COMMON FROG (Rana temporaria) a.k.a. grass frog

Common Frogs can be between 6 and 10 cm in length, although they are usually 7.5 to 8cm long. Females are usually slightly larger than males. Their average adult weight is 22.7 gms.

The frog has a robust body and short hind limbs with webbed toes. Males tend to be darker in colour than females, and can also be distinguished by the dark bluish-black nuptial swellings on their first fingers. These pads become more pronounced during the breeding season, helping the male to grip the female during mating. The skin is smooth and comes in a variety of colours: olive green, grey, yellow and various brown shades. The skin is covered with irregular dark blotches, and they have a dark mask pattern over their eyes and eardrums. Barred markings on the limbs and flanks are common. Underneath they are white or yellow, or orange in the case of females. The undersides are often covered with brown or orange speckles. Some frogs turn a blue colour during the breeding season. Albino frogs with red eyes and yellow skin have been known.

Common frogs are good at camouflage; they can lighten or darken their skin to match their environment. They have brown eyes with black horizontal pupils, and transparent inner eyelids which protect their eyes when they are underwater.

These frogs are terrestrial outside their breeding season, and can be found in gardens, fields or woodlands wherever there is shallow water. They breed in puddles, lakes and ponds. Although common frogs are active both day and night, they tend to be more active at night. During the winter they hibernate under stones and logs, in compost heaps, or underwater beneath piles of mud and decaying leaves.

Common frogs feed on any moving invertebrates of a suitable size, such as snails, slugs, insects and worms. They have long, sticky tongues which they flick out to catch their prey. Adults feed entirely on land and they do not feed at all throughout the breeding season.

Juvenile frogs feed in the water, tadpoles feed on algae and they become carnivorous when they mature into adulthood.

The Common Frog becomes sexually mature at around three years of age. During February and March it emerges from hibernation and makes its way to the breeding grounds. Common frogs have been seen to return annually to the sites where they were spawned.

Frogs spawn from December to April (the milder the weather the earlier they will breed) and the female lays 1000-4000 eggs at a time. These are fertilised by the male as they are released. Eggs are laid in still shallow water. Frogspawn is surrounded with a clear jelly-like material which swells up in the water to protect the embryos. The spawn floats to the surface in large round clumps so that the sun can warm the eggs.

After 30 to 40 days, tadpoles emerge from the spawn. They feed on the spawn for the first few days then start to eat algae.

Tadpoles change into frogs through a process called metamorphosis, which takes between 12 and 14 weeks. Both spawn and tadpoles are extremely vulnerable, and many get eaten by predators such as fish, birds and grass snakes. On average, only 5 out of every 2000 eggs will survive to become adult frogs.

The Common Frog can breathe through the skin as well as the lungs, enabling them to hibernate underwater. Their eyes and nostrils are on top of their heads so they can see and breathe even when most of their body is submerged.

In the wild, the Common Frog can live for up to 8 years.

 Adding tadpoles to the prototype pond.

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