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The Essex Naturalist
Woods. The majority of records came from streets and gardens in built-up areas,
with country lanes being a frequent source of records in more outlying villages. It
is the smaller, rural populations of stag beetles which are more difficult to monitor
effectively as they are often in large tracts of countryside with few observers.
During 1996 stag beetles were found in four times as many 5 km squares as
they had been recorded from between 1974 and 1995 (Colchester Museums
records), showing that the survey had been successful in updating distributional
data on the species. The records are plotted on Map 1.
Whilst it is impossible to quantify the number of individual beetles sighted
during the survey period (largely because many observers gave no indication of
numbers of beetles seen) a modest estimate of nearly 2,700 individuals can be
calculated from those returns where numbers were indicated and counting all
other records as just one individual; even allowing for some duplication, the true
total must be well in excess of this figure.
It thus appears that the stag beetle is, at present, widely distributed across
north-east Essex with the largest populations concentrated in urban Colchester
and with several smaller satellite colonies in the surrounding area. The survey
data also suggest that numbers of individuals are comparatively high. These
conclusions would support the view that the survival of the species is not
currently threatened in north-east Essex.
An unexpected bonus from the survey was the wealth of additional
information which respondents provided, whilst some of this might be
considered anecdotal, a significant amount is the result of direct, first-hand
observation by the public. This information is summarised below.
Activity period
The first live stag beetle sighting noted in 1996 was of a female in central
Colchester on 22nd May, with the first male being seen at Lexden on the 30th.
The literature suggests that males become active about one week before the
females (Hall, 1960; Clark, 1964). Recently there has been an indication that
beetles are appearing earlier in the year (Morris, 1991; Bowdrey, 1991; Spooner,
1992). Observations by the author on captive larvae have shown that the adults
eclose in late autumn but remain inactive until the following summer. This
observation is backed up by the occasional unearthing of wild adults during winter
(Museum enquiries). June and July were the peak periods for stag beetle activity in
1996, with the last date for a male being 20th August and a female 30th August.
Sex ratio
Of the total number of sightings where sex was distinguished (1,270
individuals), 655 (52%) were of males and 615 (48%) of females. The ratio of
the sexes is thought to vary from year to year (Hall, 1960). In 1996 males
dominated in June (63.6% : 36.4%) and females in July (57.5%: 42.5%) and in
August (76.6%; 23.4%).