Mastozoología Neotropical Instituto Argentino de Investigación de las Zonas Aridas
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ISSN (Versión impresa): 0327-9383 ISSN (Versión en línea): 1666-0536 ARGENTINA
2003 Maurício E. Graipel A SIMPLE GROUND-BASED METHOD FOR TRAPPING SMALL MAMMALS IN THE FOREST CANOPY Mastozoología Neotropical, enero-junio, año/vol. 10, número 001 Instituto Argentino de Investigación de las Zonas Aridas San Miguel de Tucumán, Argentina pp. 177-181
Red de Revistas Científicas de América Látina y el Caribe, España y Portugal Universidad Autónoma del Estado de México
Mastozoología Neotropical / J. Neotrop. Mammal.; 10(1):177-181
ISSN 0327-9383 177 Versión on-line ISSN 1666-0536
NOTAS TÉCNICAS - TECHNICAL NOTES ©SAREM, 2003
NOTAS TÉCNICAS - TECHNICAL NOTES A SIMPLE GROUND-BASED METHOD FOR TRAPPING SMALL MAMMALS IN THE FOREST CANOPY Maurício E. Graipel Depto. de Ecologia e Zoologia, Centro de Ciências Biológicas, Universidade Federal de Santa Catarina, Campus Universitário, Trindade, 88.040-970, Florianópolis - SC - Brazil; Phone/Fax: (048) 3319626/ 3315156; ABSTRACT. A simple and effective ground-based method was developed for trapping small mammals in the forest canopy. By using this method traps can be set closer to ideal grid locations, without tree climbing, with quicker set up (3 min. after looping a cable around the chosen branch), and faster rebaiting (47 sec.) when compared to other methods applied. This method is described and its efficiency and feasibility are discussed in this paper. RESUMEN. Un método simple con base en el suelo para el trampeo de pequeños mamíferos en el dosel arbóreo. Se desarrolló un método simple y efectivo para el trampeo de pequeños mamíferos en el dosel arbóreo desde el suelo. En este método las trampas pueden ser colocadas próximas de su posicion ideal en la cuadrícula, rápidamente y sin subir a los árboles. Se colocan en 3 min despues de pasar una cuerda por la rama elegida y son recebadas en 47 segundos. En este trabajo se describe el método y se discuten su eficiencia y praticabilidad. Key words: platforms, rainforest, rodents, marsupials. Palabras clave: plataformas, floresta pluvial, roedores, marsupiales.
INTRODUCTION Ecological aspects of arboreal small mammals may be investigated through several methods such as smoked paper tracking (Justice, 1961), direct observation (Voss and Emmons, 1996), spool and line (Miles, 1976) and radio-tracking (Charles-Dominique et al., 1981). Live capture of arboreal small mammals can be obtained through traps set directly on branches in canopy (August, 1983) or alternatively placed on wooden platforms (Malcolm, 1991; Vieira, 1998). These procedures have been successfully used to trap small mammals in several Neotropical forests (McClearn et al., 1994; Passamani, 1995; Leite et al., 1996;
Recibido 12 setiembre 2002. Aceptación final 23 enero 2003.
Voltolini, 1998; Vieira and Monteiro-Filho, in press). For trapping the bamboo rat, Kannabateomys amblyonyx, bait-less traps setting on artificial bridges can also be used (Kierulff et al., 1991). Nevertheless, tree climbing is required to place and remove platforms on the canopy using the pulley method described by Malcolm (1991), traps on branches (August, 1983) or artificial bridges (Kierulff et al., 1991). For traps set on branches climbing is also required to rebait (August, 1983) and to remove the captured animals (August, 1983; Kierulff et al., 1991). Techniques to climb trees have been described in several studies (Whitacre, 1981; Moffett and Lowman, 1995). “Free” climbing (Voltolini, 1998) or ladders
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(Wallauer et al., 2000) are also used. However, these methods are potentially dangerous (Laman, 1995) and time-consuming. Barker and Sutton (1997) discussed advantages and disadvantages of several climbing methods. The simplest options for canopy access are often ground-based (see Moffett and Lowman, 1995; Barker and Sutton, 1997), as in Vieira (1998). The methods described by Malcolm (1991) and Vieira (1998) for trapping small mammals demand complex platforms and result in the actual location of arboreal traps placed at some distance from the ideal locations of a grid design. Malcolm’s method requires tree climbing and the method described by Vieira (1998) uses branches parallel to the ground with diameter ranging from 10 to 25 cm. Vieira (1998) also describes disadvantages of Malcolm’s method. A simple and effective alternative groundbased method for trapping small mammals in the canopy was developed during a small mammal survey in the Atlantic rainforest in southern Brazil. By using this method, traps can be quickly set without climbing and in locations which correspond more closely to ideal grid locations, when compared to the trap locations acheived by other methods. In this study this method is described and its efficiency and feasibility are discussed.
METHODS Study area The study was developed within the boundaries of the town of Itapoá, Santa Catarina State, Southern Brazil, at 26°04' S and 48°37' W. The study area is covered with secondary Atlantic Forest vegetation at sea level. The study site was the ‘Reserva Particular do Patrimônio Natural Volta Velha - Palmital Farm’ (1.186 ha.). The forest was described by Klein (1984) as very uniform, with trees reaching around 12-15 m in height.
Field methods and analysis Spatial arrangement of grids consisted of 100 stations in a 10 by 10 configuration. A total of 225 traps were used, including 100 traps set on the ground, 100 on the understory shrubs, and 25 on canopy. Twenty five of the 100 traps set on the
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ground were of medium size (45 x 15 x 15 cm) and the rest, including understory and canopy traps, were small (26 x 19 x 9 cm). The distance between each line and between each station on the same line was 20m. However, all medium sized traps and canopy traps were set 40m distant from each other. The bait used was banana mixed with peanut butter. All traps were monitored daily for four consecutive days each month. The trapping period for canopy technique analysis was 10 months, from November 2000 to August 2001, but all captures combined ranged from September 1999 to August 2001. Trees or shrubs were not chosen randomly for trap placement. Traps were placed in canopies connected to neighbouring trees or shrubs, and as near as possible of the correspondent station. The time required to install and rebait traps was recorded to compare the efficiency of the different trapping methods: 1) Mean time to install traps after a cable was swung around the chosen branch; 2) Mean time to rebait traps, including the time to lower the trap from the branch and lift it back in place. Other procedures included measuring the mean height of platforms, and the distance between the ideal location of the trap station, based on grid configuration, and the actual trap site. The mean distance, and standard deviation from the mean, between the actual trap site and the ideal grid location is designated scatter, and is used as a statistic to evaluate the efficiency of different methods in locating strap sites within a grid design.
Platform and trap design The platform is assembled by connecting three pieces of wood board (2 x 2 x 30 cm) by their extremities in order to form a “Ì” shape structure. The trap is fixed on the lower end of it, and the unique entrance of the trap faces to inside of the “Ì” structure. A thin wire with an upside down “V” shape, from where the trap hangs, is attached to the top of the platform on its far end. After the trap and the platform are assembled together, a cable is attached to the superior part of the “Ì” structure in such a way to maintain the balance of the structure when hanging from a branch (Fig. 1). Two cables 3 to 5 mm in diameter were used in the operation of lifting the platform. One of the cables lifts the pulley. The other cable is inserted through the pulley and will hold the platform. When the pulley is fastened to the branch, the cable that was inserted through it is used to lift the platform. Both cables are fastened shoulder-high to a nearby tree (Fig. 1).
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RESULTS AND DISCUSSION
deviation) 3 min ± 50 seconds (n = 25; range 2:02 - 5:44 seconds). The whole process can be accomplished by only one person, but, in this study, two people took part in the field work. The mean time for bait reposition, including the lowering and lifting of the trap, was 47 seconds ± 12 seconds (n = 25; range from 30 - 85 seconds). This result is at least four times faster than the method used by Vieira (1998), who managed to rebait in approximately four minutes moving traps from higher levels
The method The method described here is “low-tech” as defined by Barker and Sutton (1997). The whole trap assemblage, including cables and platforms, were in perfect conditions after 10 month of field work. The mean time of hoisting the trap to the canopy after the cable has been thrown over a branch was (± standard
Fig. 1.
Technique to capture small mammals on the forest canopy. The pulley (in detail) and the platform are not totally suspended. A – Cable to lift the pulley; B – Cable to lift the platform; C – Wire with “V” shape to sustain the trap; P – Wooden platform with “Ì” shape; R – pulley. Drawing modified from Vieira (1998).
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than this experiment used. The results obtained resulted in faster time to rebaiting and trap set up than the method used by August (1983) and Wallauer et al. (2000) and the methods described by Malcolm (1991) and Vieira (1998). The mean height of the platforms was 7.25 m ± 1.40 m (n = 25; range from 4.8 - 9.8 m). This height is directly related with canopy’s height, which ranged from 12 to 15 m at the RPPN Volta Velha. Voltolini (1998) and Vieira (1998) used higher platforms (mean 9.5 m, range 7.50-12.00 m, and mean 10.1 m range 6.00-15.00 m, respectively) at forests with canopy varying from 20 to 30 m. Malcolm (1991) used platforms at mean height of 15 m near Manaus, Brazil, in canopies reaching over 30 m. The scatter from the predetermined trap site (trapping post) based on a grid design and the actual trap site was 3.91 m ± 2.08 m (n = 25; range 0.5 - 9.3 m). Although there is no recorded data on such variation in other trapping methods, it is most likely that the method described here, allowing the trap set up on branches with diameter inferior to five centimeters, or even on vines as I have done, will result in traps more closely placed to ideal grid loction than other methods mentioned earlier. Trapping success in the canopy During the capture period in the canopy I recorded 608 captures on the ground (4,000 trap-nights), 155 captures on the understory (4,000 trap-nights), and 69 captures on the canopy (1,000 trap-nights). The overall trapping success (total number of captures/total number of trap-nights) was 15.2% at ground level, 3.88% at understory and 6.9% for the canopy. The overall trapping success at the canopy was superior to the ones recorded by Voltolini (1998) (1.29%), Wallauer et al. (2000) (2.33%), Vieira (1998) (2.4%), McClearn et al. (1994) (3.7%), Passamani (1995) (approximately 5%) and Stallings (1989) (6.3%). The trapping success in the canopy per capture session ranged from 0 to 19%. The number of captures per trapping effort in the canopy was superior to the number of captures in the understory and inferior to the number at ground level. Because there is a
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different fauna assemblage at different height levels, it is not appropriate to conclude that there is a difference in efficiency of captures at different height levels. The fauna assemblage at ground level included exclusively terrestrial species, as well as species mainly associated with canopy. Besides that, Vieira (1998) noted that a trap is more easily accessed by mammals when on the ground than when placed in the canopy. The captured fauna One rodent and two marsupial species were captured in the canopy, whereas two rodent species (Nectomys squamipes and Oligoryzomys nigripes) were captured in the understory and three terrestrial small mammal species, one marsupial and two rodent species (Metachirus nudicaudatus; Akodon montensis; Oryzomys russatus) were captured only in ground level traps. All species captured in the canopy and understory were also captured at ground level (Table 1). Sciurus aestuans was visually observed near the study area, but it was not trapped.
ACKNOWLEDGEMENTS I thank Ivo R. Ghizoni Jr., Claudio R. Graipel, Marcos Azevedo, Rafael Reinicke, Jorge Cherem and undergraduate students for helping in field work. Natanoel and Lucio Machado kindly authorized the field work and provided logistical support at RPPN Volta Velha and specially to Luis and Chico. I also thank Marcelo Mazzolli for the English translation, Paul Richard M. Miller for the English revision and Enrique Gonzalez and Alfredo Languth for the translation of Spanish abstract, and Jorge Cherem, Fernando Ávila Pires, Nilton Cáceres, Enrique Gonzales and Emerson Vieira for the improvement of the manuscript. This research project was partially funded by PICDT/CAPES.
LITERATURE CITED AUGUST, P.V. 1983. The role of habitat complexity and heterogeneity in structuring of tropical mammals communities. Ecology, 64:1495-1507. BARKER, M.G. and S.L. SUTTON. 1997. Low-tech methods for forest canopy access. Biotropica, 29:243247. CHARLES-DOMINIQUE, P.; M. ATRAMENTOWICZ, M. CHARLES-DOMINIQUE, H. GÉRARD, A. HLADIK, C.M. HLADIK, and M.F. PRÉVOST. 1981. Les mammifères frugivores arboricoles nocturnes d’une foret guyanaise: inter-relations plantes-animaux. Revue d’Ecologie (Terre et Vie), 35:341-435.
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Table 1 Small mammals captured in the Atlantic forest of Southern Brazil. (TN = trap-nights) Species
Number of captures Ground level TN = 4,000
Understory TN = 4,000
Canopy TN = 1,000
MARSUPIALS Metachirus nudicaudatus Micoureus demerarae Gracilinanus microtarsus
3 11
37
22
5
58
8
RODENTS Akodon montensis
311
Oryzomys russatus
218
Nectomys squamipes
55
7
Juliomys sp.
5
46
Oligoryzomys nigripes
1
5
609
153
Total
JUSTICE, K.E. 1961. A new method for measuring home ranges of small mammals. Journal of Mammalogy, 42:462-470. KIERULFF, M.C.; J.R. STALLINGS, and E.L. SABATO. 1991. A method to capture the bamboo rat (Kannabateomys amblyonyx) in bamboo forests. Mammalia, 55:633-635. KLEIN, R.M. 1984. Aspectos dinâmicos da vegetação do sul do Brasil. Sellowia, 36:5-54. LAMAN, T.G. 1995. Safety recommendations for climbing rain forest trees with “single rope technique”. Biotropica, 27:406-409. LEITE, Y.L.R.; L.P. COSTA, and J.R. STALLINGS. 1996. Diet and vertical space use of three sympatric opossums in a Brazilian Atlantic forest reserve. Journal of Tropical Ecology, 12:435-440. MALCOLM, J.R. 1991. Comparative abundances of Neotropical small mammals by trap height. Journal of Mammalogy, 73:188-192. MCCLEARN, D.; J. KOHLER, K.J. MCGOWAN, E. CEDEÑO, L.G. CARBONE, and D. MILLER. 1994. Arboreal and terrestrial mammal trapping on Gigante peninsula, Barro Colorado nature monument, Panama. Biotropica, 26:208-213. MILES, M.A. 1976. A simple method of tracking mammals and locating triatomine vectors of Trypanosoma cruzi in Amazonian forest. The American Journal of Tropical Medicine and Hygiene, 25:671-674. MOFFETT, M.W. and M.D. LOWMAN. 1995. Canopy access techniques. Pp. 3-26. In: Forest Canopies
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(Lowman, M.D. and N.M. Nadkarni, eds.). Academic Press, San Diego, California, 624 pp. + xix. PASSAMANI, M. 1995. Vertical stratification of small mammals in Atlantic Hill forest. Mammalia, 59:276279. STALLINGS, J.R. 1989. Small mammal inventories in an eastern Brazilian park. Bulletin of Florida State Museum of Science, 34:153-200. VIEIRA, E.M. 1998. A technique for trapping small mammals in the forest canopy. Mammalia, 62:306310. VIEIRA, E.M. and E.L.A. MONTEIRO-FILHO. (In press). Vertical stratification of small mammals in the Atlantic rain forest of south-eastern Brazil. Journal of Tropical Ecology. VOLTOLINI, J.C. 1998. Estratificação vertical de marsupiais e roedores na Floresta Atlântica do sul do Brasil. Dissertação de Mestrado. Zoologia, USP, São Paulo. 78 pp. VOSS, R.S. and L.H. EMMONS. 1996. Mammalian diversity in Neotropical lowland rainforests: a preliminary assessment. Bulletin of the American Museum of Natural History, 230:1-115. WALLAUER, J.P.; M. BECKER, L.G. MARINS-SÁ, L.M. LIERMANN, S.H. PERRETTO, and V. SCHERMACK. 2000. Levantamento dos mamíferos da Floresta Nacional de Três Barras - Santa Catarina. Biotemas, 13:103-127. WHITACRE, D.F. 1981. Additional techniques and safety hints for climbing tall trees, and some equipment and information sources. Biotropica, 13:286-291.
