An 11-year-old reticulated python named Thelma produced six female offspring in June 2012 at the Louisville Zoo in Kentucky, where she lives with another female python, Louise. No male had ever slithered anywhere near the 200-pound (91-kilogram), 20-foot-long (6 meters) mother snake.
New DNA evidence, published in July in the Biological Journal of the Linnean Society, revealed that Thelma is the sole parent, said Bill McMahan, the zoo's curator of ectotherms, or cold-blooded animals. (Read: "'Virgin Birth' Seen in Wild Snakes, Even When Males Are Available.")
"We didn't know what we were seeing. We had attributed it to stored sperm," he said. "I guess sometimes truth is stranger than fiction."
Virgin births have been observed in other reptiles before, including other pythons and snake species, said James Hanken, a professor of herpetology at Harvard University in Cambridge, Massachusetts.
Fatherless reproduction in animals that normally require two parents is called parthenogenesis.
This phenomenon occurs when polar bodies, or cells produced with an animal's egg that normally die or disappear, behave like sperm and fuse with the egg.
Via NG