DOI: 10.5061/dryad.0vt4b8h2d
title: Edge effects and vertical stratification of aerial insectivorous bats across the interface of primary-secondary Amazonian rainforest

description: Edge effects, abiotic and biotic changes associated with habitat
 boundaries, are key drivers of community change in fragmented landscapes.
 Their influence is heavily modulated by matrix composition. With over half
 of the world’s tropical forests predicted to become forest edge by the end
 of the century, it is paramount that conservationists gain a better
 understanding of how tropical biota is impacted by edge gradients. Bats
 comprise a large fraction of tropical mammalian fauna and are demonstrably
 sensitive to habitat modification. Yet, knowledge about how bat
 assemblages are affected by edge effects remains scarce. Capitalizing on a
 whole-ecosystem manipulation in the Central Amazon, the aims of this study
 were to i) assess the consequences of edge effects for twelve aerial
 insectivorous bat species across the interface of primary and secondary
 forests and ii) investigate if the activity levels of these species
 differed between the understory and canopy and if they were modulated by
 distance from the edge. Acoustic surveys were conducted along four 2-km
 transects each traversing equal parts of primary and ca. 30-year-old
 secondary forest. Five models were used to assess the changes in the
 relative activity of forest specialists (three species), flexible forest
 foragers (three species), and edge foragers (six species). Modelling
 results revealed limited evidence of edge effects, except for forest
 specialists in the understory. No significant differences in activity were
 found between the secondary and primary forest but almost all species
 exhibited pronounced vertical stratification. Previously defined bat
 guilds appear to hold here as our study highlights that forest bats are
 more edge-sensitive than edge-foraging bats. The absence of pronounced
 edge effects and the comparable activity levels between primary and old
 secondary forests indicate that old secondary forests can help ameliorate
 the consequences of fragmentation on tropical aerial insectivorous bats.
description: Acoustic recordings were
 collected from the Central Brazilian Amazon, 80 km north of Manaus, at the
 Biological Dynamics of Forest Fragments Project (BDFFP; 2024’26’’S,
 59043’40’’W). Two static detectors (SM2Bat+, Wildlife Acoustics) with
 omnidirectional microphones (SMX-US Ultrasonic Microphone) were placed in
 the understory and canopy
 of 164 sample points.
 These sample points were spaced 50 m apart along four 2 km transects.
 Transects were located across two spatially independent sites to reduce
 site bias. Each
 transect extended through
 1 km of secondary forest and then continued 1 km into the neighbouring
 primary forest. Surveys were conducted in the dry season of 2013 and the
 wet season of 2014 to minimise seasonal bias, equating to eight transect
 visits in total. The understory was defined as extending from the ground
 to a height of approximately 10 m and the canopy was defined as approximately 30 m
 from ground level. To
 ensure the understory and canopy samples were independent, plastic
 dividers were attached to the detectors to create discrete directional
 microphones. Additionally, sample points were rotationally sampled so that
 actively recording detectors were always 250 m apart. Each active detector
 was programmed to record for 12 hours (18:00-06:00) for three consecutive
 nights, amounting to 11,808 recording hours. Detectors
 recorded at 384 kHz sampling rate in full spectrum with 16-bit resolution.
 The high pass filter was set at 12 kHz (fs/32), with a trigger level of
 18SNR. Recordings were split into five-second fragments with at least two
 distinguishable pulses to define a bat pass which was used as the
 surrogate measure of bat activity. Bat passes were automatically classified into
 species using the classifier for Amazonian bats, developed by
 López-Baucells et al. (2019). Bat passes that were automatically
 classified with an accuracy above the 60% threshold were subjected to manual post-validation. The
 data has been limited to species where additional analysis showed no
 significant difference in the performance of the acoustic classifier and
 manual identification of the calls.
description: # Edge effects and vertical stratification of aerial insectivorous bats
 across the interface of primary-secondary Amazonian rainforest
 [https://doi.org/10.5061/dryad.0vt4b8h2d](https://doi.org/10.5061/dryad.0vt4b8h2d) ### Column headings and details * Season: Season when the data was collected * Edge1 = dry season (July - October 2013) * Edge2 = wet season (November and June 2014) * Location: One of two sites across the Biological Dynamics of Forest Fragments Project, Cabo Frio or Dimona * Transect: One of four transects. There are two transects per location * Distance: Distance from the habitat edge (m) * Minus values represent secondary forest * Positive values represent primary forest * 0 represents habitat boundary * Habitat: Either understory (U) or canopy (C) where detectors were placed * Species: Species/sonotype codes * *Cormura brevirostris (CB)* * *Centronycteris maximiliani/centralis (CM)* * *Eptesicus brasiliensis (EB)* * *Eptesicus spp. (E1)* * *Furipterus horrens (FH)* * *Molossidae spp. (M)* * *Myotis riparius (MRN)* * *Peropteryx kappleri (PK)* * *Peropteryx macrotis (PM)* * *Pteronotus gymonotus (PG)* * *Pteronotus alitonus (P5)* * *Pteronotus cf. rubiginosus (P6)* * *Pteronotus personatus (PP)* * *Rhynchonycteris naso (RN)* * *Saccopteryx bilineata (SB)* * *Saccopteryx leptura (SL)* * No.: Sum of bat passes automatically identified to species/sonotypes