Parental and alloparental care during social hibernation [Soins parentaux et alloparentaux pendant l'hibernation].

Résumé

Metabolic heat production of hibernating alpine marmots increases again with decreasing ambient temperature (Ta) below 5°C. Such Ta exist in natural burrows for about 2/3 of the hibernation season and are couterbalanced by social hibernation. However, the presence of infants in socially hibernating groups inflitcts extra mass loss in parents and older full sibs. This indicate that they warm infants during hibernation (Arnold, 1990). The mode of parental and alloparental care was investigated during winter 1990/1991 in the natural habitat. The body temperature (Tb) of 37 alpine marmots of 7 hibernation groups as well as the Ta in their hibernacula were recorded continuously using temperature sensisitve radio transmitters. Fisrt results show that (i) infants have lower Tb during torpor, that (ii) group members huddle together in the nest and (iii) usually synchronize their regular changes from torpor to euthermia. Extra arousal of individuals from torpor occur only in groups with infants when Ta drops below 5°C. The presence of euthermic animals in the nest raises the Tb of still torpid group members. Typically, parents or helpers become euthermic earlier than expected. Hence, the cost of parental and alloparental care seems to result from an increased torpor metabolism due to warming infants as well as from additional arousal at low Ta in favor of infants. Final results will be presented at the conference.