Allerthorpe Common



	Female first seen on 25th April 2004

The records and a camera are taken to the study site on every visit. Visits take place in the morning whilst Adders are warming up, although they can be extended into the early afternoon if cloudy. On carefully approaching a basking Adder a sequence of features are observed in order to try to identify the snake. The colour, shade and type of dorsal body marking are carefully observed. At this stage positive identification can be achieved for particular specimens, either because of certain obvious unique features or because they have been observed before at that place. For example, a small number of specimens in the reserve are particularly pale, one specimen has several bands of different colours running over the body and a regularly observed grey specimen has dorsal markings that are practically all ovals. On approaching closer, head markings and scales can be observed and compared with photographic or diagrammatic records. If the Adder has not been identified at this stage, photographs are taken, if possible including full body and head only. Care must obviously be taken not to get too close, such that the snake moves off or possibly becomes aggressive. If the snake has moved off prematurely, time is allowed for it to return to it's basking spot, when the above procedure can be attempted again.

Using photographs the head scales can be more easily examined and comparisons made with Adders already on file. If the snake is not known a new file card is prepared.

CONCLUSION

Working within a known area where a population of Adders use the same basking spots day after day, certain individual snakes can be identified at some distance, using the unique body colour and dorsal markings. On approaching closer the head marking and scales are the next features that are most significant, again they can be compared with hand-held photographic or diagrammatic records. If the observer can get as close as possible, without making the snake aggressive, photographs can be taken and viewed later. In particular, the shape, arrangement and number of head scales can finally confirm the identity of an individual Adder or produce a new record.

ACKNOWLEDGEMENTS

My thanks to Sylvia Sheldon and Jim Foster for their help and advice. Thanks also to Karen Davies of Yorkshire Wildlife Trust for information and permission to enter the reserve.

REFERENCES

Arnold, E.N. & Burton, J.A. (1978). A Field Guide to the Reptiles and Amphibians of Europe. London: Wm Collins & Sons.
Evans, G. (1992). Pattern Variation in Maer Adder (Vipera Berus) Populations. The Herptile; J. of the IHS, Vol 14, No 2, PP. 86-88.
Frazer, D. (1983). Reptiles and Amphibians in Britain. London: Wm Collins & Sons.
HGBI. (1998) Adders in Amphibian and Reptile Group casework.
Sheldon, S & Bradley, C. (1989). Identification of Individual Adders (Vipera Berus) by their Head Markings. British Journal of Herpetology Vol. 1 pp. 392-396.
Smith, M. (1964). The British Amphibians and Reptiles. London: Wm Collins & Sons.
Stafford, P. (1967). The Adder. Shire Publications.