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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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