Wyre Forest Adder Census and Report 2000

By Sylvia Sheldon

(Sylvia Sheldon has been undertaking an important study of adders in Wyre Forest for many years. The following is extracted from her year 2000 report with her permission. Ed)

Year SitesSurveyed Sites withadders Maturemales Maturefemales Total Average Per site
1990 56 50 185 55 240 4.8
1991 76 61 211 56 267 4.4
1992 78 55 159 33 192 3.5
1993 80 59 186 70 256 4.2
1994 76 50 153 29 182 3.6
1995 76 44 103 14 117 2.6
1996 80 41 112 32 144 3.5
1997 84 44 102 31 133 3.0
1998 85 42 103 34 137 3.3
1999 67 35 100 20 120 3.4
2000 87 24 69 13 82 3.4

Table 1: Adder numbers

Year Firstsighting Air temp(ºC) Grass temp.(ºC) Firstslough
1990 5 Feb 13.0 14.0 08 Apr
1991 23 Feb 14.0 17.0 19 Apr
1992 23 Feb 13.0 15.0 22 Apr
1993 17 Feb 10.7 12.5 16 Apr
1994 10 Feb 10.0 15.0 18 Apr
1995 12 Feb 11.4 11.0 10 Apr
1996 16 Feb 12.2 15.0 24 Apr
1997 15 Feb 8,6 11.0 08 Apr
1998 11 Feb 13.6 12.5 17 Apr
1999 16 Feb 8.0 9.0 16 Apr
2000 19 Feb 6.3 12.5 07 Apr

Table 2: Emergence and sloughing dates of adders

Year Grass snakes   Slow-worms   Lizards  
  Mature Juv Mature Juv Mature Juv
1990 30 6 23 3 22 2
1991 16 4 24 11 20 0
1992 22 8 27 8 10 3
1993 45 4 57 5 35 3
1994 18 2 36 10 22 1
1995 19 4 23 13 11 0
1996 18 4 32 16 15 0
1997 25 3 42 11 42 0
1998 20 1 34 8 37 0
1999 26 8 32 9 18 1
2000 11 1 21 3 23 0

Table 3: Other reptiles recorded in Wyre Forest during adder census

Chart shows Adder population trends 1990 to 2000

Discussion

The result of the spring Census for 2000 has given great cause for concern. The number of mature adders recorded in Wyre Forest plummeted to an all-time low of only 82 individuals, including just 13 females. Of these females, only three were seen in the company of males. Poor weather in the summer of 1999 could have accounted for this, preventing females from feeding and building up fat reserves sufficient to permit them to breed. A cool wet September that year may also have delayed birth in pregnant females. These would then have had to hibernate still pregnant, and give birth as soon as the weather in spring 2000 was warm enough.

This appears to have happened in at least three cases. These females were seen initially to be plump and apparently in breeding condition, but by the end of April they were much thinner, as if parturition had occurred. An apparently newborn infant adder was found in the vicinity of one of the females. None of them attracted a male, and overall the evidence seems conclusive. The other seven females seen in March 2000 had all disappeared by the time mating courtship began, and they did not participate either.

The effects of the summer of 1999 on the females appears obvious from the Census results. The effects on the male and the juvenile populations is unknown, other than indicated by the Census indicates - that many did not survive hibernation!

Of the 87 currently or previously occupied sites surveyed in Wyre Forest, only 24 were found to support adders in 2000. Other sites were surveyed in Worcestershire during the spring, six were found to support adders with 22 males and seven females recorded. This brings the total overall to 111 mature adders in Worcestershire and the Wyre Forest (part of which is in Shropshire). Of these 91 are males and only 20 females. This represents another sharp decline in numbers and suggests that the future for adders in this survey area is bleak.

Acknowledgements

I would like to thank:

Chris Bradley, Jeff Hubball and Nigel Hand for their census work, .all those who reported reptile sightings and the landowners on whose property the study has been undertaken.

Address for Communications: Ms Sylvia Sheldon, Knowles Mill, Dowles Brook, Wyre Forest, near Bewdley Worcestershire. DY12 2LX.

Original Artwork: Denys Ovenden

WORCESTERSHIRE
REPTILE & AMPHIBIAN
GROUP

Reference

SHELDON, SYLVIA February 2001. Wyre Forest Adder census and report 2000: correlated with local meteorological data.
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