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A CAPTURE-MARK-RECAPTURE STUDY
OF STAG BEETLES IN COLCHESTER

During May 15 – August 12 2007 stag beetles, Lucanus cervus L. (Coleoptera: Lucanidae), were monitored in a suburban area in south-west Colchester, Essex. This area happens to be in one of Clark’s kilometre squares, TL9824, or “CRGS”, the acronym for Colchester Royal Grammar School, where he was a biology teacher. Clark was the first person to study stag beetles in Colchester (Clark, 1964, 1965). In 1996 there was another survey, with also good records for this area (Bowdrey, 1997).

In the present study stag beetles were monitored most intensively between May 15 and July 6, in the evenings from 21.00 hrs, as part of a three year phenology study. After July 6 the beetles were recorded on a casual basis until August 12. See Figure 1. Stag beetles found at other times and elsewhere were also recorded.

Each beetle, when first captured, was measured, marked and released promptly; flight was intercepted by hand. Coded marks were punctured on their elytra at the beginning using a battery operated cautery, AMI AM-21 UltraFyn, Aaron; then with a needle on a dowel because it was easier and more reliable to operate. The coding system used was the same as Mendéz (2008).

Figure 1 - Aerial photograph of the monitored area - dimensions 0.5x0.7 km2. The path marked in yellow was monitored on a bicycle, starting anticlockwise from the author’s house, the red X. The alleyway Cambridge Walk runs NNE. Known stag beetle nests are marked in green: a, b, c & d. The playground of the CRGS is partially visible at the top. Photo © getmapping.com.

Results

Total stag beetle sightings 384: 270 males, 98 females and 16 unknown; female-to-male ratio 1 : 2.8.

118 (43%) males and 43 (44%) females were captured marked and released; female-to-male ratio 1 : 2.7.

34 (29%) males and 11 (26%) females were recaptured; female-to-male ratio 1 : 3.1. See Table 1 for details of the recaptures.

Table 1

Number of times individually marked beetles were recaptured
Number of recaptured individually marked beetles
Males
Females
1
32
22
10
2
9
9
0
3
1
1
0
4
2
1
1
5
0
0
8
1
1
 
45
34
11

The majority of beetles, 204 sightings (53%), were found in Cambridge Walk (CW), an alleyway running between established back gardens which acts as a natural trap. The first males were sighted there on May 18, and hung around for a few days. Soon after the first female was sighted, May 30, the males became extremely mobile seeking them, particularly in the vicinity of three nests, where many fights and a few matings were observed. All nests except one are fairly recent: nest a is in a front garden in the in the roots of a holly (Ilex aquifolium) tree, felled Nov 2005; nest b, also in a front garden, is in birch (Betula sp.) tree roots, felled over 10 years ago; nest c is in the author’s back garden against the fence to CW, in two cherry (Prunus sp.) tree stumps which were felled in 2002 and 2005; and nest d is in the roots of a sycamore (Acer pseudoplatanus) tree felled in 2002 which is right by some railings in CW. Stag beetle larvae have been found in all nests except nest b. See in Figure 1 how close they are.

Maximum distance between recaptures was 80 m for a male recaptured in CW near nest c, he had travelled from the southern side of CW in 2 days. A female from nest a, was found 3 days later, in the northern end of CW, 149 m in a straight line, probably it flew there. A couple of males travelled 52 m, from nest a to CW to just the other side of the fence from nest c. They were found fighting for one female together with 6 other males in a ball, like rugby players*.

After June 21, past the peak flying activity, one male stag beetle which got stuck in a crevice near nest c, was ‘recaptured’ eight times, until it finally died. Longest distance between recaptures was 25m for a male, one of the eight rugby players in CW; he was found dead in the author’s garden, possibly killed by a cat. At the end of the season several females were recaptured in the area near nest c, average distance between recaptures for those was 18m.

Discussion

The year 2007 was exceptionally good for stag beetles in the monitored area, the record 384 sightings allowed for interesting analysis of the data, in particular for the females which are always outnumbered by the males (Fremlin, 2008). Despite the fact that the methodology was quite different the present urban study compares remarkably well with the study of a village garden 18 Km northeast of Colchester, in Bentley, Suffolk, with an established nest during the previous year (Hawes, 2006). Results of both studies are shown on Table 2.

Table 2

Captured males
Captured females

Captured female-to-male ratio

% Recaptured males

% Recaptured females

% Recaptured female-to-male ratio

Bentley, 2006

100
38
1:2.6
36
42
1:0.9

Colchester , 2007

118
43
1:2.7
29
26
1:1.1

There is great similarity between results on both sites. First, in both studies, as expected, more males than females were marked; note that the female-to-male ratio was the same. The percentage of recaptured beetles in the Bentley garden was higher than in Colchester which was to be expected as there the beetles were much more thoroughly monitored. Unlike in Colchester, there they were trapped and searched for under logs; plus their flight was intercepted with a long net and in Colchester it was only by hand.

What is interesting though is that in both studies there was no sex bias in the percentages of the recaptured beetles. Indeed this was evident in the Colchester study for the percentage of marked beetles, which was respectively 43% and 44%. This interesting result would deserve further analysis as it raises a few questions. For instance, are there any other capture-mark-release studies of sexually dimorphic species showing the same results?

Conclusion

This unique study shows that forty four years on from the first survey in the area (Clark, 1964), stag beetles continue to thrive in south-west Colchester. People are always felling trees in their gardens thus providing L. cervus with ideal continuous stepping stones well below the 500 to 1000 m distance recommended by Rink (2007).

Moreover it is now known that stag beetles are guided by an acute sense of smell, ( Harvey, 2007), which undoubtedly helps the females with their quick colonization of new nesting sites. Ranius (2006) suggests that species in more permanent habitats have relatively limited dispersal; possibly this explains the success of L. cervus in favoured urban areas where becoming isolated doesn’t seem to be such a threat. However the ever present threat is urban development, unfortunately.

* The picture of the 8 fighting stag beetles has been posted in the PTES 2007 Gallery here:
http://gallery.greatstaghunt.org/v/2007/4020_stag_beetle_ball.JPG.html
Other pictures also taken by the author in CW are:
http://gallery.greatstaghunt.org/v/2007/4019_male_stag_beetle_scruffy.JPG.html
http://gallery.greatstaghunt.org/v/2007/4017_fighting_male_stag_beetles.JPG.html

Acknowledgements

I wish to thank Colin Hawes for correspondence regarding his study; also to Thomas Ranius for comments on dispersal studies.

I am very grateful to Marcos Mendéz for his stimulating interest on everything that I do with stag beetles; and above all to my husband, David Fremlin, for putting me in the right track in 2005.

References

Bowdrey, J. 1997 - The stag beetle (Lucanus cervus) L. in north-east Essex: Results of the 1996 Colchester "Search for Stag Beetles" survey. Essex Naturalist, 1997, 79-88.

Clark, J.T. 1964 - The stag beetle in north-east Essex. The Essex Naturalist 31(3): 167-172.

Clark, J.T. 1965 - The stag beetle in north-east Essex - second report. Essex Naturalist 31(4): 267-270.

Fremlin, M. 2008 - Stag beetle (Lucanus cervus, (L., 1758), Lucanidae) Urban Behaviour. 5th Conference on Saproxylic Beetles, 14 -16 June 2008, Leuphana Universtiy, Germany, in preparation.

Harvey, D. 2007 - Aspects of the Biology and Ecology of the Stag Beetle (Lucanus cervus). PhD thesis.

Hawes, C. J. 2006- A CAPTURE-MARK-RECAPTURE STUDY OF STAG BEETLES, White Admiral, 65, November 2006, http://www.boxvalley.co.uk/nature/sns/wad65/W65-16.asp

Mendéz, M. as of May 2008 - How to mark Lucanidae for studies of capture-mark-recapture http://entomologia.rediris.es/gtli/engl/four/d/marking.htm

Ranius, T. 2006 - Measuring the dispersal of saproxylic insects: a key characteristic for their conservation. Population Ecology 48: 177–188.

Rink, M. and U. Sinsch 2007 - Radio-telemetric monitoring of dispersing stag beetles: implications for conservation. Journal of Zoology 272 (3), 235-243. doi:10.1111/j.1469-7998.2006.00282.x

 

      AUTHOR: Maria Fremlin