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