The ship's cat has been a common sight on many trading, exploration, and naval ships, and is a phenomenon that goes back to ancient times. Cats have been carried on ships for a number of reasons, the most important being to catch mice and rats. These rodents, when aboard, could cause considerable damage to ropes and woodwork. More serious was the threat rodents posed to the stores the ship carried. Not only could they devour the foodstuff carried to feed the crew, they could cause economic damage if the ship was carrying grain or similar substances as part of its cargo. Rats and mice were also sources of disease, an important consideration for ships which could be at sea for long periods of time. Cats naturally attack and kill these rodents.
Cats have a high ability to adapt to new surroundings, and were therefore highly suitable for service on a ship. They also offered companionship and a sense of home and security to sailors who could be away from home for long periods, especially in times of war.
The domestication of cats is believed to date back some 9,500 years, and the practice of taking cats aboard boats and ships began not long afterwards. The Ancient Egyptians took cats on board Nile boats to catch birds in the thickets along the riverbanks. Cats were also carried on trading ships to control rodents, and that concept was adopted by traders from other nations. This led to the spread of cats throughout the world, with the species eventually reaching nearly all parts of the world accessible by ship. Over the centuries their offspring developed into different breeds according to the climate in which they found themselves and the mates they took, as well as the deliberate selection by humans. Phoenician cargo ships are thought to have brought the first domesticated cats to Europe in about 900 BC.