GIRL power has reached a new level, in the animal kingdom at least. When it comes to demanding quality sperm, female birds can force males to compete not just against other males, but against themselves.
It is now widely acknowledged that females of certain species expel inferior sperm in favour of seed from a more promising mate. But researchers have discovered that female kittiwakes in monogamous relationships eject earlier deposits of semen from their partner in the hope he will produce fresher, newer stuff.
Richard Wagner at the Konrad Lorenz Institute in Vienna and his colleagues observed 634 copulations between 188 pairs of black-legged kittiwakes, Rissa tridactyla. Then they recorded whether a female ejected her mate's semen shortly after.
They found that post-copulatory sperm ejection - in which the semen is violently expelled - declined steeply about 16 days before the first egg of a clutch was laid. This suggests ...
To continue reading this article, subscribe to receive access to all of newscientist.com, including 20 years of archive content.