REPRODUCTIVE-BEHAVIOR AND OPERATIONAL SEX-RATIO IN RICHARDSONS GROUND-SQUIRRELS

Activity budgets, use of space and social interactions of adult Richar dson's ground squirrels, Spermophilus richardsonii, during the annual mating season were documented in relation to daily operational sex rat io (OSR) for males and in relation to reproductive status for females. For males, mating was a stressful period characterized by weight loss and injury. Male-male conflict was highest when receptive females wer e most abundant and OSR was least male-biased. Neighbouring males seem ed to jockey for position on a daily basis to increase their proximity to those females in oestrus that day. Males spent more time monitorin g conspecifics and less time feeding during the mating period than at other times, especially in the late afternoon of the few days on which most females copulated, often with several males. Between emergence f rom hibernation and emergence of the litter 8 weeks later, the activit y budget of females changed little except for the day of oestrus, when females fed less and spent time hiding. Some oestrous females spent m ore than 20% of their time above-ground hiding, and some precipitated aggression between males by using a hide-then-run behavioural pattern to move outside their usual area of residence. Females in oestrus temp orarily expanded their home range, and they had some ability to determ ine the identity and sequence of their mating partners. (C) 1996 The A ssociation for the Study of Animal Behaviour