Experts say a poor diet could be causing our furry friends to suffer from brittle bone disease.

At this time of year many squirrel fanciers put out food for the native red squirrels, whose numbers have declined in recent years.

But zoologists warned that it is important that people provide a balanced diet for the creatures as certain foods could do them more harm than good.

A nut-only diet can lead to the development of a disease similar to brittle bone disease in humans.

Tony Sainsbury of the London-based Institute of Zoology, carried out post-mortem examinations on red squirrels in order to find out their cause of death.

"Most died as a result of being run over. Others died as a result of theparadox virus. However, we found evidence in some of metabolic bone disease due to poor diet," he said.

He advises squirrel feeders to put out food which contains a high calcium content. Their ideal diet would be a mix of peanuts, maize, pine, wheat, sunflower seeds, carrots and apples and even boiled bones.