Using echolocation calls to measure the distribution of bats: the case of Euderma maculatum

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This study examined the distribution and abundance of spotted bats over their range in Canada and the United States. We conducted a field survey from south to north between 1 May and 13 August 1983 at 1,186 study sites grouped in 80 areas where spotted bats had been reported to or might occur. We adopted the following sampling procedure based on published data concerning the timing of Euderma feeding activity with respect to sunset and lunar and weather conditions. At each site we monitored bat activity for 20 min with pairs of sites normally being simultaneously monitored by two observers between dusk and 02:30 local time. Sites were 500 to 1,000 m apart so that spotted bats active at one site could not be heard at the other. At all sites we used echolocation calls as indicators of bats. Specifically, we noted the presence of three categories of echlocation calls: 1) those of E. maculatum, 2) audible echlocation calls not Euderma, and 3) at 604 sites (all areas), ultrasonic echolocation calls monitored with a QMC Mini Bat Detector tuned back and forth between 20 and 60 kHz. In the region where we were working some species of Tadarida and ldionycteris phyllotis are known to use echolocation calls audible to the unaided human ear. These were qualitatively different from the calls of spotted bats, and easily distinguished on the QMC Mini: E. maculatum 15 to 9 kHz; Tadarida 25 to 17 kHz; and I. phyllotis 24 to 12 kHz. The results permit us to reject the hypothesis that spoiled bats were common but rarely captured. We heard the echlocation calls of E. maculatum at 34 sites in 10 areas, two of the which represent modest range extensions for this species. The small data base for spotted bats precludes detailed statistical comparison, but there was no obvious association of spotted bat activity with any particular habitat conditions.

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Reference Code: A87FEN01IDUS

Full Citation: Fenton, M. B., D. C. Tennant, and J. Wysecki. 1987. Using echolocation calls to measure the distribution of bats: the case of Euderma maculatum. Journal of Mammalogy 68(1): 142-144.

Location: ANIMAL EF: EUDERMA MACULATUM