Cats sleep 15 to 20 hours a day, with the average cat spending about 16 hours snoozing. Cats sleep in two phases. In the rapid eye movement (REM) sleep phase, cats are thought to dream. In the non-REM phase, the cat's body goes into deep sleep.
Cats spend up to 75 percent of their lives in sleep, and the REM phase of sleep makes up about 60 percent of the cat's total sleeping time. The remaining 40 percent is spent in the non-REM, or deep sleep, phase. Each REM phase lasts between 15 and 20 minutes in cats. In comparison, humans spend about 20 percent of their total sleeping time in the dreaming phase. Kittens and younger cats will spend more time in the deep sleep phase than older cats.
It's usually not difficult to tell that your cat is in the REM stage of sleep. When your cat is dreaming she'll show outward physical signs, much as humans do. Her eyes will be moving beneath her eyelids. You may notice your cat's whiskers, ears or tail twitching. Her breathing patterns change and there may even be changes in your cat's facial expressions. Some cats, but more often dogs, will make running motions with their feet when they are dreaming. Some cats may even vocalize—or "talk in their sleep"—when dreaming.
Your cat may also dream during the deep sleep phase, but the dreams aren't as vivid and you're less likely to see physical signs of dreaming. During the non-REM phase of sleep, cats and other mammals' bodies and immune systems are repairing themselves and young animals' bones and muscles are growing and developing. Cats do spend some of their sleep time "napping" and remain alert to changes in their environment and able to quickly wake. This is not deep sleep. Usually when your cat is in the deep sleep phase, you will find him alone, tucked away in a place where he feels safe to let his defenses down for a long snooze.
It is important that your cat get enough of both types of sleep. As with humans and other animals, if your cat is sleep-deprived it affects his health and behavior. A cat who isn't getting enough sleep is more likely to become ill because of the stress sleep deprivation causes to his body. The cat is also likely to become more easily confused and may exhibit behaviors such as not using the litter box appropriately. Your cat, just like you, is also likely to become grumpy if he stays up too long past his regular naptime.
- sleeping cat image by Miguel Montero from Fotolia.com