APPLICATION OF AN HABITAT SUITABILITY MODEL AS A TOOL FOR THE STUDY OF BATS LOCATELLI A.G. ¹, TOFFOLI R.² ¹ University of Turin,
[email protected] ² CHIROSPHERA Association for the study and protection of bats and their environment,
[email protected] Introduction:The proper drawing up of environmental management plans is fundamental in order to ensure an
Results: The sampling phase allowed us to verify the presence of 21 bats species in the park with an highly
adequate conservation of species within a protected area. In this context it is necessary to find the most relevant
variable amount of the presence data. It was possible to apply the ENFA model for 13 out of the 21 species presents
information both in distribution and ecological needs for protected species by developing methods aimed at
inside SIC boundaries for which it was available a significant number of distribution's data. In particular the
maximizing the accuracy of the obtained data while minimizing time and cost of application. These issues take on a
software analysis were carried out successfully for the following species: Rhinolophus ferrumequinum, Rhinolophus
even more crucial value when investigating the conservational status and distribution of species with sampling
hipposideros, Barbastella barbastellus , Eptesicus serotinus , Hypsugo savii , Myotis daubentonii , Myotis
difficulties. This project was developed by studying the presence and distribution of bats in the Site of Community
mystacinus , Myotis nattereri , Nyctalus leisleri , Pipistrellus kuhlii , Pipistrellus pipistrellus , Plecotus auritus and
Interest IT1160056 " Alpi Marittime ". Bats are an extremely important systematic order from a conservational point
Tadarida teniotis . Obtained maps were consistent with the environmental characteristics of the area and
of view and are strongly protected by various laws and conventions both on national and international level.
corresponding with the currently knowledge on bat species ecology and allowed to visualize the variations in the
Sampling methods currently available for the study of bats suffer from a limited operational efficiency because of
distribution of the species of the park according to their different environmental needs (Fig.3-4). The maps were
their susceptibility to the elusive and extremely vagile nature of these animals, in addition to the difficulties arising
generated from matrices which showed the existing levels of correlations between the presence data of individual
from night sampling operations. For this purpose we tested the application of the ENFA (Ecological Niche Factor
species and the environmental variables considered .
Analysis ) habitat suitability model which allows to generate maps related to the potential distribution of a species within an investigated area by correlating data acquired from sampling activity with the ecological niche in which they were obtained.
Fig1: Percentage composition of the various species of bats in the park on the 1000 records analyzed.
Fig3: Habitat suitability map generated for the species Pipistrelus pipistrellus. The colors show the level of percentage probability of occurrence of the species in relation to the environmental component (white 0-25%, red 25-50% red, yellow 50-75% and green 75-100%). The blue line represents the boundaries of the Community Interest Site “Alpi Marittime”.
Materials and Metods: Preliminary stage of this work was the implementation of previously available data by collecting new records (by mist-netting, bat-detector monitoring) within the study area resulting in a dataset composed of more than 1000 georeferred information from 21 bat species (Fig.1). The habitat suitability model ENFA was developed with presence data, through the use of BIOMAPPER 4.0 software. This program allowed us to generate maps of habitat suitability through preliminarily establishing correlation matrices between single environmental variables and presence data and providing a detailed indication of the existing relationship between available habitats and the ecological requirements for a species. The environmental variables considered were: altitude, exposure, slope and the habitat categories at level III of the CORINE Charter of Use of the Soil (CUS). In detail, we considered the percentage of the following environmental categories inside a 10000 m² square (100 x 100 m ): urban areas, agricultural arable lands , open areas with sparse or absent vegetation, water bodies, mining areas , orchards, meadows , deciduous forests , coniferous forests, mixed forests, natural pasture areas and high altitude grasslands, heath and scrub and lastly beaches, gravels. The program has operated by calculating the levels of positive and negative correlation between the presence data of the species and the individual environmental variables. In addition to this, the in silico elaboration, allowed to get 2 explicative values of the distribution status of the species in the area: The Marginality and Specialization. The Specialization value indicates how narrow the niche of the species is in relation to the study area and ranges from 1 to ∞, with the width of the niche that decreases with the value of the index. For a more immediate interpretation is often provided the coefficient of global tolerance, defined as the inverse of specialization: this varies between 0 and 1 and is a direct indicator of the width of the niche (Fig.2). The variables and environmental categories were selected on the basis of their representativeness in the study area. Validation of the model was made using the “Jack-Knife” cross validation run by the software itself.
Fig4: Habitat suitability map generated for the species Rhinolophus hipposideros. The colors show the level of percentage probability of occurrence of the species in relation to the environmental component (white 0-25%, red 25-50% red, yellow 50-75% and green 75-100%). The blue line represents the boundaries of the Community Interest Site “Alpi Marittime”.
Conclusions: Based on the quality of the results the model habitat suitability ENFA proved to be an extremely versatile tool capable of providing truthful information compatible with the notions that we have today about the ecological needs of bats. The habitat suitability maps generated by the program proved to be immediate and easily interpretable showing a high potential for application in both management plans of the territory and a diagnostic tool in the hands of specialists. In general the ENFA model is useful for investigating potential distribution and ecological needs of species under condition similar to those found in the present project or in the study of vagile and elusive animals in a broad and varied area. The application of this method of investigation is therefore a tool of great utility in the study of bats , in particular for management plans inside protected areas, being able to provide information on the distribution and ecology of the different species with a standardized, faster and cheap methodology.
Fig2: Reworking of the correlation matrix realized for the species investigated. The number of positive and negative symbols indicate that, for the software, the variables are positively and negatively related to the presence of the species. The value "0" indicates an absence of significant correlation. Empty cells indicate that the variable can not be correlated in any way to the presence / absence of the species. The last two columns refer to the Marginality and Tolerance values..
