Animal behaviour

Infidelity yields better offspring

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Sexual promiscuity in female songbirds increases the reproductive success of their offspring.

Nicole Gerlach at Indiana University in Bloomington and her colleagues studied free-living dark-eyed juncos (Junco hyemalis). The birds form a 'social pair' with one partner but produce more than one-quarter of their offspring from 'extra-pair' mating. These young go on to reproduce more successfully than those sired within the social pair.

As adults, the male offspring from extra-pair matings were found to be more promiscuous than their social-pair counterparts. Female extra-pair offspring weren't — but did go on to produce more offspring with their social partners. The authors conclude that the genetic advantage of multiple sex partners may not be apparent in traits in the early life of the offspring, but might instead affect their reproductive success as adults.

Proc. R. Soc. B 10.1098/rspb.2011.1547 (2011)

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