Amphibians are vertebrate (i.e. with
backbones) animals belonging to the Class Amphibia. This includes frogs, toads, newts and
salamanders. Amphibians are cold-blooded. This means that their body temperature varies
with the surrounding air or water temperature and does not remain constant as in
Amphibians can live for much of their adult life out of
water. Nearly all amphibians and all British species, have to return to water to breed.
This is because the eggs lack a hard protective shell and must be kept moist in water. In
early spring the adults congregate in freshwater ponds and lakes. Typically the female
lays the eggs in the water which are then fertilised by a male. This is known as external
fertilisation. Huge numbers of eggs are usually laid because the tadpoles which hatch out
of the eggs, are eaten by inumerable other species and their mortality rates are very
high. Toad and frog tadpoles are initially herbivorous, later becoming carnivores.
All amphibians undergo a physical transformation known as metamorphosis in which the
tadpoles gradually acquire legs and adult characteristics. In some amphibians, such as
frogs and toads, the tadpole's tail is eventually lost by being absorbed into the
body. The external gills which are common to all amphibian tadpoles are also lost.
Adult amphibians spend much of their life out of water
living in and around damp and moist areas. They eat slugs, worms and small
In Britain and throughout the world amphibians are in
decline. Whilst all the reasons for this are not known, habitat loss is without doubt a
major cause. In Britain 75% of ponds have been lost in just 50 years. Of those that
remain, few are capable of supporting the necessary numbers of adults which is required to
preserve genetic diversity. As a result inbreeding occurs.
In the U.K all native amphibians are afforded some
protection under the Wildlife and Countryside Act 1981.