The effect of call libraries and acoustic filters on the identification of bat echolocation

Ecology and Evolution
By: , and 

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Abstract

Quantitative methods for species identification are commonly used in acoustic surveys for animals. While various identification models have been studied extensively, there has been little study of methods for selecting calls prior to modeling or methods for validating results after modeling. We obtained two call libraries with a combined 1556 pulse sequences from 11 North American bat species. We used four acoustic filters to automatically select and quantify bat calls from the combined library. For each filter, we trained a species identification model (a quadratic discriminant function analysis) and compared the classification ability of the models. In a separate analysis, we trained a classification model using just one call library. We then compared a conventional model assessment that used the training library against an alternative approach that used the second library. We found that filters differed in the share of known pulse sequences that were selected (68 to 96%), the share of non-bat noises that were excluded (37 to 100%), their measurement of various pulse parameters, and their overall correct classification rate (41% to 85%). Although the top two filters did not differ significantly in overall correct classification rate (85% and 83%), rates differed significantly for some bat species. In our assessment of call libraries, overall correct classification rates were significantly lower (15% to 23% lower) when tested on the second call library instead of the training library. Well-designed filters obviated the need for subjective and time-consuming manual selection of pulses. Accordingly, researchers should carefully design and test filters and include adequate descriptions in publications. Our results also indicate that it may not be possible to extend inferences about model accuracy beyond the training library. If so, the accuracy of acoustic-only surveys may be lower than commonly reported, which could affect ecological understanding or management decisions based on acoustic surveys.

Additional publication details

Publication type Article
Publication Subtype Journal Article
Title The effect of call libraries and acoustic filters on the identification of bat echolocation
Series title Ecology and Evolution
DOI 10.1002/ece3.1201
Volume 4
Issue 17
Year Published 2014
Language English
Publisher Blackwell Pub. Ltd.
Publisher location Oxford, England
Contributing office(s) Patuxent Wildlife Research Center
Description 12 p.
First page 3482
Last page 3493
Online Only (Y/N) N
Additional Online Files (Y/N) N