Costa Rica crocodile with no mates made herself pregnant in world first

The first case of a ‘virgin birth’ in crocodiles has been recorded in Costa Rica, helping support the theory that dinosaurs could also self-reproduce.

The crocodile, an 18-year-old female, had spent 16 years alone in a reptile park before the remarkable egg was found in January 2018.

Virgin births have been recorded in a number of species, including birds and snakes.

Known scientifically as ‘facultative parthenogenesis’, the phenomenon occurs when a female egg cell develops into an embryo without being fertilised. In this case, it is thought to have resulted from the egg fusing with genetic material left over from when it formed.

Analysis by researchers from Virginia Polytechnic showed the foetus was more than 99.9% genetically identical to the mother, which would not have been possible in a two-parent scenario.

Writing in the Royal Society journal Biology Letters, the team said: ‘It is not uncommon for captive reptiles to lay clutches of eggs, [but] given the period of isolation from mates, these would normally be considered non-viable and discarded. 

‘These findings therefore suggest that eggs should be assessed for potential viability when males are absent.’

The team also noted that there may be many more such cases that have since gone unnoticed.

‘Given that [virgin births] can occur in the presence of potential mates, instances of this may be missed when reproduction occurs in females co-habited with males,’ they said.

While the egg did not hatch, having been born stillborn – not uncommon in virgin births – the findings have implications for our understanding of dinosaur evolution.

Crocodiles and birds both descended from ancient creatures known as archosaurs. In between, dinosaurs and pterosaurs also evolved from the same branch.

‘We now know that both the most recent and most ancient lineages within the archosaurs had the potential to reproduce parthenogenetically,’ said Warren Booth, a professor in evolutionary genetics at Virginia Polytechnic who led the research.

‘As such, we can strongly infer that the extinct members of the archosaurs – the dinosaurs and pterosaurs – could also reproduce parthenogenetically.’

Speaking to The Times, he added: ‘To quote Jurassic Park, “Life finds a way”.’

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