Abstract
A preference to associate with kin facilitates inclusive fitness benefits, and increased tolerance or cooperation between kin may be an added benefit of group living. Many species exhibit preferred associations with kin, however it is often hard to disentangle active preferences from passive overlap, for example caused by limited dispersal or inheritance of social position.
Parrots are often thought to exhibit social complexity, and many species appear to show a multilevel society consisting of pair-bonded individuals moving between fission-fusion foraging groups, within larger communal roosts. Previous work has shown that, despite these fission-fusion dynamics, individuals can exhibit long-term preferred foraging associations outside their pair-bonds. Yet the underlying drivers of these social preferences remain largely unknown.
In this study, we use a multi-layered social network approach to examine the influence of kinship on social associations and interactions in wild sulphur-crested cockatoos, Cacatua galerita. We recorded roost co-membership, social associations, and affiliative and aggressive interactions in 561 individually marked birds across three neighbouring roosts. We then collected genetic samples from 205 cockatoos, and conducted a relationship analysis to construct a kinship network. Finally, we tested correlations between kinship and four social networks: spatial proximity, affiliative, low-intensity aggression, and high-intensity aggressions. We examined these potential correlations at two levels – within roost groups and between roosts.
Our result showed that while roosting groups were clearly defined, they showed little genetic differentiation. Between roost movement was high, with juveniles, especially females, repeatedly moving between roosting sites. Both within and across these roosting communities, individuals preferentially associated with kin. Supporting this, individuals were also more likely to allopreen kin. However, against our expectation, individuals preferred to direct aggression towards kin within roosts, but avoided aggressing kin of different roosts.
Our study demonstrates that sulphur-crested cockatoos prefer to associate with kin, both within and between roosting groups, and exhibit behavioural and context-dependent social interaction rules towards kin. Our results help reveal the drivers of social association in this species, while adding to the evidence for social complexity in parrots.
Competing Interest Statement
The authors have declared no competing interest.
Footnotes
↵* Co-senior authors