Cats have three kinds of sleep: the brief nap, the longer light sleep, and the deep sleep. The brief
nap is the one we call a "catnap". The light sleep and the longer sleep alternate during those
periods of time when a cat settles down for something more than a catnap. When a cat is ready for
some sleep, it begins in a phase of light sleep that lasts for about half an hour. Then, the
cat enters the period of deep sleep, which lasts for 6 or 7 minutes. After this, the cat will return
to light sleep and alternate these two phases until he or she wakes up.
During deep sleep a cat will dream, with twitchings and quivering of the ears, paws, and tail. The
mouth may make some sucking movement. There may be some vocalizations -- growls, purrs, and other
sounds. There are also bursts of rapid eye movement during the deep sleep.
A kitten, during the first month, experiences only deep sleep, which lasts for about 12 hours total
each day. After the first month, the kitten quickly switches to the adult pattern of sleep.
Cats are super-sleepers, sleeping about 16 hours a day total. Most mammals do not sleep this much,
which puts the cat into a special category -- that of the efficient hunter. The cat is so efficient
at obtaining food, that it has time to spare, so it has time for more sleep. Other carnivores,
like dogs, have to spend much more time running around, searching and chasing, to obtain their food.
But the cat sits, waits, stalks a little, kills, and eats. That done, the cat grooms and takes a
nap. Our housecats have even less to do, and they don't have to fit more activities into their day,
so they can still be super-sleepers.
Source: Catwatching, by Desmond Morris, Crown Publishers,
Inc., New York, 1986, p. 129.