35
Monitoring in January and February occurred during a period of very cold weather - ideal
conditions for illis site. Athough numbers of Natterer's bats are increasing, the location of the
summer roost has yet to be identified. In contrast, the brown long-eared bats have a breeding
colony in one of the estate buildings, with juveniles being observed during July.
At the Grays deneholes, climatic conditions also proved ideal. The cold spell in December
1997, which coincided with gales, ensured that cold air was dispersed throughout the system;
the subsequent periods of milder weather meant that optimum conditions for hibernation were
available underground. The January count of 83 bats was the second best ever, with the total of
98 in February comprising record totals of both Daubenton's and Natterer's bats.
Grays deneholes: Peak counts of bats in recent winters
As in the previous year, eight species of bat were recorded during 1998. Noteworthy records
included Daubenton's, Serotine, Leisler's and brown long-eared bat (see below).
Daubenton's bat Myotis daubentonii (Kuhl 1819)
The first record of the year was of several bats feeding over lakes at Danbury Park on 29th
April. In mid-May, approximately 40 emerged at Beeleigh Mill; later the same month, two were
recorded during a bat walk at Highwoods Country Park, Colchester. There were six new 10km
square records found during the summer:
4th June TL596245 three feeding over a pond at Little Easton
27th July TL849328 several feeding over a lake at Pebmarsh
4th August TQ392921 several feeding over a lake at Chingford
7th August TQ391886 one over Hollow Pond, Wanstead
19th August TM181217 several feeding over a fishing lake at Thorpe-le-Soken
19th August TM082196 several feeding over Thorrington tide mill
Essex Naturalist (New Series) 16 (1999)