Why are Norfolk tadpoles being held hostage?
Amphibian and Reptile Conservation
Norfolk naturalists are keeping spawn and tadpoles in captivity in a bid to increase the population of the UK's rarest amphibian.
The pool frog became extinct in the UK in the 1990s but it was reintroduced to a site in Norfolk between 2005 and 2008 by Amphibian and Reptile Conservation (ARC).
Now the charity has carried out a ground-breaking scheme to increase the animal's population.
The 'head-starting' project sees spawn or young tadpoles raised in captivity and subsequently released into the wild. This allows a greater proportion to survive the riskiest part of their life-cycle away from predators or losses to other natural causes.
Spawn was collected from the original pool frog site in June 2019.
The resulting tadpoles were reared in laboratory conditions over the summer and released into ponds at Thompson Common, near Watton, the last-known refuge for pool frogs before their extinction and a site where previous experimental releases have shown promise.
Norfolk Wildlife Trust, which owns and manages Thompson Common, has created conditions for pool frogs by restoring ancient ponds. ARC hopes that the programme will succeed in building on the first reintroductions and increase the number of pool frogs living in the wild.
Jim Foster, ARC's conservation director, said: "This is a hugely exciting but painstaking project. In 2018 we had a record number of pool frogs recorded at the first reintroduction site, while successful breeding occurred at the second reintroduction site for the first time since extinction of the original native population."
John Milton, head of nature reserves at Norfolk Wildlife Trust, said: "I'm especially excited to see pool frogs returning to Thompson Common as I was lucky to witness the spectacular vocal display of the males calling there on one balmy evening in June in the 1980s, before the population was sadly lost.
"It could become one of the UK's natural wonders once again."
Pool frogs occur in different forms, and it is the northern clade pool frog that is native to the UK. Northern clade pool frogs are found only in highly restricted areas of Scandinavia, Estonia and England.
They are variable in colour, although the type reintroduced to the UK are predominantly brown with dark brown or black blotches over the back and a lighter, often yellow, dorsal stripe. Adult males develop bright green heads in the breeding season.