The Laysan albatross (Diomedea immutablis) is known for its monogamous nature. The female and male birds mate with the same partner once a year for their whole lives. In 2008, however, biologist Lindsay C. Young discovered that their lifelong partners need not necessarily be of the opposite gender. She found that out of 125 Laysan albatross nests in Kaena Point, Hawaii, 31% were attended to by female-female couplings (Young, Zaun, and VanderWerf 323). The figure is “more than double the highest proportion of female-female pairing previously known in any animal,” making this a landmark case in the study of homosexual behaviour in animals (Ibid., 324).
These same-sex pairs of Laysan albatross do not copulate with one another–either female mates with a male, sometimes through “soliciting” for sex–but the female afterwards returns to lay its egg in a nest it shares with its female partner (“Can Animals Be Gay?”). There, the couple incubates their egg collaboratively, alternating in turns like a female-male couple. Sometimes, both females lay an egg, resulting in what is called “supernormal clutch,” when the Laysan albatross’s clutch size of 1 egg per nest is exceeded. In fact, this occurred to 44% of the female-female pairs Young studied (Young, Zaun, and VanderWerf 323). In such cases, the pair members incubate only one of the two eggs.
Young accounts for this phenomenon of same-sex pairings on the basis of the female-biased sex ratio at her study location. As a result of female-dominated migration, 59% of Laysan albatross at Kaena Point were female, resulting in a shortfall in mates for them (Ibid., 324). This spur towards homosexual behaviour due to a lack in one sex is sometimes called “the prisoner effect” (“Can Animals Be Gay?”). Two other biologists, Marlene Zuk and Nathan W. Bailey, build upon Young’s reasoning to assert that we can see animal homosexuality as an evolutionary by-product. Zuk and Bailey assert that the Laysan albatross’s behaviour represents an “alternative reproductive strateg[y],” where given the dearth of male mates, “the females were able to avoid complete loss of reproductive success by joining forces another female” (658). It remains to be seen if the reasoning behind such “adaptive” behaviour can equally apply to the male Laysan albatross, or to other animals too (659).
“Albatross Couple,” by Alex Wegmann. LiveScience. URL: http://www.livescience.com/php/multimedia/imagedisplay/img_display.php?s=animals&c=&l=on&pic=080527-albatross-couple-02.jpg&cap=Paired+female+Laysan+Albatrosses+grooming+each+other.+Credit%3A+Lindsay+Young.&title (accessed on 6 Apr 2010).
“Can Animals Be Gay?,” by Jon Mooallem. The New York Times, 29 Mar 2010. URL: http://www.nytimes.com/2010/04/04/magazine/04animals-t.html?hpw=&pagewanted=all (accessed on 6 Apr 2010).
“Same Sex Animals,” by Eric A. VanderWerf. LiveScience. URL: http://www.livescience.com/php/multimedia/imagedisplay/img_display.php?s=animals&c=rbritt-columnist-153×65&l=on&pic=090616-same-sex-animals-02.jpg&cap=This+photo+shows+a+female-female+pair+of+Laysan+Albatross.+Females+cooperatively+build+nests+and+rear+you (accessed on 6 Apr 2010).
Young, Lindsay C., Zaun, Brenda J., and VanderWerf, Eric A., 2008. Successful same-sex pairing in Laysan albatross. Biology Letters, 4(4): 323-5.
Zuk, Marlene and Bailey, Nathan W., 2008. Birds gone wild: same-sex parenting in albatross. Trends in Ecology and Evolution, 23(12): 658-60.