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.
Opioid modulation of ingestive behaviors in woodchucks and racoons
We have examined the effect on feeding of opioid blockade with naloxone in two species which demonstrate a marked seasonality in their feeding patterns, the racoon (Procyon lotor) and the woodchuck (Marmota monax). Naloxone suppressed food intake in the woodchuck which is a true hibernator. Naloxone failed to suppress food intake in the racoon and, in fact, enhanced intake of a preferred sucrose solution. In the racoon, ir-dynorphine concentrations were extremely high in the hypothalamus compared to the values obtained in rats and woodchucks. We suggest that possible explanations for the lack of responsiveness to opiates in racoons may be their extremely high daily food intake relatively to body mass when compared to woodchucks and rats and the high levels of ir-dynorphin may be sufficient to overcome the inhibitory effect of naloxone. These studies stress the occurrence of species diversity in the response to opioid antagonism.
Onset and Cessation of Hibernation under Constant Temperature and Light in the Golden-mantled Ground Squirrel (Citellus lateralis)
TOWARDS the end of the summer of 1955 we received, through the kindness of Dr. J. E. Moore (University of Alberta), a number of golden mantled ground squirrels (Citellus lateralis). These animals had been trapped during August–September in the Turner Valley, Alberta, and were shipped to Toronto by express. Our stock was further replenished in the same manner during the summer of 1956.