Britain's only poisonous snake, and one of the West Midlands rarest wild creatures, is the subject of a nationwide survey. Adders are being studied by a team from the Zoological Society of London, Oxford University and Natural England (the Government's nature conservation agency).

Although adders are still widely but thinly spread throughout the country they have declined in recent years. There are now many small, isolated populations which cannot communicate with each other. It is thought that up to a third of these populations contain less than ten individual snakes, leading to inbreeding and the risk of genetic problems or disease wiping them out.

Adders have never been very common in the West Midlands - I have only ever seen one, on Kinver Edge nearly sixty years ago! The only records in the 'Provisional Atlas of Reptiles and Amphibians of Birmingham and the Black Country' (EcoRecord 2005) are from Pensnett Chase (the Fens Pools area of Dudley) about 30 years ago, and in more recent times from Sutton Park. Wider afield there are still adders in the Wyre Forest and on Cannock Chase. Surprisingly there are no records from the apparently suitable Black Country heaths and commons. This may be because adders need peace and seclusion for hibernation and these areas deny them this.

Curiously the Atlas records more instances of the American red-eared terrapin in Birmingham and the Black Country than our native adders. The chances are though that these warm weather abandoned pets, which cannot breed here, will have been hit by the recent colder winters.

This is the best time of the year to see adders. They have very distinct zig-zag markings, the males being grey and the females brown. As they emerge from hibernation they may be found basking in sunny spots, either singly or in small groups. They will typically be seen around gorse or bracken, or on grassy banks. If you are really lucky you might see two males wrestling for the right to mate with a nearby female.

Adders rarely bite people, their instinct is to disappear when we approach. Someone once said that the only thing greater than people's fear of snakes is snake's fear of people! Even so care should be taken if you know adders are close by, their bite can be serious. The scientists carrying out the study will have to get close and personal though as they have to take swabs to analyse each snake's DNA.

Jim Foster, reptile specialist for Natural England, said: "If there are problems we still have time to deploy a number of conservation remedies. Habitat restoration and the creation of wildlife corridors will help get these snakes back on the move. We may even consider moving adders between populations, to artificially promote "gene flow" - although that carries risks and we'd need to look more closely at the genetics results before proceeding."