TELEMETRIC INVESTIGATION ON THE HIBERNATION OF EUROPEAN HAMSTERS KEPT
UNDER SEMINATURAL CONDITIONS
Thomas Waßmer & Franziska Wollnik, Department of Biology, University
of Konstanz, P. O. Box 5560 M618, D-78434 Konstanz, Germany
In each of two winters (1994 / 95 and 1995 / 96), 6 male and 6 female
European hamsters (Cricetus cricetus L.) were individually housed in 1.1
x 0.8 x 0.8 m mesh wire cages which were buried 0.6 m into the soil of
an outdoor enclosure near the university of Konstanz. From September until
May each year, continuous registrations of body temperature (Tb, thermal
resolution better than 0.1 °C), localisation of the animal (above ground
vs. inside the burrow) and general activity were taken in bins of 5 min.
using intraperitoneal temperature-sensitive HF-telemetry and a two antenna
receiver system (cage bottom and top).
Due to technical problems and natural mortality a total of only 13 complete
and 5 partial hibernation patterns (HPs) could be recorded. 12 hamsters
showed a regular pattern of 7 - 44 deep hibernation bouts (HBs) with a
decline of Tb down to almost soil temperature (minimum Tb 2.26 °C)
and durations > 24 h (maximum 165.5 h) which were separated from each
other by short periods of inter-bout normothermy. The HPs of 3 other animals
were dispersed with only a few HBs of long duration mixed with shallow
HBs of shorter duration. Finally, 3 hamsters did not hibernate: they did
not show HBs at all. Hibernation started between October 2 and January
8 and ended between January 29 and April 9. Most hamsters stopped to leave
their burrow 4 - 39 days before the first decline of Tb below 30 °C,
whereas they maintained inside their burrow for 0.5 - 22 days after the
final rewarming in spring. Of the total duration of the hibernation season
about 1.6 - 80.2 % were spent in hypothermy (Tb below 30 °C) and 19.8
- 98.4 % in inter-bout normothermy. Mean Tb during hibernation ranged between
13.46 and 37.47 °C, indicating energy savings of 1.2 - 64.7 % during
winter (baseline: normothermic values of individual animals before hibernation).
Maximum bout duration during hibernation was scattered between end of December
and end of March and did not correlate with soil temperature.
7 out of 13 hamsters interrupted hibernation for brief episodes and moved
above the ground. During the whole hibernation these animals spent a total
of 0.43 - 401.74 h above the ground. General activity was up to 85 % lower
as compared to the normothermic conditions before hibernation.
Further analyses on the influence of sex and age on the HPs, food consumption
and weight loss during winter, and registration of oestrous cycle in female
hamsters through measurements of general activity and Tb after the hibernation
period will be presented at the conference.
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