Common frogs have smooth moist skin. Adults can grow to 9 cm (nose to tail). They are generally a shade or olive-green or brown, with a dark patch (or 'mask') behind the eyes. Frogs often have bands of darker striping on the back legs. Many individuals have irregular dark markings on the back. Colouration is extremely variable: yellow, pink, red, orange and black individuals have been reported. Also, the females can often develop a red colour during the breeding season.
Males and females emerge from hibernation and head straight ponds to breed in around February/March. Males are much smaller than females and grab the females and remain clasped to their body for days or weeks before spawning takes place. Frogspawn is laid in clumps (and typically consists of 300 - 400 gelatinous eggs containing black embryos with a white spot) usually in shallower parts of ponds.
The very young tadpoles are black but soon become speckled brown in colouration making them distinguishable from the permanently black tadpoles of the Common Toad. Tadpoles generally take up to sixteen weeks to grow back legs, then front legs before they metamorphose into tiny froglets. Those are ready to leave the water in early summer (often June, but in some ponds this may be as late as September).
In the wild, the common frogs can live for up to 8 years but they have many predators including birds of prey, herons, foxes, stoats, badgers and others that allow frogs to live only a very few years. Tadpoles are also eaten by birds and by larger water animals such as fish, beetles and dragonfly larvae.
Common frogs are largely terrestrial outside the breeding season, and can be found in a variety of damp habitats ranging from grassland and woodland to high up on mountains (up to 1000m high) where suitable breeding sites can be found. They breed in puddles, ponds, lochs and canals, preferring areas of shallow water.
Common frogs do not feed at all throughout the hibernation season, but when they are active they will feed on any moving invertebrates of a suitable size, such as insects, snails, slugs and worms, which they catch with their long, sticky tongues. Adult frogs feed entirely on land, whereas younger frogs will also feed in the water. Tadpoles are herbivorous and feed on algae but become carnivores when they mature into adult frogs.
In Britain, common frogs are protected by law under Section 9(5) of the Wildlife and Countryside Act, 1981. This prohibits sale, barter, exchange, transporting for sale and advertising to sell or to buy. Populations can be threatened in areas where breeding ponds are disturbed or polluted.
Erik Paterson, CARG Secretary