Amphibians and reptiles are on the whole, both globally and nationally threatened. All amphibian and reptile species found in the UK are protected by law. Most species are experiencing nation-wide declines in populations for a variety of reasons, including habitat loss, pesticide pollution, and the introduction of non-native invasive species. For further information see the and websites.
Sussex is home to five species of amphibian: smooth newt, palmate newt, great crested newt, common frog and common toad. The natterjack toad may once have occurred on the lowland heaths of Sussex, but it is now assumed extinct. All amphibians and reptiles associated with wetlands in Sussex are thought to be suffering from declines.
Great Crested Newts
The great crested newt occurs in at least 23 countries, with significant strongholds in the UK, France, Germany, Poland and Sweden. However, it is declining rapidly across this range and is now recognised as threatened in 11 of these countries. This decline, together with the fact that the UK holds a significant proportion of the world population has resulted in much importance being attached to its conservation in the UK. A year-long study published by Natural England in 2011 showed that great crested newt are still in decline and that although widespread across lowland England, they are now uncommon in the UK. Sussex is a National and European stronghold for great crested newt but their distribution is by no means uniform across East and West Sussex. The greatest concentration of breeding ponds appears to be in the middle of Sussex and areas of the Downs around Brighton, Eastbourne, Newhaven and Seaford.
Common toads are also thought to be declining in numbers. Adult toads emerge from their overwintering sites in late spring and start migrating towards the pond on mild, damp evenings; tending to return to ancestral breeding ponds along the same routes each year. The loss of breeding ponds and the disruption of migration routes, particularly by the construction of roads and other impenetrable barriers to migration are thought to be the primary cause of their decline.
The common frog, (Rana temporaria), 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. The farthest west it can be found is Ireland. The common frog is listed as a species of Least Concern on the IUCN Red list of Threatened Species.
Sussex also hosts a large population of marsh frogs (Rana ridibunda). These were first introduced into Walland marsh in Kent in 1935, this non-native frog is now widely distributed throughout Kent and East Sussex and is spreading rapidly. There is limited research into the effect that marsh frogs have on our native populations of frogs, however marsh frog numbers are so high that it is assumed that merely through competition for food resources and habitats, they are likely to be impacting considerably on native amphibian populations.
The more localised decline of amphibians in Sussex is thought to be mostly attributable to the loss of ponds and wetlands and their surrounding habitats, the intensification of agriculture and the use of pesticides. Two recently occurring amphibian diseases also pose a serious threat to our native amphibians: Ranavirus or ‘Red-Leg’ disease and Chytridiomycosis (a fungal disease)
There are six species of reptile common to Sussex, however only one of these, the Grass snake, can be described as having a specific association with wetland habitats. The Grass snake is the largest British snake, generally reaching up to 80cm in length. There is almost always a distinct yellow and black collar just below their head. Eggs are laid in compost or other heaps of rotting vegetation. Grass snakes are distributed throughout lowland Britain.