Dominant male chimps more likely to father offspring
Washington: Male chimps are quite choosy about forming coalitions when it comes to siring offspring, with dominant individuals more likely to become fathers and rise in rank.
A new study led by Duke University in North Carolina found that it may not just be the coalition that is important, but that who the coalition is with determines future success.
Researcher Ian Gilby found that male chimpanzees with central positions in the coalitionary network were most likely to father offspring and increase in rank.
Specifically, those who formed coalitions with males who did not form coalitions with each other were the most successful.
Coalitionary aggression is when at least two individuals jointly direct aggression at one or more targets. Aggression and coalition formation between males is important for attaining a higher dominance in many animal species.
The most dominant males are more likely to mate and therefore, sire offspring. Males with high coalition rates are more likely to mate more often than expected for their rank.
Gilby and his colleagues studied data from wild chimpanzees gathered over 14 years in Tanzania.
Of the four measures they used to characterise a male's coalitionary behaviour, the only one that was related to both of these factors was 'betweenness' - a measure of social network centrality - which reflects the tendency to make coalitions with other males who did not form coalitions with each other.
The only non-alpha males to sire offspring were males that had the highest 'betweenness' scores. These males were also more likely to increase in rank, which is associated with higher reproductive success.
Researchers postulate that this shows that male chimpanzees may recognize the value of making the 'right' social connections. By choosing their coalition partners carefully, they are demonstrating an ability to recognise the relationships of others.
They conclude that "...Our data suggest that there are consequences to the recognition of third party relationships. As such, it represents an important step toward a more complete understanding of the adaptive value of social intelligence and the evolution of co-operation."
The study was published in the Springer journal Behavioural Ecology and Sociobiology.