Caretakers at a Louisiana home for retired research chimps are puzzled by a strange turn of events: two female chimpanzees there have become pregnant recently, in spite of the fact that all of the male chimps there have had vasectomies. Nature finds a way.

The Strange Happenings at Chimp Haven (great title for a Nancy Drew book, by the way) began on Valentine's Day, when a worker at the facility noticed a 29-year-old female chimp carrying around what looked to be a stuffed animal but actually turned out to be an infant.

Caretakers were concerned that some errant sperm was making its way into the female chimps, and so they performed ultrasounds on every female chimp living there. A 49-year-old chimpanzee was also found to be With Baby Chimp.

As a result, sanctuary employees plan on putting all of the females on birth control, and re-sterilizing some of the males. Apparently chimps are especially difficult to sterilize, as severed sperm-carrying tubes in male chimpanzee genitalia often grow back.

LA chimpanzees get pregnant despite vasectomies [AP]