Sex and Age Differences in Mass, Morphology, and Annual Cycle in European Ground Squirrels, Spermophilus citellus

Abstract

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Body temperature patterns before, during, and after semi-natural hibernation in the European ground squirrel

“…Healing of the surgery wounds and long term eects of anaesthesia, possibly inducing body mass loss, may have played additional roles. The tendency of males to start hibernation later and stop earlier than females corresponds with ®eld observations (Millesi et al 1999b). The dierences between hibernation onsets in the ®eld and enclosure sharply contrasts with the close resemblance of hibernation end between free-ranging (Millesi et al 1999b) and enclosed females presented here (Females: enclosure 26 March±1 April, ®eld 28 March±6 April; males: enclosure 24 February± 11 March, ®eld 5 March±19 March).…”

“…The tendency of males to start hibernation later and stop earlier than females corresponds with ®eld observations (Millesi et al 1999b). The dierences between hibernation onsets in the ®eld and enclosure sharply contrasts with the close resemblance of hibernation end between free-ranging (Millesi et al 1999b) and enclosed females presented here (Females: enclosure 26 March±1 April, ®eld 28 March±6 April; males: enclosure 24 February± 11 March, ®eld 5 March±19 March). This indicates the presence of an accurate annual timing mechanism during 6±7 months of hibernation, which persisted in the animals that participated in this study.…”

“…In general, hibernation started later than reported from ®eld observations (Millesi et al 1999b) on the same species (Females: enclosure 27 September±16 October, ®eld 6±19 August; males: enclosure 9 October±13 November, ®eld 27 August±26 September). This dierence may partly re¯ect the release dates of 14±26 September, but does not explain why four animals delayed hibernation onset until October or even November.…”

“…Animals, housing and data acquisition Animals used in this study were either caught from a population near Vienna, Austria (Millesi et al 1999b) or born under laboratory conditions from females caught pregnant from the same population. Body temperature patterns were recorded every 48 min for 7±8 months by implanted loggers (Onset Computer Corporation, Pocasset, Mass., USA; customised Stowaway Tidbit temperature loggers; 12.8 g; range ±4°C to 44°C; 0.18°C accuracy).…”

Annual rhythms that underlie phenology: biological time-keeping meets environmental change

“…Subsequently, species may hibernate for five to eight months, during which core body temperature can fall to as low as 238C. Hibernation is followed by an active season characterized by a brief spring breeding period of two to three weeks followed by a weight gain of two to three times their emergence weight [29,30]. While circannual rhythms in hibernating ground squirrels drift under constant conditions, hibernation cycles in the wild are synchronized with the external year.…”