Androgen receptor genes (AR) have been found to have associations with reproductive development, behavioral traits, and disorders in humans. However, the influence of similar genetic effects on the behavior of other animals is scarce. We examined the loci AR glutamine repeat (ARQ) in 44 Grevy's zebras, 23 plains zebras, and three mountain zebras, and compared them with those of domesticated horses. We observed polymorphism among zebra species and between zebra and horse. As androgens such as testosterone influence aggressiveness, AR polymorphism among equid species may be associated with differences in levels of aggression and tameness. Our findings indicate that it would be useful to conduct further studies focusing on the potential association between AR and personality traits, and to understand domestication of equid species.
