Endangered reptiles rescued from Mauritian islands that were contaminated by a devastating oil spill have bred successfully in captivity for the first time, raising hopes that populations can be restored to the wild.

Bojer’s skink – a small, shiny reptile only found on tiny islets off Mauritius – has been bred by Durrell Wildlife Conservation Trust scientists at Jersey zoo. Two other imperilled species, the lesser night gecko and Bouton’s skink, have also been brought to the zoo, with the geckos breeding successfully as well.

The islands and reefs off Mauritius were contaminated by a Japanese carrier, MV Wakashio, which ran aground last July and spilled 1,000 tonnes of heavy fuel oil into the sea.

The accident threatened species that were once found across Mauritius – where the dodo once lived – but now only survive on islets.

People in white protective overalls and rubber boots working with tools and containers on a heavily polluted beach
Leaked oil from the MV Wakashio being collected in August 2020. Photograph: Daren Mauree/L’Express Maurice/AFP/Getty Images

The lesser night gecko was believed to be extinct after disappearing from the main island until it was discovered on these islands in recent decades. The small populations of these geckos and the Bojer’s and Bouton’s skinks are acutely vulnerable to extreme weather and accidents caused by humans, such as fires.

Durrell, which has worked with Mauritian conservationists for many years to save Mauritian species, scrambled to rescue the reptiles in the midst of the pandemic. Conservationists had to wear gas masks because the oil was so toxic, and on several islets they had just an hour to collect what they could find.

The pandemic meant there were no means of looking after the animals on Mauritius, so Dr Nik Cole of Durrell and the Mauritian Wildlife Foundation kept the 66 rescued reptiles in his spare room until an air transfer to Jersey could be arranged.

A man looking at a tiny lizard that he is holding in his fingers
Herpetologist Dr Nik Cole holding a Bojer’s skink. Photograph: Courtesy of Mauritian Wildlife Foundation

Because there were no scheduled flights during Covid, Durrell turned to one of its supporters who was willing to loan a private jet, offsetting its carbon emissions via its Rewild Carbon scheme to restore Atlantic rainforests.

All the animals reached the zoo safely, and this spring the 30 Bojer’s skinks have produced 52 juveniles, with 30 lesser night geckos producing 26 offspring so far. The six Bouton’s skinks have not yet laid fertile eggs but Durrell’s herpetologists aim to produce an “ark” population of 180 of each species to preserve the genetic diversity of the rescued animals.

Matt Goetz, head of herpetology at Durrell, said that while some reptiles had survived on undamaged northern islands, the oil spill could drastically reduce the genetic diversity of wild populations. “We rescued the genes, not the species,” he said. “We rescued these animals to keep their unique genes alive to be able to feed them back into the ecosystem in Mauritius for long-term adaptability. If some particular genes were wiped out, the long-term robustness of the species around the islands would have disappeared.”

Durrell is now devising a digital stud book for the reptiles to ensure it pairs the right individuals to retain all the genetic diversity present in the rescued species.

Goetz said they wanted to return animals to the islands “as soon as possible” but warned that it could take anything from two years to two decades before the oil damage disappears. The visible impact of oil spills vanishes quickly but residues move through the food chain from plants to invertebrates to larger animals. Little research has been done into the effects of oil spills on terrestrial reptiles but other studies have found oil residues affect animals’ nervous and reproductive systems.

“The whole ecosystem needs to be working again before we can put the reptiles back,” said Goetz. “The reptiles are really important for the food chain. They keep everything ticking – they eat tiny invertebrates and make that energy available for larger animals, be it snakes or birds.”

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