These frogs are of a type called Iberian Water Frogs (Pelophylax perezi) although most people know them as Marsh Frogs. They are not a native species but have taken to the UK climate very well. They have a bright yellow line down their backs, make a distinctive croaking noise and when many of them join together it is quite a cacophony. They are most numerous at Ham Wall and easily seen at the ponds by the car park.