They have lived with us for at least 15,000 years, yet dogs still have so much to tell us. Here are 15 scientifically verified facts about dogs — some will surprise you, some will make you smile, and others will help you understand your four-legged friend a little better.

1. Every dog's nose is as unique as a fingerprint

The ridges and creases of a dog's nose form a one-of-a-kind pattern. In some countries (the United States, Australia), "nose printing" is already being used as an identification method, as an alternative to microchipping.

2. They smell 10,000–100,000 times better than we do

While humans have around 5 million olfactory receptors, dogs have between 225 and 300 million. A Bloodhound can follow a trail that is 13 days old.

3. The oldest dog in history died at 31

His name was Bobi, a Portuguese Mastiff who died in 2023, recognised by the Guinness World Records (although the record was later revoked due to doubts about the documentation). On average, small-breed dogs live 13–16 years, while giant breeds live 7–10.

4. They really do dream (and dream about the same things we do)

Neurological studies have shown that dogs enter REM sleep around 20 minutes after falling asleep. They dream about the events of their day: hunting, playing, their owner. Those little paws twitching in their sleep are their equivalent of "running on the spot".

5. They can understand up to 250 words

Dogs with the greatest language ability (Border Collies, Poodles, German Shepherds) can recognise 165–250 words — on a par with a 2-year-old child. The record belongs to Chaser, a Border Collie who could remember the names of 1,022 different objects.

6. The tail communicates more than you might think

Italian studies (University of Trento) have shown that dogs wag more to the right in positive situations (play, their owner) and more to the left in stressful situations. This is a reflection of brain asymmetry.

7. They recognise human emotions from voice and facial expressions

Functional MRI has shown that dogs have specific brain areas for processing positive versus negative human emotions. They can tell whether you are happy or sad, even without words.

8. They can experience jealousy

Research from the University of San Diego showed that dogs become jealous when their owner interacts with a fake robotic dog, but not when they interact with a bucket. They feel social exclusion.

9. They only sweat through their paw pads

To release heat, dogs pant (up to 200 times per minute) and release moisture through the pads of their paws. Never leave them in a car in the sun: heatstroke can be fatal within 15 minutes.

10. They have "lateralisation" just like us

Dogs can be right-pawed, left-pawed, or ambidextrous. You can tell by which paw they use first when trying to retrieve a toy from under a piece of furniture.

11. They can predict certain illnesses

Trained dogs are able to detect several types of cancer (lung, breast, bladder), epileptic seizures, and blood sugar drops in diabetics with an accuracy of over 90%.

12. Their time doesn't follow the "×7" rule

The rule "1 dog year = 7 human years" is an oversimplification. The reality is non-linear:

  • 1st year: equivalent to around 15 human years
  • 2nd year: +9 human years
  • From year 3 onwards: +5 human years per year (varies by size)

13. The oldest breed is the Saluki

Images of Saluki dogs appear on Egyptian tombs dating back to 2,100 BC. It is considered the "royal dog of ancient Egypt".

14. The world's smallest dog weighs 700 grams

"Pearl", a Chihuahua standing 9.1 cm tall, holds the record. The tallest breed, on the other hand, is the Great Dane: the record holder is "Zeus", measuring 1.12 metres at the shoulder.

15. They see very well... at twilight

Dogs do not see in black and white (that is a myth): they can distinguish yellow and blue. However, their vision is optimised for low-light conditions: they have the tapetum lucidum, the membrane that makes their eyes "glow" in photos taken with a flash.

In conclusion

Living with a dog means sharing your life with a complex, sensitive, communicative being. The more you learn to read them, the deeper the bond becomes. To learn more about their language, read our guide on positive training and how to respect their natural needs with the BARF diet.