Microsatellite analysis of paternity and reproduction in Arctic grizzly bears

We report data from analyses of microsatellite loci of 30 grizzly bear family groups which demonstrate that each cub in a litter can be sired independently, and we derive estimates of maximum reproductive success for males, from an Arctic population in northwestern Alaska that is minimally affected by human activities. These analyses were made possible by the use of single-locus primers that amplified both of an individual's alleles at eight microsatellite loci and by detailed knowledge of maternal/offspring relationships that allowed the identification of paternal alleles. No single male was responsible for more than approximately 11% of known offspring, and no more than 49% of breeding-age males successfully bred. These data contribute to an understanding of the genetic and demographic basis of male reproductive success, which is of vital importance in the maintenance of small, isolated grizzly bear populations.