Homosexual Behaviors in Other Animals

Homosexual Behaviors in Other Animals

Same-sex sexual or homosexual behaviors in other animals have been observed in about 1500 species. Of course, the basis of homosexuality remains complicated and controversial. Several researchers and writers who perceive homosexuality with positivity usually begin their discussions by implying that this sexual orientation is natural.

Nonetheless, science has directed its attention toward other animals to explore how homosexuality occurs in the greater natural environment. Bruce Bagemihl has been widely credited for uncovering sexual diversity in nature.

His 1999 review showed that homosexual behavior has been documented in about 500 animal species ranging from primates to gut worms. He further noted that the animal kingdom demonstrates sexual diversity—including homosexual, bisexual, and non-reproductive sex.

But neuroscientist Simon LeVay reminded that the existence of homosexual behavior in the animal kingdom remains rare considering that sexual behaviors leaning toward heterosexuality are significantly more frequent. Furthermore, Bagemihl also reminded that the observed homosexual behaviors in nature are often limited by human interpretations.

Using Homosexuality to Describe Non-Heterosexual Behaviors

The use of homosexuality to describe the sexual behaviors of animals other than humans is also confusing to a certain extent. According to Volker Sommer and Paul L. Vasey, unlike humans, other animals do not have sexual orientation and gender identities. Their sexual behaviors are driven by sex alone.

Some researchers have also argued that homosexual behaviors observed in animals are not primarily motivated by sex but a socio-sexual purpose. In other words, some animals might be engaging in homosexual behaviors not because they are sexually pleasurable but because they have adaptive social functions.

In her piece published in the magazine Scientific American Mind, science writer Emily V. Discroll discussed several studies that investigated homosexuality in the animal kingdom. These studies suggest that homosexual behaviors are a natural part of the overall sexual behavioral repertoire of a particular animal species.

Most of the time, animals that exhibited homosexual behaviors also exhibited heterosexual behaviors, thus making them bisexuals. In addition, some researchers believe that these observations are suggestive of the fact that bisexuality is a natural state among animal species, possibly including humans as well.

It is very important to take into account the aforementioned reminders. A study by Inon Scharf and Oliver Y. Martin involving 110 species of insects and arachnids revealed that apparent homosexual behaviors observed in active male species were a result of mere confusion.

The passive or receiving males trigger this misidentification whenever they release sex pheromones or carry female pheromones that were attached to them during prior mating activities with female species. Scharf and Martin noted that insects and arachnids mate quickly and this results in a greater predisposition toward misidentification. The cost to identify the gender of their mates or the cost of hesitations appears to be greater than the cost of making mistakes.

Observed True Homosexual Behaviors in Other Animals

True homosexual behaviors observed in a significant number of species, especially in social animals, are still worth considering. Discroll has summed up several critical reasons why animal species apart from humans demonstrate varying degrees of homosexual behaviors.

First, some animal species might engage in homosexual acts to diffuse social tensions or maintain order in a group. Bonobos, for example, have exhibited high levels of promiscuousness. They are sexually active and about half of these activities involve same-sex partners.

Some scientists believe that the frontally-placed clitoris of female bonobos has evolved to facilitate same-sex activities, particularly genital-genital rubbing. Male bonobos have been observed to mount, fondle, and perform oral sex on one another. Based on observations, these homosexual behaviors seem to ease social tension and promote social bonding. As mentioned, the more homosexuality, the more peaceful the species.

Some species of birds exhibit same-sex unions. Males tend to steal eggs from females and raise them with other males. Two male black swans, for example, are able to make better nests because they are bigger and stronger than male-female partnerships.

Oystercatchers exhibit polygamous partnerships because of intense competition for male mates. Some oystercatcher nests have two females and one male. To promote bonding between the two females, they perform mounting. This polygamous trio produces more offspring because the nests are better tended and protected from predators.

Homosexuality might be hardwired in several species. The study of wild fruit flies showed that males carrying a particular mutation are prewired for both heterosexual and homosexual behaviors, and either of these two is activated by external stimuli.

Homosexual Behaviors in Other Animals Due to Captivity Effect

Homosexuality in some species appears to be far more common in captivity than in wild. Accordingly, the captivity effect influences the emergence of homosexual behaviors because of the absence or lack of opposite-sex mates. This has been observed in penguins.

In addition, similar same-sex attraction might be a mechanism used to relieve stress as observed from koala bears. Take note that in domesticated cattle, homosexual behaviors in females signal sexual receptivity and in wild, they need not display this sexual readiness because they are free to roam and interact with males.

There is also a possibility that homosexual behaviors in human males are a result of being in similar environments that require the easing of sexual tension, relief from stress, or promotion of social bonding. However, this should never be accounted as the sole cause of homosexuality in humans because sexual orientation and human sexuality are both complex. In addition, other studies suggest that humans have a natural predisposition toward homosexuality because they too are also wired for bisexuality.

Different Degree of Homosexuality Between Humans and Other Animals

Exclusive homosexuality is somehow unique to the human species to a certain extent, except for the fact that sheep have also demonstrated similar sexual behaviors. In his book, Aldo Poiani mentioned that the uniqueness of human homosexuality centers on having unique mental faculties that are absent from other species.

Nonetheless, homosexuality across several species, including humans and social animals both in wild and in captivity, might be a result of interplays between several factors and predispositions. These factors might include social benefits, environmental function and genetic mechanism, and biological including psychological and neurological mechanisms, among others.

Current research on homosexuality in the animal kingdom remains young and complicated. According to a book chapter by Paul L. Vasey, homophobia has played a role in dissuading researchers from studying this subject. During the 1990s, homophobia repressed the scholarly careers and research agenda of researchers.

But apart from this, homosexual behaviors in the animal kingdom challenges prevailing understanding about animal behaviors. The lack of research on this subject may be due to the overall complications surrounding sexual behaviors.


  • Bagemihl, B. 1999. Biological Exuberance: Animal Homosexuality and Natural Diversity. MIT Press. ISBN-13: 978-0312253776
  • Discroll, E. V. 2008. “Bisexual Species: Unorthodox Sex in the Animal Kingdom.” Scientific American. Available online
  • Poiani, A. 2010. Animal Homosexuality: A Perspective. Cambridge University Press. ISBN-13: 978-0521145145
  • Scharf, I. and Martin, O. Y. 2013. “Same-Sex Sexual Behavior in Insects and Arachnids: Prevalence, Causes, and Consequences.” Behavioral Ecology and Sociobiology. 67(11): 1719-1730. DOI: 1007/s00265-013-1610-x
  • Sommer, V. and Vasey, P. L. 2006. “Introduction: Topic, Hypotheses, Research trajectories.” In Homosexual Behavior in Animals: An Evolutionary Perspective. Cambridge University Press. ISBN-13: 978-0521182300
  • Vasey, P. L. 2006. “Where Do We Go from Here? Research on the Evolution of Homosexual Behavior in Animals.” In eds. Sommer V. and Vasey, P. L., Homosexual Behavior in Animals: An Evolutionary Perspective. Cambridge University Press. ISBN-13: 978-0521182300