Lindström, J. 1998: Harvesting and sex differences in demography. - Wildl. Biol. 4: 213-221.

In studies of population dynamics and harvesting, differences in the demographic parameters of males and females are rarely dealt with explicitly. However, polygyny and sexual dimorphism, commonly observed in game animals, often result in sex differences in demographic parameters. A structurally simple deterministic two-sex model was used to study the equilibrium population size and adult sex-ratio under constant-quota harvesting. The model allowed varying harem and brood size, condition dependent sex allocation and sex differences in recruitment probability and adult survival. The results show that demographic sex differences may lead to a recommendation for female biased culling. Adult sex-ratio optimal for population growth is not evolutionarily stable. However, constant-quota harvesting can lead to the optimal adult sex-ratio for population growth in situations in which the mating system and female reproductive strategies would result in a radically different adult sex-ratio if the population were left unharvested.

Key words: demography, game management, harvesting, sex allocation, Trivers-Willard hypothesis, two-sex model

Jan Lindström*, Department of Ecology and Systematics, Division of Population Biology, P.O. Box 17 (Arkadiankatu 7), FIN-00014 University of Helsinki, Finland

*Present address: Department of Zoology, Downing Street, University of Cambridge, Cambridge CB2 3EJ, UK - e-mail: j.lindstrom@zoo.cam.ac.uk

Received 15 October 1997, accepted 4 May 1998

Associate Editor: Peter J. Hudson