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Penguins Revive Debate of Homosexuality in Animals |
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By Julio Godoy*
At a German zoo, six endangered Humboldt penguins prefer mates of the same sex. Scientists debate whether this behavior has biological or social origins -- or both.
PARIS - At a German zoo, the behavior of six penguins that formed same-sex couples has revived the incipient scientific debate about the origins of homosexuality in the animal kingdom. Biological or social?
When Heike Kuek, director of the zoo in Bremerhaven, in northern Germany, decided in late January to bring in female Humboldt penguins (Spheniscus humboldti) from a Swedish zoo, her intentions were -- biologically speaking -- understandable.
The Humboldt penguin is an endangered species. Today there are just 20,000 of these birds left, and most live along the Pacific coast of Chile and Peru. At the Bremerhaven zoo are 14 of them -- 10 males and four females -- as part of a European program to ensure protection of the species.
In theory, in a protected environment, the penguins should reproduce and multiply.
But the arithmetic of procreation occasionally runs into a twist: the 14 penguins formed seven pairs with the four females mating with four males and reproducing just once. The remaining six males formed three homosexual pairs, which in their fruitless attempts to produce offspring have attempted to incubate rocks that they have confused for eggs.
So Kuek decided to import four females, which were charged with attracting the males who had formed same-sex couples.
But the effort came too late. The Bremerhaven males ignored the female penguins from Sweden, and continued their homosexual behaviors.
Studies of the birds' sexuality suggest that the formation of a pair occurs many months before the end of the natural incubation period, in this case, at the end of the northern hemisphere winter.
''The relationship between our penguin pairs is very deep. Now we have to wait until the beginning of 2006 to see if they will form heterosexual couples,'' Kuek said in a conversation with Tierramérica.
Kuek's effort triggered a strong reaction from gay and lesbian groups around the world. From Austria to Australia, homosexual activists condemned what they considered illegitimate intervention in the sexual freedom of animals.
Beyond the protests, the experience could reinforce the biological thesis which suggests that homosexuality among animals is not a circumstance derived from the relative number of members of the opposite sex.
According to a study of sheep at the University of Oregon's school of medicine, in the U.S. northwest, animal sexuality could be determined -- among other variables -- by a network of nerves located in the hypothalamus (a region of the brain responsible for the production of several hormones), which conditions sexual behavior.
In the study published in 2004, physiologist Charles Roselli and his team said they discovered groups of brain cells that were different amongst the sheep and that showed a strong correlation with their sexual preference. Roselli dubbed this knot of nerve cells ''ovine sexually dimorphic nucleus, oSDN.
The team examined 27 adult sheep, four years old and of different breeds, raised on an agricultural research station in the northwestern state of Idaho. The sample included eight males who manifested heterosexual behavior, nine with homosexual behavior and 10 females.
The research determined that the oSDN of the males who preferred females was considerably larger and contained many more neurons than in the other 19 sheep.
''Ours and other similar studies strongly suggest that the sexual preference among animals is biologically determined,'' Roselli told a press conference. When he presented the report the physiology and pharmacology professor added, ''This possibility is also valid for humans.''
If that is true, the Bremerhaven penguins are homosexual, and even though the females brought in from Sweden show all their charm, their efforts will be futile.
However, research of other species implies that homosexuality could be a sort of survival strategy, determined by social factors.
A study of Japanese macaque females, who are bisexual and particularly promiscuous, illustrates this argument. The monkeys showed occasional homosexual preferences, but nevertheless make every effort to excite the males, while also competing with them for the sexual favors of other females.
According to Paul Vasey, psychology and neuroscience professor at the University of Lethbridge, in Canada, this behavior occurs especially when the females are faced with defenseless males.
The bisexual behavior of the macaque females is a strategy intended to excite the sexually inactive males, Vasey told Tierramérica.
He explained that during his research, published in 2002 in the Archives of Sexual Behavior, he manipulated the numeric relation of females with respect to male macaques in order to analyze the females' sexual preferences in function of the availability of potential mates of the opposite sex.
''I found that when the number of males is reduced, the homosexual behavior of the females increases,'' said the scientist.
According to Vasey, captivity -- like the case of the Humboldt penguins of Bremerhaven -- does not explain homosexual behavior. ''The evidence available to us suggests that the animals that show homosexual behavior in captivity also do so in the wild.''
There are numerous examples of homosexuality among animals. At the Central Park Zoo in New York City, two male penguins of the species Pygoscelis Antarctica, Roy and Silo, have been a couple for the past seven years, showing what experts refer to as the ecstatic sexual behavior typical to the species.
When the Central Park Zoo tried something similar to the experiment at Bremerhaven -- introducing female penguins in the same area as Roy and Silo in an attempt to change their sexual behavior -- the two males ignored them.
Like their ''cousins'' in Germany, Roy and Silo tried to incubate rocks in their nest. When the zoo provided them with an egg, they incubated it and hatched a female named Tango. Roy and Silo acted as perfect parents, taking care of Tango as if she were truly their offspring.
Based on these experiences, scientists believe that a more comprehensive theory of sexual selection among animals is needed, and should take into account social as well as biological aspects.
* Julio Godoy is an IPS correspondent.
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