Depending on the size of our four-legged friend, his pulse beats at a frequency of 60 to 140 beats per minute. A healthy person's pulse is 60-80 beats per minute, so a dog's heart can beat almost twice as much. ¹⁾

Dogs' eyes contain a special membrane that allows them to see better in the dark. ²⁾

Color is discerned by the nerve cells in the eye. The retina of the eye has two main types of cells: rods, which detect light levels and motion, and cones, which differentiate colors. Dogs possess only two types of cones and can only discern blue and yellow colors. This limited color perception is called dichromatic vision. ³⁾

The longest-lived dog (as documented) was an Australian Shepherd named Bluey. He worked as a shepherd for 20 years. He died at the age of 29 years and 5 months. ⁴⁾

Dogs and humans have the same REM sleep type, so dogs can have dreams. The movements that occur during sleep are signs that your pet is dreaming. ⁵⁾

Dingo dogs came to Australia not yet completely domesticated and close to wild Asian wolves. The dingo diet includes rodents, spiny dogfish, crabs, fruits, and insects (mainly beetles). Fraser Island dingoes are known to eat fish. ⁶⁾

Bavarian mountain hounds are specialized hunting dogs from the group of hounds. Thanks to their excellent sense of smell, sensitivity to the scent of animal blood, they are able to track down the shot game and lead a hunter to it. They do not allow a wounded boar or deer to be lost. The Bavarian mountain hound tracks a wounded animal without resting for up to 40 hours after the shot. ⁷⁾

Husky dogs are famous for their blue eyes. Heterochromia - the color difference between the left and right eye - is also quite common. ⁸⁾

The Rottweiler is one of the oldest herding breeds, named after the German town of Rottweil, where the breed originated. It is possible that they are descended from the ancient Roman Drover dogs, brought to what is now Germany by Roman legionaries. In the Middle Ages, the dogs were known as “butchers' dogs” because they were used to pull carts of meat and other products to market. ⁹⁾

The Yorkshire Terrier was used to fight rat and mouse infestations. Originally, the Yorkie belonged to the working class, especially weavers. Yorkies were used to exterminate pests in yarn, textiles, and later also in mines and mills. There was a humorous saying that the dogs' long, silky coat was the ultimate product of the loom. ¹⁰⁾

There are over 150 dog breeds, divided into 8 classes. ¹¹⁾

Kublai Khan owned 5,000 Mastiffs. ¹²⁾

The first dog chapel was established in 2001. Located in Vermont, it was built by Stephen Huneck, a children's book author whose five dogs helped him recover from a serious illness. ¹³⁾

Those born under the sign of the dog in Chinese astrology are considered loyal and discreet, although with a strong temperament. ¹⁴⁾

Dogs have sweat glands in the pads of their paws. However, to cool themselves they simply pant. ¹⁵⁾

Dogs' noses secrete a thin layer of mucous that helps them absorb scent. They then lick their noses to taste the scent through their mouths. ¹⁶⁾

At the end of the Beatles' song “A Day in the Life”, Paul McCartney recorded an ultrasonic sound, audible only to dogs. ¹⁷⁾

Dogs hear best at 8000 Hz, while humans hear best at about 2000 Hz. ¹⁸⁾

While Chow Chow dogs are well known for their distinctive blue-black tongues they are born with pink tongues. At 8-10 weeks of age, they become blue-black. ¹⁹⁾