(Credit: Candice Davis, courtesy Missouri Department of Conservation) It’s been nearly a decade since this female yellow-bellied water snake came in contact with a male snake, but it hasn’t stopped her from starting a family. For the second time in as many summers, this snake at the Cape Girardeau Conservation Nature Center in Missouri managed to give birth sans a male counterpart. These so-called “virgin births” aren’t what you’d call miracles, but they are certainly quite rare to see in snakes.
In nature, a “virgin birth” is actually accomplished through a process of asexual reproduction called parthenogenesis. Basically, offspring grow and develop from unfertilized eggs. The process occurs with frequency in insects and microscopic animals called rotifers. However, it can also occur in some species of fish, amphibians, birds and reptiles. Most of the species that reproduce parthenogenetically can also reproduce sexually. When times are good and food and other resources are aplenty, parthenogenetic creatures will fly solo to reproduce rapidly and flood the market with their genes. But when food is scarce, or the environment changes, these same creatures will opt for sexual reproduction, which is slower and generates fewer organisms.
Snakes Flying Solo
Parthenogenesis in variety of snake species has been observed in the wild, so snake “virgin births” aren’t unheard of, but it was never documented in this particular species. For years, scientists believed "virgin births" in snakes weren't the result of parthenogenesis at all. It was thought that females actually produced offspring in the absence of a male because there was residual sperm stored in their bodies, which eventually met an egg. However, the Missouri snake has been isolated from males far too long for this theory to apply, says Jeff Biggler, a herpetologist at the Missouri Department of Conservation. "For many years, it was believed that such birth in captivity was due to sperm storage," Briggler explained. "However, genetics is proving a different story," Biggler said in a news release. So why would a sexually reproducing female snake suddenly have offspring? In the Missouri snake’s case, she may have started the process as a survival technique due to her isolation, the Washington Post reports. Two babies she gave birth to last summer are still alive today, but no snakes from this summer survived. Interestingly, scientists have learned that all of the offspring resulting from parthenogenetic births are male, due to the way reproductive cells divide during the process. Virgin births were once the stuff of myth and legend, but today the science behind this phenomenon is becoming clearer and it may be more common than we thought.