One of two Eurasian beavers - a species that became extinct in Britain 400 years ago and was only reintroduced to London earlier this year - has been found dead.
The pair were released at a country park in Enfield three months ago as part of a scheme to reintroduce them back into the UK.
They were the first to be introduced to the capital since the species became extinct in Britain in the 16th century.
The Eurasian beaver was once widespread across both Europe and Asia, but was hunted to near-extinction for both its fur and castoreum - sacks beavers use to mark territory - until at the turn of the 20th century only around 1,200 survived.
It has since been reintroduced to much of its former habitat and is now found in Spain, Central Europe, the UK and Scandinavia, as well as in parts of China and Mongolia.
Over the past decade the UK's beaver population has grown, with several hundred now roaming Scotland’s rivers and streams, and smaller groups dotted around England and Wales.
In March this year a male taken from Yorkshire and a female from Scotland were released into Forty Hall Farm, Enfield.
It was hoped the pair would mate, but on Friday the male was found dead.
A spokeswoman for Enfield Council: “We are saddened and sorry to confirm one of the two beavers at Forty Hall Farm has died. The results of a post mortem have confirmed that the male beaver died of natural causes."
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The spokeswoman said that the "stringent monitoring programme" was in place to observes the health of the animal within the enclosure to ensure they have adequate food and water supply, and to monitor topography and other environmental factors.
The hunt is now on for a replacement male to accompany the female.
Video footage of their habitat and observations by experts confirmed she is still safe and well, the council added.
The spokeswoman said: “The council continues to work with these partners to ensure the health and wellbeing of any beavers contained within the enclosure remain of the uppermost importance.
“It is our intention to find a suitable replacement beaver as soon as it is feasible. Enfield Council is in discussions in respect to another beaver release at the appropriate season.
“This will also give us time to make some adjustments to the enclosure to further enhance the conditions for the inhabitants.
“In the meantime, we will continue to monitor the remaining female beaver as closely as possible without disturbing her or the habitat.
“We can confirm that on-the-ground observations and video footage show she is safe and well and is settling in happily.”