Reptiles and amphibians of Cumbria

Grass frog

Identification

 

Female grass frogs are slightly larger than males of the same age, and tend to be less contrastingly coloured. Typical colours for both genders range from dark brown to olive-green and sometimes even red or black. Often there is dark pigment overlaying the ground colour and a dark upside-down "V" between the shoulders. A dark streak runs from each nostril through the eyes and creates the 'mask' typical of all brown frogs of the genus Rana. Albino grass frogs are occasionally reported, but these often fail to survive in the wild for a long time due to increased risk of predation.

Habitat

 

This species is found throughout the county in suitable habitats. Often seen or heard in garden ponds, especially in early spring. In Cumbria suitable habitats like ponds and lakes are very numerous. Outside the breeding season this species lives in woods, moors, farms, parks and gardens. It is active mainly at night outside the breeding season.

 

 

Diet

 

Grass frogs are predators of invertebrates like worms, beetles and spiders. These prey animals are caught either with the tongue or simply with the mouth. Once crushed in the jaws, the animal is swallowed whole.

 

 

Reproduction & hibernation

 

In late winter or early spring the male grass frog can be heard calling from large ponds and lakes across Cumbira. A vocal sac beneath the chin inflates and a dull rasping "grook.... grook.... grook...." is produced. The animals making this noise are normally floating on the surface of the water or sitting in shallow water. Not all males call; some save energy and reduce risk of predation by sitting near a calling male and intercepting any females attracted to him.

 

The female grass frog will deposit one or two clumps of spawn containing between 700 and 4,500 eggs each. These are deposited over water vegetation. The spawn is fertilised by the female's mate who grasps her behind the arms during copulation and sheds his sperm into the water as she deposits her eggs. The eggs develop in about two weeks and small black tadpoles hatch out. After a few months the tadpoles will have lost most of their tails and grown legs, and lungs, and metamorphosis will almost be complete. The tiny froglets emerge from the water around July in this county.

 

Hibernation lasts from October or November until February for most frogs; the animals hibernate in the mud at the bottom of a deep pond or on land beneath logs or rocks. Early animals may be seen active beneath ice in January.