There are over 500 breeds of domestic dog. All are descended from the wolves first tamed 12,000 years ago to help humans hunt. Dogs have kept some wolflike traits such as guarding territory and hiding bones.
Many pet dogs were originally working dogs. Collies were sheepdogs. Terriers, setters, pointers and retrievers all get their names from their roles as hunting dogs.
The heaviest dog breed is the St Bernard, which weighs over 90 kg. The lightest is the miniature Yorkshire terrier, under 500 g.
Cocker spaniels were named because they were used by hunters to flush out woodcocks in the 14th century.
Chihuahuas were named after a place in Mexico — the Aztecs thought them sacred.
The first domestic cats were wild African bushcats tamed by the Ancient Egyptians to catch mice 3,500 years ago.
Like their wild ancestors, domestic cats are deadly hunters — agile, with sharp eyes and claws — and often catch mice and birds.
Cats spend a great deal of time sleeping, in short naps, but can be awake and ready for action in an instant.
Tabby cats get their name from Attab in Baghdad (now in Iraq), where striped silk was made in the Middle Ages.
A female cat is called a queen. A group of cats is called a clowder. A female dog is a bitch. A group of dogs is a kennel.
All pet golden hamsters are descended from a single litter which was discovered in Syria in 1930.