Marine biologists will agree that the following story also happened to our tilapias and bangus - Studies show that in seeking mates, fish switch sex. Exactly how the female fish pull off their sex-changing stunt is not clear, though researchers say it's a natural phenomenon not connected to pollution or other man-made factors.In a 2006 University of New Hampshire lab study, female fish kept in coed tanks for nine months remained female. But in a group of female-only tanks, six out of 24 females switched sides... (...read more about this HERE)
Here is a list of animals displaying homosexual behavior. You can read this in Wikipedia with enormous bibliography of references. Read it HERE
Homosexuality is quite common in the animal kingdom, especially among herding animals. Many animals solve conflicts by practicing same gender sex.
From the middle of October until next summer the Norwegian Natural History Museum of the University of Oslo will host the first exhibition that focuses on homosexuality in the animal kingdom.
"One fundamental premise in social debates has been that homosexuality is unnatural. This premise is wrong. Homosexuality is both common and highly essential in the lives of a number of species," explains Petter Boeckman, who is the academic advisor for the "Against Nature's Order?" exhibition.
The most well-known homosexual animal is the dwarf chimpanzee, one of humanity's closes relatives. The entire species is bisexual. Sex plays an conspicuous role in all their activities and takes the focus away from violence, which is the most typical method of solving conflicts among primates and many other animals.
"Sex among dwarf chimpanzees is in fact the business of the whole family, and the cute little ones often lend a helping hand when they engage in oral sex with each other."
Lions are also homosexual. Male lions often band together with their brothers to lead the pride. To ensure loyalty, they strengthen the bonds by often having sex with each other.
Homosexuality is also quite common among dolphins and killer whales. The pairing of males and females is fleeting, while between males, a pair can stay together for years. Homosexual sex between different species is not unusual either. Meetings between different dolphin species can be quite violent, but the tension is often broken by a "sex orgy".
Homosexuality is a social phenomenon and is most widespread among animals with a complex herd life.
Among the apes it is the females that create the continuity within the group. The social network is maintained not only by sharing food and the child rearing, but also by having sex. Among many of the female apes the sex organs swell up. So they rub their abdomens against each other," explains Petter Bockman and points out that animals have sex because they have the desire to, just like we humans.
Homosexual behaviour has been observed in 1,500 animal species
"We're talking about everything from mammals to crabs and worms. The actual number is of course much higher. Among some animals homosexual behaviour is rare, some having sex with the same gender only a part of their life, while other animals, such as the dwarf chimpanzee, homosexuality is practiced throughout their lives."
Animals that live a completely homosexual life can also be found. This occurs especially among birds that will pair with one partner for life, which is the case with geese and ducks. Four to five percent of the couples are homosexual. Single females will lay eggs in a homosexual pair's nest. It has been observced that the homosexual couple are often better at raising the young than heterosexual couples.
When you see a colony of black-headed gulls, you can be sure that almost every tenth pair is lesbian. The females have no problems with being impregnated, although, according to Petter Boeckman they cannot be defined as bisexual.
"If a female has sex with a male one time, but thousands of times with another female, is she bisexual or homosexual? This is the same way to have children is not unknown among homosexual people."
Indeed, there is a number of animals in which homosexual behaviour has never been observed, such as many insects, passerine birds and small mammals.
"To turn the approach on its head: No species has been found in which homosexual behaviour has not been shown to exist, with the exception of species that never have sex at all, such as sea urchins and aphis. Moreover, a part of the animal kingdom is hermaphroditic, truly bisexual. For them, homosexuality is not an issue."
Petter Bockman regrets that there is too little research about homosexuality among animals.
"The theme has long been taboo. The problem is that researchers have not seen for themselves that the phenomenon exists or they have been confused when observing homosexual behaviour or that they are fearful of being ridiculed by their colleagues. Many therefore overlook the abundance of material that is found. Many researchers have described homosexuality as something altogether different from sex. They must realise that animals can have sex with who they will, when they will and without consideration to a researcher's ethical principles."
One example of overlooking behaviour noted by Petter Bockman is a description of mating among giraffes, when nine out of ten pairings occur between males.
"Every male that sniffed a female was reported as sex, while anal intercourse with orgasm between males was only "revolving around" dominance, competition or greetings.
Masturbation is common in the animal kingdom
"Masturbation is the simplest method of self pleasure. We have a Darwinist mentality that all animals only have sex to procreate. But there are plenty of animals who will masturbate when they have nothing better to do. Masturbation has been observed among primates, deer, killer whales and penguins, and we're talking about both males and females. They rub themselves against stones and roots. Orangutans are especially inventive. They make dildos of wood and bark," says Petter Boeckman of the Norwegian Natural History Museum.