Mice on Tainted Site Deformed

Something strange is happening to rodents at a wildlife refuge where thousands of birds were poisoned by selenium years ago.

Both male and female reproductive organs were found in one-third of the 87 field mice, house mice, harvest mice and California voles trapped last year on land that once collected toxic runoff at the Kesterson National Wildlife Refuge. Just 3% of rodents trapped there showed such characteristics in 1995.

“The number of intersex mammals was a surprising finding to everybody,” said Michael Delamore, chief of the U.S. Bureau of Reclamation’s drainage program in Fresno. “We’re not sure what it means, because it’s new, and the phenomenon hasn’t been widely reported.”

Technically, the rodents seem to be pseudo-hermaphroditic, according to biologist Gary Santolo, who led the investigation. They appear to be males from the outside but have a fully developed set of female organs internally.