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UBC Theses and Dissertations

Quiescent states of sleep, torpor and hibernation in the Sanders, Colin E.


Brazilian tegus (Tupinambis merianae) were instrumented with telemetry encoder implants that measured and broadcast heart rate (HR), breathing rate (fR), and deep body temperature (Tb) and were then allowed to freely roam in outdoor enclosures mimicking their natural environment for a full year (2004) in order to monitor the circadian and circannual patterns in behaviour and cardio-respiratory physiology. The year was divided up into 5 seasons based upon the physiology and behaviour of the tegus: early activity season (Sept.-Nov.), late activity season (Dec.-Feb.), entrance into hibernation (March-April), hibernation (May-July), and arousal from hibernation (August). The activity seasons were characterized by warm weather with frequent rainfall which slowly decreased in temperature and precipitation as tegus started entering hibernation so that the end of the dormant season was marked by dry, cold weather. Tegus in the early activity season demonstrated high activity associated with breeding demands, displayed elevated HR and fR, and were able to maintain a large temperature differential (4-7°C) between deep body temperature (Tb) and their respective burrow (Tburrow) during sleep. As the season progressed into late activity season, average Tb remained constant but average HR and fR progressively declined indicating nightly torpor. Periods of inactivity during the active seasons were rare and associated with inclement weather. Tegus entered hibernation through bouts of inactivity that progressively increased in frequency and duration. During this time, Tb was regulated but declined at different rates in regards to daytime and nighttime values. Heart rate through the entrance into hibernation and hibernation periods frequently demonstrated arrhythmias that increased in duration but decreased with frequency as hibernation progressed. Through hibernation, Tb continued to decline for the first month but HR and fR were constant, demonstrating a temperature independent suppression of metabolism. Through the hibernation season tegus sporadically aroused and emerged from their burrows to warm up and after a short basking period would return to the burrows and swiftly resume hibernation. While hibernating, heart rate was characteristically regular but breathing was sporadic orepisodic. Arousals became more frequent towards the end of hibernation so that when they entered arousal from hibernation season most tegus were emerging daily. At this time daily maximum deep body temperature (Tbmax) swiftly returned to active season values but nighttime daily minimum deep body temperature (Tbmirt) values only showed a gradual increase through August, indicating different body temperature set points (Tbset) for active and sleep states. Changes in heart rate and breathing rate during the year showed greatest correlation with changes in photoperiod, although throughout hibernation HR and fR also showed tight correlation with Tb.

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