In Britain there are only six native species
of Amphibia, but in addition two species
of frog have recently been introduced from the continent and survive in southern
England. One species of reptile, the grass snake, is partially aquatic, and the adder
sometimes takes to water.
The newts are the most aquatic of the
British Amphibia. The warty or crested newt
Triturus cristatus is found throughout mainland Britain and breeds mainly in deep
ponds. The smooth newt T. vulgaris (which is the only species found in Ireland), is
mainly a lowland species frequenting weedy ponds, while the palmate newt T.
helveticus is the only species found at high altitudes where it may occur in quite
large corrie lakes. This species is also found at low altitudes and may even occur in
brackish pools at sea-level.
The common frog and common toad, both
found throughout mainland Britain, may
breed in the same water-body, but toads are generally found in deeper water and
do not breed in extremely shallow pools as do frogs. Frogs also extend to higher
altitudes and can occur in Britain at up to 1000 m. Both species may be found
breeding in waters ranging from peat pools to highly calcareous lowland lakes and
even, in the case of toads, brackish pools. The natterjack toad is mainly a coastal
species in Britain but is also found in sandy heathland areas inland. Its scattered
distribution is probably a result of its requirement for mobile sand into which to
burrow. Its breeding sites are usually small, often temporary, and frequently
brackish pools and dune slacks. The edible frog Rana esculenta has been
introduced into some ponds around London and the marsh frog R. ridibunda into
Romney Marsh, the Pevensey Levels and the Somerset Levels where it breeds in
weed-choked, calcareous or slightly brackish dykes, in which it appears to have
displaced the common frog.
The grass snake, distributed throughout
lowland England and Wales, is usually
found near water. It is a powerful swimmer and much of its prey consists of fish and
amphibians.
