They are already close to extinction in Oxfordshire, Buckinghamshire, Hertfordshire, and Greater London, and are thought to be extinct in Nottinghamshire. The high levels of rainfall and flooding this year could be the final nail in their coffin, especially for populations close to wet meadows and similar habitats where the ground has remained flooded into March.
Because the adder only reproduces every 2 or 3 years it can struggle to recover from a population crash. As a species it has struggled nationally from habitat loss and fragmentation due to urbanisation and agricultural intensification. Scientists have studied adder genetics and found that in small populations, problems caused by inbreeding may also be preventing them from reproducing.
Predation is also a problem for adders and may be the most controversial cause of their decline. Foxes are the Adders’ natural predators but Pheasants have also been known to kill young adders and in areas of high pheasant density adders are very scarce. In middle England, however, it is more likely to be the spread and increase in buzzard numbers that is having the biggest effect on the adder population. More research is needed into the relationship between adder and buzzard as it can be a delicate subject, especially as the buzzard has itself only recently recovered from persecution.
There is still hope for the adder to remain present in middle England but only with our help. The remaining breeding sites must be protected, and some small isolated populations may need to be supplemented with snakes from elsewhere in order to improve their genetic diversity.
Source: Guardian online March 2014