Habitat amount partially affects physiological condition and stress level in Neotropical fruit-eating bats

Abstract

Hematological measures are increasingly being used to analyse the impact of several stressors on the physiological condition of animals. Landscape degradation and habitat loss impacts terrestrial and volant mammals occurrence, however rarely the effects of these factors on physiological conditions and stress levels were analyzed. Here, we measured several hematological parameters to analyse the impacts of habitat amount on the physiological condition (body condition and health status) and stress level of four species of Neotropical fruit-eating bats. We measured hematocrit, hemoglobin concentration and calculated the hemoglobin-hematocrit residuals (HHR) and mean cell hemoglobin concentration (MCHC), as well as the neutrophil to lymphocyte ratio (N/L ratio) of four common frugivores bat species (Artibeus lituratus, Artibeus planirostris, Sturnira lilium and Carollia perspicilatta). The bats were captured in 20 landscapes within the Atlantic Forest biodiversity hotspot, in a gradient from 10 to 85% of habitat amount. We tested the influence of habitat amount, species, sex and reproductive condition on the physiological variables. We fit GLM to each of the response variables and performed a model selection to identify the most plausible to explain the patterns. N/L ratio was negatively influenced by habitat amount, while the other variables were not related to habitat amount. Overall, we found that habitat loss apparently did not jeopardize the physiological condition of fruit-eating bats and that stress level apparently is not high enough to have any deleterious effect. We suggest that the increase in glucocorticoids, indirectly assessed by the N/L ratio, is a predictive, beneficial response, that allow these bats to cope efficiently with the stressors associated with habitat loss.