The hibernation temperature niche of the steppe marmot Marmota bobak Müller 1776

Abstract

Before hibernation, steppe marmots (Marmota bobak Müller 1776) close their burrows to prevent convection transfer of heat to the inside of the burrow. As a result, the temperature inside the burrow differs only slightly from that of the surrounding soil. Using data on soil temperature, I described the temperature regime of steppe marmot burrows (depth from 140 to 450 cm) during hibernation (from August to April), within the species and subspecies ranges. Taking into account the total soil depth of the hibernation chamber and the dates for the beginning and end of hibernation, the steppe marmot enters hibernation at a temperature of 8-16 °C, and ends hibernation at a temperature of 2-4 °C. The hibernation temperature regime differs significantly between the subspecies. M. b. bobak winters at a temperature of 3-4 °C higher than M. b. schaganensis. In the range of M. b. schaganensis marmots start hibernation 1 to 2 months earlier than in the range of M. b. bobak. The cause of subspecies differences in dates of onset of hibernation appear to lie in the zonal properties of seasonal changes in air temperature. In the course of hibernation, the soil temperature declines gradually at a rate approaching 1 °C per month.