The eVects of primiparity on reproductive performance in the brown bear

• Main Authors: Andreas Zedrosser, Bjørn Dahle, Ole-Gunnar Støen, Jon E Swenson
• Other Authors: The Pennsylvania State University CiteSeerX Archives
• Format: Text
• Language: English
• Published: 2009
• Subjects: Ursus arctos
• Online Access: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.1072.3232; http://bearproject.info/wp-content/uploads/2014/07/2009-Zedrosser-et-al-primiparity-Oecologia.pdf

Abstract We studied the eVects of primiparity on litter size, oVspring size, and cub loss in brown bears (Ursus arctos) in two study areas (north, south) in Sweden from 1987 to 2006. Sexually selected infanticide (SSI) has been suggested previously as a mortality factor in our study populations. Females in the south became primiparous earlier than females in the north. Primiparous females had signiWcantly smaller litters of cubs than multiparous females. We found no evidence that primiparity was costly in terms of the interlitter interval. Primiparous mothers had a higher probability of cub loss than multiparous mothers. The probability of cub loss was analyzed separately for the premating and the mating season. The probability of cub loss by primiparous females in the pre-mating season increased with both increasing population density and deteriorating food conditions, whereas the probability of cub loss during the mating season decreased with increasing age of primiparity and increased with male turnover (a variable predicting SSI). The temporal patterns of cub loss by primiparous females suggested that the critical times for reproductive success by primiparous females were the pre-mating season (from birth to shortly after leaving the den) and the mating season. Cub loss in these periods was independent and caused by diVerent factors. Cub loss before the mating season seemed to be most inXuenced by food conditions, whereas that during the mating season appeared to be caused by SSI.