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  • 16 August 2005
  • Research into frog’s croak aids native species comeback

    Return of the native: northern pool frog (Image courtesy of Jim Foster/English Nature)

    Return of the native: northern pool frog (Image courtesy of Jim Foster/English Nature)

    Ten years of painstaking research by academics at the University of Sussex have helped bring about the reintroduction of a long-lost native species of frog to England.

    The decade of detective work helped identify the northern pool frog (Rana lessonae) as a native English species, linked to colonies in Scandinavia by genetic evidence - and a distinct Norfolk accent.

    The team - molecular ecologist Professor Trevor Beebee and postgraduate research students Inga Zeisset and Julia Wycherley - are part of the Pool Frog Species Action Plan, led by English Nature and The Herpetological Conservation Trust, which has just reintroduced 75 northern pool frogs from Sweden into the wild at a secret location near Thetford, Norfolk. It is hoped that these 75 frogs will mark the return of a lost native species in England.

    The Swedish frogs were used to start the new English colony after researchers clinched a genetic link between the northern pool frog population in Norfolk, which died out in the 1990s, with present-day colonies in Sweden and Norway. The research also showed that the Norfolk population was indeed the last of a native variety of frog, and not a "foreign import", as had been previously thought. It was also found to be part of a wider family or 'clade' of northern pool frog, which includes Scandinavian frogs.

    Professor Trevor Beebee's team analysed the genetic make-up of Scandinavian and Norfolk frogs and examined and compared the frogs' mating calls, which identified a "regional calling accent" that was distinct to the northern clade. This work provided crucial evidence supporting the frogs' historic native status in Britain, thus justifying the reintroduction to Norfolk, from Sweden.

    Julia Wycherley recording the frog mating calls

    Julia Wycherley recording the frog mating calls

    Dr Julia Wycherley, who carried out the bioacoustics research into the mating calls, says: "It was fascinating to detect subtle differences in the mating calls as I sampled pool frog populations across Europe. Those of Norfolk and Scandinavia generally had a lower frequency (pitch) and this in turn gave the calls a unique 'accent'."

    Professor Beebee, who is an authority on the molecular ecology and conservation biology of amphibians, and who has been involved in the project since its inception a decade ago, says: "Britain has very few native amphibians, indeed only six discounting the pool frog. By showing that pool frogs were recent inhabitants of this country we helped pave the way for the reintroduction, which if it works will increase our British amphibian diversity significantly."


    Notes for editors 

    • Research by Professor Beebee and his team and others involved in the pool frog project is published in Beebee T, Buckley J, Evans I, Foster J, Gent A, Gleed-Owen C, Kelly G, Rowe G, Snell C, Wycherley J, Zeisset I (2005) Neglected native or undesirable alien? Resolution of a conservation dilemma concerning the pool frog Rana lessonae, Biodiversity and Conservation, 14 (7): 1607-1626
    • For images, interviews and further information, please contact the Press Office. Press Office contact: Maggie Clune, tel: 01273 678 888 or email
    • The Pool Frog Species Action Plan involves English Nature, The Herpetological Conservation Trust, Anglian Water, University of Greenwich, University of Sussex, DICE - University of Kent, Forestry Commission. For further information, see English Nature:


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