, Volume 92, Issue 1, pp 1-10

Free-running circadian activity rhythms in free-living beaver (Castor canadensis)

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Summary

The members of a beaver family studied under natural conditions in SW Alberta, Canada (115 °03′ W, 51 °02′ N) displayed a free-running circadian rhythm of activity with a period length of about 27 hours in winter, at a time when they were living under ice and had no access to land (Fig. 1, A and C). In summer, the period length of their activity rhythm was close to 24 hours (Fig. 1, B).

This work was supported by the National Research Council of Canada (grant no. A 4880/6639 to J.B.). The computer work was performed by Mr. J. M. Poulin, Centre de Traitement de l'Information, Université Laval. The logistic support of the Environmental Science Center, University of Calgary, is gratefully acknowledged. We thank Drs. Jürgen Aschoff, Jeremy McNeil and Daryl K. Sherman for critically reading the manuscript.