43% of cats live in a multi-cat household. Cats are independent by nature. Felidae (the biological family of cats) are solitary predators that, with the exception of lions, do not live in socially structured groups. However, while the wildcat ancestors of domestic cats are solitary animals, the social behaviour of domestic cats is more variable depending primarily on the density of cats in the area and availability of food sources. Felis catus (the species that is the domestic cat) has proved to be a remarkably adaptable species, and while retaining its roots as a solitary hunter, in a number of situations (both natural and artificial) will adapt to group living through the development of social structures.