In 2006 a capture-mark-recapture field study of stag beetles (Lucanus cervus L.) was carried out in one Suffolk garden at Bentley (TM 1129 3670). The garden was one of a large number in the parish that have had a regular annual emergence of stag beetles. The insects were captured in pitfall traps, in flight with a butterfly net, or by hand. The garden was visited daily at 07:00 and 21:00 hours from 02 June to 15 August inclusive to examine the traps and search for stag beetles. On the first capture each beetle captured was weighed, measured and then marked with an individual identification code on its ventral surface. Recaptured beetles were remeasured and their identification codes recorded. All beetles were released quickly and as near as possible to the place in the garden where they had been captured. Air temperature was measured on arrival at the study site and every 15 minutes thereafter until 22:00 hours.

Results

100 male and 38 female stag beetles were captured. Fifteen of these were found in pitfall traps (4 males, 11 females). It was not possible to catch beetles in flight if they were 3.5 metres or higher. After release, 52 (38%) of the 138 individually marked beetles were recaptured at least once in (Table 1). 36% of the males and 42% of the females were recaptured. The majority of the males were flying or climbing trees when captured whereas most captured females were found crawling on the ground or under logs.

Discussion

Pitfall traps and collection by hand were the most effective methods of capturing females. Only one female was caught with a net. Netting and collection by hand were the most effective methods of capturing males. Recaptured males outnumbered females in a ratio of 2.25: 1, a result which is probably a reflection of the difference in the behaviour of the two sexes. Males were more conspicuous in flight and when clambering in trees or crawling rapidly on the ground in search of females, while females generally crawled slowly and often remained stationary or hidden under logs. The number of times females were recaptured and, often under the same log, suggested that they tend to remain close to the site from which they emerged. There was a plentiful supply of suitable decaying wood in the garden for ovipositing habitat and food for larvae, which suggested that females did not need to expend valuable energy searching further for dead-wood habitat.

Capture and recapture numbers were influenced by air temperature. On cool evenings, when the temperature was 15 °C or below there was little beetle activity andmost beetles were found under logs or partly burrowed into the soil. There was evidence that some beetles had burrowed and hidden beneath the soil surface. In general beetle flight occurred when the temperature was 16 °C or above.

Conclusions

Observations and analysis of data seem to indicate that stag beetle dispersal is limited, especially in the case of females and when there is a plentiful supply of suitable decaying wood close to the site of their emergence. If the majority of female beetles present at other locations show similar limited dispersal, this needs to be taken into account when deciding where to concentrate conservation effort for the species. Perhaps such effort should be focused on using suitable dead wood to continually replenish decaying wood at known stag beetle emergence sites.

Footnote—this short communication is a short version of a longer paper presented at the 4th Symposium & Workshop on the Conservation of Saproxylic Beetles held at Vivoin, France 27-29 June 2006. The paper is due for publication early in 2007.

Acknowledgements

I am grateful to the PTES for funding my visit to the symposium; to Martin Sanford of the SBRC for his help with the computer; especially to Bob Mawkes for free access to his garden and assisting with some of the fieldwork. I gratefully acknowledge, too, the financial support of Natural England for the purchase of radio-tracking equipment.