Socioecology of Marmots: Female Reproductive Strategies

Abstract

Abstract. The relationship between female reproductive success and both spring food and hibernacula resources was examined in a high-altitude population of yellow-bellied marmots (Marmota flaviventris). The number of offspring a female weaned was significantly associated with the estimated number she could potentially produce, based on food resources. The production of young by these females is probably food limited to varying degrees. Hibernacula may be a restricted resource; young reared in an area without a hibernaculum were not recaptured as yearlings. Delaying pregnancy until forage is available fails as a strategy because young have insufficient time to accumulate fat for hibernation. Adult females deposit fat at a single maximum rate regardless of reproductive history; few females gain weight prior to weaning their young. In areas with short growing seasons, measured as the period during which nonreproductive adults gain weight, females may occasionally or regularly fail to reproduce in consecutive years. The short period of time following weaning may not permit the accumulation of fat sufficient to provide energy for hibernation, postemergence activity, and reproduction. The growth rate (g/day) of young marmots is greater at high than at intermediate elevations. This increase in growth rate warrants further examination of the hypothesis that increased sociality among marmots living in areas with short growing seasons is a response to decreased growth rates of young animals.

Reproductive energetics of adult male yellow-bellied marmots (Marmota flaviventris)

“…Exclusive defense of females through out the season may be critical to male reproductive success the following active season because defending males are likely to have sole access to their defended females during the short mating season (Andersen et al 1976). Thus, in con trast to those sciurid species where males experience intense scramble competition and energy expenditure during mating, male yellow-bellied mannots appear to avoid high levels of activity, male-male competition, and associated energy expenditure during mating.…”

“…Males are generally polygynous (Armitage 1991) and exclusively defend females in territories throughout the active season, the period of the year during which marmots are not hibernating (Armitage 1974). A male that successfully defends the females in his territory throughout the active season is likely to be the only male to hibernate near the females and, in turn, to mate with the females during the short mating season immediately following emergence from hibernation (Andersen et al 1976). Males may defend from one to sev eral (six or seven) females by routinely patrolling their terri tories; the number of females defended is positively related to male reproductive success (Armitage 1986(Armitage , 1991.…”

Yellow-Bellied Marmot Population Dynamics: Demographic Mechanisms of Growth and Decline

“…Low summer precipitation combined with a long winter (late snow cover) apparently results in more females being in poor condition when they emerge from hibernation. Poor condition is expressed as insufficient fat to both survive the hibernation and reproduce (Andersen et al 1976). Finally, the major causes of yellow-bellied marmot mortality are predation and failure to survive hibernation (Schwartz et al 1998, Schwartz andArmitage 2002).…”

Aboveground Productivity and Floristic Structure of a High Subalpine Herbaceous Meadow

“…Permanent snowfields occur in the higher portions of the basin. Fifty percent snowcover occurred in late June 1974, early July 1973and 1976, and mid-July in 1975(Johns, pers. comm., 1978Johns and Armitage, 1979).…”

“…Marmots (Marmota flaviventris) were relatively abundant (Andersen et al, 1976) The relative impact of invertebrate herbivores is unknown.…”