Pet owners are being warned to be vigilant after five animals — cats and dogs — were baited in the space of a week in Perth and regional Western Australia, one fatally.

The RSPCA issued the warning after a dog from the Wheatbelt town of Northam was found bleeding to death in its backyard after ingesting food laced with poison thrown over the fence.

Four other dogs and cats in the Perth suburbs of Dianella, Gosnells, Seville Grove and East Victoria Park were also taken to vets because of baiting.

One dog owner in the Perth suburb of Seville Grove received a threatening letter stating: "You have no idea how close we are to baiting your dog."

"You are the only people in the street to allow their dog to bark, let alone howl. It's a horrible noise.

"One more morning like today and we will poison it. If we don't do it, our neighbours will."

RSPCA spokeswoman Natalie Foster said it was shocking there were five baiting incidents in the spate of one week.

"The horrible thing about the dog in Northam, is that it is in its own back yard and someone has thrown poison over the fence, the dog's eaten it, the family has come home to the dog laying down bleeding," she said.

"They've rushed it to the vet, but unfortunately it had to be euthanased, it was too far gone.

"It's a shocking and appalling way for a family pet to actually die."

Ms Foster said that most dogs were baited with rat poison, which was easily accessible. The pet then died from internal bleeding.

"Not a nice death for a pet, and certainly not nice for a family to watch that happen," she said.

Dogs barking, cats wandering biggest complaints

Ms Foster said that barking dogs were the biggest reasons for disputes between neighbours over pets.

"A lot of people go out to work, they don't realise the dog is barking, they are not there," she said.

"We are living closer together, the houses are closer together, people are trying to sleep and their bedrooms are close to where the dogs are.

"And people are busy and don't have the time to take the dogs out. So the dogs are frustrated, they are doing what dogs do.

"Cats don't bark but they do wander into people's gardens and fossick around and go around the pot plants and to their business, which people don't like, and roaming cats at night."

Ms Foster said there were several steps to take before threatening your neighbour

"You need to take reasonable measures to talk to your neighbours, and then the next step is to contact your council," she said.

"The amount of suffering caused by baiting is severe, and those people will face significant penalties if we catch them."

Those found guilty of poisoning an animal fines of up to $50,000 and five years in prison.