Theories abound why we sleep -- from the concept which holds that sleeping consolidates memories to that which claims that sleeping is a way of conserving energy. At an average, humans sleep eight to 10 hours every day, bats and opossums for 18 to 20 hours, while elephants and giraffes for only three to four hours. But now, you have probably noticed that your dog sleeps twice longer than you do. And, most probably, your observation caused you some worries. In the end, you may end up thinking just why your dog is spending long hours sleeping on its crate ?

Take a look at the following facts to help you understand the underlying factors on your dog's extraordinary sleeping habit:

Since dogs are good hunters, they spend less energy landing at a prey, which gives them more sleeping time (approximately up to 16 hours) than humans. Dogs enjoy this unfair advantage over humans. Because they only spend little from the energy stored in their body, they dedicate most of their time slumbering significantly longer than humans do.

Dogs' sleeping hours are greatly affected by various orientations. These orientations pertain to dogs' activities, health, age, and breed, as well as environmental or weather conditions. Consider these:

-- Dogs who are treated as pets generally sleep longer compared to dogs who are doing different activities, and since dogs basically have fewer tasks and responsibilities than humans, they are expected to have longer sleeping hours.

-- Dogs that are suffering from illnesses, undergo medications, suffer from depression, hypothyroidism, and senility generally sleep longer than normal.

-- Middle-aged dogs require approximately 16 hours of sleep daily, while older ones slumber much longer. This perhaps, is why dogs of this age bracket tend to be less mobile than the younger ones. Hence, they have the luxury of being idle. And idleness, like in the case of humans, is a perfect excuse for sleeping.

-- Dogs have the tendency to sleep more during sunny days.

Determining the desirable sleeping hours that your pet should only have every day is a hard task. This is basically due to the interaction of the different factors mentioned earlier. Thus, there can't really be a standard regarding dogs' sleeping hours because it is dependent on the above-mentioned elements.

Basically, you shouldn't be worried if your dog sleeps longer than you do. Just make sure that it immediately reacts to sudden bursts of noise or other activities. Older dogs fall under a slightly different case as their failure to be alert may be caused by difficulty in hearing.

Experts advise that you immediately contact a veterinarian when your dog suddenly deviates from the activities that it normally does as this is indicative of an unseen problem. However, always remember that only prolonged changes in your dog's sleeping habits need an expert's advice. To be sure, ask for help if you notice indications, like when your dog is sleeping at a higher or lower rate than the usual or is visibly lethargic-- shows signs of sadness, depression, aggressiveness, or a sudden change in weight.