Marsh Frog
Identification: Length up to 15 cm. Females larger than males. Snout broad and flat. Eyes close to each other. Skin often warty and coarse. Back grey to olive brown, sometimes dark to- light green or yellowish with a pattern of dark spots. A light green or yellowish stripe occurs over the middle of the back, the head is usually greenish. Belly whitish, with dark spots. Back of thighs white to grey (never yellowish) with brown or olive green spots. On the border between the flank and back, there are dorsolateral folds, which alternate just in front of the hind legs. Well-developed webbing on the relatively long hind legs. Metatarsal tubercles small, low and asymmetric (25-40% of the length of the toe on which the metatarsal tubercle is standing). Males with thicker front legs, dark grey nuptial pads on the thumbs and two (dark) grey vocal sacs behind both corners of the mouth.
Range: Mainly mid and Eastern Europe. Also deliberately introduced into several countries, including France, Switzerland and southeast England. The marsh frog was deliberately introduced to the UK, and it is by far the most successful introduction of an amphibian. First introduced in 1935 to Walland/ Romney Marsh, Kent, this frog is now found in several areas of Kent and in East Sussex. Other introductions were also successful, including colonies in south-west and west London.
Habitat: In the north of its range, they are found mainly in larger, nutritious, deep, still or slow running waters like lakes, canals and waters along rivers with sun-exposed, well-overgrown borders and shallow parts. Seldom found on sandy soil or moors. Prefers open landscapes. In Britain, thought to occupy a vacant ecological niche, as 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 its unknown impact on native herpetofauna. Introductions are illegal under the Wildlife and Countryside Act 1981. In the south of its range, it is found in all types of water, up to altitudes of 2000 metres.
Habits: Active from April to October. Mainly diurnal, in the breeding season also active at night. Basks extensively during the day. Stays mostly in the water, but goes on land to forage, mainly at night. In the breeding season (May and June) the males often call in dense associations. Females lay up to 12,000 yellowish eggs, which are divided between multiple clumps of a few hundred that are attached to the aquatic vegetation. These hatch after 1-2 weeks, when the larvae are 6-8 mm long. Larvae grow up to about 6-8 cm. Newly metamorphosed frogs have a length of 2-2.5 cm. After 2-3 years, they mature. The Marsh Frog sometimes migrates over vast distances. They go into hibernation in October, usually under water in the mud or in holes in the bank of the water body.
How to find: The best chance is in the breeding season (May and June). The animals gather together and form large, dense and loud associations. Calls mainly in the evening, but on warm, sunny days also during the day. Calls are most intensive in the breeding season from May to July, but they can also be heard in the rest of their active period.
Call: Calls loud, a wide variety of resonant croaks and chuckles, "kè - kè - kè - kè - kè", increasing and decreasing in tone. Also other sounds like "krooks-krooks" and a metallic "pink-pink". They call by day and night. The chorus often fluctuates erratically.