11
caving groups could descend during the summer.
At a stroke the site was spared from the damage
of regular descents and the bats were spared
the disturbance at a critical time of the
year. Since then the numbers have peaked in
February of this year at 43 (34 Daubenton's, 7
Natterer's and 2 Brown Long—Eared) , making
Grays deneholes the second most important
hibernaeulum (after Westerham caves) in South-
East England. The Pipistrelle season was a
difficult one to monitor. At some roosts bats
were present for a short time in the spring,
not staying to breed, while at others they
moved during June. For example, at a house in
Little Baddow that held over 500 bats in 1989,
only 147 turned up in June 1990, leaving after
a few days. Essex did play host to, possibly,
the largest bat colony in England. At Maldon
in June, 1041 bats emerged from a single house
and probably' about 1500 were present in July.
Certainly 1142 adults and juveniles emerged and
the volume of squeaking still coming from the
roost suggested several hundred more bats still
present. The next largest colony discovered
was of at least 783 bats behind wood cladding
at Ramsden Bellhouse.
Brown Long-Eared bat colonies were found
breeding in several houses that had previously
been timber-treated for wood boring beetles.
At these, with the use of permethrin-based
chemicals at the right time of year, bats have
been able to reoccupy traditional roosts
without being killed as would have happened
previously when lindane was sprayed in loft
spaces. Three individuals had a lucky escape
at Great Canfield, being rescued from a hot