Seasonal Changes in Weights of Marmots

Publisher Website
Google Scholar
Abstract
Seasonal changes in the body weights of yellow-bellied marmot (Marmota flaviventris) populations were studied for 8 yr in western Colorado [USA]. Marmots may be classified by size into 4 age groups: juvenile, yearling, 2 yr old, and 3 yr old or older, each group with significantly different mean body weights. For each age group, the mean body weight of males was significantly larger than that of females. Mean body weights in June of yearlings and older were smaller, the later the onset of the growing season. All age groups made significant weight gains each year; there was no significant difference in growth rates among years. When the rates of weight gain of juveniles are corrected for time of appearance aboveground, the regression coefficients are virtually identical. The earlier young marmots are weaned, the more they weigh at hibernation and the more likely they are to survive hibernation. The percentage of young surviving their 1st winter of hibernation is significantly greater the earlier spring begins. Marmots at 3400 m elevation had growth rates similar to those of marmots at 2900 m elevation. The adaptive strategy of marmots includes rapid growth rates, high tissue growth efficiencies and extension of the growing season by reproducing immediately following hibernation.