Ardleigh (R. lessonae), Basildon (R. lessonae) and Witham (R. ridibunda). These are the
most likely areas where further populations may be found. If anyone has any other Essex
record of these frogs then please send in the details.
The public could be one of the reasons why these animals are spreading. By collecting
tadpoles from the named places above, then releasing them into their garden ponds,
believing them to be Common Frogs. The frogs grow up and can easily escape from
unsecured gardens. There is evidence that these frogs will follow along river corridors
and can spread very quickly.
We have had reports that the Marsh Frog population in Hadleigh Castle Country Park
originated from Romney Marsh in Kent. 5 individuals were released behind the golf
driving range near Two Tree Island in August/September 1990. The population has spread
along borrow dyke system and ditches and are spreading northwards. In 1998 it was
reported that 'hundreds of frogs' have been seen along ditches. Some have made it up to
the fishing lakes in Chapel Lane.
Their spread into further habitats may have implications for rare invertebrate populations. It
is considered that these frogs may compete with our native amphibians. The Marsh Frog
though seems to prefer marshy ditch systems; a habitat not utilised by our Common Grass
Frog Rana temporaria so it is unlikely to have a major effect. There is a lot of research needs
to be carried out on this aspect of the frog's ecology. It is clear that some species do actually
benefit from the high numbers of frogs. For instance the Grass snake Natrix natrix population
seem to be increasing in the Hadleigh Castle Country Park ditch systems.
There is an opinion that established UK colonies are beyond any form of eradication.
The monitoring of populations and the control of further spread seems to be the most
important task for conservationists in the UK. Members can help by recording the calls
of these frogs (May to July) using abasic tape recorder for around 30 minutes. Information
on the habitat type, date, time and grid reference can be included with the tape recording.
All information analysed from the recordings will be forwarded to David Scott, the Essex
Field Club Amphibian and Reptile Recorder.
Records and tape recordings can be sent to Essex Amphibian and Reptile Group at
47, Wedgwood Way, Ashingdon, Essex SS4 3AS email essex arg@hotmail.com
Surrey Amphibian and Reptile Group, Julia Wycherley, 31 The Crossways, Merstham,
Surrey RH 1 3NA.
Identification recordings can be obtained from Froglife @ Mansion House, 27-28
Market Place Halesworth Suffolk IP19 8AY 01986 873733
or email froglife@froglife.org
Essex Field Club Newsletter No. 39, September 2002
7