The domestic cat seems to sleep more than any other animal. Indeed, adult cats sleep between 13 and 20 hours in every 24 hour period, with the average being around 16 hours a day. So why do cats sleep so much? Are there any patterns to their sleep? And how does this fit in with a cat's daily activity?
All members of the cat family have high sleep needs, which are caused by their diet and lifestyle. Herbivores need to graze steadily for hours to meet their energy requirements. However, carnivores, like cats of all types, feed themselves by brief burst of hunting activity, followed by a protein-rich meal. Feline hunting is particularly energy-consuming and intensive, so it makes sense for members of the cat family to conserve as much of their strength as possibly between bouts of chasing after their next meal. Additionally, small animals tend to need more sleep than larger ones. Their higher metabolic rates may mean a greater toll in wear and tear to cells. This necessitates more repair work, which is carried out during sleep.
All this means that small carnivores, such as small cats, need a great deal of sleep. Despite the fact that our cats are domesticated and rarely need to hunt for their food, this need for lots of sleep remains – and it explains why your cat seems to curl up and snooze at the slightest opportunity.
There are two basic kinds of sleep in all mammals. Rapid eye movement or REM sleep is so called because the eyes move rapidly in response to spikes of activity in the brain, while the rest of the body is deeply relaxed. In humans at any rate, dreams occur during this type of sleep. Non-REM sleep, or slow wave sleep, has slow brain activity, some muscle activity, and is generally considered to be a lighter type of sleep.
Settling down for a period of eight hours sleep would be a bad idea for a small predator. Instead, cats sleep in several periods throughout the day. They start in slow wave sleep, moving on to REM sleep. In humans, sleep cycles of the two types last 90-110 minutes, and REM sleep makes up 20-25% of the total. However, cats have a cycle of periods of light sleep lasting about 25 minutes, followed by six or seven minutes of REM sleep; then either wakefulness or another period of light sleep. In laboratory studies, cats were found to spend 35% of their time awake, 50% in light sleep, and only 15% in REM sleep. During periods of light sleep cats can wake up and move very quickly. These are the 'cat naps' for which they are famous.
Sleep in used both to repair the body and to reorganise the brain. Growth hormones are released during sleep, particularly in kittens. Disturbance of REM sleep during kitten development has been found to cause abnormalities in their visual systems. Studies also show that sleep is important to brain 'plasticity', or adjustment to new environmental challenges. In one study, the kittens had one eye covered for six hours, after which the electrical activity of their brains was recorded. Some of the kittens were allowed to sleep for the six hours, while others were kept awake. The level of changed activity doubled in the kittens who were allowed to sleep, but did not increase in those kittens which were kept awake.
Cats are governed by the same 24 hour circadian rhythm as all other animals, including humans, with preferred times for activity and sleep. Many people think that cats are nocturnal, but actually they are by nature crepuscular, that is they are most active at dusk and dawn. But a cat's sleeping and activity patterns are moderately flexible, and can change to suit their circumstances, in the same way as cats can in many other aspects f their lives. Some studies have found that barn cats sleep less than pet cats, which perhaps indicates that when there is more going on to stimulate them, cats are more alert, but they tend to curl up and go to sleep when life offers them no excitement or threats. Outdoor cats have plenty in their surroundings to keep them alert and busy, so they are likely to sleep less than relaxed indoor cats which have no other cats to interact with and no prey to hunt and catch.
Our own cats have often adapted their activity and sleep cycles to suit the family with which they live. In past generations cats were often put outside at night, and these cats did indeed become nocturnal, usually hunting at night, and coming home in the morning to sleep the day away. Indoor only cats may sleep the day away while their owners are at work, coming to life when their people return to the home. Cats that are asleep alone in a house all day may revert to what is probably their default pattern of activity, waking their owners some hours before dawn. But if their owners are at home all day, many cats will stay awake during this time, and sleep soundly throughout most of the night, to a large extent imitating their owner's sleep and activity patterns.
Knowledge of the sleeping and activity behaviour of cats can be very helpful to cat owners. If your cat tends to keep you awake at night, or demands to be played with in the early hours, you probably need to provide more stimulation for him during the day. While he is doing what is normal for a cat, his behaviour in this respect can be changed to a pattern that is more suitable for the household. So hopefully you will now have more knowledge to enable both you and your cat to be active and sleep at more convenient times, for both of you.