In most animal species, disputes between males over the right to mate with a female are usually settled with fisticuffs. This is also true of male fruit flies, who will put up their tiny dukes and throw down in the name of procreation. But a new study published in Current Biology singles out one weird exception among the fruit flies: a type of fruit fly that woos a mate through peace, not war.
Researchers led by Youcef Ouadah at the California Institute of Technology found that males of Drosophila santomea don’t fight at all. When placed together under conditions that normally spark some love-based fist fights, they instead court each other by putting on elaborate displays of physical beauty and prowess with some wing flaps and singing mating songs.
“All the conditions we’ve used to study aggression in other fruit fly species were the same, so we were expecting fighting, but these males behaved sexually toward one another,” Ouadah said in a recent Caltech article. “They courted one another all the livelong day, even though they were set up in the lab by us to fight.”
Visually, it looks like a confused mess. But through the data, the researchers found that these fruit flies can still distinguish males from females and reproduce normally despite the pack of flexing males attempting to demonstrate their virility through song and dance, the way human men used if mid-century Broadway musicals are to be believed.
These Fruit Flies Evolved a Strong Sexual Preference
D. santomea shares its habitat in the wild with related species of fruit fly. When the two interbreed, they produce sterile offspring. To avoid that genetic dead end, females evolved a strong preference for mates of their own species. The way they distinguish those males is through pheromones.
In response, male D. santomea reduced production of a specific pheromone that typically suppresses male-to-male courtship. Without it, same-sex behavior increases as a side effect of being able to distinguish potential mates between species. Avoiding the wrong partner reshaped how males interact with each other.
There’s also a much more practical issue of fighting being a waste of time and energy that can lead to injury or even death. Why risk dying for the slight chance of having sex when you can just flutter your wings and sing a beautiful song and live to flutter and sing another day? It’s like American Idol if the prize at the end were a chance to procreate.
The researchers found similar behavior in another distant species, suggesting this strategy evolved independently more than once.
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