Common frog
| Common frog | |
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| The common frog | |
| Scientific classification | |
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| Species: | R. temporaria
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| Subspecies: | R.t.temporaria
R.t.honnorati R.t. parvipalmata |
| Binomial name | |
| Rana temporaria Linnaeus, 1758
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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 well north of the Arctic Circle in Scandinavia 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.
Appearance
Adult Common Frogs have a body length of between six and nine centimetres[1] and their backs and flanks vary in colour, with olive green[2] grey-brown, brown, olive-brown, grey, yellowish or rufous possible.[3] However, Common Frogs are known to be able to lighten and darken their skin in order to match their surroundings.[2] It is also not unknown for more unusual colouration- both black and red individuals have been found in Scotland, and male Common Frogs have been known to turn greyish blue in the mating season (video on page).[2] Additionally, albino Common Frogs have been found with yellow skin and red eyes.[2]
Common Frogs' flanks, limbs and backs are covered with irregular dark blotches[2] and they usually sport a chevron-shaped spot on the back of their neck.[3] Unlike other amphibians, Common Frogs generally lack a middorsal band, and when they have one, it is comparatively faint.[3] In many countries the moor frogs do have a light dorsal band which easily distinguishes them from common frogs.
The frogs' underbellies are white or yellow (occasionally more orange in females) and can be speckled with brown or orange.[2] Common Frogs have relatively short hind legs and possess webbed feet.[2] The legs of the agile frog are much longer which distinguishes them from common frogs along with the agile frogs fainter coloration. Their eyes are brown with transparent horizontal pupils, and they have transparent inner eyelids to protect their eyes while underwater, as well as a 'mask' which covers their eyes and eardrums.[2]
Males are distinguishable from females due to hard swellings (called nuptial pads[2]) on their first finger. These are used for gripping females during mating.[1] Also, during the mating season, males' throats often turn white. A final differentiation can be the colour- during the mating season, males are generally light and greyish in colour, whereas the female is browner, or even red.[3]
The moor frog also has males changing color in a similar manner, but the moor frog is known for the striking blue coloration it can develop. Mating season in both species is only short, just a week in March and after the mating season the frogs move back to their land habitat.
Distribution
The Common 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. A full list of the countries in which the Common Frog can be found is Albania, Andorra, Austria, Belarus, Belgium, Bulgaria, Croatia, Czech Republic, Denmark, Finland, France, Germany, Greece, Hungary, Ireland, Italy, Liechtenstein, Luxembourg, Republic of Macedonia, Montenegro, Netherlands, Norway, Poland, Romania, San Marino,Scotland, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland and the United Kingdom.[4] Other areas which the Common Frog has been introduced to include the Isle of Lewis, the Shetland Islands, the Orkney Islands[2] and the Faroe Islands.[5] The Common Frog can also be found in Ireland, where is the only frog species found there.
The common frog in Ireland
The Common Frog in Ireland has long been thought to be an entirely introduced species.[6] However, recent genetic analysis conducted by Teacher et al. (2009) suggests that the Common Frog in Ireland, in particular populations in the south west of Ireland, are indeed indigenous to the country.[7] They propose that Common Frogs in Ireland are composed of a mixed population that includes - native frogs that survived the last glacial period in ice free refugia, natural post-glacial colonization and recent artificial introduction from Western Europe.[8] [7]
Diet
Although not feeding throughout the breeding season, adult Common Frogs will feed on any invertebrate of a suitable size.[2] Favourites include insects, (especially flies[3]) snails, slugs and worms.[2] The frogs hunt/catch these animals by catching them on their long, sticky tongues.[2] The diets of Common Frogs change significantly throughout their lives; whereas the oldest frogs will feed only on land, younger frogs will also feed in the water.[2] Tadpoles are mostly herbivores, feeding on algae, detritus and some plants, although will also eat other animals in small amounts.[3]
Habitat and habits
Common frogs are active almost all of the year, only hibernating when it gets very cold and the water and earth are consistently frozen. In the British Isles, 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.[6] Where conditions are harsher, such as in the Alps, they emerge as late as early June. Common frogs hibernate in running waters, muddy burrows and can hibernate in layers of decaying leaves and mud at the bottom of ponds. The fact that they can breathe through their skins allows them to stay underwater for much longer periods of time when they are hibernating.[2][3][9]
Breeding
Common frogs breed in shallow, still, fresh water such as ponds, with breeding commencing in March. The adults congregate in the ponds, where the males compete for females. The courtship ritual involves croaking, and a successful male grasps the female under the forelegs. During the mating season the males can be recognised by a darkened swelling, the nuptial pad on their 'thumbs'. The females, which are generally larger than the males,[2] lay between 1,000 & 2,000 eggs[10] which float in large clusters.
Diseases
Frogs can catch an often fatal disease called 'red leg'. This causes septicemia due to bacterial infection. Poor water conditions give rise to bacteria which cause the infection, such as Aeromonas, Pseudomonas, Proteus, Citrobacter, Salmonella, and Escherichia coli.[11]
Predators
These include crows, grass snakes, hedgehogs, foxes, otters, polecats and rats.
Domestic cats kill a large number, although they rarely eat them. Large numbers are also roadkill.[12]
See also
Gallery of images
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Dorsal view -
Lateral view -
Adaptive camouflage
References
- ^ a b Sterry, Paul (1997). Complete British Wildlife Photoguide. London: HarperCollins. ISBN 0 583 33638 8.
- ^ a b c d e f g h i j k l m n o p "Common frog, grass frog". bbc.co.uk science and nature. BBC. Retrieved 2007-08-09.
- ^ a b c d e f g Sergius L., Kuzmin (1999-11-10). "Rana temporia". AmphibiaWeb. Retrieved 2007-08-09.
- ^ Kuzmin, S. (2004). "Rana temporaria". The IUCN Redlist of Threatened Species. IUCN. Retrieved 2007-08-09.
- ^ Rana temporaria have established themselves as a wild population in Nólsoy
- ^ a b "The Common Frog - (Rana temporaria)". enfo.ie. ENFO. Retrieved 2007-08-09.
- ^ a b Teacher, A G F (2009-01-21). "European phylogeography of the common frog (Rana temporaria): routes of postglacial colonization into the British Isles, and evidence for an Irish glacial refugium". Heredity. 102 (5): 490–496. ISSN 0018-067X. Retrieved 2009-09-07.
{{cite journal}}: Unknown parameter|coauthors=ignored (|author=suggested) (help) - ^ ZSL SCIENCE NEWS: http://www.zsl.org/science/news/irish-frogs-may-have-survived-ice-age,568,NS.html
- ^ Dunlop, David (2004-2-26). "Common Frog final" (PDF). Lancashire BAP. Retrieved 2007-08-09.
{{cite web}}: Check date values in:|date=(help); Cite has empty unknown parameter:|coauthors=(help) - ^ The Macdonald Encyclopedia of Amphibians and Reptiles - Rana temporaria 80
- ^ Animal Planet Website
- ^ RSPB Birds Magazine Summer 2004, page 66
- Template:IUCN2006 Database entry includes a range map and justification for why this species is of least concern