Cub adoption by polar bears (Ursus maritimus): determining relatedness with microsatellite markers

Sixteen microsatellite markers were used to determine the genetic relatedne ss between adult female polar bears and their accompanying cubs for three r ecent occurrences of natural adoption recorded in the Canadian Arctic. The estimation of the degree of relatedness was powerful and provided a high de gree of separation between first order relatives and unrelated individuals with the loci used. The analysis showed that the cubs were unrelated to the ir adoptive mothers and that the mothers were unrelated to one another. Alt hough the circumstances and mechanisms whereby these adoptive events occurr ed are unknown, the data do not support kinship theory as an explanation fo r the exchange of cubs. We suggest that these adoptive events probably repr esent instances of the misidentification of cubs by adult polar bears.