Black cats are generally held to be unlucky in the United States and Europe, and to portend good luck in the United Kingdom. In the latter country, a black cat entering a house or ship is a good omen, and a sailor's wife should have a black cat for her husband's safety on the sea. Elsewhere, it is unlucky if a black cat crosses one's path; black cats have been associated with death and darkness. White cats, bearing the colour of ghosts, are conversely held to be unlucky in the United Kingdom, while tortoiseshell cats are lucky. It is common lore that cats have nine lives. It is a tribute to their perceived durability, their occasional apparent lack of instinct for self-preservation, and their seeming ability to survive falls that would be fatal to other animals.