科研之友
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摘要
Being a member of a cohesive group can have fitness benefits such as decreased predation risk, increased feeding efficiency as well as enhanced access to social information and mates. However, competition and the risk of parasite transmission exert centrifugal forces on group-living. Thus, the actual degree of cohesion is expected to vary as a function of the relative importance of several social and ecological factors. White-breasted mesites Mesitornis variegata are medium-sized ground-dwelling birds endemic to the dry deciduous forests of western Madagascar. They live in stable breeding pairs or small family groups, mate monogamously and often form temporary heterospecific associations with canopy-dwelling bird species that give alarm calls to which mesites respond with anti-predator behaviours. We investigated the potential effects of predation risk and mate defence on mesite group cohesion by analysing inter-individual distances of 20 groups as a function of mesite social organization, alarm call events, the size of associated heterospecific flocks, and the adults' reproductive state. Mesite social units were very cohesive, particularly in families, when associated with smaller heterospecific flocks, and after an alarm call event. Adult reproductive state did not influence breeding partners' cohesion. Therefore, the pronounced group cohesion in mesites seems to be mainly a response to the high predation risk typically associated with a terrestrial life-style, and not to mate-guarding. However, we suggest that high group cohesion due to predation risk could limit opportunities for solitary extra-territorial forays to obtain extra-pair copulations, thereby contributing to a strictly monogamous system in this species.
- 出版日期2015-7
