Dogs are one of the most popular pets in the world and have been living with humans for thousands of years. However, how much do we really know about the canines we share our homes with? Well, here are fifteen fun facts about our four-legged friends.

1. One of the reasons dogs spook easily in thunder storms or at the sound of fireworks is that they have incredibly powerful hearing. In fact, a dog can register sounds at 35,000 vibrations per second. Humans, on the other hand, can only register 20,000 vibrations per second.

2. Many dogs are known for their speed. However, none can rival the Greyhound, which can reach speeds of up to 45mph. Subsequently, Greyhound racing remains a popular and exciting sport.

3. Throughout the centuries, dogs have been used in wars. During the Second World War, Russian troops strapped mines to the backs of dogs and sent them on 'suicide missions' to destroy German tanks.

4. Similarly, during the Middle Ages, Mastiffs were used in battle. Armies would dress the dogs in lightweight armour and strap pots of flaming sulphur to them. The dogs were then sent out to battle against horsemen.

5. It is widely documented that dogs were sent into space during the early years of space exploration. The first dog, named Laika, was sent into orbit by the Russian space program in 1957.

6. The heaviest and longest dog ever recorded was an English Mastiff called Zorba. Zorba weighed in at an astounding 343lbs and measured 8ft and 3" from nose to tail.

7. The tallest breeds of dog are the Irish Wolfhound and the Great Dane. Conversely, the smallest breeds are Chihuahua, Toy Poodle and Yorkshire Terrier.

8. Chocolate is poisonous to dogs. An ingredient in cocoa, theobromine (which is similar to caffeine) can make dogs seriously ill and even prove fatal.

9. All breeds of dog have an amazing sense of smell. Some, however, have a more incredible sense than others do. The German Shepherd, for example, has 220,000,000 scent sensory cells. When compared against a human's 5,000,000 sensory cells, it is clear why we are not used to sniff out drugs at the airport!

10. The average lifespan of a dog is sadly no more than a decade or so. However, the oldest recorded dog lived to the ripe old age of 29 years and 5 months.

11. The belief that dogs are color-blind is actually a myth. In fact, they can see colors just as vividly as we can. However, it is believed that their vision is similar to a human's vision at dusk.

12. A dog only has sweat glands between their pads. Most of their regulation is done with the tongue and it is, therefore, easy for them to overheat.

13. The US has the highest dog population on the planet with France running second highest.

14. The Newfoundland is a wonderful swimmer thanks, in part, to its webbed feet. Basset Hounds, on the other hand, are unable to swim.

15. A dog's nose print is just as individual as a human fingerprint and can, therefore, be used to identify them just as effectively.

There are, of course, many more fascinating facts about dogs. If you are thinking of welcoming a new dog into your home, it is a good idea to do some research about the specific breed. Always bear in mind, a dog is a lifelong commitment and will require patience, time and the financial means to care for him, or her, properly.