Study

Cooperation and competition within coalitions of male lions: kin selection or game theory?

Packer, C.; Pusey, A. E.

Nature, 1982

Peer-reviewedlongitudinal studywild

What they did

Male coalitions were followed through formation, pride takeover, tenure and eventual displacement, with relatedness between coalition partners established from known maternal histories in a population monitored since the 1960s.

Studied in: Panthera leo
Sample size: male coalitions followed across the Serengeti population

What they found

Males leave their natal pride as adolescents and form coalitions, usually with brothers and cousins but sometimes with unrelated males. Larger coalitions take over prides more successfully and hold them longer. In small coalitions, partners share reproduction relatively evenly; in large ones, reproduction is more skewed.

What it means

The authors' reading, and ours. Where they differ, that difference is the point.

How the authors put it

Coalition behaviour is explained by a combination of kin selection where partners are related and mutual benefit where they are not, since even an unrelated partner improves takeover success.

How NatureHQ reads it

The unrelated coalitions are the informative case. Kin selection explains brothers cooperating without much difficulty; it does not explain unrelated males doing the same, and they do. The answer is that a coalition of two beats a coalition of one regardless of relatedness, so the partnership pays for itself. This is also where the popular picture of a pride goes wrong — a pride is not one male's harem but a group of related females that a coalition of males holds temporarily, and the males are the transient part.

Limitations

Relatedness is inferred from observed maternal history rather than from genotyping in this early work.
One population, though followed continuously for decades.
Reproductive skew is estimated from observed mating rather than from paternity assignment.