Parental Care Evolution

Summary

Care by one or both parents evolves when benefits to offspring outweigh costs to parents.

In depth

Care is more common in females, but exclusive paternal care occurs in seahorses and some frogs. Costs include energy and reduced future breeding. Certainty of paternity affects male care.

Care types: guarding, feeding, brooding. Cost-benefit analysis predicts who cares. Biparental care is common in birds.

Key idea: care is favoured when offspring survival benefits are high.

Care increases offspring survival but costs adults. Which sex cares depends on certainty of parentage, the mode of fertilisation (external fertilisation often leads to male care in fish) and mating opportunities. Examples: seahorses and pipefish, where males brood in a pouch; giant water bugs, where males carry eggs; mouthbrooding cichlids; emperor penguins sharing incubation; and mammals, where lactation favours maternal care. Biparental care is typical in birds (over 90 percent).

Care shows in extended forms: cooperative breeding (helpers at the nest, as in many birds and meerkats), provisioning and teaching. Conflicts arise between parents and offspring (weaning conflict) and between mates (who deserts first). Brood parasites avoid costs.

Key idea: care is an investment that is favoured when it increases the lifetime fitness of the parent.