torpor (Geiser, 1988). Due to that some forms of torpor are called differently and borders between these forms are fuzzy. In relation to animals which enter into the state of torpor in winter, the following terms are often used: winter sleep, winter rest, winter lethargy or hibernation. In some species during the rest thermoregulation is not stopped, body temperature drops minimally and the animals do not leave their winter refuges and do not feed. In each of these cases the purpose is to achieve hypometabolic state to save energy. The state of torpor usually consists of cycles: entering, maintaining and awakening from torpor. Many hormonal changes occur in a body of the animal. Entering the state of torpor is characterized by the following features: • • • • • • • •

significant drop in metabolism, slowing down heartbeat down to several beats a minute, narrowing blood vessels, reduction of pace of breathing, including occurrence of apnea, drop in oxygen consumption, significant drop in body temperature, often to the level of slightly higher than ambient temperature, decrease in brain activity, decrease in nervous excitability which manifests itself in body torpor and faint reaction to external stimuli.

All physiological functions are reduced to a minimum. Despite large-scale research on winter sleep of animals, basic natural mechanisms of hypometabolism are still hardly known.

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2.2. The phenomenon of hibernation in bats In the temperate climatic zone the sustenance of bats are insects and other arthropods. Insects show significant fluctuations of numerical strength throughout the year. In cool season of the year when there is lack of food bats must migrate or limit drastically the use of energy to survive (Fig. 1). To a great degree the specificity of thermoregulation and energetics of bats is determined by the type of food and geographical distribution. Taking into account ability to regulate body temperature (Tb) depending on the influence of ambient temperature (Ta) bats may be artificially divided into three groups (Davydov, 2004): definite homoitherms • relative homoitherms, which are able to enter into torpor • homoitherms which are able to regularly enter into torpor and are able to hibernate. Specific feature of hibernation is switching off thermoregulation. The external stimulus which provokes the process of change is above else lowering ambient temperature. Basic strategy of hibernating bats is searching for an appropriate refuge (hibernaculum) in which ambient temperature does not drop below 0 °C, appropriate humidity and air flow velocity is preserved and the animal is hidden from predators. Threshold temperature is different for particular species. Above the threshold temperature hibernation can not occur. In hibernation typical for bats body temperature drops within 20-30 minutes, depending on the size of a bat and its fat reserves, to about several °C for the period of from a few to a dozen or so weeks, which is the precondition to survive without feeding. Body temperature is then kept around the ambient temperature (Fig 2). Energy to live is obtained from fat reserves accumulated for this purpose. Bats produced winter sleep glands which are characteristic for them, i.e. brown adipose tissue which accumulates fat of high energetic value. Energy contained in it is used for fast heating up the body during awakening, when surrounding conditions exceed threshold value. If ambient temperature rises, an animal returns to regular activity, whereas drop in temperature below 0 °C threatens the organism with freezing, which is why the animal increases pace of metabolism to maintain its body temperature on the level slightly above 0 °C or awakes to replenish fat reserve or change refuge. Awakening may occur also under influence of other strong external stimuli. Large role during hibernation is played by social thermoregulation. Since most of species hibernate in aggregations, while they sleep they cuddle up to one another which reduces heat loss (Ransome, 1990). Larger bats have lower ratio of space to volume than small ones. Therefore they will use up their energy reserves slower than smaller ones. 17


Fig. 1. Annual cycle of activeness of bats from the temperate zone.

Fig. 2. Wintering greater mouse-eared bats Myotis myotis. Infrared photographs (FLIRSYSTEM for the author). 18


2. 3. Choice of place of hibernation 2.3.1. Migration or hibernation? For many organisms which live in the zone of temperate climate, including bats, winter is a critical period. Only proper adaptation to low temperatures in the period of lack of sustenance allows bats to survive in such conditions. Among strategies of survival one may enumerate: transition to an alternative and more substantial type of food, storing food in the times of abundance, migration to a place where food can be found entering the state of hibernation. Most of bats choose the last strategy, which may be called “an escape in time” in contrast to the strategy of: “an escape in space” concerning migration of many species of birds (Wołoszyn, 2007, 2008). Like in many other animals also in bats there are sedentary, nomadic and migrating species. In Central Europe species are considered sedentary if they wander no further than 50-100 km. This group of bats includes among others genera Rhinolophus, Plecotus and also some small species of the genus Myotis. There are also such species which regularly change place of stay from 100 to several hundred km. They require appropriate underground systems for wintering. They are among others: pond bats Myotis dasycneme and greater mouse-eared bats Myotis myotis. Bats from the group of “migrating” ones cover annually a distance of over a thousand kilometres. Species of the genus Nyctalus, the species of Nathusius’ pipistrelle Pipistrellus nathusii and parti-coloured bat Vespertilio murinus belong here. In some migrating species it happens that local population has a convenient hibernaculum at their disposal; in that case they resign from migration. When bats migrate they not always choose south direction, which means a warmer zone, but sometimes also north to a known hibernaculum. It is often seen as a precondition of colonization of areas of low temperatures (Raphae et al., 2000). Hence hibernation seems to be the best solution for bats of the temperate climatic zone.

2.3.2. Characteristic features of refuges Availability of observation of hibernating bats is varied. Most of data comes from caves and underground systems in which access of an observer is the easiest one. To the remaining refuges access is limited and data on bats which hibernate there are rather accidental. 19


Bats are usually very flexible animals as far as the choice of refuge is concerned. They settle refuges of both natural and anthropogenic origin (Table 1). Table 1. The most frequently found refuges of bats in Poland. Type of refuge

Chosen works Natural shelters

Caves

Kowalski K., 1954; Wołoszyn, 1994.

In heaps of stones, under the stones in soil, animal burrows

Strielkow, 1970; own observations

Tree hollows, crevices in tree trunks and under the bark

Krzanowski, 1956; Ruprecht, 1976; Postawa et al., 1994.

Crevices in rocks

Vlaschenko, Naglov, 2005; Strielkow, Ilin, 1990; Borissenko et al., 1999. Anthropogenic shelters

Bunkers, mines, bomb shelters, drain pipes, cellars, sewers and other underground systems

Kepel, 2005; Kłys, 1994; Lesiński et al., 2004.

Wells

Kowalski M., 1995; Ignaczak, Radzicki, 2002.

Cracks in buildings, under window sills

Lesiński, 2006; Kłys, 1996; Wołoszyn, 2008.

Parts of buildings above the ground, ventilation ducts, attics, empty space in walls

Kłys, 1996; Krzanowski, 1980; Olszewski, 2003; Iwaniuk, Szkudlarek, 2002.

Nesting boxes for birds and bats

Kłys, Hebda, 2010.

Timbering, window shutters, gaps between beams

own observations

Concrete structures, bridges

Wojtaszyn et al., 2005; Ciechanowski, 2001.

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Natural shelters Caves and crevices in rocks are used by bats mainly during winter (places of hibernation) and autumn (mating shelters), more rarely during summer. Breeding colonies of bats in Polish caves are created sporadically, however it concerns only two species: greater mouse-eared bat (currently only one colony is known, in Studnisko Cave in Krakowsko-Częstochowska Upland) (Wołoszyn, 2008) and lesser horseshoe bat. These places may also play the role of daytime hiding places for males in spring and summer period. Hiding places in tree hollows and under the bark may be settled by bats in all seasons of the year. Some species prefer cracks in tree trunks and boughs (e.g. barbastelle bat and lesser noctule), while others (e.g. common noctule) prefer tree hollows made by woodpeckers. Noctule bats and pipistrelle bats can winter in hollows of thicker trees. In mating season, males of some species (noctule bats, pipistrelle bats) occupy separate hollows treating them as their mating shelters. Sometimes, they are also shelters of breeding colonies. Practically nothing is known about bats which winter deep in narrow crevices in rocks or which bury themselves below ground level.

Artificial shelters (anthropogenic) Anthropogenic shelters are currently the most important refuges for bats in Western Palearctic. Drifts, tunnels, city sewers or wells create similar conditions as caves. They replace caves for bats in areas where no caves are present. Cracks and gaps in walls of buildings and bridges resemble crevices in rocks, similarly gaps in roofs and shutters substitute hiding places in old trees. Anthropogenic shelters are used mainly during winter, as hibernation places, and autumn as mating shelters. Objects of this type are used for wintering by most bat species (Rhinolophus, Myotis, northern bat, Plecotus, Barbastella). Small, home cellars are used for wintering most often by Plecotus and Daubenton’s bats (Lesiński, 2006). Wells, which have microclimate like vertical caves, are an important place of hibernation in areas devoid of other, larger underground sites. City sewers as winter habitat of bats were discovered only a dozen or so years ago (Wojtaszyn et al., 2005). Parts of buildings which are above ground level are for some species (particoloured and serotine bats, noctule bats, pipistrelle bats) main winter shelters. Breeding colonies of bats are usually placed in attics of buildings, as well as cracks and gaps in walls and under boarding, or even space between gutters and walls of a building. Some species (e.g. greater mouse-eared bats) require large and spacious 21


attics, while others use also smaller shelters and often hide in gaps (between layers of a roof, between walls, etc.). In mating season males of some species may use nooks in attics or crannies in walls of buildings as their mating shelters. All species of bats in Poland were observed among other places in buildings. Nesting boxes for bats and birds are hung in places with few natural shelters. Bats (some species) settle in them mainly during spring, summer and autumn, but rarely in winter, due to poor insulation against external conditions. They may be shelters for entire breeding colonies. Old buildings, especially wooden, like sheds, damp cellars, attics, outbuildings and church towers used to be inhabited by bats on a large scale. Currently, buildings are usually insulated and impenetrable, so bats return to caves and hollows, under bridges and into old wells, any place where microclimatic conditions of the interior are favourable enough for them to hibernate. State of knowledge of wintering places of bats is still unsatisfactory.

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3. The notion of ecoclimate – microclimate of an underground system and refugioclimate

In research on hibernation of bats (biospeleological, speleoclimatic) there is certain divergence in terminology and interpretation of issues concerning climate of underground systems (caves) between botanists, zoologists and climatologists. It results mainly from divergence in the research subject of those three branches of science. While carrying out research on climate of caves as habitat of animals and plants one should use a term of habitat climate or ecoclimate. This term is presented by B. W. Wołoszyn (1976) and describes a set of meteorological factors which influences given environment, which in this case are underground systems. On the other hand if the purpose of research is to determine a set of climatic factors which occur in underground systems for a period of many years (a year and longer) a term of speleoclimate seems to be more adequate (Skalski, 1973). Microclimatology has been sectioned off as one of the branches of climatology (Whittow, 1986). Just like climate or topoclimate (local climate) it has some distinctive features in relation to surrounding areas (Yoshino, 1975). Wiglej and Brown (1976) present different approach to the subject. According to these authors many speleological issues, among other things connected with climate which occurs inside underground systems, may be reduced to physical problems, which is why they use the term of cave meteorology. In this context the term meteorology is used in a broader sense and includes also climatology. To be precise, this term refers also to dynamic elements of quickly changing atmospheric conditions, while climatology deals with long-term changes. This approach results from a fact that underground systems are dynamic environments and temperature, humidity, air flow, etc. show short and long-term spatial and temporal changeability. In Polish speleological literature the most frequently used term is cave microclimate, as a description of a set of climatic conditions existing in caves, while state of external atmosphere and changes which occur there are examined by topoclimatology and climatology. The term micrometeorology is also used, as it deals with processes of exchange of momentum, heat and matter between atmosphere and its substratum (Paszyński et al., 1999). In meteorological lexicon (Niedźwiedź, 2003) microclimatic conditions of closed spaces (artificial and natural), including caves and animal burrows, are called cryptoclimate (interior microclimate, climate of a closed space).

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In the current work a notion of interior microclimate was adopted as a set of conditions existing inside the examined system. It is considered to be “background” of values of existing generally particular factors of the underground system. The term refugioclimate used in the work was proposed in 2005 (Kłys, Wołoszyn) for physical conditions in the immediate proximity of hibernation place (several cm around a wintering bat). It results from the fact that measurements of thermal background, air movement and humidity (microclimate of the underground system) were often significantly different from these factors in the immediate proximity of the wintering bat. Many times they are rock niches or recesses while sometimes the examined object hangs centrally in a part of the gallery and then these values do not differ significantly from values of factors of the interior’s microclimate. This notion defines the problem correctly and at the same time it refers to the specific values essential for further discussion. It refers to a specific place of hibernation, not to the microclimate of entire or a part of the underground system. Obviously, a microclimate as a set of meteorological factors (local peculiarities of climate) influences directly conditions of a refugioclimate and what follows the existence of the organism. In underground systems, which are often places of hibernation of bats, there are different microclimatic conditions of the interior in relation to the surface conditions. They change already in short distances (Chromow, 1977). Microclimate of an interior is more stabilized and mild. It depends of course on the size of the underground system and the scale of climatic change, long term, seasonal or daily ones. It is usually characterized by lower than ambient temperature and higher humidity, as well as air circulation which changes throughout the year. However in the other, opposite part of the system the changes are reverse to the observed ones. Climatic conditions of an underground system are influenced by height of the entrance opening above sea level, exposure of the opening, existence of flora above the opening, morphology of the cave (length and shape of corridors and chambers), streams of water transferring heat and taking it out, thermal energy from the Earth’s interior.

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4. Characteristics of physical elements which have influence on hibernation of bats As heterothermic organisms bats can regulate body temperature within certain limits. Their thermoregulation is so special, that they can lower their body temperature almost to the level of ambient temperature. However, within moments (Davydov, 2004) bats can raise temperature considerably higher than ambient temperature even to 40 °C at ambient temperature of just several degrees. So bats of temperate zones enter into torpor in cold season to wait out the period in which there is lack of appropriate sustenance. They lower their body temperature during hibernation almost to ambient temperature (McNab, 1982). It causes significant reduction of metabolism (Thomas, 1995). Independently of research on biological factors of bat hibernation there are also performed microclimatic observations of underground systems. Apart from biological factors, such as ensuring safety from predators, there is a large number of physical factors which have an influence on hibernation. 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11.

chemical and physical composition of air ability to attach itself to the substrate (Fig. 3) air movement air temperature temperature of surrounding objects (rock) air humidity thermal conduction of rocks phasic changes of air permeating geothermal heat air pressure influence of external conditions

In underground systems microclimatic conditions play a very crucial role. They depend on functioning of the entire system. These statements are confirmed by abundant literature devoted to underground microclimate. In case of formation of microclimatic 25


conditions of underground systems three closely connected processes bear the essential meaning (Piasecki et al., 2001): exchange of air between the underground environment and its surroundings; flow and exchange of heat between the orogen and air and water in the underground system; circulation of water in the underground system, including circulation of moisture in the form of vaporization and condensation. Through operation of these factors a relation appears between microclimatic conditions in the underground systems and the topoclimate and, in consequence, the refugioclimate (Kłys, 2008).

Fig. 3. A roof of an underground system with marked attempts of bats to attach themselves to it. Photographed by the author.

Taking into account the set of these factors, one may empirically determine climatic zones for particular species and strategies of bats. In research on hibernation of bats air temperature is often considered to be the most important factor, since it is a universal indicator which reacts quickly for even slight changes in circulation and humidity of underground systems. However, it is very 26


hard to examine temperature of a given system without knowledge of direction and intensity of air movement and humidity. Underground environment, including caves, is considered to be stable, which means the one in which both temperature and humidity, as well as other factors are considered to be constant elements. In reality however, these parameters undergo significant changes, though they are not so clear as outside in the open atmosphere. So underground environment has got a dynamic character in which factors show spatial and temporal diversity (Kłys, 2008). One may distinguish many factors which shape temperature inside underground systems. However, the most important ones include: air movement and influence of so called “cave winds”, which moderate and even out thermal differences between an underground system and its surroundings as well as in the interior of the system. It is accepted that average annual outside temperature corresponds to inside temperature of the underground and decreases as height above sea level grows. While investigating changeability of air temperature profile, the processes of releasing or absorbing latent heat due to condensation and evaporation cannot be ignored. The air that gets inside an underground system usually gets warmer or cooler in contact with a rock. Depending on temperature of the rock being higher or lower than dew point, water vapour condensates or evaporates from the surface of the rock. In both cases during transition of particular amount of substance from one phase into another at constant pressure and temperature, certain amount of heat will be emitted or absorbed, called latent heat or heat of phase transition. However, heat of condensation is equal in terms of absolute value to heat of vaporization, but with opposite sign. Both immediate heat exchange between the rock and the air as well as latent heat absorbed or emitted are very vital in determining air temperature profile in underground systems. Certain amounts of heat (cold) are supplied to underground systems by inflow of external air. They are subjected to quick transformation in underground environment. They take part in determining spatial diversity of course and profile of temperature. In parts which are located deeper amplitude of temperature is small and extreme values of temperature are caused by a more intensive flow of warm or cool air. By absorption and emission of heat rock regulates changes of air temperature caused also by other factors.

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5. Material and methods 5.1 General Remarks Research was conducted both in caves and artificial shelters. In the first stage an inventory of winter refuges was made, an insight into composition of species was gained and numerical strength of bats was recognized. Next, ecological observations were started, namely examination of structure of groups and interactions between species of wintering bats. This stage of research allowed to accept a working hypothesis that the course of hibernation in bats is significantly and directly influenced by a lot broader spectrum of physical factors than it was believed so far. Six most common in underground systems bat species were selected for the research: lesser horseshoe bat Rhinolophus hipposideros, greater mouse-eared bat Myotis myotis, Daubenton’s bat Myotis daubentonii, Natterer’s bat Myotis nattereri, brown long-eared bat Plecotus auritus and Western Barbastelle Barbastella barbastellus). Description of places chosen by particular species in winter period concerned temperature, humidity and air flow. Temperature of surface on which bats winter was randomly recorded as well as the type of material on which they winter in order to attribute thermal conductivity. Data was collected mainly in the period of peak of hibernation (December – February). Due to the fact that waking bats was avoided, sex and age were not determined, so there is no data if these two factors have influence on the choice of particular place of hibernation. The research was conducted on the basis of permissions of Provincial Nature Conservation Authorities and the Minister of Environment (DOPog-4201-04A-2/03/al.; DOPog-4201-04A-6/04/al.; DLOPiK-op/Ozgi-4200/IV.D-16/6568/06/aj.) and thanks to courtesy of the management of Moravsky kras Landscape Protection Park (Chráněná krajinná oblast Moravský kras).

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5.2. Places of research The most important criteria of choice of places of research was among other things large number of particular bat populations. Data of refugioclimate were collected in the years 2002 – 2007 in the following underground systems of Poland and the Czech Republic (Table 2): Table no. 2. List of underground systems in which research was conducted. Name of underground system

longitude

latitude

Sewers and shopfloor in Police

E 14° 32' 5

N 53° 33' 4

Międzyrzecz Fortified Region

E 15° 29' 2

N 52° 23' 4

Mopkowy Tunel (Barbastelle Tunnel)

E 15° 12' 4

N 51° 48' 4

Cold store in Cieszków

E 17° 22' 3

N 51° 37' 1

A cellar in Ładza

E 17° 87' 1

N 50° 84' 7

Szachownica Cave

E 18° 48' 2

N 51° 31' 5

Underground systems of Tarnowskie Góry and Bytom

E 18° 49' 5

N 50° 24' 8

Fortifications in Nysa

E 17° 18' 5

N 50° 29' 4

A drift in Sławniowice

E 17° 16' 4

N 50° 20' 1

Drifts in forest administration region of Senderki

E 23° 34' 2

N 50° 32' 2

The Balcarka Cave

E 16° 45'2

N 49° 22' 3

Sloup – Šošůvka Cave

E 16° 44'1

N 49° 24' 3

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Sewers and shopfloor in Police Network of underground sewers 4000 m long and shopfloor which are remains of prewar factory of aviation fuel (synthetic petrol) – Hydrier Werke Politz. The biggest winter habitat of bats in Western Pomerania (780 specimens – winter period 2003). Six bat species winter here: Barbastella barbastellus, Myotis myotis, Myotis brandtii, Myotis daubentonii, Myotis nattereri, Plecotus auritus. It is located in Zachodniopomorskie province. The facility has been included into the Natura 2000 network the purpose of which is to preserve specific types of habitats and species which are considered valuable and endangered in entire Europe (area code: PLH320015).

Międzyrzecz Fortified Region Refugium Nietoperek encompasses a vast network of old underground fortifications i.e. 30 km of reinforced concrete bunkers, 30-50 m under ground level. They form a part of so called Międzyrzecz Fortified Region constructed by the Nazi in the years 1933 – 1945. The underground system is connected with the surface by several vertical ventilation shafts and corridors leading to the bunkers. The area encompasses the most important winter habitat of bats in Central Europe and their feeding grounds. About 30 thousand bats winter here (Kokurewicz et al., 2013). The most numerous are: Myotis daubentoni, Myotis myotis, Plecotus auritus and Myotis nattereri. The following species also occur: Barbastella barbastellus, Myotis dasycneme, Myotis bechsteinii, Eptesicus serotinus, Myotis brandtii, Myotis mystacinus, Pipistrellus pipistrellus, Plecotus austriacus. It is located in Lubuskie province. The facility has been included into the Natura 2000 network the purpose of which is to preserve specific types of habitats and species which are considered valuable and endangered in entire Europe (area code: PLH080003).

Mopkowy Tunel (Barbastelle Tunnel) Underground drain of a former factory located near Krzystkowice with the outlet to the Bóbr river. The largest known in Poland winter grouping of Barbastella barbastellus. Around 2000 specimens winter here. Several specimens of Myotis daubentonii and Plecotus auritus also occur here. It is located in Lubuskie province. The facility has been included into the Natura 2000 network the purpose of which is to preserve specific types of habitats and species which are considered valuable and endangered in entire Europe (area code: PLH080024).

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Cold store in Cieszków It is a spacious underground brick ice cellar located in a wood in the vicinity of the village of Cieszków. Probably it was built in the 19th century and served then to the needs of the palace in Cieszków. Later, it was used as a cold store by various users. It is located in Dolnośląskie province. It is one of the largest winter habitats of bats in Poland. The guide Natura 2000 (2004-05) lists 200 specimens of Barbastella barbastellus, 10-15 Myotis myotis and Eptesicus serotinus, Myotis daubentonii, Myotis nattereri, Plecotus auritus, Plecotus austriacus. Apart from playing the role of hibernaculum, the cold store is also important for bats which migrate. Late in summer and autumn a large number of specimens are observed which were not spotted here in winter period, for which it is a mating site. It is now secured by Forest District Office in Milicz. A number of changes was introduced in the structure of the facility the purpose of which was to improve microclimatic conditions to make them optimal for bats. Among other things additional partition walls were constructed as well as a pool which ensures appropriate humidity. The facility has been included into the Natura 2000 network the purpose of which is to preserve specific types of habitats and species which are considered valuable and endangered in entire Europe (area code: PLH020001).

A cellar in Ładza A small cellar in a building of a former school (currently management of Stobrawski Landscape Protection Park) in Ładza in Opolskie province. Each year 2 specimens of the following species winter here: Plecotus auritus and Plecotus austriacus. It is located in Opolskie province.

Szachownica Cave Proglacial cave system in Upper Jurassic limestone in the central part of Wieluńska Upland. The cave system is composed of five separate caves separated by excavation of the quarry. They used to form one cave, destroyed during exploitation of limestone performed by local inhabitants till 1962. Currently, the place is treated as one cave system of total length of 1000 m, which before destruction was probably longer than 2 km. It is one of the largest winter habitats of bats in Poland. Each year over 1000 bats representing 10 species hibernate in the cave: Barbastella barbastellus, Myotis dasycneme, Myotis bechsteinii, Myotis myotis, Eptesicus serotinus, Myotis brandtii, Myotis daubentonii, Myotis mystacinus, Myotis nattereri, Plecotus auritus.

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It is located in Śląskie province. The facility has been included into the Natura 2000 network the purpose of which is to preserve specific types of habitats and species which are considered valuable and endangered in entire Europe (area code: PLH240004).

Underground systems of Tarnowskie Góry and Bytom Underground excavations remaining after exploitation of heavy metals ore. One of the largest underground systems in the world. The excavations were formed from the 12th to the 20th century. Currently they cover over 300 km of corridors as well as numerous chambers and pits. The underground system encompasses 5 drain adits, numerous shafts and outcrops in quarries. It is probably second largest winter habitat of bats in Poland. The following 10 species of bats were observed here to winter: Myotis myotis, Myotis nattereri, Myotis mystacinus, Myotis brandtii, Myotis daubentonii, Myotis bechsteini, Myotis emarginatus, Eptesicus serotinus, Plecotus auritus, Plecotus austriacus (Kłys, 2008). It is located in Śląskie province. The facility has been included into the Natura 2000 network the purpose of which is to preserve specific types of habitats and species which are considered valuable and endangered in entire Europe (area code: PLH240003).

Fortifications in Nysa A vast defensive complex of buildings from the 19th century with a large number of corridors, constructed in topographic low of the valley of Nysa Kłodzka river, currently located in the town park in Nysa. One of the most important wintering habitats of bats in Silesia (Hebda 2001). The guide Natura 2000 informs about wintering of the following species: Rhinolophus hipposideros, Barbastella barbastellus, Myotis emarginatus, Myotis bechsteinii, Myotis myotis. It is located in Opolskie province. The facility has been included into the Natura 2000 network the purpose of which is to preserve specific types of habitats and species which are considered valuable and endangered in entire Europe (area code: PLH160001).

A drift in Sławniowice Underground corridor located near the village of Sławniowice on the premises of a marble quarry. About 200 specimens of lesser horseshoe bat Rhinolophus hipposideros winter here. It is the largest known winter habitat of lesser horseshoe bat in the Polish part of Sudety mountains (Kepel et al., 2005). In the vicinity there is a breeding colony of this species. It is located in Opolskie province. The facility has been included into the Natura 2000 network the purpose of which is to preserve specific types of habitats and species which are considered valuable and endangered in entire Europe (area code: PLH160004). 33


Drifts in forest administration region of Senderki They are drifts remaining after exploitation of sandstone for production of milling stones in Forestry Commission of Zwierzyniec and on private grounds west from a village of Potok Senderki, behind a grove intersected by a road which is a continuation of the main road which leads through the aforementioned village. The drifts are located at the bottom of tree-covered ravines which cut into fields. It is one of the most interesting winter colonies of bats in Lublin region. Nine bat species winter here: Barbastella barbastellus, Myotis dasycneme, Myotis bechsteinii, Myotis myotis, Myotis brandtii, Myotis daubentonii, Myotis mystacinus, Myotis nattereri, Plecotus auritus. It is located in Lubelskie province. The facility has been included into the Natura 2000 network the purpose of which is to preserve specific types of habitats and species which are considered valuable and endangered in entire Europe (area code: PLH060020).

The Balcarka Cave (Jeskyně Balcarka) Balcarka Caves are located in a valley close to a small town of Ostrov u Macochy. Underground maze of corridors, crevices and chambers is created on two levels. The cave is also a valuable paleontological and archaeological site. Bones of Pleistocene animals, instruments made of bone and stone and a bonfire of people from the Old Stone Age were found there. Subsequent parts of the cave were successively discovered in the years 1923 – 1948 and are characterized by rich, various and colourful dripstones. It is one of the most important wintering places of Rhinolophus hipposideros in Europe. It is located in southern Moravia in the Czech Republic. The facility has been included into the Natura 2000 network the purpose of which is to preserve specific types of habitats and species which are considered valuable and endangered in entire Europe (area code: CZ0624130 - Moravský kras).

Sloup – Šošůvka Cave (Sloupsko-šošůvské jeskyně) An extensive complex of chambers, corridors and underground chasms created on two levels. Abundant cave fauna (bears, lions, hyenas...) was found there. Remains of Neanderthal man from 120,000 years ago were also found in that place. It is one of the most important wintering places of Rhinolophus hipposideros in Europe (Zima et al., 1994). It is located in southern Moravia in the Czech Republic. The facility has been included into the Natura 2000 network the purpose of which is to preserve specific types 34


of habitats and species which are considered valuable and endangered in entire Europe (area code: CZ0624130 - Moravský kras).

5.3. General overview of devices and methodology of measurement of hibernation environment (refugioclimate)

So far microclimatic (ecoclimatic) research concerned mostly general state of atmosphere of an underground system and rarely microclimate of refuges (Kłys et al., 2005; Kłys, Wołoszyn, 2005; Kłys, 2008), which are direct places of wintering of bats. Microclimate of refuges many times differs greatly from microclimatic “background” of the underground system. One may use various measuring devices, but methodology of measurement should be precisely described. So far it was impossible to introduce to measuring technology a device which would measure a sum of factors having influence on hibernation comfort of a bat. Most of works concerning microclimatic conditions in a place of occurrence of bats lack the description of methodology of measurement and kind of devices used, which makes correct interpretation of such data impossible (Kłys et al., 2005). Usually influence of the measuring person on the result of measurement is not taken into account as well as time for stabilization of the device, which is often 30 minutes or even longer (Caputa, Kłys, 2005). Apart from measurement of ecoclimate of a refuge the “background” of the underground system was also measured. Physical factors which determine microclimate of underground systems are discussed below. 5.3. 1. Air temperature (T)

The measure of empirical temperature is usually a change in volume or pressure of a standard body which is in the state of thermodynamic balance with the body the temperature of which is measured. There are theoretical and empirical scales of temperatures. The first group includes e.g. scale of perfect gas, thermodynamic scale of temperatures. Empirical scales based on empirical data includes International Practical Temperature Scale. Depending on the way of heat transfer between the sensor and the body the temperature of which is determined; devices are divided into contacting ones called 35


thermometers, non-contacting ones (pyrometers) and special ones. In research on bats (estivation, hibernation) the range of measurements should be between -20 0C and 50 0C. A frequent measuring device used so far in measuring temperature was Assman aspiration psychrometer. However, values obtained in this method bear major errors and these measurements also average the values (drawing in larger quantities of air). They give only a very general picture of microclimatic values and they are totally useless to measure refugioclimate. In the literature there is a notion of dry-bulb temperature (Ts) - it is temperature displayed by a normal (i.e. dry) thermometer and if there is no reference to the kind of temperature, it means that dry-bulb temperature is concerned. Wet-bulb temperature (Tw) is the temperature shown by a wet thermometer, e.g. in a psychrometer or covered by ice. It should be pointed out that in small underground systems and relatively stable microclimate, measurements performed with the use of traditional methods are hindered and bear grave errors, also due to presence of the researcher and people who accompany him or her, as well as time of their stay in the place where the measurement is performed (Fig. 4). There is a number of publications concerning influence of tourism in caves on their microclimate, including temperature (Kwiatkowski, Piasecki, 1989; Piasecki, 1996, 1996a; Pflitsch et. al., 1999; Zelinka, 2002; Piasecki et. al., 2007). Measurement of temperature and air flow in a refuge should be performed from the side the air comes in (Fig. 5). For the purpose of this research a thermoanemometer and a gas parameter gauge made by SENSOTRON, specially modified and calibrated to the needs of recording, were used. Special attention was paid to graduate thermometers (devices) in relation to a bench-mark in various ranges of temperature before the measurements were performed. In the immediate place of hibernation of bats temperature was measured with the use of an extension arm (aluminium rod), in such a way, that the observer did not interfere with readings of the gauge, always against the stream of inflowing air.

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Fig. 4. Influence of human presence on measurement of temperature (9 Mar 2002). Measured at the place bat hibernation. Vertical lines show the range of data omitted in analyses (Kłys 2003). 37


5.3. 2. Substrate temperature (Tch - temperature of the surface of hibernation) To measure temperature of a side wall of an excavation or surface of objects which are close to wintering bats, thermometers or non-contacting devices are used. Usually temperature is measured with thermoelectric or resistance thermometers, less often expansion thermometers are utilized. For the purpose of this work an electric contact thermometer made by SENSOTRON was used. In order to enlarge the surface of contact silicone of high thermal conductivity was utilized.

5.3. 3. Air flow velocity (v) A very important element of ecoclimate which should be registered is measurement of air flow velocity, both the background of ecoclimate and directly in the place of hibernation. This parameter should be approached very carefully. In case of the background of an underground system these measurements require determining average velocity in time and certain cross section or determining spot speed for refugioclimate. In order to measure spot and average velocity in time anemometers, impact pressure tubes, flowmeters, hot-wire anemometers and katathermometers are used. Air flow velocity in underground systems is usually given in m/s, m/min and sometimes cm/s (100 cm/s = 1 m/s = 60 m/min). Sometimes these devices have scales in imperial system units in/s, ft/s, yd/s. (1m/s = 39.3701 in/s = 3.28082) Specifying air flow in the hibernation place of a bat with the use of anemometers is difficult due to technical reasons. Above all it refers to measurements (recording) of movement of small velocity which occurs in niches. Measurements of air velocity lower than 0.1 ms-1 are difficult or impossible to perform with the use of regular anemometers. Using mechanical anemometers of various types is not as effective as it was expected due to small inertia of receptors, necessity to overcome internal and external friction, as well as small space of a niche. In the current work a specially modified and calibrated to the needs of recording SENSOTRON hot-wire anemometer was used. In order to minimize influence of a human and a wintering bat measurements were performed from leeward side while standing face front to coming air (Fig. 5). 38


In narrow (low) corridors and chambers of small volume emission of heat (3 - 4 thousand kcal/24h) and breath of the observer may significantly influence results of observation (Kłys et al., 2005).

Fig. 5. Performing measurement of air flow and temperature. The arrow shows direction of air flow. An infrared photograph for the author by P. Rutkowski, Flir Systems. In measurements in cross section of a corridor (“background”) air velocity is not same in all points of the section (Fig. 6). The highest velocities are usually in central parts of a corridor, while the lowest ones are at walls. There are often observed streams of air flowing in and out which flow through the entire inside diameter of the opening in one direction or interchangeably, i.e. in the cross section of the corridor two opposite fluxes of air are moving.

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While measuring background due to gross interferences of flows a crosswise division of cross section of an underground system should be made. In order to avoid errors, measurement of velocity in particular determined places should be performed several times (Pawiński et al., 1995) and an arithmetic mean should be calculated from these measurements.

Fig. 6. An exemplary distribution of air velocity in a corridor of an underground system. The place of hibernation of a bat is indicated. (The photograph and the drawing are made by the author).

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5.3. 4. Relative humidity of air (Rh)

Atmospheric air in underground systems is considered to be a mixture of dry air and water vapour. One should remember, that when temperature of air saturated with vapour drops, part of vapour condenses and mist occurs. As temperature of air saturated with steam increases, state of insatiability occurs (it is shown in a Mollier diagram (Biernacki, 1993). Air humidity (relative and absolute) is a value changeable in time and space. It depends on climate, season of the year, intensity of precipitation and direction of air flow (into or out of a cave). Differences in air humidity of a zone next to an entrance and deeper ones may be significant. Air humidity is an equally complex factor as air temperature. It is formed as a result of moisture incoming from the surface, cooling of air inside, becoming damper in contact with groundwater flows and infiltration water (Kwiatkowski, Piasecki, 1989). To measure humidity the following methods are used: gravimetric, condensation (dew point), psychrometric, hygroscopic ones as well as hygrometer sensors. To measure relative humidity of background of the underground system usually an Assman aspiration psychrometer was used of an accuracy up to 0,2 0C. Despite very precise measurement of relative humidity the devices used so far (Assman aspiration psychrometer) are totally useless for measuring refugioclimate. The author used an electronic gas parameter gauge made by SENSOTRON. It allowed to measure relative humidity in microniches. The measurement was performed while standing face front to coming air in order to minimize influence of the human and the wintering bat. The bats often use seeps of water from walls (Fig. 7); air humidity is then higher only in the immediate proximity of the wintering bat.

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Fig. 7. In an environment where humidity is lower then the desired one, greater mouseeared bats choose microniches of higher humidity of rock and air (photographed by the author).

5.3. 5. Thermal conduction of materials (λ)

Thermal conductivity, thermal conduction coefficient (marked with the symbol of λ) is one of the most important parameters of substance for heat conduction. In same conditions more heat will flow through a substance of higher thermal conduction coefficient. Thermal conductivity is a quantity characteristic for a substance in a given state of aggregation and its phase. It depends on its chemical composition, structure, porosity, state of aggregation and temperature. The substances which best conduct heat are metals, while gases are the poorest conductors. There are significant difficulties in field measurement of thermal conductivity. 42


In the work there were no field measurements of conductivity, only a rough analysis of the substance on which bats wintered. Taking into consideration the type of the substrate approximate values of thermal conductivity were used (Table 3). Table 3. Exemplary approximate values of thermal conductivity of materials which one may encounter at bat hibernation (grey fields show average values of the factor). The unit of the thermal conduction coefficient in SI is J/(m s K) = W m-1 K-1 (watt per meter kelvin). material

Thermal conductivity in (W m-1 *K-1). The average value is given

Air

0.025

Expanded polystyrene

0,03; 0,06; 0,1

Wood

0,04; 0,12; 0,21

Rubber

0,16

Water

0,5; 0,55; 0,6

Brick

0,6 - 0,15; 0,6; 0.69; 1.31

Concrete

0,8; 1,0; 1,28

Limestone

1,33

Soil

0,6; 2,3; 4

Sandstone

1,83; 2,4; 2,90

Marble

2,07; 2,5; 2,94

Granite

1,73; 2,8; 3,98

Cast iron

55;

Iron

71,8; 80,2; 55.4; 34.6; 60,5 43


5.3. 6. Air pressure (p) Air pressure depends on basic quantities, which must be taken into consideration in research on underground systems. Knowing the value of pressure is useful for estimation of velocity of flow, volume of flux and mass of air. During comparison of data of refugioclimate with humidity and temperature a program calculating Mollier diagram was used (Wykres i-x Molliera). In underground systems depending on the way of measurement the following items are used: devices to measure absolute pressure: mercury barometers, aneroid barometers, barolux, micro-barolux; devices to measure pressure above or below atmospheric: micromanometers, manometers, differential manometers. According to the principle of operation one may distinguish: liquid gauges, elastic pressure gauges and electric converters. The author used an electronic gas parameter gauge made by SENSOTRON, which had a built-in barometer. In the current work values of pressure of refugioclimate were converted into values for 1000 hPa of absolute pressure (the program Wykres i-x Molliera). It facilitates comparison of data of relative humidity from different measuring points as well as days of measurement.

5.3. 7. Level of cooling (Ka) While entering the state of hibernation a body of a bat may give up heat to the environment by radiation, vaporization, convection and conduction. The amount of heat which is given up in convection depends on thermal conductivity of the body of the bat and difference of temperatures of skin and air or rock that surrounds the body. In certain combination of such factors as: temperature, air movement and humidity one may assume that the bat achieves comfort of hibernation. In order to determine optimal values for hibernation of bats dry-bulb temperature, relative humidity and air flow velocity was measured in the place of hibernation. Thermal comfort is determined by measurement of intensity of cooling with the use of wet Hill’s katathermometer. The quantity of cooling power of the atmosphere, which is intensity of cooling Ka°, is expressed by loss of heat from 1 cm2 of surface in 1 second (Frycz, 1974). 44


The unit of intensity of cooling is 1 Kata degree mcal/cm2 • s. Due to the commonly binding SI the intensity of cooling effect of the atmosphere should be expressed in W/m2. The unit of intensity of cooling is NKa° (new Kata degree) expressed in W/m-2. Due to frequent use of the old unit in literature, a conversion formula has been given. NKa° = 42 x Ka° [W/m-2] There are the following empirical relations between the cooling effect of the atmosphere given in Kata degrees and air velocity υ and its temperature T expressed in 0 C (Budryk, 1961). υ ≤ 1ms-1

Kw = (0,35 + 0,85 • ³�w) • (36,5 -Tw)

Where: w – air velocity, ms-1 Tw – wet-bulb temperature Due to measuring difficulties (in our case low temperature, disturbances by human presence itself, heating up the katathermometer, repeating the measurement at least 5 times and above all else difficulty in placing it close to the hibernating bat) the above mentioned formula was used. So the following components were measured: air flow velocity and temperature in the proximity of a hibernating bat, but the wet-bulb Hill’s katathermometer was not used due to the above mentioned measuring errors. Unfortunately, there is no direct formula which allows to calculate wet-bulb temperature Tm on the basis of dry-bulb temperature Ts and relative humidity Rh. Due to the fact that dry-bulb temperature Ts and relative humidity Rh was measured, not wet-bulb temperature Tw which is necessary for the formula, Tw was calculated with the use of the computer program Wykres i-x Molliera the purpose of which is to simplify calculations connected with transformations of humid air. The list of devices used during research as well as their parameters are included in Appendix no. 1.

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6. Wintering strategies

While describing microclimatic conditions in hibernation place of bats, the sum of basic physical parameters usually is not usually taken into consideration, the methodology of measurement is not described (so is it not known what was measured in fact??), it is also usually forgotten to present wintering strategy of bats. The works are not numerous (Zukal et al., 2005). We do not know if the bats winter individually, socially, are they hidden in crevices. Therefore in the current work the following division (depending on participation of physical factors which have influence on cooling of a bat) into wintering strategies is proposed (Fig. 8): Individual wintering “Ia” hanging freely “Ib” hanging on the wall “Ic” in a crevice

Group wintering (social) “IIa” hanging freely “IIb” hanging on the wall “IIc” in a crevice In social behaviour we may distinguish further complexity e.g. in strategy “IIb” particular specimens may winter placed loosely one next to the other, overlapping or create a cluster in which particular specimens are placed one on another (Fig. 9).

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Fig. 8. Depending on contact with physical factors wintering strategies used by the bats taking into account factors (air flow, humidity, rock temperature, air temperature) and possibility to give up heat by convection or conduction.

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Fig. 9. Social behaviour in “IIb” strategy. a - Myotis myotis - overlapping, b - Barbastella barbastellus - cluster (one on another), c - Myotis daubentonii and Myotis nattereri loosely one next to another (Photographed by the author). Of course not all species use all strategies and they are not observed in equal percentage. It is commonly known, that lesser horseshoe bat always uses “Ia” strategy and no other behaviour during hibernation was observed. Brown long-eared bat is often observed in strategy “Ia”; “Ib” rarely in “Ic”, though own observations while catching them alive (Kłys, 2008) show, that the last strategy is probably more common, but difficult to observe. They are also found in mixed colonies with other species.

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7. Thermal comfort of a hibernating bat The balance of exchange of matter and energy between a hibernating specimen and environment, meaning general qualitative and quantitative metabolism must include: sum of heat transmitted to the system from environment sum of heat transmitted outside by the system thermal effect of processes occurring inside the system If the loss of energy in the organism is balanced by reserve substances, the organism of a hibernating bat is in the state of thermal (energy) equilibrium. The organism of a hibernating bat has possibility to achieve thermal balance in quite wide range of physical parameters of surrounding environment and their changes thanks to the system of thermoregulation of the organism. It has to maintain continuously controlled temperature, a bit higher from ambient, but within the optimal range (which we do not know usually). The parameters which characterize metabolism in quantitative terms in the state of energy balance depend, similarly as in humans, from constant factors (species, size, weight, sex, age of the specimen) and variable ones (regulation of heat exchange of the body in contact with environment). The energy effect of metabolism may be referred to body weight or to surface area of the organism, or, for best results, to both factors simultaneously. The organism of a bat may change surface area of the body (by spreading or folding wings, hiding or sticking out ears (Plecotus), snuggling to objects or protruding from them). It is then relatively labile (flexible). Only highly specialized species like e.g. Rhinolophus hipposideros have different strategy of managing physical conditions of environment. A bat wrapped in his patagium can part it or wrap it more tightly, which gives him possibility to achieve thermal balance and ensure comfort of hibernation (Fig. 10).

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Fig. 10. Possibility to regulate influence of physical factors on the organism by Rhinolophus hipposideros (Photographed by the author). The climate of wintering place (refugioclimate) are numerical values of those physical and chemical parameters which have influence on amount of heat exchanged between the organism of a hibernating bat and its environment. The amount of heat transmitted from an organism to environment is called heat loss. In order to characterize the hibernation environment a notion of refugioclimate is used, which means the state of climatic conditions occurring in natural way or created artificially in small space surrounding a hibernating bat, hence formed among other things by influence of: - average air temperature, - amount of moisture in the air, - air flow velocity, - temperature of surrounding objects.

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Common (joint) influence of these factors on the organism of a hibernating bat may be called thermal comfort of hibernation, which should be presented in numerical form; that would be the hibernation coefficient. An attempt was made here to integrate these values into wet Kata cooling power degree (see chapter 3.2). These values are only an approximation of the searched hibernation coefficient and are not noticeable enough in all examined species. So by the thermal comfort of a wintering bat one should conceive such a state of satisfaction of a specimen (group) in thermal conditions of environment in which it feels neither warmth nor coolness. The necessary condition to feel thermal comfort is achieving the state of thermal balance of organism. Such a state is characterized by levelling the amount of heat of metabolism with energy exchanged between the organism of a hibernating bat and environment (Fig. 11).

Fig. 11. Possibilities of regulation of thermal condition of a bat’s organism. A hibernating bat may stay in various conditions characterized by various values of physical quantities enumerated above. The most beneficial refugioclimate is created by such conditions in which a bat feels well and the heat management of its organism is most economical. This state is achieved in various mutual combinations of temperature, relative humidity and air flow velocity and it is called the state of thermal comfort. Due to biological differences in particular population there is no possibility for all specimens of a given species which are present in a place of a given refugioclimate to feel well and comfortably in given thermal conditions. For this reason it should be assumed that the optimal refugioclimate is a state in which a possibly high proportion (e.g. 80-90%) of a hibernating bat population accepts prevailing physical conditions. Sometimes there may be a disturbance of the process of carrying heat from organism to the environment. Such a state may occur when production of heat of metabolism is higher than the amount of heat that may be carried to the environment in given conditions. Such a state is called discomfort of hibernation. 53


Bats may be forced to change the hibernation place; it happens for two reasons: When the organism of a hibernating bat transmits heat too slowly, its body temperature rises. Whereas it transmits too much heat it cools down below the optimal value. The organism dies or must use more energy to get warm (loses reserves faster) or fly away to find favourable conditions to survive. In both cases a bat tries to change its hibernation place. An organism transmits heat to the environment thanks to existence of difference of temperatures of a specimen and environment and difference in saturated vapour pressure in temperatures of skin and environment. While entering the state of hibernation the body of a bat may give up heat to the environment by: radiation, vaporization, convection and conduction (Fig. 12).

Fig. 12. Processes of heat exchange between an organism and the environment. 54


7. 1. Conduction Heat transfer from an organism to the environment through conduction may occur when a part of the body is in contact with solid body, such as a side wall, a recess, a rock crevice, etc. Depending on a strategy of hibernation adopted by a bat (see chapter 5.1. Wintering strategies) and surface area of contact of the body of the animal with substrate, amount of heat transferred this way will be very varied. Currently, due to the scope of research only approximate values may be discussed (1 – 70% ?).

7. 2. Radiation In bats which hibernate on the surface, outside underground systems, in heat exchange between their organisms and surrounding environment a crucial role may be played by solar radiation and thermal radiation originating on Earth. In underground systems only thermal radiation occurs. Each surface emits flux of radiation of energy depending on its absolute temperature and emissivity according to Stefan-Boltzmann law.

7. 3. Convection Removal of heat through convection from a body which is not covered by fur is characterized by coefficient of thermal insulation of a layer of hair at the wall, air around the body, which is inverse of coefficient of heat transfer. Value of thermal insulation is connected with surface layer of air around a body and constitutes a crucial element of total thermal resistance of the organism. In case of high velocity of cool air flow quantity and quality of hair plays an important role. The amount of heat which is given up in convection depends on thermal conductivity of the body of the bat and difference of temperatures of skin and air (rock) that surrounds the body. In normal conditions an organism loses most heat through vaporization (Schmidt-Nielsen, 1997). Relative humidity of air surrounding a bat has enormous significance in this case. When humidity is close to saturated condition giving up excess heat from an organism to environment may be hindered or even impossible. Through convection, which is direct lifting from skin surface, intensity of heat exchange rises on the surface of body itself. Giving up heat from an organism through 55


convection and conduction depends on air velocity. Mechanisms which regulate amount of heat created in an organism must operate in such a way that in short time thermal balance becomes even, otherwise it may be impossible to maintain body temperature at a constant level.

7. 4. Vaporization Influence of relative humidity is often more important than nutritional status of animals (Thomas, Cloutier, 1992; Thomas, 1995). Even in conditions of high relative humidity (90-98%) the loss of moisture may reach significant values. The loss of moisture occurs through external surface of the animal’s body and through breathing. Flux of heat is always directed from warmer to colder body, in underground conditions it means that as long as air or rock that surrounds a bat is cooler than its skin, heat will be transmitted from skin surface to air or rock. Through convection, which is direct lifting or conduction of heat from skin surface, intensity of heat exchange rises on the surface of the body of a bat itself. It is the only method of decreasing body temperature in a short time. Slow entering into hibernation state (long-term decrease in body temperature) would cause an increase in energy loss. The quantity of cooling power of the atmosphere, which is intensity of cooling, expresses loss of heat from 1 cm2 of surface in 1 second. So a bat needs to shorten the time of entering into the state of hibernation as much as it is possible. Therefore, the factor of wind (air flow velocity) has two tasks; first, to shorten the time of entering into the state of hibernation, second, to carry away heat. Giving up heat from an organism through convection and conduction depends on air velocity and is in direct proportion to the difference of temperatures of air and body surface. During winter in the temperate zone bats enter into a state of deep torpor. During that period body temperature drops within the range of 1-2 oC above ambient (Hock, 1951; Henshaw and Folk, 1966; Herried and Schmidt Nielsen, 1966; McNab, 1974). At such difference in temperature costs of metabolism during hibernation are exceptionally low in comparison to euthermic animals (Hock, 1951; Herried and Schmidt-Nielsen, 1966; Thomas et al., 1990a, 1990b). Wintering in this period depends on fat reserves, which are source of energy during hibernation, and effective usage of them. After all, hibernation period may last even 6 months. Assuming then, that the difference between the temperature of a hibernating bat and the temperature of the refugioclimate is 1°C, the cooling factor of the atmosphere will be of value within tenth of Kata degree (at the same parameters of atmosphere). It depends, of course, also on thermal conductivity of a bat’s body. In typical hibernation temperature drops almost to ambient, energy loss will be then even lower, which allows to survive several months without feeding, and energy to sustain life is drawn from fat reserves.

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So far no clear-cut methodology was found to assess in thermal terms the environment in which humans live and work as well as bats hibernate. In adequate number of points one may measure certain changeable parameters of this environment, which shape the state of heat exchange between an organism and its environment. Estimation if a refugioclimate is proper constitutes a necessary condition to work out indicators of thermal comfort. Engineers, psychologists and physiologists are interested in this issue from their point of view. Current work constitutes then certain possibilities to predict and evaluate given physical conditions of refugioclimate from the point of view of hibernation. Conditions of environment should be considered as comfortable if a hibernating bat feels neither warmth nor cold.

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8. Choice of place of hibernation 8. 1. Introduction Research on bats is methodologically complicated due to their specific lifestyle. Information about bats is often gathered as a result of an accidental encounter; rarely it is due to planned long-term research. Earlier research undertook estimation of changes in number of bats in relation to microclimate of the underground system. The majority of research concerned thermopreferendum of bats (Gaisler, 1970; Bauerova and Zima, 1988). Harmata, (1969) stated that temperature is the most important factor responsible for hibernation. We know that each species has specific needs as far as hiding place is concerned in relation to types of shelter, temperature, humidity and stability of environment (Kunz, Anthony, 1982). According to the author the above-mentioned conditions are not sufficient parameters to describe refugioclimate. (Kłys et al., 2002; Kłys, 2004, 2008) suggests and points to one more factor, which is air flow velocity and in this paper also thermal conduction of rocks and strategy of hibernation. In order to evaluate influence of the sum of these factors on the choice of hibernation place the author performed measurements of refugioclimate of dry-bulb temperature (Ts - n = 6389), relative humidity (Rh - n = 6389), air flow (v - n = 6389) and atmospheric air pressure (p - n = 6389). Only part of results of physical values of refugioclimate of chosen six species of bats were used for the analysis. It produced in total 23352 items of data. The analysis did not take into consideration data from mixed social strategies (multi-species groups) and species which were observed sporadically during research (pond bat Myotis dasycneme; Brandt’s bat Myotis brandtii; whiskered bat Myotis mystacinus; Geoffroy’s bat Myotis emarginatus; Bechstein’s bat Myotis bechsteinii; serotine bat Eptesicus serotinus; and grey long-eared bat Plecotus austriacus). Majority of data published so far which concerned physical quantities (Ts, v and Rh) from hibernation places of bats are difficult to interpret and sometimes simply unacceptable. In the published works the detailed methodology of measurements is not usually given and one does not know if the described data refer to hibernation place (refugioclimate). For example Nagy, Postawa (2011) informs that a measurement was performed 1.5 m below hibernation place. It is unacceptable because physical parameters in underground systems often differ significantly even in short distances (several 59


cm from a hibernating bat). Using a katathermometer for measuring air flow velocity by Kokurewicz (2004) should be excluded absolutely from analysis. Using Assman psychrometer by the above-mentioned author is also methodologically erroneous (see chapter 5.3. General overview...). Data collected by the current author also contain certain error. Usually we do not know in which phase of hibernation a given specimen was in the moment of measurement of physical quantities of refugioclimate. The full range of physical conditions of refugioclimate was not always available. Therefore, mainly at small number of data the formulae of mathematical functions of a hibernation place will be subject to changes along with supply of new data on physical quantities from hibernation places. However, the conditions of research on refugioclimate were given for potential verification and supplementation of data.

8. 2. Whether there is a relation of choosing by bats higher temperature at first rather than in later months of hibernation In the scientific literature temperature (T = Ts) is usually taken into consideration without other microclimatic factors. It is also mentioned that bats choose higher T at the beginning of hibernation than in the latter months; it is probably due to the fact that small underground systems have higher internal temperature in autumn since they are heated after summer. It is more probable that bats are very economic and choose the most optimal places as far as heat loss is concerned. Due to the above mentioned facts a comparison was performed of measured Ts of refugioclimate for Western Barbastelle Barbastella barbastellus in three months: December, January, February (APPENDIX – Table 1). The analysis of statistical significance was performed with the use of Kruskal– Wallis test since the groups, as far as specific strategies are concerned, differ in size and some of them are low in number, e.g. there were 29 measurements in December, so influence of abnormality of factorization on results induces non-parametric analyses. Particular months of hibernation were compared with the use of Dunn’s test (APPENDIX – Table 2). Highly significant differences (p