The marsh frog ("Pelophylax ridibundus", a non-native species introduced from Europe in the 1930s) is now commonly found in the upper Mole and its tributaries around Newdigate and Gatwick. There is no evidence that the presence of the frogs has had a deleterious effect on indigenous amphibians. A second non-native species, the edible frog ("Pelophylax" kl. "esculentus") was introduced to a site at Newdigate in the early 1900s. It has in 2008 been recorded in tributaries of the River Mole at Capel and Brockham.