Influence of abiotic variables on the bat fauna of a granitic cave and its surroundings in the state of São Paulo, Brazil

Influência de variáveis abióticas sobre a fauna de morcegos de uma caverna granítica e seu entorno no estado de São Paulo, Brasil

Abstract

In the present study we analyzed the bat assemblage of the granitic cave Gruta do Riacho Subterrâneo and its surroundings (Itu, São Paulo state, Brazil) aiming to verify the influence of seasonality on its species composition and population abundances. Five samplings were carried out with three days of duration each, along the period from October 2013 to September 2014. Captures of bats were performed by setting mist nets in cave entrances, its interior and surroundings, making a total capture effort of 6,090 m².h. Our results indicate that this cave is shelter for a rich bat assemblage with fifteen species captured. Carollia perspicillata, Desmodus rotundus and Myotis sp. were the most abundant species. A comparison of the assemblage composition with that of other caves of São Paulo state revealed that its composition is very similar and typical of the Atlantic Forest Atlantic cave chiropterofauna independently of cave lithology. A multiple regression analysis performed to check for the existence of correlation between the seasonal fluctuation of the climatic variables temperature, pluviosity and air humidity did not reveal significant relationships among these and the changes in the abundance of bats. However, the analysis of canonical correspondence including these variables and also moonlight luminosity indicated a significant relationship of the changes in bat abundance with the air relative humidity. Changes in bat abundances are probably related to the seasonality in food availability. The accumulation curve obtained from the relationship between the accumulated richness of species and the number of samples showed that more samplings are required to reach the asymptote of species richness. Considering that Gruta do Riacho Subterrâneo is the largest granitic cave in Brazil and that it shelters a high number of bat species, including common and rare species, we suggests the preservation of this cave for maintenance of bat diversity in São Paulo state.

Keywords
bats; granitic cave; seasonality; biodiversity