She obviously feels she gets something from the trees that she needs

Phil Buckley, UK Kennel Club

Police caught the dog and her 28-year-old owner in the act as the terrier chewed a chestnut tree in one of Lausanne's esplanades.

They said that the owner had not only stood by as the dog wreaked destruction on the tree but had actively encouraged it.

Phil Buckley from the UK Kennel Club told BBC News Online that the dog's pregnancy may have affected her behaviour.

Cravings

"She obviously feels she gets something from the trees that she needs," he said, comparing it to cravings women experience during pregnancy.

But he condemned the owner's behaviour as "irresponsible".

Lausanne's city authorities are taking civil action

The owner has been charged with causing criminal damage and the case has been referred to the criminal authorities.

The city is also taking civil action against him.

The dog was taken away for observation but was later returned to the owner.

Although often associated with the much larger American Staffordshire terrier and pit bulls, Mr Buckley says that the aggression has been bred out of Staffordshire bull terriers and he has never heard of this kind of behaviour from the breed before.

It is one of the most popular dogs in the UK and is known as the "nanny dog" for its characteristic of being good with children.