If you haven’t heard about the corkscrew kookiness that is duck genitalia by now, you need to check that stuff out ASAP.
Ducks’ twisting vaginas and telescoping penises are well-known part of an evolutionary arms race between the sexes that’s been going on for millennia, with each side trying to exert control over which males’ sperm fertilize the female’s eggs—a battle that, especially in birds, is fierce, occasionally violent, and weird as all-get-out. The most recently discovered example of what biologists deem “sexual conflict,” a little behavior hens have developed called sperm ejection, upholds that fine tradition.
Hens, like many female birds, don’t always have a lot of control over who mates with them. Roosters tend to resort to “sexual coercion,” aka rape, and so a female might have any number of sexual partners that she didn’t get to choose. What’s a hen to do? Well, according to a new study in The American Naturalist, evolve a method for getting rid of sperm from males she didn’t particularly like, thus making sure her offspring are of the best quality.
Scientists had already noticed that hens tended to squirt out semen after some acts of intercourse. To see if males low on the totem pole within the group had their sperm shown the door more frequently than high-caste males, the team monitored the sperm ejection of a group of hens, keeping track of which roosters they had mated with, when they ejected, and how much of the ejaculate was ejected. After tallying up the data, they found that low-status males were more likely to have their sperm ejected (and for a larger volume of it to be ejected) than were high-status males, confirming the idea that ejection is a weapon employed by hens to control the paternity of their offspring.
Ah, but what about the velocity of ejection? Does that indicate the vehemence of the hen’s rejection? Inquiring minds want to know.
Image courtesy of Atli Harðarson / flickr