The female diamond-backed rattlesnake can store sperm for five years (Image: Chris Johns/NGS)

FAMILY planning campaigners looking for a mascot should consider the eastern diamond-backed rattlesnake. A female of the species can store sperm in her body for at least five years before using it.

The rattlesnake (Crotalus adamanteus) in question was collected in Florida in 2005 and kept in a private collection for five years, with no contact with other snakes. In late 2010, she unexpectedly gave birth to 19 snakelets. To find out what had happened, Warren Booth of North Carolina State University in Raleigh took samples of DNA from the mother and her young.

Booth studies “virgin birth“, in which a female produces young without any contribution from a male. But in this case the snakelets carried genes that their mother didn’t, so she must have mated before she was captured and stored the sperm (Biological Journal of the Linnean Society, DOI: 10.1111/j.1095-8312.2011.01782.x).

Previous studies have hinted that reptiles can store sperm for several years, but this is the first case confirmed by genetics. Booth suspects other reptiles can store sperm even longer. “How long is anyone’s guess,” he says.

It’s becoming clear that snakes have unconventional ways of reproducing, including virgin birth and long-term sperm storage, says William Holt of the Institute of Zoology in London, though so far no one knows how they do it.