Circadian rhythms of small carnivores and the effect of restricted feeding on daily activity.

Restricted daily feeding can entrain an endogenous circadian clock of rodents. Carnivores have not been tested even though, unlike rodents, the availability of their foods can naturally vary with the light-dark cycle. In addition, very little is known of the characteristics of carnivore circadian rhythms in constant illumination. The locomotor activities of weasels and minks were measured on running wheels and tilt floors in LD 12:12 and constant illumination. The animals were then subjected to daily restricted feeding to determine their ability to anticipate the arrival of food. Weasels and minks anticipated food delivery but endogenous control was not unequivocally demonstrated. Anticipatory activity was suppressed during days of food excess but exhibited during days of deprivation when these conditions were presented on alternating days. The characteristics of mink activity rhythms in constant light and dark are consistent with Aschoff's rule for nocturnal animals. Free-running rhythms were not measurable for most weasels due to arhythmicity or lack of data.