Trente-deux ans d'études démographiques chez la marmotte à ventre jaune (Marmota flaviventris). A 32-year demography of the yellow-bellied marmot (Marmota flaviventris).

Résumé

Yellow-bellied marmots (Marmota flaviventris) in the East River Valley of Colorado were annually live-trapped and individually marked from 1962 to 1993. We used the pooled data from this population to produce an average demography and life-table of marmots for these years. Females have significantly better survivorship than males beyond the first year age class. Factors that cause mortality act evenly on all age classes as shown by the constant rates of survivorship. Principal sources of mortality are unsuccessful hibernation and predation. Females produced litters from ages 2 to 10 yr.; litter sizes did not differ significantly among age classes. Female generation length at 4.49 yr. was three times the life expectancy and median survivorship. The net reproductive rate (Ro) was 0.67, yet the population did not continually decline. Reproductive values (Vx), were approximately equal across the reproductive ages and identified no life stage as part of a reproductive strategy. This marmot population is regulated by the extrinsic forces of energy availability and predation and by movement into and out of the study area.