They are Scotland’s only native snake but there are fears the country’s adder population is facing a “significant decline”.

The first nationwide survey of the venomous reptile in nearly 30 years is calling on farmers and land managers to provide a better understanding of how their numbers are faring.

Figures from England have highlighted a big decrease in the population which prompted concerns among conservationists of a similar fate north of the border.

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NatureScot, Amphibian and Reptile Conservation (ARC) and the Amphibian & Reptile Groups of the UK (ARG UK) want farmers, landowners and land managers in an online survey which could shed more light on habitat loss as a whole.

“We are very concerned about the state of adders across Scotland,” Rachael Cooper-Bohannon of ARC said.

READ MORE: Adder facts: Survey launched to trace Scottish haunts of secretive snake

“While these shy and well-camouflaged animals can be difficult to spot, we are worried that their numbers may have significantly declined.”

The species is “particularly” sensitive to habitat change, including increasing urbanisation or agricultural expansion as well as climate change impact.

Ms Cooper-Bohannon added: “Adders are really good bio-indicators – they give a really good idea of how the environment is doing.

“They are one of the first to start to decline and can give us an indication of what is happening in the wider environment.”

She warned that many of their preferred habitats, which includes moorland and heathland, have been destroyed and fragmented.

However, there is very little information about the population of the venomous snake which is considered to be “really data-deficient”.

The last systematic survey of adders in Scotland was carried out in the early 1990s and involved a questionnaire to a sample of 50 farm and land holdings across Scotland.

Conservationists are now looking replicate as much of the approach taken 30 years ago to ensure a meaningful comparison and help guide future conservation methods.

“Farmers, crofters and other land managers form about 80 per cent of our land in Scotland and they are really important custodians of the environment,” the ARC conservationist added. “They are really key and often it has been farmers, crofters and other land managers who get in touch and say ‘we aren’t seeing adders anymore’”.

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It will also fill a gap for other reptile sightings such as the common lizard and slowworm which “haven’t been systematically recorded” over the years.

Adders are currently protected under the Wildlife and Countryside Act 1981 and is listed as a priority species under the UK Post 2010 Biodiversity Framework.

Rob Raynor, NatureScot’s specialist advisor on mammal, reptile and amphibian conservation, said: “We know there are some parts of Scotland where adders seem to be doing quite well, but there are also large parts of the country with suitable habitat but with little or no recent information.

“Better information on the current conservation status of the species and on population trends would help us to minimise the risks to adders arising from threats, for example, land-use change and possibly also climate change. The more information we have, the better we are able to target conservation action.”