Elevation variation in life-history characteristics of populations of yellow-bellied marmots (Marmota flaviventris)

We examined life history characteristics of populations of yellow-bellied marmots (Marmota flaviventris) at 2900 m elevation and 3400 m elevation to test hypotheses about effects of elevation on life history traits. The accumulation of fat is strongly influenced by short growing seasons and marmots living at high elevations often have shorter active seasons than populations at lower elevations due to prolonged snow cover. We compared growth rates and reproductive effort of marmots amongst age and sex classes from the two elevation sites. Growth rates of yellow-bellied marmots vary significantly with sex, age, and location. Juvenile growth rates were significantly higher at lower elevation sites. Yearlings at the high elevation site had significantly higher growth rates compared to low elevation yearlings. Low elevation yearling males were twice the size of high elevation yearling males at the beginning of the summer; the higher growth rates in high elevation populations reduced the mass differences between the two groups prior to hibernation. Adult growth rates and masses were not significantly different between elevation sites. At higher elevation, females did not reproduce in consecutive years. Differences in growth rates between elevation sites may be explained by reproductive status and time allocated to foraging.