Edible and Marsh Frogs in Essex - notes for 2001
breeding colonies seem to have become established. However, on the evidence available so far, it
may be that Marsh Frogs do have the potential for longer-term establishment, and I would welcome
any further records of any of these species. Any 'green frogs' with a loud call at breeding time will
merit further investigation. While we are always concerned about the establishment of non-native
species, and the effects they may have upon native flora and fauna, it docs appear that our Marsh
Frogs are occupying a subtly different niche from Common Frogs Rana temporaria. Indeed, it has
been suggested that their main ecological impact so far has been as prey, allowing an increase in
the Grass Snake Natrix natrix population of Hadleigh Castle Country Park (Cranfield 2002).
References
ARNOLD, E.N. & BURTON, J.A. (1980) A Field Guide to the Reptiles and Amphibians of Britain and
Europe. Collins, London.
CRANFIELD, J. (2002) F.uropean green frogs in Fsscx. Essex Field Club Newsletter 39: 6-7.
SMITH, M.A. (1973) British Amphibians and Reptiles. Collins, London.
Bats in Essex in 2001
JOHN DOBSON
148 Main Road, Danbury, Essex CM3 4DT
A major highlight of the year was the continuing success of the recently adapted bunkers at Coggeshall.
These sites were converted into bat hibernacula several years ago and, as well as providing safe
winter quarters for the local colony of Brown Long-eared Bats, are becoming increasingly important
for Natterer's Bats. Peak totals for recent winters are as follows:
Natterer's Daubenton's Brown Long-eared Total
31/01/96 7 1 10 18
02/01/97 16 15 31
02/02/98 15 18 33
22/02/99 25 16 41
04/01/00 25 19 44
01/02/01 39 21 60
The complex is evolving as a "cold-weather" site with numbers of bats highest after several days of
frosty weather. During these times, alternative roost sites become too cold for the bats and the
bunkers then provide optimum conditions for hibernation. When the weather relents, other sites
such as tree holes or buildings become suitable and the population in the bunkers declines. It would
be of interest to know where the summer roost(s) is for the increasing numbers of Natterer's Bats. If
this site is not protected, then the conservation efforts at Coggeshall will have been in vain.
In contrast, the Grays deneholes appear to be a "warm-weather" site. When the weather above
ground is mild, then the deneholes offer a cold reservoir that provides appropriate hibernation
conditions. During a protracted cold spell, cold air will accumulate in the system that will then be
attractive for bats as mild weather occurs above ground. During the 2000/01 winter, the peak count
was of 57 bats - 26 Natterer's and 31 Daubenton's Bats.
Notable records of other species were as follows:
Essex Naturalist (New Series) 19 (2002)
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