ANIMAL ESTATE client 8.03: COMMON FROG
FOR ANIMAL ESTATE 8.0: LONDON
SCIENTIFIC NAME: Rana temporaria
RANGE: The Common Frog, Rana temporaria also known as the European Common Frog or European Common Brown Frog is found throughout much of Europe as far north as northern Scandinavia inside the Arctic Circle and as far east as the Urals, except for most of Iberia, southern Italy, and the southern Balkans. The farthest west it can be found is Ireland, where it has long been thought erroneously to be an entirely introduced species; genetic analyses suggest that particular populations in the south west of Ireland are indeed indigenous to the country. Other areas that the Common Frog has been introduced to include: The Isle of Lewis, Shetland, Orkney and the Faroe Islands.
HABITAT: Common frogs are largely terrestrial outside of the breeding season and can be found in meadows, gardens and woodland. They prefer areas containing shallow water where they can breed, such as puddles, ponds, lakes and canals. In fact garden ponds are now extremely important for Common Frogs and many populations in suburban areas depend on them. They are also most active at night, and hibernate during the winter in pond mud or under piles of rotting leaves, logs or stones. Common frogs typically hibernate from late October to January. They will re-emerge as early as February if conditions are favourable, and migrate to bodies of water such as garden ponds to spawn.
HOME CONSTRUCTION: The adult frogs will live anywhere where there is sufficient moisture, food and protection from predators. Sites such as tall grass, piles of leaves, holes in the ground, under stones and logs and compost bins will provide the moisture and shelter required as well as a ready food source of insects, slugs, snails and worms.
BUILDING MATERIALS:The adults do not construct homes or nests as such, but will dig their way into any suitable cover as mentioned above. The females, which are generally larger than the males, lay between 1,000 & 4,000 eggs, which are fertilised by the males as they are released. The eggs form large clusters called spawn, which swells up in the water creating a jelly-like substance, and floats to the surface allowing them to be warmed by the sun.
BUILDING MOTIVATION: The frogs only form of protection from predators is to hide and further to this they are mostly active at night when there are fewer predators around. The primary purpose of spawn, apart from the points already mentioned, is to protect the fragile embryos while they develop. Despite this however, a large number of predators will still feed on the spawn and tadpoles and as a result a large number of eggs are needed to ensure some young will survive.
MAKING A FROG BREEDING SITE: Frogs are not fussy. All they require is plenty of cover, moisture and shallow areas of freshwater. These conditions can easily be created in your garden by simply not being too tidy and leaving a few piles of leaves, logs and stones around in dark areas for them to hide in. Compost heaps are also provide good conditions for them to hibernate. Any puddle, pond, or collected water can potentially attract frogs as long as it is not likely to dry out, can be entered and exited easily, has shallow areas for spawn, shaded areas around the edge for hiding and a food source for both the tadpoles and adults. However please do not be tempted to transfer the spawn of Common Frogs to garden ponds as there is a risk that in doing so you may spread the Red Leg disease.
THREATS: The common frog is protected under the Wildlife and Countryside act of 1981 against exploitation for sale, however populations can still be easily affected by the removal, disturbance or pollution of breeding ponds sites. Currently there is the spread of a highly contagious bacterial disease called Red Leg that is thought to be at least partly responsible for its recent population decline. Many frogs are also killed by cats, being squashed by cars and people, forked in compost bins and burned in bonfires. Natural predators include: fish, beetles, dragonfly larvae and birds (for tadpoles) and birds of prey, crows, gulls, ducks, terns, herons, pine martens, stoats, weasels, polecats, badgers and otters (for adult frogs).
- Common frogs can breathe through their skin as well as their lungs.
- Their eyes and nostrils are on top of their heads so they can see and breathe even when most of their body is underwater.
- Only around 5 out of every 2000 eggs will usually survive to become adults.
- Males emit a low purring croak during the breeding season, but this can only be heard up to 50m away because common frogs do not have vocal sacs.
- Frogs will not feed at all throughout the breeding season.
- Tadpoles are herbivorous and feed on algae, but become carnivores when they mature into adult frogs.
- In the wild the common frog can live for up to 8 years.
London Wildlife Trust
Royal Society for the Protection of Birds
Herpetological Conservation Trust
Amphibian and Reptile Conservation
Down Garden Services
Arizona Ecological Services
Wild About Britain
COMPILED BY: Mark Martines