During part of the breeding season, the cooperative incubation behaviour was prevented by temporarily removing eggs.
Groups consisted of one or three males and one, three, four or six females, similar to the range of group sizes seen in the wild.
"We set out to study the costs and benefits of group size under consistent ecological conditions, to separate out the effect of individual differences from group attributes on reproductive success and disentangle how competition and cooperation change with group size," explains Melgar.Īt the start of each breeding season in May across eight years, experimental groups of ostriches were established by placing different numbers of males and females in large enclosures in Klein Karoo, South Africa. "But in the wild, groups are highly variable in size and it is not clear why."Ī common explanation is that group sizes change with fluctuations in ecological conditions, but this does not explain why groups with different compositions live under similar conditions. "The competing forces of competition and cooperation are expected to result in there being an optimal group size in nature," explains lead author Julian Melgar, a postdoctoral researcher at Lund University, Sweden. However, this cooperative breeding is not without its costs, because there can be intense competition over mating and who's eggs get incubated. Groups breed in a communal nest and individuals take it in turn to incubate eggs. Like humans, ostriches cope with the challenges of parenthood by joining together to take care of their offspring.
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