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IS THE RESPONSE OF INSECTIVOROUS BATS TO VEGETATION COVER SCALE-DEPENDENT?
Cerrado is the second largest biome in Brazil, market by a mosaic of grassland, savannah and forest phytophysiognomies. Considered one of the Brazilian hotspots of biodiversity, it has been severely threatened by human activities, as agricultural practices, habitat loss, landscape fragmentation, charcoal, unbridled urbanization and seasonal burnings. All these factors contribute to vegetation loss, which can put in risk the maintenance of bat populations in degraded areas. Therefore, it is important to know the spatial extent over which vegetation cover in the surrounding landscape influence bat activity at a site. Thus, to better understand how insectivorous bats respond to vegetation cover, we carried out a study in the fully – protected area of the Parque Estadual de Terra Ronca, located in the northeast of Goiás, Brazil. We sampled two nights during the wet season of 2015, from 18:00 to 06:00. We used 10 ultrasound records (SM2Bat+ 384kHz, Wildlife Acoustics) connected to a unidirectional microphone each (SMX – US, Wildlife Acoustics). The recorders were placed 1km from each other along two parallel line transects, 3m above the ground and positioned at 45º. We triggered them to register all calls with thresholds of 7kHz of frequency and 12dB of intensity. Bat calls were manually clustered and analyzed using the sound analysis software Avisoft SASLab Pro (Avisoft Bioacoustics). Therefore, we also counted the number of bat passes to estimate bat activity and measured the following acoustic parameters of each bat call: start, final and peak frequencies, pulse and interpulse durations, repetition rate and duty cycle. To identify the calls at species level, we compared average values to the literature and grouped bat species or morphotypes in guilds, considering foraging and hunting strategies of each of them. We used ArcGIS Pro 10.6.1 (ESRI, 2016) to map and quantify percentage of vegetation cover at 10 landscape scales, 50 – 500 in radius, surrounding each sampling site. To evaluate insectivorous bat response to vegetation cover, we ran generalized linear models to find the most explanatory model to our data. We then examined the relationship between bat activity and percent vegetation cover to each guild. Overall, 3.528 calls were identified as bat calls, which . Forty-five species were registered, classified in two guilds: Aerial Uncluttered Space bats (n = 22) and Aerial Cluttered Background bats (n = 23). We found that bat activity in both guilds were higher in sites with high percent of vegetation cover. The effect of scales differed among guilds and species, being Aerial Cluttered Background guild more influenced by lower scales. This might be due to the fact that these bats hunt mainly insects that fly near foliage or water surfaces. Our results suggested that information on differential bat responses to vegetation cover is useful to bat management decisions, especially when suppressing or adding vegetation in degraded areas.
Small scale, foraging guilds, acoustic activity, Chiroptera, Cerrado.
CNPq, FAPDF, Programa de Pós - Graduação em Ecologia da UnB (PGECL - UnB)
Camila Moniz Freire Rodrigues, Claysson Henrique de Aguiar Silva, Amanda Araújo Bernardes, Ludmilla Moura de Souza Aguiar