Dog owners and walkers have been warned to watch out for adders after reports of more sightings than usual in woods such as Shouldham Warren.
Adders are Britain’s only venomous snake and although not aggressive they will bite if they think they are under threat.
Alex Dallas, vet at London Road Veterinary Surgery, Lynn, said: “There are more adders about because it was a mild winter. We get adder bites every year but haven’t had any yet this year.
“When a dog gets bitten all the owner tends to know is that it comes back looking upset.”
Adders are most likely to be seen in early spring when they emerge from their hibernation dens and bask in the sun and dogs can accidentally stumble upon them. Horses and cattle are also prone to getting bitten.
Mr Dallas said he would expect to see six to ten adder bites on dogs each year and it is important to get immediate treatment.
Adder bites result in local swelling that is often dark coloured and can become severe. Bites could be deadly if untreated.
People are unlikely to be bitten unless they try to pick up the snakes, but should dial 999 if they are. No-one has died from an adder bite in Britain for more than 20 years.
The NHS advises that anyone who suffers a snake bite should try to remember the shape, size and colour of the snake and keep the part of your body that has been bitten as still as possible.
A Norfolk Wildlife Trust spokesman said adders are a nationally declining species and increased sightings do not mean numbers are going up. Adders are a protected species.