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Transactions out soon in 2012 with conference talks |
STAG BEETLE RESEARCH UPDATE Mark-release-recapture Further to my article A capture-mark-recapture study of stag beetles (White Admiral 65 Autumn 2006 pp 35-36) I can report that I have at last received proofs of the paper presented at the 4th Symposium and Workshop on the Conservation of Saproxylic Beetles held in June 2006. The paper, titled ‘The Stag Beetle Lucanus cervus (Linnaeus, 1758) (Coleoptera: Lucanidae): a mark-release-recapture study undertaken in one United Kingdom residential garden’ will be published in Rev. Écol. (Terre Vie), Vol. 63, 2008, which will be devoted entirely to the papers presented at the symposium. Radio-telemetryEarly indications from radio-tracking stag beetles confirm results obtained in mark-release-recapture surveys. Both female and male beetles can fly, but females spend most of their time on the ground hidden under logs, leaf litter or other material, except at dusk when they can be found crawling in the open. Males fly further than females, but they too spend the majority of the day land-based, in trees or under cover on the ground. Further research is required to determine the dispersal distances of both sexes. Road casualty surveysSeveral methods for monitoring stag beetle populations have been examined and
tested by the author over the period 2000-2007. To date, road casualty surveys
remain the most effective and reliable method of collecting data that give a measure
of the beetles’ abundance. 25 volunteers returned stag beetle road-casualty data c.f. 28 in 2006.
Returns were received from 7 different counties and London.
Table 1: Numbers of beetles counted in the 2007 roads survey
546 stag beeNovember 19, 2011 8:5913 volunteers surveyed throughout the ‘stag beetle season’ and the average number of times a route was surveyed was 20, cf. 22 in 2006. 9 routes were surveyed at least once every 4 days. The total number of road casualty and live stag beetles observed along an individual transect over the ‘season’ varied from 0 to 91 (0-90 in 2006). Excluding the beetles whose sex was not identifiable (Unident.), female beetles killed on the roads outnumbered males in a ratio of 3.1: 1. Previous stag beetle road casualty surveys (Hawes 2000, 2003, 2004, 2005 and 2006) show female to male ratios of 3.5, 2.4, 3.4, 2.2 and 1.6:1 respectively. The mean ratio of identifiable female to male stag beetle road casualties for the years surveyed is 2.7: 1. Of the 91 stag beetles whose sex could not be identified by the surveyors the proportion of females to males is to date unknown. Comments and discussion Stag beetle road casualty belt transect surveys have been carried out over 7 years (2000, 2001, 2003, 2004, 2005, 2006 and 2007). Six volunteers have taken part in all seven years of the project, all six repeating the same transect route each year. Fifteen volunteer surveyors have taken part for four years or more, repeating their same transect route each year. The Suffolk respondent who had recorded beetles along his road transect in the years prior to 2003 but not since then, again reported seeing no stag beetles in 2007. This reinforces the view that colonies along this route are probably extinct. Seven other transects gave zero sightings. One surveyor collected and recorded 39 stag beetles of unidentified sex. These were corpses crushed beyond sex recognition, or had parts missing, which made sex identification difficult. Where beetles were unidentified, it was usually because the head was missing from the corpse. Surveyors were not expected to examine corpses in more detail. So far seven surveyors have submitted the stag beetle remains and corpses that they collected. The dead beetle remains are useful in: (i) confirming the species (ii) confirming the sex (iii) attempting to determine the sex of specimens (by examining the tibia of the front legs, and/or the genitalia) where this had presented difficulty for the surveyor and, (iv) providing material for DNA analysis and body measurements at RHUL. Examination of the corpses, where sex could not be determined, has yet to be carried out by the author. As stated in 2007, surveys carried out several times a week gave better results than those carried out once a week. Surveying throughout the adult season is essential if the method is used to calculate the sex ratio. The sex ratio changes as the season progresses. Males are more abundant early in the season, emerging approximately one week before the females. As the season moves on females become more abundant than males, the latter dying and declining in number before the females. Surveying throughout the adult season is also essential if this method is used to calculate an annual index of abundance.
Table 2: Stag beetle road casualty surveys - cumulative totals
for 2000, 2003, 2004, 2005, 2006 and 2007
Conclusions
Road casualty transects are designed to give an indication of trends in stag beetle abundance. The method used is not suitable for calculating stag beetle population size. However, road casualty numbers of Stag beetles could be used to calculate an annual index of abundance for specified transects, thus providing a monitoring system for the species, much in the same way as transects are used to monitor butterfly numbers. The 2007 results provide further confirmation that the method is reliable both in local and national surveys, is easily repeatable and can be carried out quickly. It is valuable as a good indicator of stag beetle presence or absence. It is intended that the method should complement but not replace trapping, although to date it has proved to be more effective than pitfall and cross-vaned flight interception trapping that have been carried out in parallel by the author. It is a ‘user-friendly’ method requiring no special equipment or chemicals and can be used along footpaths, pavements, tracks and roads of all types, where it is safe to walk. Surveyors find no difficulty in distinguishing stag beetles from other species, which suggests that annual road casualty belt transect surveying to monitor these insects can be undertaken by volunteers from the general public. Stag beetles produce roughly equal numbers of female and male offspring (Hawes, 2005). However, there are more female than male road casualties. A possible explanation for this difference lies in the behaviour of the two sexes. Although both sexes can fly, females spend most of their active time on the ground searching for a suitable place to lay eggs, whereas males spend the greater part of their active time flying in search of females. Thus females are more likely than males to be found crawling on footways and highways, where they are vulnerable to injury. Acknowledgements I am indebted to all the volunteer surveyors who took part in the 2007 survey, and especially to those* who have contributed to all six surveys referred to above. Suffolk: Janet Baker, Janet & Jim Buis, Adrian Chalkley, Bob Deex, Chris Ellis, John Glazebrook, Doug Harper*, Rosemary Milner*, Nicola Moxey*, Naomi Newton, Gill & Chris Pink, Mrs F. Strang, John Tombs*, Mark Usher, David Walker*. Sussex: Norman Allcorn, Miss C.P.S. Griffiths, Elaine Sinclair, Hampshire: H. J. Bacon, J. Willbourne. Dorset: Mr & Mrs I. Barnes, Essex: Maria Fremlin. Kent: D.W. Bishop, Surrey: Mark Wagstaff. Any errors and omissions in the above are the responsibility of the author. Reference Hawes, C. J. (2005). The stag beetle Lucanus cervus L. (Coleoptera: Lucanidae) in the county of Suffolk (England): distribution and monitoring. Proceedings of the 3rd symposium and workshop on the conservation of saproxylic beetles. Riga/Latvia, 07-11 July, 2004. Latvijas entomologs, Supplementum VI. Colin Hawes |
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