Amphibians
Agile Frog
Rana dalmatina · also called agile frog, spring frog
The agile frog earns its name. On the open floor of a European wood, with little to hide behind, its defence is a single explosive leap of around two metres — the longest of any frog on the continent — that carries it into the nearest cover before a predator can react. It is still common across central and southern Europe, but at the western edge of its range it is fading, and on Jersey it survives only because people breed it by hand.
Overview
The agile frog, Rana dalmatina, is a slender, pale, long-legged brown frog with a pointed snout and a dark ear patch, found in lowland deciduous woodland and adjoining meadows across central, southern, and southeastern Europe. Outside the breeding season it is a terrestrial woodland animal, often far from water, hunting beetles, ants, spiders, and slugs in the leaf litter.
The jump
Its hind legs are the longest, relative to body, of any European frog. Folded forward, the ankle reaches well past the snout — the standard way to tell it from the common frog — and a single bound covers roughly 2 metres, an escape suited to life on open ground with little cover.
Early breeder
Agile frogs are among the first amphibians to spawn, moving to still, sunlit, fish-free pools in late winter. The male’s call is a weak underwater croak, and the female wraps her egg clump around a submerged stem rather than letting it float, which may shield it from late frost.
Status
Least Concern overall — widespread in central and southeastern Europe — but declining, with losses at the northern and western range edges in Denmark, northern Germany, and France as woodland ponds are filled in and woods cleared or shaded. The isolated Jersey population is Critically Endangered locally and depends entirely on captive breeding and pond creation by Durrell and the island government.
Agile Frog: common questions
How do you tell an agile frog from a common frog?
The two overlap widely in Europe and look alike at a glance, both brown frogs of similar size, but several features separate them. The agile frog is slimmer and paler, a clean light brown, fawn, or pinkish colour, usually without the heavy dark blotching and often without the dark chevron on the shoulders that many common frogs show, and its snout is more pointed. The decisive test is the hind legs. If you gently hold the frog and fold a hind leg forwards along the body, in an agile frog the ankle reaches past the tip of the snout, whereas in a common frog it reaches only to the eye or nostril. The agile frog also has a more clearly defined dark ear patch, a translucent look to the lower flanks, and it tends to sit high on straight legs rather than in a squat.
Why can agile frogs jump so far?
Because they are built for it. The agile frog has the longest hind legs, relative to body length, of any European frog, with elongated shank and foot bones and powerful thigh and calf muscles, and a light, slender body for its leg length. That combination stores and releases a lot of energy in a single extension of the legs, launching the frog roughly 2 metres, and sometimes considerably more, in one horizontal bound, as well as high vertical jumps. The behaviour makes sense for its lifestyle. It lives on the open woodland floor with little dense cover, so its main defence against a snake, bird, or mammal is an explosive escape that carries it several body lengths in an instant and into whatever shelter is nearest.
Is the agile frog found in Britain?
Not on the mainland, where it is not native and does not occur. The only British population is on Jersey in the Channel Islands, which lies close to the French coast and shares much of its wildlife with Normandy. There the agile frog is the island's rarest amphibian and came very close to disappearing, down to a tiny number of breeding sites, because of habitat loss, pollution, and predation. Since the 1980s a dedicated conservation programme run by the local government and Durrell Wildlife Conservation Trust has collected spawn, reared tadpoles and froglets in captivity away from predators, released them, and dug and restored breeding ponds, which has stabilised the population, though it remains Critically Endangered locally and fully dependent on continued management.
When and where do agile frogs breed?
Very early in the year and in warm, still, fish-free water. Agile frogs are among the first frogs to spawn, often in February or March and sometimes while there is still frost, moving from their woodland home ranges to sunlit ponds, flooded hollows, ditches, and the quiet margins of larger pools. Males gather but are inconspicuous, with only a faint underwater croak rather than a loud chorus, and mating happens over a short period. The female lays a single rounded clump of a few hundred to about a thousand eggs and, unusually, wraps it around a submerged stem or twig below the surface rather than letting it float, which may protect it from late frosts. The tadpoles develop over two to three months and leave the water in early summer.