Effect of brief exposure to a potential predator on cortisol concentrations in female Columbian ground squirrels (Spermophilus columbianus)

Abstract

We examined the effect of exposure to a potential predator on cortisol concentrations in captive female Columbian ground squirrels (Spermophilus columbianus) and determined if lactation mitigated this cortisol response. Lactating and nonlactating females were exposed to a dog (Canis familiaris) for 5 min once a week over a 8-week period. Blood was collected 5 min and 2.5 and 4.5 h after exposure to the dog. Females exposed to the dog had higher concentrations of total (but not free) cortisol than unexposed females only in the 5-min blood sample. Over the active season, total- and free-cortisol levels were 37-47% higher in females exposed to the dog than in unexposed females in early to mid-July when young were being weaned. The cortisol response to the dog was suppressed during lactation. Cortisol levels were, on average, 41-59% lower during lactation than during nonlactation 5 min (but not 2.5 or 4.5 h) after exposure to the dog.