Duck penis competition.

This is so going to trigger spam filters, but I don’t care. Science News has reported breaking news… that male ducks grow bigger penises when they’re around other males:

A drake’s penis substantially wastes away at the end of one breeding season and then regrows as the next season begins. Among lesser scaup and ruddy ducks, the regrowth varies in length or timing depending on whether males have to compete with a bunch of other guys, said Patricia Brennan of Yale University.

Her new measurements offer the first evidence in vertebrates that social circumstances influence penis growth, she reported July 29 at the annual meeting of the Animal Behavior Society.

In the competitive groups, a few big males grew prodigious organs as if dominating the group. Other males grew more moderate penises, which started wasting away weeks earlier than those of dominant males or males with no competition.

Thus, Brennan said, male ducks are “prudent.” In a crowd, a ho-hum male apparently doesn’t bother sustaining a big investment in tissue that’s not going to pay off.

Click the link for a photograph of “the corkscrew-shaped penis of a ruddy duck.”