Same-sex attraction in non-human animals

Biased science communication can have detrimental consequences. For example, facts about animal reproduction have been twisted to justify discrimination against the LGBTQIA+ community. Some people call homosexuality a “Darwinian paradox”, because it does not fit their preconceived belief that an animal’s job is to stay alive and make babies. This belief ignores how some animals, like humans, have complex social structures and do things just for fun. Same-sex sexual behaviours (SSSB) have been observed in 1500 animal species, none of whom do it to make babies. This article describes some of these behaviours in birds, mammals, and invertebrates.

Same-sex sexual behaviour (SSSB) in birds

The first recorded example of SSSB in non-human animals comes from Aristotle about 2300 years ago. He wrote about male pigeons, partridges, and quails mating with other male conspecifics. Since then, same-sex relationships have been recorded in other bird species. Greylag geese form “gander pairs” of two males, whose behaviours resemble pairs of opposite-sex mates. In Oahu, Hawaii, female-female Laysan albatross pairs looked after 31% of nests between 2004 and 2007. These pairs, one of which is pictured in Figure 1, were equally good at raising chicks as male-female pairs. SSSB was also observed in unbonded king penguins, meaning penguins which had not committed to a mate for that breeding season. Using DNA to assess individual sex, 26.4% of courtship displays between unbonded king penguin couples were same-sex. There was also one male-male and one female-female pair of bonded king penguins, but both couples broke up and re-bonded with opposite-sex mates in the same season. The most famous same-sex bird couple is Roy and Silo from Central Park Zoo. They were a pair of chinstrap penguins who raised a chick named Tango when given a fertile egg. This family was the subject of a children’s book (Figure 2) and an American culture war. Thus, many bird species pair with individuals of the same sex in captivity and more importantly, in the wild.

SSSB in mammals

Humans are not the only mammals to mate with individuals of the same sex. Male bats from the Myotis genus have been observed getting intimate with each other, and Mytois lucifugus releases sperm during this activity. In another bat species called the Bonin flying fox, males groomed each other in a way scientists perceived as sexual. Japanese macaques have monogamous female-female pairs called consortships, in which females carry out the same mating behaviours seen with male-female pairs. 

SSSB in insects

In addition to birds and mammals, some insects conduct sexual activities to others of the same sex. In a 2012 study, 16% of male field crickets did courtship displays to and/or tried to mate with another male. The authors conducted experiments to rule out some leading Darwinian causes of SSSB, such as establishing dominance relationships (similar to an ‘alpha male’) or defusing hostile encounters. SSSB is well studied in flour beetles, where the males mount other males and release capsules of sperm like they would to females. In these beetles, the sexes are sexually dimorphic - distinguishable by appearance, smell, and/or sound - so a male beetle is intentionally choosing to mate with another male. When 59 male damselflies were offered a male and female in the same cage, 10 approached and began mating with the male. More damselflies chose the male over the female after spending a few days in a male-only population, perhaps because they were used to only having males to choose from. Therefore, analogies to both homoromantic and homosexual partnerships in humans exist in insects.

Conclusion

Since mammals, birds, insects, and molluscs all have evidence of SSSB in the wild, it is normal and certainly not unnatural for humans to do the same. These behaviours range from preferentially approaching the same sex to intentional, intimate actions. All the papers I used in this article are over a decade old, with the earliest evidence of non-human same-sex behaviour being 2300 years old. This means using biology to justify homophobia is very outdated, and factually incorrect.

Written by Simran Patel

REFERENCES

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