Variation in diet of frugivorous bats in fragments of Brazil’s Atlantic Forest associated with vegetation density

Abstract

Species distribution and persistence have long been known to vary with landscape structure; however, continued human activities in altered landscapes raise many questions as to how habitat fragmentation impacts the biology of persistent animal populations. Using carbon and nitrogen stable isotope analysis, we examined interspecific variation in the diet of frugivorous bats among remnant habitat patches of Brazil’s Atlantic Forest. We hypothesized that the diet of individuals captured in habitat patches would be different than those captured in contiguous habitats. We predicted that bats would alter their realized dietary niche breadth, taking food items (i.e., fruits or insects) according to landscape structure. However, more mobile species should be less impacted by small-scale landscape changes. We predicted that (1) a wide-ranging species (Artibeus lituratus), which move through open areas, will be less affected by small-scale landscape attributes, patch size, composition, and isolation; while (2) two narrow-ranging species (Carollia perspicillata and Sturnira lilium) will have more variation between populations in niche breadth and isotopic ratio ranges dependant on the local environment. Using Akaike’s Information Criterion (AIC) to rank a priori selected candidate models to explain variation, we found that fragment composition, largely involving vegetation density rather than spatial aspects of landscape structure (i.e., patch area, isolation) best explained diet variation in frugivorous bats. Additionally, there was evidence that wide-ranging A. lituratus were less impacted by differences in the landscape than narrow-ranging species. This supports the prediction that bats resident to fragments have altered feeding behavior, in response to environmental perturbation.

Occurrence patterns of sympatric forest wallabies: assessing the influence of structural habitat attributes on the coexistence of Thylogale thetis and T. stigmatica

“…Vegetation may drive the fine-scale spatial distribution of sympatric species by dictating the availability of resources at multiple scales ( Kubiak, Galiano & de Freitas, 2015 ), both spatial and temporal. Drawing on markedly different studies in the same forest type highlights the importance of vegetation; in Brazil’s Atlantic Forest, bat diet was best explained by landscape composition, particularly vegetation density ( Oelbaum et al, 2022 ), while in the same forest, the diversity of ants was explained by a combination of shrub leaf density and tree circumference ( Sampaio et al, 2023 ). Among macropods, Le Mar & Mcarthur (2005) showed that sympatric wallabies in Tasmania had similar food requirements and foraged in the same habitats by night, but that their selection of daytime refuges differed markedly, probably due to their contrasting predator avoidance strategies.…”