Abstract

The social structure and genetic make-up of the hoary bat (Lasiurus cinereus) during its fall migration is not well known. Recently, pairs of male hoary bats were observed flying together in the Humboldt Redwoods during the autumn migration. When one individual was netted, the other member of the pair circled around and remained in the area while the two bats called to one another. This suggests a strong social, and a possible genetic, bond between the two males. In order to determine whether these males were related, wing tissue samples were collected from 15 pairs and 76 singleton individuals from the general migrating population. All but two individuals were genotyped at 14 microsatellite loci. The genetic relatedness analysis revealed that although the behaviorally interacting pairs were not more related than the general population, there was a wide range of relatedness within the population ranging from 0.0 to 1.0. Unexpectedly, 31 singleton individuals were found to have high relatedness values with another individual in the population that indicated a full-sibling or parent-offspring relationship. Furthermore, five pairs of singleton individuals possessed relatedness values of 1.0 that reveal an identical twin relationship. Altogether, our results suggest that this area is part of a commonly used migration route for male hoary bats and that this migratory behavior is shared within families even if the individuals are not observed exhibiting co-migratory behavior.