Seasonal range size in relation to reproductive strategies in brown bears Ursus arctos

1. Data on seasonal ranges of 93 radio-collared adult brown bears (Ursus arctos ) were used to test hypotheses explaining variation in range size in relation to male and female reproductive strategies. 2. Both males and oestrous females used large ranges in the mating season, but decreased their ranges after the mating season. These results suggested that both sexes in this species roam to mate, because the results could not be explained by a seasonal change in food availability nor by increased foraging movements of oestrous females to replenish body reserves after previous cub raising. 3. Females with cubs-of-the-year (cubs) restricted their range size in the mating season and increased their ranges in the post-mating season. This finding suggests that females with cubs restricted their ranges to avoid contact with infanticidal males, an important cause of cub mortality, because the proposed alternative explanation - limited mobility of small cubs - was unable to explain the small size of mating season ranges. 4. Our results suggest that range size in females is influenced by sexually selected infanticide, selecting for large mating season ranges and multiple mating in oestrous females to hide paternity and for restricted mating season ranges in females with cubs to avoid infanticidal males. 5. To our knowledge, we are the first to report a significant relationship between seasonal range size and reproductive status in female brown bears and the first to report an effect of oestrus on seasonal range size in female carnivores.