Sleep all day, sleep all night—here’s what really goes on in Fido's life.

If you have a dog, take a guess: What’s he doing right now? Chances are, the answer is sleeping! Scientists and pet experts aren’t sure why dogs doze so much, but it’s typically how they spend at least half of their day. One theory: Unlike humans who generally stay up all day and then sleep for one long stretch at night, spending as much as 25 percent of their sleep in [sleep_term id="636"] sleep, dogs’ shorter sleep stints mean just about 10 percent of their snoozing is REM. The result is that they need more total sleep in order to log enough of the restorative kind that they need.

How Much is Normal?

The average dog sleeps for about 12 to 14 hours per 24-hour cycle. That’s just the beginning, though. Puppies, who expend a lot of energy exploring and learning may need as much as 18 to 20 hours. Older dogs also tend to need more rest, as do certain breeds. Technically, both small and large breeds can be long sleepers, but it tends to be the big guys, like Newfoundlands, mastiffs, St. Bernards, and great Pyrenees that earn the nickname “mat dogs” for seemingly endless naps.

A Dog’s Day

Dogs often spend 50 percent of the day sleeping, 30 percent lying around awake, and just 20 percent being active. But unlike humans, who rest best when they stick to a regular schedule, dogs are flexible sleepers: They can easily pop up when there’s action (like when there's a mail carrier at the door) and sleep when they’re bored. Dogs also sleep less when they have more to do. Working pups, like police or farm dogs, sleep less than those that have little more to do than sit around a house all day.

When To Be Concerned

While there can be a lot of variability in dogs’ sleeping habits, the one thing to keep an eye out for is a dramatic change. If your usually active dog is suddenly sleeping all the time—or the reverse—it’s never bad idea to touch base with your veterinarian to make sure that Fido isn't experiencing any health problems. The answer could be something as simple as tweaking his diet, or as complex as treating a heart condition or thyroid problem.