Dog Facts

Happy Hound
Originally uploaded by Elfleda.

All 400 breeds of domestic dog belong to the same species: Canis familiaris. The vast diversity is down to humans carefully selecting valuable inherited traits but often encouraging unusual ones - such as dwarfism or lack of a tail - that, in the wild, might prevent a dog surviving long enough to reproduce.

A dog's nose has 220 million olfactory cells, a human's just five million. A dog's sense of smell is not only hundreds of times better than ours: it's four times better than the best odour-detecting machines. They can even smell cancer.

Doctors in California have found that both Labradors and Portuguese water dogs can detect lung and breast cancer with greater accuracy than mammograms or CT scans. The dogs correctly identified 99 per cent of lung cancer sufferers and 88 per cent of breast cancer patients simply by smelling their breath.