Laysan Albatrosses. Photo by James Lloyd
I first came across this story a few weeks ago at the 12th Pan-African Ornithological Congress outside of Cape Town in South Africa where Professor Peter Ryan of the University of Cape Town referred to it in a plenary speech. I note that it has received some early attention elsewhere but that there had been no real follow-up on the research or further material published about what appears to be an unusual breeding behaviour.
I didn’t manage to discuss this further with Peter while I was in South Africa but I’ve now been able to have a bit of a fiddle around on the web and tracked down the source of Peter’s information.
The Laysan Albatross has a large range across the northern Pacific Ocean that appears to be expanding. One consequence of this expansion is that, in the Laysan albatross at least, immigration to new breeding areas appears to be skewed on a gender basis in that the ratio of females to males at some colonies is substantially higher. At one of these newer colonies on Oahu in the Hawaiian islands the ratio is as high as 60:40 female to male.
The 23rd August 2008 edition of the Royal Society’s Biology Letters has a paper entitled Successful same-sex pairing in Laysan Albatrosses by Linda C. Young, Brenda J. Zaun and Eric A. VanderWerf that reports on research into aspects of the breeding biology of the Laysan Albatross on the Hawaiian island of Oahu.
I haven’t been able to locate a full copy of their paper but the abstract, in part, reads:
“Unrelated same-sex individuals pairing together and cooperating to raise offspring over many years is a rare occurrence in the animal kingdom. Cooperative breeding, in which animals help raise offspring that are not their own, is often attributed to kin selection when individuals are related, or altruism when individuals are unrelated. Here we document long-term pairing of unrelated female Laysan albatrosses (Phoebastria immutabilis) and show how cooperation may have arisen as a result of a skewed sex ratio in this species.
Thirty-one percent of laysan albatross pairs on Oahu were female-female, and the overall sex ration was 59% females as a result of female-biased immigration. Female-female pairs fledged fewer offspring that male-female pairs, but this was a better alternative than not breeding. In most female-female pairs that raised a chick in more than one year, at least one offspring was genetically related to each female, indicating that both females had opportunities to produce.”
Maybe I’m not reading this right or I’m missing something that may be better explained in the full text, but I’d like to know how it is that the offspring of “most female-female pairs” can be genetically related to each female.
I note the reference to “female-biased immigration” at what is apparently a relatively new colony and am curious as to the factors that might cause that bias. I’m also interested in how the skewed sex ratio at this colony (60:40 female/male) affects breeding biology and behaviour – obviously the chick-rearing behaviour discussed in this report is one aspect of this but I’d be particularly interested in how different pre- and post-copulation behaviour is at this colony from other, more established colonies, the identification of other drivers to same-sex pairings (other than the gender imbalance) and reasons behind the reported higher chick mortality in same-sex couples.
I’ll follow up this report with Peter Ryan in the near future but in the meantime I’d welcome your thoughts and comments on this note or your observations of similar breeding behaviour elsewhere in the avian or animal worlds.
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