Stream frogs enter water only to breed; the rest of the time they live alone, on land. Despite their name, the females lay eggs in patches of water where the current is absent or slow. For this important task, they need camouflage, to which their colouring is entirely suited. This particular species of stream frog (Rana graeca) lives in the woods and hills of southern and Eastern Europe, eating insects and slugs.
There are more than 3,500 species of frog, and these smooth-skinned carnivores, adept at jumping, are found on all continents except Antarctica.
Surprisingly, many, like the stream frog are semi-terrestrial, and there are arboreal and burrowing frogs which cannot swim at all.
Amphibians are very sensitive to their environment. Many species are rapidly declining in numbers; in the past five years, 20 frog and toad species in Costa Rica alone have disappeared.
Despite their clever camouflage, it may be only a hop, skip and jump into extinction.