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 differences in resting oxygen consumption, respiratory quotient, and free thyroxine in woodchucks.
The relationships among seasonal differences in body weight, food intake, metabolism, and thyroid hormone in woodchucks were investigated in 12 woodchucks. Six woodchucks had been maintained on a photoperiod simulating that found at 42°N (boreal woodchucks). The other group of six animals had been maintained similarly in all respects except that the light simulated that found at 42°S (austral woodchucks). An open-flow respirometer, calibrated using the N2-dilution method, was used to determine metabolism twice in a 2-wk period near the September equinox, while at the same time food intake, body weight, and free thyroxine concentrations (fT4) were measured. Body weight was the same for both groups of woodchucks. However, compared with boreal animals near their autumnal equinox, austral woodchucks near their vernal equinox had significantly higher ( P < 0.01) daily food intake (5 ± 2 vs. 35 ± 2 g ⋅ kg-1 ⋅ day-1), oxygen consumption (4.4 ± 0.3 vs. 7.3 ± 0.3 ml ⋅ min-1 ⋅ kg-1), carbon dioxide production (2.8 ± 0.2 vs. 6.0 ± 0.2 ml ⋅ min-1 ⋅ kg-1), respiratory quotient (0.65 ± 0.01 vs. 0.82 ± 0.02), and fT4 (0.21 ± 0.01 vs. 0.65 ± 0.05 ng/dl). It was concluded that photoperiod has a strong effect on resting metabolism in the woodchuck and that there is an association between fT4 and changes in food intake and metabolic rate.
Persistence and Change in Minkowski Spacetime
There are famously two main metaphysics of persistence, namely three and four-dimensionalism. Both yield a particular solution to the so called puzzle of change. I argue that typical three-dimensionalist solutions to the puzzle face insurmountable difficulties even in the simplest relativistic setting, that of Minkowski spacetime