5
It is now official, Britain's most common bat is in fact two distinct sped es. In 1993 Gareth Jones
showed that the Pipistrelle had two forms which used different frequencies for their echolocation calls,
one at around 45KHz, the other at around 55KHz.
Scientists at London Zoo have shown that two genetic types exist, corresponding exactly to the two
echolocating types. Results suggest that the two species have been disitnct for 5 to 10 million years. It
is speculated that the two different frequencies permit the two species to eat different prey, thus
minimising competition between them.
The two species are difficult but not impossible to distinguish physically. Bat enthusiasts are going to
have to fine-tune their detectors, and revise distribution maps (and invent temporary names?).
A fungal disease, Phytophthora, is killing Alder trees, Alnus glutinosa, along many of Britain's streams
andrivers. The trees are important for birds such as Siskin and Redpoll, which feed on the small cones
in winter, but also for theirstabilising effect on banks, thereby reducing erosion.
The Environment Agency and Forestry Commission want help from the public, to help build up a good
picture quickly of the present extent of this very potentially very damaging disease, and to monitor its
rate of spread.
Dead Alders should be noted and their localities reported to the local Environment Agency or Forestry
Commission office.
The above notes were taken from Urban Wildlife News Volume 14 No. 4, November
1997, published by English Nature.
The report on the second national Badger survey, funded by People's Trust for Endangered Species,
just published, shows a substantial increase in the badger population, following improved protection of
setts, and has also revealed a deal of information about Badger ecology.
The first survey established a baseline for future population change measurements, the new survey was
undertaken between October 1994 and early 1997. Over one percent of the whole of Britain was
covered. Number of main setts occupied increased by 24%, annexe setts by 87%, subsidary setts by
54%, and outlying setts by 55%. Numbers of Badgers were estimated to have increased by 77%.
The figures are encouraging, showing the effectiveness of conservation legisiation, but not all the news is
good. In the nine years between the two surveys, good Badger habitat had declined by 19%,
underlining the dramatic changes taking place in the countryside.
The reason for the increase in the Badger population appears to lie in the reduction in levels of
persecution. Extent of Badger digging had declined to half that shown up by the first survey, and
appears to have been accompanied by reductions in other forms of persecution, such as shooting at
night
The full report costs £ 16 (including postage and packing) from People's Trust for Endangered Speci es,
15 Cloisters House, 8 Battersea Park Road, London SW8 4BG.
Severe browsing damage has been reported in Mammal News, issue No. 112 (Winter 1997-8) on
coppi ce regeneration in Blake's Wood, Essex, an ancient woodland site following an increase in
Muntjac sightings. Hornbeam coppice cut since 1995 has received the heaviest browsing, but a clear
species preference is shown. Total destruction of Hornbeam, heavy grazing of Oak and thorn, but no
damage to Sweet chestnut or Sycamore. Bluebells, of which Blake's Wood has a great density, have
notbeen touched.
Essex Field Club Newsletter No. 24, February 1998