Present address: Division of Natural Sciences and Engineering, University of South Carolina Upstate, Spartanburg, SC 29303, USA
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Thermal benefits of clustering during hibernation: a field test of competing hypotheses on Myotis sodalis
Article first published online: 14 MAY 2008
DOI: 10.1111/j.1365-2435.2008.01423.x
© 2008 The Authors. Journal compilation © 2008 British Ecological Society
Additional Information
How to Cite
Boyles, J. G., Storm, J. J. and Brack Jr, V. (2008), Thermal benefits of clustering during hibernation: a field test of competing hypotheses on Myotis sodalis. Functional Ecology, 22: 632–636. doi: 10.1111/j.1365-2435.2008.01423.x
Publication History
- Issue published online: 11 JUL 2008
- Article first published online: 14 MAY 2008
- Received 30 November 2007; accepted 7 April 2008; Handling Editor: Brian McNab
Keywords:
- bats;
- behavioural thermoregulation;
- heat loss;
- huddling;
- Indiana bat
Summary
- 1Clustering lessens heat loss in euthermic animals by decreasing exposed surface area. However, clustering is also used during heterothermic periods such as hibernation, when heat loss should be minimal because body temperature (Tb) is near ambient temperature (Ta).
- 2We tested two hypotheses that attempt to explain the thermal benefit of clustering by cave-dwelling bats during hibernation: (i) clustering buffers individuals against fluctuations in Ta (‘thermal inertia hypothesis’), and (ii) clustering minimizes heat loss during energetically expensive arousals and subsequent periods of euthermy (‘arousal hypothesis’).
- 3We created path models parameterized with data obtained from thermal and digital images of naturally hibernating Myotis sodalis clusters and temperature-sensitive dataloggers placed near each cluster.
- 4Akaike weights (ωi) indicate the arousal hypothesis has nearly complete support (ωi = 0·9999), while the thermal inertia hypothesis has little support (ωi = 0·0001). As predicted by the arousal hypothesis, mean Ta is the strongest predictor of cluster size. Further, after accounting for mean Ta, cluster size is negatively related to variation in Ta.
- 5Our results indicate that most of the thermal benefit of clustering during hibernation is from decreased heat loss during brief euthermic periods. Further, our results predict that clustering may lessen mass loss during hibernation in stable environments, may be minimized during hibernation when there are large fluctuations in the thermal environment, and that the propensity to cluster may be negatively related to body condition.