Domestic cats sleep for about two thirds of their lives - that's around sixteen hours a day for adult cats, and in the mammal world, only the opossum, the sloth and some varieties of bats sleep for more hours! Cats are essentially hunters and predators as their ancestors were for many centuries, and their body clock tends to make sure they are awake in the early morning and at dusk when their prey is most likely to be active, even if you provide all of their dietary needs and they don't go out. Cats are very active at certain periods during the day, especially when they are likely to be fed or they have managed to gain your full attention, but they will sleep soundly after strenuous exercise, a big meal or if their surroundings are very warm. The weather will have quite a significant effect on your cat's sleeping habits and he will tend to curl up when it's cold or wet outside, and there's no chance of any sunshine. They will also sleep for longer periods if they are bored - most cats appreciate company, human or feline, with a selection of toys to keep them entertained as they usually have very active brains! And like humans, cats will also become very irritable if they are deprived of the sleep they need for their particular lifestyle. Cats appear to be able to sleep almost anywhere, and won't necessarily use the very expensive beds that you buy for them from your local pet store. They are often just as happy to have a simple beanbag or duvet variety of cat bed (which must be fully machine washable) on top of the sofa or near a radiator. Cats will normally tell you where they want to sleep, but take care that they don't choose a place that isn't safe for them or that will affect your lifestyle, and try and coax them to an ideal spot whilst they are still very young. Many cats like to sleep near a television or other electrical appliance that gives out a lot of heat, although this can be potentially dangerous if they block air vents and shed copious amounts of loose hair into the workings of the item. Likewise, you may want to discourage them from sleeping in the airing cupboard, in the kitchen or even on your bed - a tiny kitten is one thing, but being pinned down by a 15lb bruiser of a fully grown male neuter is something else! And once cats get into a habit, it is very hard to change their routine.Like many other mammals (including humans), the sleep pattern of a cat falls into two distinct phases - Rapid Eye Movement (REM) sleep, and Non Rapid Eye Movement (Non REM) sleep and you will be able to see which phase your cat is in. Humans tend to start off with a light sleep, and then go into a deep sleep for several hours before returning to light sleep, but cats will alternate between dozing and a deeper sleep, each phase sometimes lasting for less than half an hour. Whereas humans tend to sleep for longer periods of up to about 8 hours at a time, cats really do 'cat-nap' and tend to have more frequent, but shorter, periods of sleep. During REM sleep, cats will twitch their ears, whiskers and limbs - this is perfectly normal and is not cause for concern, they are not about to have a fit. In this stage, which constitutes about 60% of a cat's sleep, they are really dozing in human terms, and their eyes are actually moving behind their eyelids. Scientists believe that cats dream, and it is during this REM sleep that they are dreaming of catching mice and birds perhaps - you will notice paws ready to attack and sometimes the teeth making the chattering sound that they make when they are fully awake and just about to leap on their unsuspecting prey! When your cat is dozing in this way, you will probably notice him in a position with his head raised and his paws tucked neatly under him, maybe even sitting up ready to spring into action if necessary. This is not a deep sleep and he is subconsciously aware of potential danger around him, ready to open his eyes and investigate if something sounds or smells interesting. Most cats have a very rapid reaction state when they hear the sound of their food bowls being moved or smell some tasty chicken or fish being prepared for your own supper in the kitchen! The Non REM phase is more of a deep sleep when your cat replaces his energies after a big meal or a bout of activity, and when the immune system builds up strength again. The posture is usually different to when they are 'dozing' and you will see him relaxed and lying to one side - and if there is a sudden noise he will jump just as you would if you're woken by a loud noise during the night. After a bout of deep sleeping, cats wake up with similar routines to their owners with a good deal of blinking, stretching, yawning and the need for a wash and brush up! Kittens need a lot of Non REM sleep, as it's when they build up their muscles and bones ready to face the world as an adult cat, and in the wild it has the added advantage of keeping them safe from danger without attracting any predators. As domestic kittens grow older and more mobile they will venture from their nest area and rush about playing - and then all of a sudden they will be overcome by the need to sleep and will fall asleep in the middle of the floor, or sometimes even in their food bowl! At the other end of the spectrum, elderly cats are in far less need of such a deep sleep as they are not using up so much energy as their younger counterparts, although they will probably doze and rest their bodies for a good part of the day.