Reintroduction of northern clade pool frogs (Pelophylax lessonae) to the UK

Extensive research established, in the late 1990s, that the northern clade pool frog, otherwise only found in Norway and Sweden, was a native species in Britain prior to its extinction in 1995. In 2005 a reintroduction program was initiated which has resulted in the establishment of a breeding population of northern clade pool frogs from Sweden at a site in Norfolk. This population is closely monitored and research is being undertaken to ensure the continued success of this reintroduction.


The project carried out research into northern clade pool frog ecology in order to inform management practises at the reintroduction site. During this project we investigated the possible effect habitat matrix has on pool frog distribution across the reintroduction site, how pond use is influenced by chemo-physical parameters as well as grazing intensity at pond edges and finally how anthropogenic management affects pond utilisation by this species.

The research team comprised, Dr Inga Zeisset, Danielle Smith (MRes Ecology) and other members of the Pool Frog Expert Group: Amphibian and Reptile Conservation Trust, Natural England, Anglian Water, The Forestry Commission, Canterbury University, Greenwich University, The University of Sussex.

High grazing intensity at pond edges, high dissolved oxygen levels, higher water temperature and pond margin complexity were all identified as important factors positively affecting pond occupation during the breeding season. Also, recent anthropogenic management of ponds had a positive effect.

Altogether, this project has made an important contribution to our understanding of what constitutes suitable northern clade pool frog habitat in the UK and how management practises can be used to create more suitable habitat for this species.

Information gained from this project will be used to inform future management of this as well as future northern clade pool frog reintroduction sites.

Outputs from project

Smith, D. (2015): “a multivariate study investigating the habitat use and distribution of the northern clade pool frog (Pelophylax lessonae) at their reintroduction site in Norfolk, UK.” MRes Ecology thesis. University of Brighton.

Smith, D. , and I. Zeisset (in prep) “Assessing habitat use of northern pool frogs (Pelophylax lessonae) at a site restored for pool frog reintroduction in the UK”.

Previous relevant publications:

Zeisset, I. and T. J. C. Beebee (2007). "Two clades of north European pool frogs Rana lessonae identified by cytochrome b sequence analysis." Herpetological Journal 17(4): 255-260.

Beebee, T. J. C., J. Buckley, I. Evans, J. P. Foster, A. H. Gent, C. P. Gleed-Owen, G. Kelly, G. Rowe, C. Snell, J. T. Wycherley and I. Zeisset (2005). "Neglected native or undesirable alien? Resolution of a conservation dilemma concerning the pool frog Rana lessonae." Biodiversity and Conservation 14(7): 1607-1626.

Zeisset, I. and T. J. C. Beebee (2001). "Determination of biogeographical range: an application of molecular phylogeography to the European pool frog Rana lessonae." Proceedings of the Royal Society of London Series B-Biological Sciences 268(1470): 933-938.