Genetic estimates of annual reproductive success in male brown bears: the effects of body size, age, internal relatedness and population density

• Published in: Journal of Animal Ecology
• Main Authors: Zedrosser, A., Bellemain, E., Taberlet, P., Swenson, J. E.
• Other Authors: Institute for Wildlife Biology and Game Management, Universität für Bodenkultur Wien = University of Natural Resources and Life Vienne, Autriche (BOKU), Department for Ecology and Natural Resource Management, Norwegian University of Life Sciences (NMBU), Laboratoire d'Ecologie Alpine (LECA), Université Joseph Fourier - Grenoble 1 (UJF)-Université Savoie Mont Blanc (USMB Université de Savoie Université de Chambéry )-Centre National de la Recherche Scientifique (CNRS), Norwegian Institute for Nature Research (NINA)
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2007
• Subjects: Ursus arctos; age; annual reproductive success; body size; brown bear; density; heterozygosity; [SDE.BE]Environmental Sciences/Biodiversity and Ecology; [SDV.BID]Life Sciences [q-bio]/Biodiversity; [SDV.EE]Life Sciences [q-bio]/Ecology; environment
• Online Access: https://hal.science/halsde-00276492; https://doi.org/10.1111/j.1365-2656.2006.01203.x

Times Cited: 2 International audience 1. We studied male yearly reproductive success (YRS) and its determinants (phenotypic characteristics, age, population density) in two Scandinavian brown bear populations, using molecular techniques to determine paternity. 2. We found a significant difference in male YRS between the study areas, with lower YRS in the south than in the north. 3. In general, older and larger males had higher YRS. Older males may be more experienced in competition for reproduction (male dominance). Large body size is of direct benefit in male-male competition and of advantage in endurance competition for the access to females. 4. Age was relatively more important for YRS in the north and body size was more important in the south, due perhaps to differences in male age structure due to illegal killing. A single old male dominated the reproduction in the north during the study, which resulted most probably in the relatively higher importance of age in the north. In the south, with a more even male age structure, no single male was able to dominate, probably resulting in a more intense competition among males, with body size as the deciding factor. 5. Male YRS was correlated positively with population density. This may be related to the structure of the expanding bear population, with female densities declining towards the population edge. 6. Internal relatedness, a measure of genetic heterozygosity, was correlated negatively with YRS, suggesting that outbred individuals have a higher YRS. Individual heterozygosity at key or many loci may reflect male physical qualities and condition-sensitive traits, which may benefit males directly in contest or in sperm competition.