Energetics of yellow-bellied marmot populations [Energétique des populations de marmotte à ventre jaune].

Résumé

Chez cette marmotte, l'efficience respiratoire (E maintenance/ E assimilée) est de 77% alors que chez les homéothermes typiques elle est de 98% ; l'efficience de croissance tissulaire (E production/E assimilée) est de 23% excédant largement les 1,5 à 2,5% reportés pour les mammifères herbivores ; le rapport Production/ Maintenance est d'environ 30%, alors qu'il est typiquement de 1,1 à 3% chez les homéothermes. The energy dynamics of 2 colonies of yellow-bellied marmots (Marmota flaviventris) were studied in the Rocky Mountains of central Colorado in 1969 and 1970. The Intake-Rejecta and Maintenance-Production models, which included an analysis of seasonal variations in energy flow parameters yielded similar estimates of population energy flow. Colony energy flow ranged from 64.0 to 94.6 kJ m-2 yr-1. Differences between colonies in annual energy flow can be explained by variations in biomass. Peak energy flow occurred at diffferent times in the 2 colonies and the timing was related to reproductive conditions. The marmot populations consumed 94.6 to 119.2 kJm-2 yr-1, which represented 0.8 to 3.1% of the aboveground primary production. The efficiency with which the marmot populations exploited the available net primary production was 2 to 6.4%. Seventy-one to 75% of the energy ingested by the populations was assimilated: only 77% of the assimilated energy went into maintenance of the population biomass. Tissue growth efficiency averaged 16.8%, 5 x greater than typical homeotherms.The production/maintenance ratio averaged 29.6%. The marked differences in the respiration efficiences, tissues growth efficiencies, and production: maintenance ratios between the heterothermic marmot and typical homeotherms suggest that heterothermy represents a distinct strategy in secondary production.