Kevin James, from the Lincolnshire Wildlife Trust, said it was feared that 90% of the adder population would be extinct within a decade due to disturbance by the public.
He said: “If people get too close, if they’re disturbed, they slither off into the undergrowth and then they come back again.
“But this continued disturbance means they’re losing condition, they’re being stressed out and they’re relying on their fat reserves.
“They’re slowly starving to death and the majority of the general public don’t realise what damage they’re doing.”
James, who is based in the Woodhall Spa area, advised people to avoid disturbing wildlife and keep dogs on a lead when around adders.
“They’ll only bite someone if you accidentally stand on them or if you’ve got a dog off a lead,” he added. “It’s a last resort.”
Elspeth Ingleby, a senior ecologist at North York Moors National Park, said adders were active most of the time during warm weather.
“With more people out and about, walking near their habitats, we are probably more likely to come across them, which is why it’s so important dog walkers are aware of them,” she said.