Entry into hibernation in Marmota flaviventris : sleep and behavioral thermoregulation [Entrée en hibernation chez M. flaviventris : sommeil et thermorégulation comportementale].

Résumé

L'enregistrement en continu de l'activité comportementale, électrocéphalographique et de la température cérébrale ont donné des résultats permettant une comparaison avec d'autres hibernants de poids et de taille très différentes. Hibernators of the genus Marmota (wt = 3-5 kg) differ from smaller hibernators (wt =1 kg) in thermoregulatory characteristics during entry into hibernation. They might be expected to differ also with respect to the distributions of activity, awake and sleep states during entry. Marmots implanted stereotaxically with electrodes to record electroencephalograms and brain temperature (Tbr) were monitored remotely by a polygraph as well as video transmission as they entered hibernation. During entry, awake (A), slow wave sleep (SWS), and paradoxical sleep (PS) states could be identified. Activity which includes nest building, grooming, and shivering slowed entry and became progressively more stereotyped as Tbr decreased. All animals exhibited at least one PS bout between Tbr = 33-32o C. SWS as percent total sleep increased (80 to 92%) as Tbr decreased from 35-25oC. This increase represented a decrease in number and increase in duration of SWS episodes. The length of individual SWS and PS episodes of the marmot did not differ from those reported in Citellus. These data suggest that entry into hibernation is a more complex phenomenon than merely an extension of slow wave sleep. Similar changes in arousal state distribution occur in hibernators of different sizes.