Seasonal variations in the food consumption of woodchucks (Marmota monax).
Food consumption of 155 woodchucks ( Marmota monax ) was measured immediately after capture to determine whether a seasonal rhythm obtained in feeding of a natural population. Food intake of adults was lowest in March. It reached a maximum in May, then declined through the summer; some individuals increased food intake temporarily in late autumn. Comparative ata from a laboratory colony showed that a similar rhythm occurred under conditions of constant temperature and photoperiod. Variability in food consumption axima associated with different age groups, considered in the context of vailable life history information, suggested that the rhythm had a period omewhat less than 1 year.
Seasonal changes in metabolic activity of non-hibernating woodchucks.
The metabolic activity of non-hibernating woodchucks (3Iarmoda tnunax) was meafrured over a 1-year period. The Haldane method of indirect cntorirnetry was used to measure CO? production to provide an irldcv of metabolism. The metabolic rate was seasonally cyclic, reaching n peak in May and decreasing p+adti;llly throughout the summer. The Iowrst monthly valua occurred Irorn Novernller through February (the normal timc of hibernation lor these animals), though the animals were kept from hibrmating. 'I'he seavonal decrease in metabolism probably creates a pl~ysiologirnl PI-ertieposition for hibernation and allows fat drposition without a great increase in food intake.
Responses of a New Hibernator (Citellus variegatus) to Controlled Environments
THE phenomena of hibernation and æstivation have both been recorded in the genus Citellus, and although it is not known whether the two phenomena are physiologically the same1, nevertheless hibernation seems to be an adaptation to an unfavourable cold seasonal environment, and æstivation an adaptation to an arid hot environment with seasonal drought. It is of interest, therefore, to find that the rock ground squirrel, Citellus variegatus, the habitat of which is the arid south-west from Utah to southern Mexico2, is capable of hibernating but does not appear to sestivate. Hibernation as used here refers to a mammal with a homothermic temperature of approximately 37° C, but which is able to lower this temperature to the environment and raise it again against the gradient.