Ambient temperatures in hibernacula and their energetic consequences for alpine marmots (Marmota marmota) [Températures ambiantes dans les hibernacula et leurs conséquences énergétiques pour les marmottes alpines].

Résumé

Temperatures inside natural winter burrows of alpine marmots (Tbur) dropped exponentially throughout the hibernation season from about 12°C in autumn to almost 0°C in spring. Laboratory measurements of oxygen consumption (VO2) showed that torpid marmots have minimal energy expenditure at ambient temperatures (Ta) above 5°C. Metabolism increased with decreasing Ta below 5°C. At Ta near O°C, VO2 was already four times higher than the minimal value. Tbur was below 5°C for about two thirds of the hibernation season. The more animals hibernated together in a burrow, the latter Tbur fell below this critical threshold. Hence, overwintering conditions in the natural habitat are severe for the animals, but mitigated by social hibernation.