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Species native to the United Kingdom
Introduced or alien species
Alien species that present a threat to wildlife

Marsh Frog - Pelophylax (formerly Rana) ridibunda - Alien


Tailless Amphibian - warty and granular skin

Largest European frog.

A very aquatic frog, often difficult to locate, as they will dive into water at the slightest disturbance.

Similar in general appearance to the other introduced water frogs in the UK, the pool frog and edible frog.

Dorsal surface green occasionally with dark spots. May have a faint vertebral stripe more typical of the pool and edible frog

Distinguishable from other water frogs by larger size, males have prominent vocal sacs at side of mouth, which appear grey as opposed to the whitish appearance in the other two species.

The three introduced species of water frog may be difficult to positively identify without capture, the marsh frog has a proportionally longer heal to the hind leg, which when extended along the body reaches the tip of the snout.

Females, up-to 13cm, males smaller and slimmer.

UK Distribution

First introduced to Walland Marsh, Kent in 1935, this frog is now found in several areas of Kent and East Sussex. Other introductions exist, including colonies in Southwest and West London.


Exotic - The marsh frog has been deliberately introduced to the UK. It is by far the most successful introduction, thought to occupy an ecological niche; they choose breeding sites such as dykes and ditches not generally chosen by our native amphibians. However, the marsh frog is a voracious predator and further spread of this species in the UK is inadvisable due to unknown impact on native herpetofauna, and illegal under the Wildlife and Countryside Act 1981.

Marsh Frog
© Lee Alan Fairclough/ONEWILDWORLD LTD 2003

Marsh frog, showing usual lack of vertebral stripe and skin that is granular and warty.

Marsh Frog calling
© Lee Alan Fairclough/ONEWILDWORLD LTD 2003

Male marsh frog croaking, note the grey appearance of the inflated vocal sacs, a useful aid to identification of this species.

Release of exotic species into the wild is a criminal offence under the Wildlife and Countryside Act 1981.

This includes introduction of exotic or alien species that may already have become established.

The interpretation of "wild" in the act includes private gardens from which escape is possible.

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