Chickens eject sperm from males they don't fancy

Female domestic chickens generally mate with multiple males and are known to sometimes eject sperm following mating encounters.

It was unclear, however, whether the sperm ejection was a consequence of receiving a large amount of ejaculate, or because hens are actively trying to rid themselves of undesirable sperm.

A team led by Oxford researcher Rebecca Dean investigated the phenomenon in a group of feral chickens kept at Stockholm University in Sweden.

After controlling for ejaculate size and other factors, Dean and her colleagues found that hens ejected a larger proportion of inseminations by socially subordinate males.

"These results show that promiscuous females can actively bias sperm utilization to exert a strong and predictable influence on the struggle for fertilization," Dean said. By doing so, females "retain control of paternity even in species such as fowl where males can force mating."

More information: Rebecca Dean, Shinichi Nakagawa, and Tommaso Pizzari, "The Risk and Intensity of Sperm Ejection in Female Birds.", American Naturalist, September 2011.

Provided by University of Chicago