Using acoustic survey data to assess Indiana bat (Myotis sodalis) populations

Hoggatt, Meredith Louise

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https://hdl.handle.net/2142/116089 Copy

Description

Title

Using acoustic survey data to assess Indiana bat (Myotis sodalis) populations

Author(s)

Hoggatt, Meredith Louise

Issue Date

2022-07-19

Director of Research (if dissertation) or Advisor (if thesis)

O'Keefe, Joy M

Committee Member(s)

• Brawn, Jeffrey D
• Benson, Thomas J

Department of Study

Natural Res & Env Sci

Discipline

Natural Res & Env Sciences

Degree Granting Institution

University of Illinois at Urbana-Champaign

Degree Name

M.S.

Degree Level

Thesis

Keyword(s)

• bats
• acoustics
• density
• population
• echolocation

Abstract

Surveys to estimate bat populations are typically conducted during the winter, though this is only feasible for bats that aggregate during winter. While it is essential to measure summer bat population sizes for management, we have not identified a reliable method. Acoustic surveys have promise, as this is a less expensive and more efficient method than mist-net surveys. Passive acoustic monitoring is often used to gather data for population indices such as distribution, activity, and occupancy. However, we need to be certain about species identification of bat calls to have a reliable acoustic dataset. We conducted summer acoustic surveys at six conservation areas in northeast Missouri over a period of three years (2019—2021). We developed a filter in an automated acoustic identification program with an increased number of pulses to reduce the number of false positives but still maintain a robust acoustic dataset. We then assessed the application of generalized random encounter models for estimating Indiana bat population density using the acoustic dataset. We investigated the effects of year, volancy period, and conservation area, and their interactions on estimated density. Volancy period was the best predictor, with predicted density increasing 61% from pre-volancy (83 bats/km2) to post-volancy (134 bats/km2); however, the magnitude of the effect differed by conservation area. We showed that passive acoustic surveys yield informative density estimates that are responsive to temporal changes in bat population size, which suggests this method may be useful for long-term monitoring. Future work to refine this approach should include assessments of bat behavior and detection parameters and testing the method’s efficacy in areas where population sizes are known.

Graduation Semester

2022-08

Type of Resource

Thesis

Copyright and License Information

Copyright 2022 Meredith Hoggatt

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