Optimizing bat bioacoustic surveys in human-modified Neotropical landscapes

Area of Science:

• Ecology
• Bioacoustics
• Conservation Biology

Background:

• Bioacoustics is a growing non-invasive method for ecological sampling, particularly for bats.
• Tropical bat acoustic survey protocols are underdeveloped, hindering reliable conservation efforts.
• Determining minimum sampling effort is crucial for cost-effective and accurate ecological change detection.

Purpose of the Study:

• To assess the minimum survey effort for accurate bat assemblage inventories and habitat selection analysis in fragmented Amazonian forests.
• To evaluate the impact of landscape fragmentation and temporal sampling schemes on acoustic survey effectiveness.
• To provide guidelines for optimizing bat acoustic survey protocols in Neotropical regions.

Main Methods:

• Utilized a comprehensive tropical bat acoustic dataset from the Amazon.
• Evaluated 20 temporal sampling schemes (hours/night, nights/site, seasons).
• Assessed survey effort under two landscape scenarios: primary fragments in secondary forest and re-isolated fragments.

Main Results:

• Required sampling effort for 90% inventory completeness varied greatly, averaging ~80 nights before and 10 nights after fragment re-isolation.
• Recording >4 hours/night offered minimal reduction in required sampling nights.
• Bat responses (richness, diversity, activity) were consistent across schemes post-re-isolation, but pre-re-isolation required 4-6 hours/night and 3-5 nights/site for significant effect detection.

Conclusions:

• Sampling effort for bat acoustic surveys in fragmented Neotropical forests is highly dependent on landscape context and research objectives.
• Proposed guidelines aim to optimize sampling protocols for reliable conservation management and ecological assessments.
• Effective acoustic monitoring requires adapting survey design to landscape changes and specific research questions.