The impact of edge-effects on aerial insectivorous bat assemblages in the Amazon

Yoh, N

Abstract

Edge effects, the abiotic and biotic changes associated with habitat boundaries, are amongst the most important factors determining a species’ distribution in human-modified landscapes. Bats are the second most diverse mammalian order, however many species are not targeted in studies on edge-effects, particularly in tropical forests which suffer the highest rates of deforestation. This study aims to quantify the magnitude and extent of edge effects on Amazonian aerial-insectivorous bats by relying on a suite of theoretical models previously applied to other taxa. Acoustic sampling was conducted across two seasons at the Biological Dynamics of Forest Fragments Project along four 2km transects consisting of primary forest which intersected with secondary forest. As part of this study, the effectiveness of using an automatic classifier to identify species’ calls was compared against manual identification using relevant acoustic keys. A total of six models (mean, linear, power, sigmoid, unimodal and cubic) were used to assess the changes in the relative activity of both forest specialist and open/edge forager species in response to edge effects, as well as changes observed at the assemblage level. Responses were assessed for seven individual species, two of which demonstrated a response to edge effects detectable over a minimum extent of 400m - Centronycteris maximiliani/centralis and Pteronotus parnellii (60KHz). Insect volume was only weakly associated with the activity of these two species, and that of total bat activity, therefore prey availability does not explain activity patterns. Our results suggest edge responses may be more complex than previously considered, however they also imply that a low contrast matrix of mature secondary forest may mitigate the impact of edge effects for many bat species. Therefore, allowing for forest regeneration between forest patches may reduce the extinction pressure on aerial insectivores in tropical fragmented landscapes.

Citation

Yoh, N. (in press). The impact of edge-effects on aerial insectivorous bat assemblages in the Amazon. (Dissertation). University of Salford

• Thesis Type: Dissertation
• Acceptance Date: Jan 31, 2019
• Deposit Date: Feb 11, 2019
• Publicly Available Date: Feb 11, 2019