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Lindsay Young and Eric Vanderwerf (Pacific Rim Conservation, Oahu, Hawaii, USA) have studied female-female pairs in Laysan Albatrosses Phoebastria immutabilis within the Kaena Point Natural Area Reserve on Oahu

Their findings have been published online and open access in the Proceedings of the Royal Society Biological Sciences.

The paper’s abstract follows:

“Same-sex pairing is widespread among animals but is difficult to explain in an evolutionary context because it does not result in reproduction, and thus same-sex behaviour often is viewed as maladaptive.  Here, we compare survival, fecundity and transition probabilities of female Laysan albatross in different pair types, and we show how female–female pairing could be an adaptive alternative mating strategy, albeit one that resulted in lower fitness than male–female pairing.  Females in same-sex pairs produced 80% fewer chicks, had lower survival and skipped breeding more often than those in male–female pairs.  Females in same-sex pairs that raised a chick sometimes acquired a male mate in the following year, but females in failed same-sex pairs never did, suggesting that males exert sexual selection by assessing female quality and relegating low-quality females into same-sex pairs.  Sexual selection by males in a monomorphic, non-ornamented species is rare and suggests that reconsideration is needed of the circumstances in which alternative reproductive behaviour evolves.  Given the lack of males and obligate biparental care in this species, this research demonstrates how same-sex pairing was better than not breeding and highlights how it could be an adaptive strategy under certain demographic conditions.”

With thanks to Pacific Rim Conservation for information.

A Laysan Albatross flies over Kaena Point, photograph by Lindsay Young

Reference:

Young, L.C. & VanderWerf, E.A. 2013.  Adaptive value of same-sex pairing in Laysan albatross.  Proceedings of the Royal Society Biological Sciences  doi:10.1098/rspb.2013.2473.

John Cooper, ACAP Information Officer, 30 November 2013