Several snakes have been spotted along the banks of Grantham Canal in recent weeks, prompting a warning to walkers and dog owners.
Jim Wheeldon, a water bailiff for the Grantham Angling Association, said he has seen two adders by the water between Trent Road and Springfield Road, while another was reported along the stretch between Earlesfield Lane and Trent Road.
Jim said: “People need to be careful, particularly with their dogs.
“The trouble is, people see them and go walking up to them, but they can strike without warning.”
The adder is the only venomous snake native to Britain. It has the most highly developed venom injecting mechanism of all snakes, but they are not aggressive, according to the Forestry Commission. The snake, which can measure 75cm but usually less, will use venom as a last means of defence, usually if caught or stepped on.
If bitten and treatment is sought, the worst effects are nausea and drowsiness, followed by severe swelling and bruising in the area of the bite.
Advice from the Forestry Commission is to “treat adders with respect and leave them alone”.