Growth and survival of juvenile yellow-bellied marmots (Marmota flaviventris)

We compared patterns of growth in juvenile yellow-bellied marmots (Marmota flaviventris) between 2 years in which precipitation differed, and we determined if mass at entry into hibernation affects over-winter survival. Juveniles exhibited an asymptotic growth pattern with mass gain for a mean of 60.8 days, followed by stable mass until entry into hibernation. Growth ceased in early September, shortly after the end of the plant growing season. Juveniles born in 1991, a year of late snowmelt and low summer precipitation, entered into hibernation at significantly lower mass than juveniles born in 1992. Juveniles born in 1992 survived better despite experiencing a long winter during which they spent more days in hibernation and lost more mass. Overall, heavier juveniles were more likely to survive hibernation. Further, mass at entry into hibernation apparently had a greater effect on over-winter survival than did winter severity.