Abstract
AbstractDuring the last decades, the use of bioacoustics as a non‐invasive and cost‐effective sampling method has greatly increased worldwide. For bats, acoustic surveys have long been known to complement traditional mist‐netting, however, appropriate protocol guidelines are still lacking for tropical regions. Establishing the minimum sampling effort needed to detect ecological changes in bat assemblages (e.g., activity, composition, and richness) is crucial in view of workload and project cost constraints, and because detecting such changes must be reliable enough to support effective conservation management. Using one of the most comprehensive tropical bat acoustic data sets, collected in the Amazon, we assessed the minimum survey effort required to accurately assess the completeness of assemblage inventories and habitat selection in fragmented forest landscapes for aerial insectivorous bats. We evaluated a combination of 20 different temporal sampling schemes, which differed regarding number of hours per night, number of nights per site, and sampling only during the wet or dry season, or both. This was assessed under two different landscape scenarios: in primary forest fragments embedded in a matrix of secondary forest and in the same forest fragments, but after they had been re‐isolated through clearing of the secondary forest. We found that the sampling effort required to achieve 90% inventory completeness varied considerably depending on the research aim and the landscape scenario evaluated, averaging ~80 and 10 nights before and after fragment re‐isolation, respectively. Recording for more than 4 h per night did not result in a substantial reduction in the required number of sampling nights. Regarding the effects of habitat selection, except for assemblage composition, bat responses in terms of richness, diversity, and activity were similar across all sampling schemes after fragment re‐isolation. However, before re‐isolation, a minimum of four to six sampling hours per night after dusk and three to five nights of sampling per site were needed to detect significant effects that could otherwise go unnoticed. Based on our results, we propose guidelines that will aid to optimize sampling protocols for bat acoustic surveys in the Neotropics.
Highlights
The use of bioacoustics has massively increased in recent years as a non-invasive and cost-effective method to answer ecological questions, address biodiversityManuscript received 3 December 2020; accepted 15 January 2021; final version received 23 April 2021
Forest fragments were initially surrounded by cattle pasture, which due to abandonment regenerated into tall secondary forest (Farneda et al 2018, Rocha et al 2018)
Based on the whole data set, jack1 estimated a total of 21 different species/sonotypes to occur in the study area before and after fragment re-isolation
Summary
Acoustic surveys can effectively complement traditional mist-netting (Flaquer et al 2007, Walters et al 2013), vastly increasing inventory completeness in bat assemblage studies, especially in the species-rich tropics (MacSwiney et al 2008, Furey et al 2009, Silva and Bernard 2017). Acoustic surveys can cover large temporal and spatial scales, even in habitats where particular environmental conditions such as vegetation clutter, strong winds or large areas covered by water (e.g., lakes and ponds) make mist-netting inefficient or unfeasible (Murray et al 1999, MacSwiney et al 2008, Torrent et al 2018, Wordley et al 2018)
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