Genetic vs. environment: variation in torpor patterns of marmots and woodchucks under constant laboratory conditions [Génétique et l'environnement: variation dans les canevas de torpeur des marmottes en conditions constante de laboratoire].

Résumé

Hibernation is characterized by reduced metabolic rate and multi-day torpor bouts during which body temperature (Tb) declines to near ambient temperature (Ta) but the animal periodically re-warms to normal Tb (37° c). The characteristics of torpor during hibernation at different latitudes are unclear. Woodchucks (Marmota monax) have a population range extending from the South-Eastern United States of America to northern Alaska. To determine whether the phenotypic expression of torpor is genetically determined or varies due to environment, we investigated torpor patterns from woodchucks obtained from 3 populations Maine (latitude 43°42’N, n=2), Pennsylvania (latitude 40°22’N, n=2), and South Carolina (latitude 34°40’N, n=2) and placed all animals at constant a (5° C) in Fort Collins (latitude 40°45’N), Colorado. Marmots (Marmota flaviventris) from Colorado were used as a reference out-group (n=2). Body temperature data loggers (I buttons maxim Inc.) were surgically implanted into the animals’ abdomen to record Tb (every 3 hours) from September 2007 to April 2008. Food intake was recorded prior to hibernation; during hibernation food was removed. Monthly body mass measurements were recorded from July 2007 to April 2008. We hypothesized that torpor patterns would be highly variable and therefore indicative of the Ta under which the animal was maintained. We found that although there was variation in torpor patterns within each population, basic torpor characteristics were similar to field results. This suggests that torpor patterns have a strong genetic component. This research was supported by NIH grant (r25dk067017) to GLF.