Lesbian albatrosses, boy-on-boy bat bugs...

http://www.theregister.co.uk/2009/06/17/animal_research/

Lesbian albatrosses, boy-on-boy bat bugs...

Posted in Biology, 17th June 2009 10:31 GMT

Researchers have concluded that homosexual behaviour among animals is so impressively rife that it can "reshape their social dynamics and even change their DNA" - something which could have "evolutionary consequences" for species indulging in same-sex shenanigans.

Nathan Bailey and Marlene Zuk of the University of California write in the journal Trends in Ecology & Evolution: “The variety and ubiquity of same-sex sexual behaviour in animals is impressive - many thousands of instances of same-sex courtship, pair bonding and copulation have been observed in a wide range of species, including mammals, birds, reptiles,
amphibians, insects, molluscs and nematodes."

The pair attribute this behaviour to a number of factors. In the case of boy-on-boy fruit flies, it's simply because the chaps "are lacking a gene that enables them to discriminate between the sexes", according to Bailey.

Bailey continued: “But that is different from male bottlenose dolphins, who engage in same-sex interactions to facilitate group bonding, or female Laysan albatrosses that can remain pair-bonded for life and co-operatively rear young.”

Indeed, studies have shown that "a third of chick-raising pairs of Laysan albatrosses were found to be all female in one Hawaiian colony", as the Times puts it. They don't raise as many young as heterosexual couples, but girls who "shared parenting did much better than solitary
females". Bottlenose dolphin homosexuality, on the other hand, may appear to offer no practical advantage to the survival of the species, but "male-on-male mounting and genital contact appear to strengthen alliances and provide practice for later opposite-sex encounters".

For the dolphins, "around half of male sexual encounters are with other males". The bearded vulture, meanwhile, is not quite as promiscuous but a study demonstrated "as many as a quarter of mountings were male-to-male".*

Other species indulging in unnatural** sexual liaisons are bonobos (formerly called "pygmy chimpanzees"), who get their rocks off with "same-sex genital rubbing and even oral sex", while male bat bugs "pierce the bodies of other males with their penises and ejaculate into their blood, just as they do to females".

The upshot of all this is that gay animal behaviour may be an evolutionary driving force. Bailey elaborated: “Same-sex behaviour can have evolutionary consequences that are beginning to be considered. For example, male-male copulations in locusts can be costly for the mounted male, and this cost may increase selection pressure for males’ tendency to release a chemical which dissuades other males from mounting them."

The researchers conclude by warning that we shouldn't necessarily apply human sexual orientation labels to animals, despite the apparent behavioural similarities. They note: “It is impossible to know what animals ‘desire’; we can only observe what they do."