A field study of body temperature variation in yellow-bellied marmots during hibernation [Étude de terrain de la vatiation de température corporelle chez les marmottes à ventre jaune durant l'hibernation].

Résumé

Yellow-bellied marmots (Marmota flaviventris) cope with extreme variations of environmental conditions with behavioral and physiological adaptations. These adaptations include social hibernation, seasonal variations in activity, hypothermia, and selection of hibernacula. We investigated body temperatures of hibernating yellowbellied marmots in Central Washington and determined relationships between marmots and their thermal environment. Three individuals were trapped in July 1999. Each was fitted with a temperature-sensing radio collar and surgical implant. Marmots entered their burrows in August 1999 and emerged in March 2000. Hibernating marmots maintained body temperatures (12-20o C), well below seasonally active marmots, yet above environmental temperatures. We observed periodic bouts of arousal from torpor, where marmot Tb climbed from 12o C to 35o C in only three hours. Body temperatures during arousal averaged 34-36o C, which is slightly below active Tb. Body temperatures of hibernating marmots have been measured in the laboratory, but our study is the first to monitor hibernating Tb of yellow-bellied marmots in the field. Communal use of hibernacula and heterothermy in other sciurids have been shown to conserve energy during hibernation. Our results show that yellow-bellied marmots conserve energy by allowing Tb to drop 25o C below active temperatures for extended periods.