Social ties may shape how genes affect spotted hyena reproductive success

In wild spotted hyenas (Crocuta crocuta) in Tanzania’s Ngorongoro Crater, researchers examined how an animal’s genes, social relationships and surroundings relate to its lifetime reproductive success—the number of offspring it produces over its life, used here as a measure of fitness.
Social and spatial surroundings change the picture
An initial analysis found inherited genetic differences associated with lifetime reproductive success. But when the researchers accounted for shared social and spatial environments, the estimated direct additive genetic variance—variation attributed to an animal’s own inherited genes—fell close to zero.
Instead, they found strong indirect genetic effects linked to social associations. An indirect genetic effect occurs when genes in one animal affect another animal’s traits or fitness through their interactions. Fine-scale overlap in where hyenas lived also explained substantial variation in fitness. By comparison, indirect effects of social associations not linked to genetic differences were relatively small.
The findings suggest that, in this population, heritable variation in reproductive success may be expressed largely through social interactions rather than through individuals’ own genes alone. Taking social surroundings into account may therefore improve understanding of how fitness varies and how populations evolve. The study concerns one spotted hyena population and is a preprint that has not been peer reviewed.
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