Head-starting, re-introduction and conservation management of the agile frog on Jersey, British Channel Isles

Summary

The agile frog (Rana dalmatina), Least Concern across Europe but Critically Endangered on Jersey, the only British Isles population, had been reduced to a single 10-hectare site by 1988 through habitat loss and predation, worsened by a 1987 pesticide spill that wiped out a second population and triggered the first conservation intervention. Since then, the Jersey Amphibian and Reptile Group, bringing together the States of Jersey Department of the Environment, Durrell Wildlife Conservation Trust and local stakeholders, has run a program of habitat management, in-situ spawn protection, and head-starting of collected spawn at a Durrell biosecure facility since 1986, achieving survival rates to metamorphosis far above the typical wild rate for anurans. Head-started tadpoles enabled reintroductions to Noirmont in 2000 following water-quality improvements, and to two further sites by 2012, bringing the total to four monitored locations, with both principal breeding sites designated ecological Sites of Special Interest with dedicated management plans. Annual night surveys recorded an increase from 12 spawn clumps at one site in 1987 to 134 clumps across three sites in 2014, alongside wild breeding recorded at three additional locations. Difficulties included identifying suitable, connected release sites on a densely developed island, differences between Jersey's coastal habitat use and mainland ecology, unpredictable recruitment tied to water levels, and resourcing head-starting effort; captive-breeding enclosures proved less cost-effective than head-starting collected wild spawn. The project rates itself successful, crediting intervention for averting total population loss, formal site protection, and rising population trends.