Villagers on the edge of Dartmoor are becoming increasingly concerned about wild boar in the area.
Farmers are concerned about the threat to livestock as boar breed
About 12 of the tusked creatures have been spotted near Buckland Monachorum and Roborough.
Some people's dogs have been threatened, including one belonging to an 80-year-old woman who beat them off after they surrounded her pet.
The RSPCA called for calm, saying that the wild boar were only protecting their young.
Experts believe the boars are from several packs set free from two local farms by animals rights campaigners.
Police have warned walkers to be careful, but animal groups said the boars were unlikely to attack unless they were cornered or with their young.
An RSPCA spokeswoman said there had been only two attacks on humans in the UK in the past eight years.
She said: "People should remember that the recent incidents are a form of passive aggression, they are just protecting their young.
"They generally avoid people.
"We appreciate that the area is popular for dog walkers, but we would ask people to be patient during the breeding season which is only a month long."
Rosemary Hamilton-Meikle, from Plymouth, was walking her dachshund Bosun on Dartmoor near Buckland Monachorum when her pet dashed into undergrowth.
She followed him and found her pet lying on the ground, surrounded by three wild boar.
Ms Hamilton-Meikle swung the dog lead at the boar, hitting one on the nose.
She said: "I was absolutely livid.
"I was screaming at them: 'Leave Bosun alone, you're not going to hurt my dog'.
"I think I was very lucky because the boar had tusks about 5in long and he looked pretty mean.
"I've got a feeling that if I hadn't gone in they would have savaged him and eaten him."
Local farmer Richard Cole said that now the boar were breeding the situation was getting serious.
"If we don't get these pigs sorted out when we start lambing it could be devastating," he said.
"With the amount of lambs we would lose there would be no income at all."
Mr Cole added: "They are breeding and there is not going to be an end to this unless we get on top of it now."
Spread of disease
Ian Johnson, regional spokesman for the National Farmers Union, said: "Wild boar do not represent a more challenging threat to livestock than other predators such as foxes, crows and even badgers.
"The biggest threat is is from uncontrolled dogs."
But he said there were real concerns about the spread of disease such as foot and mouth by the animals.
"They are an effective conduit of disease and from that point of view they should be dealt with," Mr Johnson said.
The Department of Environment, Food and Rural Affairs held a public consultation on the issue last year, and decided it was up to the owner of the boar or landowner to take action.