Age and sex differences in hibernation patterns in free-living Anatolian ground squirrels

Anatolian ground squirrels, Spermophilus xanthoprymnus (Bennett, 1835), are nearly endemic to Turkey. Various aspects of the biology of Anatolian ground squirrels have been studied. However, a detailed description of hibernation, with special attention to age and sex differences, has not previously been reported. Thus, in this study, we aimed to present a detailed description of hibernation in a population of free-living Anatolian ground squirrels, with special attention to age and sex differences, in relation to soil temperature (Tsoil) at the expected depth of the hibernacula. This study is the first such study for Old World ground squirrels (the genus Spermophilus sensu stricto) and incorporates an additional species from a different environment (e.g. warmer than those of others) into comparative studies of hibernation patterns in Holarctic ground squirrels (the tribe Marmotini) under natural conditions. Body temperature (Tb) was continuously recorded from late summer to spring by intraperitoneally implanted temperature loggers and Tsoil by a temperature logger at a depth of 1 m in the field. Anatolian ground squirrels spent about half of the year in hibernation. However, differences in timing of the beginning and end of hibernation resulted in differences in the duration of hibernation among age-sex classes. The duration of torpor bouts was short at the beginning of hibernation, increased as Tsoil decreased, reached its maximum toward the end of hibernation, and decreased thereafter. Adult males exhibited hibernation characteristics rather different from those of other age-sex classes, spending less time in hibernation, exhibiting shorter torpor bouts and longer interbout arousals, especially toward the end of hibernation, and spending proportionally less time in torpor. In conclusion, we observed that hibernation patterns in free-living Anatolian ground squirrels were influenced by age-sex classes, as well as environmental conditions.