Virgin Birth in Wild Snakes

Snakes have been found to reproduce asexually in the wild, with somewhat surprising frequency. (Photo by joshgray on Flickr.)

Immaculate conception? It turns out that some snakes, sharks, birds, and lizards can have virgin births without a miracle involved. — Click to Tweet.

These births have been recorded occasionally since the early-to-mid 90s, but the earliest occurrences were in captive species. We’d assumed for several years since then that “virgin births” — also called parthenogenesis — were a last-ditch evolutionary tactic for a species to continue its genes.

Scientists were under the impression that parthenogenesis only occurred in these isolated situations, when animals had no other viable options for potential mates.

Wild Parthenogenesis
But a number of virgin birth have now been recorded in the wild, even when perfectly good males were around to produce offspring.

Warren Booth is a biologist at the University of Tulsa who is investigating why and how often these virgin births occur in the wild. His team is responsible for the first discovery, which was published recently in the journal Biology Letters.

In his study, he captured pregnant copperhead and cottonmouth snakes, which he then kept until they’d given birth. Afterward, he analyzed their DNA for signs that they weren’t conceived in a normal fashion, with a male involved. The signs are 100 percent accurate and fairly easily found, as parthenogenesis is, in many ways, an extreme form of inbreeding.

It’s not certain whether snakes born of parthenogenesis can have successful reproductive lives themselves or not. (Photo by Sophro on Flickr.)

What surprised his team most was that the rates of parthenogenesis are so high in wild snakes. Out of 22 copperheads, he found 1 that had a virgin birth, and in 1 out of 37 cottonmouths he found the same thing. And this is just his first sample.

What Causes It?
There’s really no word yet as to whether it’s a choice that the mother makes, or perhaps if it’s caused by some bacteria or virus. Any comment that offers an answer is mere speculation.

One interesting find, though, is that every virgin birth recorded thus far has been male. There have been no females whatsoever. It’s not certain whether these males can be “viable,” which means that they can survive to reproduce themselves. The males that we’ve seen in captivity haven’t been able to do so, but that’s not a guarantee that it doesn’t happen sometimes.

Can it Happen in Mammals?
It’s thought that mammals aren’t capable of parthenogenesis because their reproduction requires certain types of genes from each parent. So there’s no worries there.

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