Marsh Frog at Hollow Ponds

On July 4th 2012, I visited the Hollow Ponds on Leyton Flats with fellow-naturalist Kathy Hartnett. As we approached the smaller of the two ponds, we heard a load, raspy, croaking sound coming from the pond, which soon stopped.

Our first impression was that it had been a frog, although not the European Common FrogRana temporaria, our common frog. This sounded like a Marsh Frog - one of a number of difficult-to-identify introduced frog species that have become naturalised in Britain. Marsh Frogs were originally introduced near Romney Marsh from Hungary in the 1930s and have become well established in Kent and the south-east of England since then. The nearest that I know of to the Wanstead area are at Rainham Marsh, and I have heard of no reports from this area.

A Marsh Frog at Hollow Ponds, LeytonstoneKathy was positive that the sound was of a frog - she'd heard them relatively recently elsewhere. I was less than convinced, as I know how easy it is to mis-identify something based on just a brief sighting - or sounding in this instance. We walked around the pond, and heard the sound intermittently but always from the same general area.

Persistence paid off. In scanning the area from which the croaking sound was coming with binoculars, I could see the algae pulsating with the sound. Moments later Kathy homed in on it and could see the light-green frog - almost the same colour as the algae. We could even see its cheeks bulging as it inflated them up ready to emit that loud sound.

We only heard and saw one. It would be interesting to know how it got there, if there are others, or if others will join it. If they do, the area will soon be resounding to evening sounds from a more-southern Europe!

Paul Ferris, 5th July 2012