Hibernation biology of Richardson's ground squirrels : hibernaculum systems and energy utilization

Abstract

I studied free-living Richardson's ground squirrels (Spermophilus richardsonii) using telemetry and total body electrical conductivity (TOBEC) to evaluate overwinter energy utilization and the impact of seed caching on body composition of males. I excavated 51 hibernation systems and found that 66% of 35 males cached 1 to 4 species of seed in the hivernaculum. Pre-emergent euthermy was shorter for 3 non-caching (0.7 = 0.2 days) than for 13 caching males (4.0 = 2.8 days), and metabolic predictions of overwinter mass loss approximated actual loss for non-caching males, but over-estimated mass loss for caching males. I concluded that caching males recouped some of the mass lost during hibernation by eating the cache during the longer period of pre-emergence euthermy. Based on TOBEC, the recouped mass included both fat and lean tissue. I suggest that caching in one year is a cost of reproduction that offsets the energetic demands of mating the following year.