Echolocation Calls of the Long-Tailed Bat: A Quantitative Analysis of Types of Calls

Abstract

The echolocation calls of long-tailed bats (Chalinolobus tuberculatus) were recorded in the Eglinton Valley, Fiordland, New Zealand, and digitized for analysis with signal-processing software. Univariate and multivariate analyses of measured features facilitated a quantitative classification of the calls. Cluster analysis was used to categorize calls into two groups equating to search and terminal-buzz calls described qualitatively for other species. When moving from search to terminal phases, the calls decrease in bandwidth, maximum and minimum frequency of call, and duration. Search calls begin with a steep-downward FM sweep followed by a short, less-modulated component. Buzz calls are FM sweeps. Although not found quantitatively, a broadband pre-buzz group of calls also was identified. Ambiguity analysis of calls from the three groups shows that search-phase calls are well suited to resolving the velocity of targets, and hence, identifying moving targets in stationary clutter. Pre-buzz and buzz calls are better suited to resolving range, a feature that may aid the bats in capture of evasive prey after it has been identified.