ハシブトガラスつがい内の利他行動にみられる非対称性はペアごとに異なる

抄録

Altruistic behaviour, such as allogrooming and allofeeding, has been suggested to be crucial for maintenance of cooperative relationship especially between non-kin individuals. Monogamous pair-bond, which is widespread in birds, is a form of cooperation for breeding between a male and a female. Many previous studies reported that altruistic behaviour within pair-bonds occurred primarily from males to females. However, most of those findings were obtained from the observations during the breeding season, and therefore it remains unknown what sex-different patterns of altruistic behaviour occur outside the breeding season for life long monogamous birds. The present observation study investigated sex differences of altruistic behaviour within pair-bonds outside the breeding context in a life-long monogamy, large-billed crows (Corvus macrorhynchous). Specifically, frequency of allopreening and allofeeding were compared between sexes and also between pair-bonds. We found that frequency of both behaviour was different between sexes, and inconsistent within and between pair-bonds. Our findings suggest that altruistic behaviour within pair-bonds may occur asymmetrically between sexes but vary between pair-bonds in large-billed crows.