New Zealand Journal of Zoology abstracts
Influence of season, habitat, temperature, and invertebrate availability on
nocturnal activity of the New Zealand long-tailed bat (Chalinolobus
tuberculatus)
COLIN F. J. O'DONNELL
Science and Research Unit
Department of Conservation
Private Bag
Christchurch, New Zealand
and
Department of Zoology
University of Otago
P.O. Box 56
Dunedin, New Zealand
Abstract Nocturnal patterns of activity by the New Zealand
long-tailed bat (
Chalinolobus tuberculatus) varied significantly in
relation to habitat, season, time of night, temperature, and invertebrate
activity. Automatic bat detection units recorded 12072 bat passes containing
593 feeding buzzes during 580 nights of sampling. Overall, 46.3% of passes were
along roads within forest, 42.7% along forest edges, 8.1% in open grassland and
2.9% within forest. Pass rates averaged 30.8/night (95% confidence interval
(CI) = 23.3-38.4) during spring, 31.7 (CI = 21.3-42.1) during summer, 6.7 (CI =
4.4-9.0) during autumn and 1.6 (CI = 0.2-3.0) during winter. Bats were active
throughout the night in all habitats, but the patterns of their activity were
different in each. During spring and summer a significantly higher proportion
of bat passes in edge and open habitats were recorded in the first 2 h after
sunset, and activity then declined steadily towards dawn. In road habitats
activity peaked in the second hour but was more consistent during the remaining
hours of the night. Activity in forest did not vary through the night. Patterns
were similar, though less pronounced, in autumn but in winter there was little
activity during the first three hours after sunset or in the 5 h before dawn.
Analysis of deviance models indicated that habitat, season, minimum overnight
temperature, and invertebrate activity contributed to explaining the activities
of bats. Overnight temperature was more important than invertebrate activity in
explaining total bat activity in a night. Invertebrate activity was more
significant than minimum temperature in the model explaining the amount of
foraging activity per night, inferring that minimum temperature determines
whether bats fly at night, while invertebrate activity determines how long bats
feed. Techniques for indexing bat activity that are designed to survey
distribution or monitor population trends should control for temporal variation
and temperature to enable valid comparisons between counts.
Keywords bats; Chiroptera; habitat use; activity patterns;
temporal variation; Chalinolobus tuberculatus; monitoring; survey
design; New Zealand
Z99042
Received 1 October 1999; accepted 10 March 2000
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