Ruff ruff? Use the Wagometer

Dog owners may think it is easy to tell when their pet is happy - simply check if the tail is wagging - but the reality can be very different.

A wagging tail can also mean that a dog is about to attack.

Now a new device called a wagometer promises to help gauge the mood of man's best friend.

Created by canine behaviourist Dr Roger Mugford, who retrained Princess Anne's bull terrier Dottie after it bit two boys, the device is a small sensor strapped to a dog's tail.

The sensor measures the number of tail wags, as well as their speed and vigour. The owner then observes the dog's posture, expression and tail height while wagging, and combines this information with the wagometer results to establish the animal's mood.

A fast and energetic wag with the tail held low shows the dog is happy. But a high tail with a slower wag means it is angry and about to attack. Dr Mugford, who runs the Animal Behaviour Centre in Chertsey, said the idea came to him as he was judging a competition to find the dog with the "waggiest" tail.

"A wagging tail doesn't always imply a dog is happy," he said. "It can display a range of emotions, depending on the nature of the movement. There are low, high and horizontal wags. A springer spaniel might make enthusiastic circular wags when it is excited, for example, when on the trail of a rabbit. Then there's the low-slung, side-to-side tail wag - when a dog is a bit uneasy about an opponent.

"A friendly dog will often make an enthusiastic high-speed wag. But a high and small side-to-side wag may mean it is about to attack."

Beverly Cuddy, editor of Dogs Today, said the wagometer would be a "useful interpreter" for dog owners, adding: "There is a huge vocabulary they are missing. The subtle changes in a wag can make all the difference between whether a dog is feeling happy or sad."

But Labour peer Roy Hattersley, whose dog Buster is a cross between an alsatian and Staffordshire bull terrier, said the device would not be needed by those close to their pets.

"I can tell by Buster's body language whether he is happy, sad, bored or angry," he said. "If I'm late getting his breakfast he barks his head off. I can tell the difference between one type of tail wag and another."

The wagometer will be launched at a the Wag and Bone Show in support of animal charities at Ascot Racecourse in August. Elton John is expected to pen a tune to launch the show, also supported by Geri Halliwell, Graham Norton and Amanda Holden. Tickets are on sale at Crufts, which opens today at the NEC arena, Birmingham.