Bellemain, E., Swenson, J.E., Taberlet, P. 2006. Mating strategies in relation to sexually selected infanticide in a nonsocial carnivore: the brown bear. Ethology, 111, 1-14

Based on the sexually selected infanticide (SSI) hypothesis, infanticide can be an adaptive mating strategy for males, but this is controversial. This phenomenon should not benefit females, so one would expect females to evolve mating counter strategies in order to defend their infants against infanticidal males. Cases of SSI are extremely difficult to document in the field, especially for nonsocial species. Using field observations and genetic methods, we describe mating strategies employed by both sexes of brown bears (Ursus arctos) in relation to SSI. We present evidence that infanticide might be an adaptive male mating strategy in this non social carnivore, as all requirements for SSI are fulfilled i) infanticide shortens the time to the mother’s next estrus, ii) the perpetrator is not the father of the killed infants, and iii) putative perpetrators sire the next litter. One would expect that infanticide in nonsocial species should be ascribed primarily to immigrant males, as in social species. However, our results indicate that SSI by resident adult males can also be common. Perhaps they recognize females they have mated with previously. Moreover, we use DNA-based parentage testing to demonstrate a minimum of 14.5% of multiple paternities (up to 28% for litters with 3 young or more). Female promiscuity to confuse paternity may therefore be an adaptive counter strategy to avoid infanticide.

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