Page 97 - University of Pretoria Research Review 2017

Foreword
Introductory Messages
DEVELOPMENT AND CHANGE
Animal Behaviour
Cooperation and competition
David Gaynor, Mammal Research Institute, Department of Zoology and Entomology
Life is a balance between knowing when
to cooperate and when to compete. This
is especially so for meerkats inhabiting the inhospitable Kalahari desert where cooperation can be the key to survival.
The Kalahari Meerkat Project, a collaboration between the Mammal Research Institute and Universities of Cambridge and Zurich, has continued its long-term study of more than two decades on social cooperation and competition in meerkats in the Kalahari desert in southern Africa.
Kalahari meerkats are famously known for their distinctive cooperative breeding where members of the group forgo their own breeding to help the dominant breeders by baby-sitting and feeding their young. But this system is not only collaborative; the dominant females actively attack subordinate females who attempt to breed by chasing them out of the group. This aggression is a response to competition between the dominant female and older subordinate females who might attempt to breed and compete with the single dominant female.
Dr David Gaynor, who coordinates the project, has collaborated with Professors Nigel Bennett and
André Ganswindt at UP, and Professor Tim Clutton- Brock at the University of Cambridge, in investigating the hormonal basis for cooperation. Their findings
have indicated a correlation between the levels of the stress hormone cortisol in different individuals and their contributions to cooperative behaviour. In an experiment spanning six years, they have manipulated the levels of cortisol by feeding individual meerkats with scorpions laced with cortisol or a cortisol antagonist.
The findings showed that increased cortisol activity increased cooperative behaviour, both in babysitting and pup feeding in subordinate females, demonstrating the potential of dominant females to manipulate subordinates by being aggressive to them, and thereby increasing their cortisol levels and their levels of
cooperative behaviour. Further analysis, however, failed to show that females adaptively modified their level of aggression to increase cortisol levels when the need
for help was higher, which suggests that the function
of the observed aggression directed at subordinates was primarily to reduce the probability that they would breed. The researchers published this in the Proceedings of the Royal Society B.
In a separate study published in Biology Letters the researchers found that by experimentally increasing the food supply to dominant females, their aggression to subordinate females increased, demonstrating
that reproductive competition was the reason for
their aggression rather than competition for food (which was alleviated by feeding the dominant
female). The importance of reproductive competition in explaining the aggression of dominant females towards subordinate females was confirmed in a paper published in Behavioral Ecology where the researchers reported that subordinate females experienced higher aggression levels and associated cortisol levels when dominant females were pregnant and about to breed. This was not the case for subordinate males, who are obviously not reproductive competitors but otherwise shared the same social and ecological conditions as the subordinate females.
These results highlight that cooperation cannot exist
or be studied in isolation of competition and the associated social conflict and aggression. For meerkats surviving in a harsh desert world, evolution dictates a delicate balance between cooperation and competition.
PEOPLE AND CONTEXTS
HEALTH AND WELL-BEING
PLANET AND SUSTAINABILITY
Awards
Lead Researchers
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David Gaynor