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.
THE ROLE OF ENVIRONMENTAL FACTORS IN HIBERNATION OF WOODCHUCKS (MARMOTA MONAX)
Laboratory experiments, based on knowledge of the natural environment, have been conducted to determine the role of various factors in the entrance into and emergence from hibernation. Woodchucks, captured in the wild were kept in rooms at several tempera- tures or in coolers at 6?C. They were fed or deprived according to the experimental program. Experiments showed that woodchucks deprived of food and kept at 60 C became torpid but woodchucks fed at 6?C did not. Some woodchucks deprived of food at 20?C became lethargic in winter. Minor disturbances in the laboratory do not arouse woodchucks. Woodchucks that eat when aroused do not become torpid again unless again deprived. Thin wood- chucks become torpid as readily as fat ones. The latency of torpidity varies with season, being short (a week) in December and March and long (a month) in summer. The wood- chuck has bouts of torpor that are short (4 to 5 days) at first but become longer (10 to 12 days). The arousal bouts last 2 to 3 days. Hibernation in nature lasts 3 to 4 months although presumably the woodchuck is torpid for only 2 months. In the laboratory woodchucks may remain in hibernation (alternating bouts of torpor and arousal) up to 8 months. The stimulus for final arousal was not determined. Emergence from the burrow at Chambersburg, Penn- sylvania occurred between January 29 and 8& February in 8 years. The date had no relation to local weather. Woodchucks exposed to very low temperatures (-20?C) aroused promptly.
Aging live Antarctic fur seals and southern elephant seals
This study describes a method for extracting post-canine or incisor teeth from live antarctic fur seals (Arctocephalus gazella) and southern elephant seals (Mirounga leonina) respectively and their use to determine age in a field situation. Dental elevators were used to loosen the teeth from the alveolus and periodental ligament. Most teeth were removed within l-2 min and a total of 214 and 81 teeth were collected by this method from antarctic fur seals and southern elephant seals respectively. No seal recaptured at intervals up to a year after a tooth was extracted showed signs of infection or distress related to removal of the tooth. Teeth were thin-sectioned for the purpose of aging. In both species cementum growth layer groups were a more satisfactory indicator of age than dentinal growth layer groups. Estimates of age from cementum growth layers were confirmed for Antarctic fur seals using seals which had been tagged as pups up to 16 yr before sampling.