Why the world's first crocodile 'virgin birth' might not be the last

The female croc had been living alone for 16 years but managed to get herself pregnant.

A female crocodile has become the first known case to get herself pregnant in what's called a "virgin birth".

But while it's "very impressive", it's not overly surprising, crocodile specialist Brandon Sideleau told Yahoo News Australia — and it could be the first of many more to come.

Virgin births, or parthenogenesis, are commonly seen in other animals including sharks, birds and snakes, but never before in crocodiles. So scientists were shocked to learn the croc produced a foetus that was 99.9 per cent genetically identical to herself — confirming it had no father.

large crocodile with mouth open.
A crocodile in Costa Rica has become the first known female to get herself pregnant. Source: Getty

"What people don't know is that crocodilians are actually archosaurs," Brandon said, describing a group of animals of which birds and crocodilians are the only living representatives. Dinosaurs were also archosaurs.

"So crocodilians are actually much more closely related to birds than any other living animal," he added.

Because of this Brandon said "it's not surprising that crocodilians are able to do this [if birds can]". "I'm sure it happens more often than we know of," he said.

croc eggs
Female crocodiles often lay eggs without a male, not never before have they been fertilised. Source: Getty

Self-reproduction is not a new phenomenon

In fact, the recent research published in the Royal Society journal Biology Letters suggests self-impregnating is an ancient trait and that dinosaurs may also have been capable of self-reproduction.

Female crocodiles, in the absence of males, sometimes build their nests and lay eggs on their own, but until now they have always been infertile. "The fact that they were fertilised is very impressive,' Brandon said.

The egg was laid by a female crocodile at a zoo in Costa Rica in 2018. She'd been living alone and without a male for 16 years. The foetus inside was fully formed but stillborn, and so did not hatch.

crocodile facts
Interesting crocodile facts. Source: Yahoo

Reason why crocs could continue to self-impregnate

So why now? Warren Booth, an associate professor at Virginia Tech who has studied the crocodile eggs explained to BBC animals may begin self-impregnating when their species brinks on extinction.

As the planet warms, "we are likely to see a greater female-to-male ratio of crocodilians", Brandon explained, suggesting it would very much change crocodilian, mating and breeding behaviour. This could possibly result in more situations like this one.

"In order for a crocodile to be born a male, it requires a very specific temperature. So if that temperature is not maintained, then the crocodile will be female — it won't develop male sexual organs," Brandon explained. "Whereas anything above or below that [temperature] will be female".

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