Home Animals Yellow-bellied “virgin” water snake births fatherless babies

Yellow-bellied “virgin” water snake births fatherless babies

A watersnake in Missouri appears to have given birth to fatherless babies for the second time in two years. Researchers believe she is the first of her kind to do so.

green watersnake
"Mississippi Green Water Snake" by John Sullivan - Own work. Licensed under CC BY-SA 3.0

A watersnake in Missouri recently gave birth, a normal enough occurrence, except this snake hasn’t had contact with a male snake for eight years. The snake lives at the Cape Girardeau Conservation Nature Center, and researchers believe she may be the first snake of her kind to be observed giving virgin births.

The births don’t mark the first virgin births from the snake however. Last year she gave birth to two snakes, both of which managed to survive. This year, unfortunately, none of the birthed babies survived. The babies she had last year, however, are still alive and otherwise healthy.

The particular snake in question was a yellow-bellied watersnake. These heavy bodied snakes measure 30 to 48 inches in length and generally prefer quiet, swampy waters. These watersnakes tend to mate during the late spring and birth their live babies around August, so the virgin mother in question stuck to the general timeless, she just skipped the mating part.

These  watersnakes are often thought to be venomous, but are not.

While an alleged human virgin birth resulted in one man being crowned the son of God, virgin births are actually somewhat common in nature. Called parthenogenesis, such virgin births do not require male fertilization in order for an egg to develop. Parthenogenesis is rare among snakes, and is generally seen in insects, certain lizards and amphibians, and plants.

Researchers believe that since the snake is in her prime breeding age, but lacks access to a male, her body has reacted as part of a reproductive survival technique. Since the snake is still driven to reproduce, but cannot access a male, her body has changed to allow her to reproduce on her own.

The specific breed of watersnake gives birth to live snakes, rather than eggs. While virgin births are rare among snakes, they are not unheard of. Cottonmouths, Burmese pythons, and copperheads have all been observed giving virgin births. In 2014 a Burmese python laid 61 eggs and six of the eggs turned out to be fertile. At first her handlers assumed that she had used stored sperm, but genetic tests confirmed that the babies were virgin births.

Parthenogenesis works by fusing an egg with a polar body, which is essentially a byproduct of dividing cells that contains genetic material. More or less, the female creates her own sperm from her own genetic material and then uses it to impregnate herself. This is most likely what occurred with the watersnake, though some animals have been observed storing sperm for several years.

Besides reptiles, insects, and amphibians, virgin births are also occasionally seen among birds. No known case of natural virgin births among mammals have has ever been observed. From the point of view of evolution, virgin births are actually undesirable because the babies born will be near clones of their mothers. Evolution works by increasing genetic diversity, so virgin births and near clones are highly inefficient.

By combining the genetic material from two different organisms, traditional sex ensures genetic diversity. Genetic diversity, in turn, drives evolution with the strong passing on their genes and the weak dying off. For this reason, most organisms rely on two genders and the combination of an egg and sperm.

Still, if a mother is unable to obtain genetic material from a male, it could be advantageous to birth virgin babies. At the very least, the mother will give her own genetic material another shot at being spread on as it is possible that one of her virgin babies will eventually copulate with a male.

Besides virgin births, some species have also shown an ability to switch genders. For example, Anemonefish are all born as males, but if the dominant female of a group dies, the dominant male can then change over to a female. Parrotfish, on the other hand, can be born as male or female, but actually come equipped with both sex organs, and can change to the opposite sex if need be. Hawkfish, meanwhile, are able to switch genders back and forth. A hawkfish might be born a male, switch to female, then switch back to male.

Still, while virgin births are not necessarily uncommon among fish and other animals, they are very rare among snakes. Thus the recent birth of the yellow-bellied watersnakes marks a major occasion and refutes the long-held theory that said snakes were storing sperm.