Beetles are among the more than 100 specials of insects that have been observed engaging in same-sex mating behavior, but researchers have never been able to figure out why. Was it a way to establish dominance or resolve conflict? Were these beetles just born that way?
Researchers at the University of East Anglia’s School of Biological Sciences have a theory: They’re just sloppy.
In a study published in Animal Behaviour, scientists bred six populations of red flour beetles and maintained them for 80 to 100 generations under either male-dominant or female-dominant groups. They found that when there were ample female partners available, male beetles mated indiscriminately, regardless of their partner’s sex.
But if there were fewer available females, the males were much more selective: They spent more time with a particular female and same-sex behavior was much less commonly observed.
Same-sex mating behaviour amongst male insects is much more likely to be due to incompetence than sexual preference, male-male competition or evolutionary motivation @ueaceec @biouea @EnvEast. Find our open access paper here https://t.co/ryb7KJSRjw #matechoice #sexualselection pic.twitter.com/JwPq3W3hj5
— kris sales (@KrisSales1992) May 10, 2018
That doesn’t necessarily explain why homosexuality exists in hundreds of other species, though.
“These results cannot be generalized to explain the behaviors of animals with more complex cognitive function and social structures like birds and mammals, which are likely to have very different reasons for same-sex mating,” researcher Kris Sales told The Telegraph.
In birds and mammals, homosexual behavior has been shown to have evolutionary benefits including maintaining allegiances, and providing “practice” for young adults. But those benefits don’t seem to apply in the insect world, where homosexual mating expends time and energy, boosts the risk of injury, disease, and predation, and doesn’t end in offspring. In an earlier study, those factors shortened the lives of heterosexually active males by an average of 25%.
Instead, the same-sex hookups appear to be accidental.
“Insects and spiders mate quick and dirty,” says Dr. Inon Scharf of Tel Aviv University’s Department of Zoology. “The cost of taking the time to identify the gender of mates or the cost of hesitation appears to be greater than the cost of making some mistakes.”