It would be extremely useful to conservationists if all those who breed and release rare British butterflies could mark every individual specimen clearly (e.g. with a fluorescent marker), perhaps in an agreed standard fashion. It would be even more useful if there was a standard register kept
(for example in the E.L.G. newsletter) of such releases. As recorder for Hertfordshire and Middlesex, I have received a number of unusual sightings of butterflies that are suspected captive-bred releases, and I would be grateful if anyone has any information about the following:
Purple Emperor: sporadic reports from woods in south Hertfordshire 1996-1999. Queen of Spain Fritillary: Digswell, Herts, 17th August 1996. European Map: Abbots Langley, Herts 8th June 1996. (Small?) Pearl-bordered Fritillary: Brickenden, Herts., 16th June 1996. Pearl-bordered Fritillary: Northaw Great Wood, Herts., 1996. Silver-washed Fritillary: near Codicote, Herts., 15th July 1997. Monarch: High Barnet, Middlesex, 12th August 1997. Duke of Burgundy: Aldbury Nowers, Herts., 28th March 1998. Swallowtail: Bedfont Lakes, Middx., 20th May 1998. Greta morgane oto: Hampstead Heath, north London, 17th August 1998. Purple Emperor: Tring, Herts., 10th and 30th July 1999. Large Tortoiseshell: Wiggington, Herts., 31st August 1999 Dark Green Fritillary: Brent Reservoir, north London, 18th July 1999. Wood White: Trent Country Park, 22nd May 2000
Apart from the non-residents, all the above are considered extinct or virtually so in Hertfordshire and Middlesex, so it is vital to know if there really are any natural populations surviving. If you have released any of the above species at locations and dates near those indicated, I'd be very grateful for further information. Perhaps not all E.L.G. members are aware of recent thinking concerning the release of rare butterflies without consultation with organisations such as Butterfly Conservation. Such releases can hinder conservation in a number of ways:
1. They artificially increase the numbers seen at or near the place of release. This is rather like a mischievous boy adding water to a rain gauge, in that it gives false information on which important decisions are later made. For example, if unmarked specimens of a rare butterfly are released into a wood which is being badly managed, thus artificially bumping up the numbers, then the false impression is gained that this bad management is good for the butterfly. This could easily be remedied by marking all released specimens as suggested above.
2. If the butterfly is not already extinct in the region, there is always the chance that released specimens may introduce disease or viruses into the surviving native stock and exterminate it.
3. The genetic background of the introduced stock may not be suitable for the area, so that interfbreeding with the remaining local population may weaken it and actually hasten its extinction. If you think about it, under natural survival rates, if every female lays 200 eggs, then on average 198 must die every generation for the population to remain stable. There is
thus an extremely efficient "survival of the fittest" process continually in operation, so that only the top one percent of the best camouflaged, least susceptible to disease etc. individuals survive. It may be that this ruthlessly efficient method of adaption in nature is why insect introductions are so very rarely successful in the long term. These extremely finely-tuned adaptations developed at one site may not be at all suitable for another nearby. If the released individuals are captive bred, then the chances may be much worse, as captive breeding means that large numbers of less well-adapted individuals are allowed to survive, and a per se weaker stock is developed, particularly if several generations continue to be bred from the same original stock.
John Murray, Field End, Marshalls Heath, Herts. AL4 8HS. E-Mail:firstname.lastname@example.org
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