Common frog  (Rana temporaria)

Protected in Britain under Schedule 5 of the Wildlife and Countryside Act (1981), with respect to sale only (3). Listed under Annex III of the Bern Convention (4).

Undoubtedly Britain's most well-known amphibian, the common frog is often found in garden ponds (2). They are typically brown or greyish in colour, but some individuals may be yellow or reddish. The flanks are usually yellow, the underside white, and the upper surfaces feature variable blackish markings (5). The large hind legs feature webbed feet; they power strong jumps and an excellent swimming ability, and are covered with dark bands, which provide camouflage (5). Males tend, on average, to be slightly smaller than females, and they can be identified by whitish swellings on the inner digits of the front feet, which support dark pads during the breeding season that allow the male to effectively grasp a female (5).

Found throughout Britain and Ireland (2). Elsewhere, the common frog occurs in most of Europe, with the exception of Portugal, most of Spain, Italy and Greece (4).

Found in a wide range of habitats, and breeds in puddles, ditches, ponds and large lakes as well as urban and rural garden ponds (5). They have even been recorded breeding in running water (5).

Common frogs hibernate through the winter, either at the bottom of ponds (breathing through their skin) or on land under refuges such as compost heaps (5). During the rest of the year they hunt on land on damp nights; they feed on snails, slugs, worms and a range of insects (5).

In spring, males arrive at breeding areas before females, and it is thought that individuals return to their natal ponds by following scents (5). There is typically heavy competition amongst males for females, involving much croaking and wrestling. Males grab a female and remain clasped to her body for days or weeks before spawning takes place. All of the frogs in a pond tend to spawn roughly within a few days of each other. The female releases 1000 to 2000 eggs, the male then releases sperm. The eggs are coated in jelly, and are popularly known as 'frogspawn'. After 10-14 days, the tadpoles hatch, becoming free-swimming a few days later, and undergoing metamorphosis into adults 10-15 weeks after hatching. Tadpoles are vulnerable to predation by a range of aquatic creatures, including water beetles, newts and fish (5).

For several decades up until the 1970s, this frog suffered a serious decline in Britain. Since the increase in popularity of garden ponds, however, it has experienced a welcome recovery. It is not currently threatened, but populations are vulnerable to the destruction and pollution of water bodies (4). Inbreeding in garden ponds caused by isolation is thought to be a serious problem in some areas, leading to reduced immunity and an increase in disease (5).

It is illegal to sell common frogs under the Wildlife and Countryside Act, 1981 (2).

For more on this species and other amphibians and reptiles of the UK see The Herpetological Conservation Trust:
http://www.hcontrst.f9.co.uk
For more on amphibians of the world see Amphibia Web:
http://elib.cs.berkeley.edu/aw/search/index.html

• Hibernate: a winter survival strategy characteristic of some mammals in which an animal's metabolic rate slows down and a state of deep sleep is attained. Whilst hibernating, animals survive on stored reserves of fat that they have accumulated in summer. In insects, the correct term for hibernation is 'diapause', a temporary pause in development and growth. Any stage of the lifecycle (eggs, larvae, pupae or adults) may enter diapause, which is typically associated with winter.
• Metamorphosis: an abrupt physical change from the larval to the adult form.
• Natal: site of birth

1. National Biodiversity Network Species Dictionary (January 2003): http://www.nhm.ac.uk/nbn/
2. The Herpetological Conservation Trust- common frog fact sheet (January 2003): http://www.hcontrst.f9.co.uk
3. The Environment Agency (1998) 'Look-up' chart of species and their legal status. Species and Habitats Handbook. The Environment Agency, Bristol.
4. Amphibia Web- common frog (January 2003): http://elib.cs.berkeley.edu/aw/search/index.html
5. Beebee, T & Griffiths, R. (2000) The New Naturalist: Amphibians and reptiles- a natural history of the British herpetofauna. Harper Collins Publishers, London.