|Common name:||Marsh frog|
|Taxonomy:||Pelophylax ridibundus [Pallas, 1771].|
(Previously classified as Rana ridibunda).
Eurasian marsh frog
In 1935 the wife of E.P. Smith, MP for Ashford, wanted to surprise him with some edible French frogs to put in the garden. Unfortunately French frogs were unavailable so she bought some large Hungarian frogs instead. These promptly escaped from their garden in Stone-in-Oxney and spread across the ditches of the Marsh with great success: colonising the entire Romney Marsh area by the 1960s.
This is the largest European water frog, can measure up to 15cm, and generally has a warty appearance.
Although it can be found in all water bodies this powerful swimmer prefers lakes, rivers and streams.
The range of this introduced species is expanding. There is no solid evidence of deleterious effects on native amphibians. It is recorded in many counties occupying ponds, fishing lakes and streams.
It is possible to determine the main source of origin of marsh frogs as there is a subtle change in the frequency components of their calls as longitude changes from east to west.
The marsh frog is a robust, warty frog with a wide mouth and close-set eyes; long hind legs with heels extending beyond head; the metatarsal tubercle is small with a low profile.
It is variable in colouration but typically has a brown/grey dorsal surface with greenish tinge and green/olive on back with dark spots.
Thighs are striped/spotted greyish/white.
It has dark grey vocal sacs, unlike the Edible frog (light grey) or Pool frog (white).
The dominant colour can be bright green or (rarely) blue.
Females do not possess vocal sacs or develop metatarsal tubercles.
The Marsh frog can be mistaken for other water frogs (Pelophylax species); Edible frogs Pelophylax kl. esculentus and Pool frogs Pelophylax lessonae.
The Edible frog has a variably coloured dorsal stripe, narrower gape, light grey vocal sacs and its slightly shorter legs reach to between eyes and nares.
Pool frogs are much smaller, have short legs reaching only behind the eyes and the males have white vocal sacs.
Marsh frog males also develop a yellow facial colouration in the breeding season.
The Marsh frog can be found from Central and Eastern Europe and the Balkan peninsula to East and Central Asia. It is not as well adapted to cooler climes as the pool frog but as global climate warms, it may be able to extend its range.
Most northerly UK colonies known in 2007 are in Humberside.
Within Surrey, it is local but widespread. Main occurrence around Newdigate and River Mole tributaries, Gatwick and tributaries to River Mole, Wisley and River Wey.
These very aquatic animals prefer large, deep ponds, lakes and rivers and are tolerant of slight salinity as found in upper estuarine conditions. Requiring insolation they are usually found gregariously sunning on south-facing banks adjacent to the water body or on floating rafts of vegetation on the water body. On disturbance, they leap into the water with a characteristic ‘plop’.
Marsh frogs hibernate in water.
The Marsh frog is mostly diurnal but will often call throughout the night in breeding season.
Marsh frogs are opportunistic feeders and feed on seasonally abundant invertebrate species. Hunting is usually triggered by movement of the prey item; the feeding activities usually take place adjacent to the water body. Adult marsh frogs are the only water frog that can feed under water.
Although insects and molluscs make up the bulk of their food items, occasionally small birds and even mammals my also be eaten. There is evidence to suggest that infrequent canabalism occurs, with adults eating Marsh frog tadpoles or new metamorphs, when the feeding instincts are triggered by an appropriate sudden movement1.
Predation is mainly by species of heron (including the Bittern) and the Grass snake. Marsh frogs are extremely sensitive to movement and when predators are nearby will stop calling, flatten bodies to ground relying on camouflage, slip underwater or dive into the water from their sunning areas with a mighty leap.
Hibernation occurs in mud/vegetation on pond base. In season, they are often found at the base of bank side vegetation facing south.
Marsh frogs are territorial and communicate by means of a variety of calls produced by vocal sacs on either side of the mouth. Initial declaration of territory is by a series of simple ‘query’ sounds “qwark” with a rising cadence. This may receive a response from male competitor as a “qwark” with a descending cadence.
The full mating call is composed of a series of harsh repetitions ‘bre-ke-ke-ke-ke-ke-keh and is often delivered as a repetitive series. Transition calls between the two call types also occur. A low pitch rhythmic release call is heard when one male mistakes another for a female or when an unresponsive female is approached.
Female marsh frogs only approach the breeding pond in response to the production of mating calls by the males. They tend to be attracted to the calls of dominant males and after fertilisation and egg-laying leave the breeding pond.
As an introduced species, the Marsh frog is not covered by UK conservation legislation. Priority for conservation resources are targeted at endangered native animals. There are well over 200 records for Marsh frogs in the UK. Often these reports occur in clusters as marsh frogs expand their range from the original site of introduction.
|Species of conservation concern:||No|
|Bonn Convention (1979):||No|
|Wildlife & Countryside act (1981):||No|
|Bern Convention (1982):||No|
|Conservation Regulations (1994/2007):||No|
|EC Habitats & Species Directive:||No|
|IUCN Red List:||LEAST CONCERN|
|Principal Author:||Main Illustrator:||Review:||Updated:|
|Dr Julia Wycherley||Steve Langham||Reviewer||28 Jan 2008|