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Abstract



Citation. Tester, J. R. 1987. Changes in daily activity rhythms of some free-ranging animals in Minnesota. The Canadian Field-Naturalist 101(1):13-21.   [1153  LTERCC]

Abstract. Activity patterns of many vertebrates have been monitored by an automatic radio tracking system at the Cedar Creek Natural History Area in east-central Minnesota Activity rhythms of Gray Squirrels (Sciurus carolinensis), Red Foxes (Vulpes vulpes). Muskrats (Ondatra zibethicus), Ruffed Grouse (Bonasa umbellus) and Barred Owls (Strix varia) show marked seasonal changes which are believed to be responses to environmental conditions or physiological and behavioral requirements of the animal. Variations in number of activity periods, total minutes of activity, timing of activity in relation to sunrise and sunset and in the amount of rest during the normal active period are shown to be related to changes n such factors as temperature, snow cover, food supply and breeding behavior. These modifications of activity rhythms suggest that controlling mechanisms are sufficiently plastic to allow animals to alter their behavior significantly in response to a changing environment. In contrast, animals in captivity show remarkably precise timing with respect to activity rhythms This regularity appears to be highly dependent on caging and the uniformity or environmental conditions under which such animals are maintained

Keywords. Activity rhythms, Gray Squirrel, Sciurus carolinensis, Red Fox, Vulpes vulpes, Muskrat, Ondatra zibethicus, Ruffed Grouse, Bonasa umbellus, Barred Owl, Strix varia, Minnesota


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