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• A dog can classify the functions and forms of objects, comparable to the intelligence of a three-year-old child. The Border Collie named Chaser learned to distinguish over 1000 objects.
• Dogs can detect the smell of 2,3-dimethyl-2,3-dinitrobutane at concentrations as low as 500 trillionths. They can identify the source of the smell and distinguish it in a mixture.
• Dogs are surprisingly strong for their size — some can carry heavy loads on their backs, haul sleds and other large items. Six sled dogs can pull a sled weighing one ton for several hours in a row.
• Dogs are less adapted to survive in the wild than wolves. They are unable to perform complex nonverbal communication, unlike their ancestors.
• Dogs can feel the slightest touch on their fur. When the air temperature decreases, the fur becomes fluffier.
• Dogs can see ghosts and predict the approach of human death. Having confirmed the unique sharpness of dogs' sense of smell, people assumed this.
• Dogs can understand human vocal expressions and facial expressions and determine their intentions. They are the only animals that can follow where a person is looking and use this during interaction.
• The English Mastiff named Zorba was the heaviest dog in the world, weighing 155.6 kilograms in November 1989. At that time, his withers height was 94 centimeters.
• The oldest dog lived 29 years and 5 months. It was an Australian Shepherd named Blue, who almost 20 years herded cattle and sheep.
• The unique dog sense of smell saved many lives. Since the 17th century, Saint Bernards found people in trouble after avalanches or during snowstorms in a monastery nearly 2500 meters above sea level.
• Dogs remember human commands as well as wolves. In intelligence tests, they even perform better than wolves in tasks.
• The oldest American dog split from others 16.7 thousand years ago. Its age is 10.15 thousand years, and its ancestors ate fish and leftovers from seals and whales.
• Dingo has the oldest type of mitochondrial DNA among dogs and canids. Australian dingoes split from the common ancestor earlier than others.
• The genetic structure of Eskimo sled dogs is unique, similar to dingo DNA, not wolves or other breeds. Their DNA is so ancient, it resembles dingo DNA more than wolf DNA.
• In Homer’s poem "Odyssey," dog Argus is the only one who recognizes Odysseus returning home after years of wandering. In ancient times and in Homer’s poem, dogs recognized their owners.
• Shepherd breeds have abilities suitable for service, sports, and military tasks. Their characteristics, including high trainability and caution, make them suitable for these duties.
• Dogs remember the meaning of many words and phrases without special training, which happens due to constant communication with humans. In laboratory conditions, they can remember up to 100 words and phrases.
• The strongest instinct in dogs is social behavior, which is expressed not only towards their own species but also in interspecies interactions. In English foxhounds, a pleasant voice is achieved through selective breeding.
• The sharpness of dogs' daytime vision is about three times lower than human vision, as they lack the yellow spot on the retina responsible for visual acuity. Humans have this spot, which increases visual acuity.
• Dogs can warn of an epileptic seizure, bark or gently bite the owner's hand. Neurobiologists from the University of Florida (USA) found that 11% of dogs belonging to people with epilepsy react to unnoticed signs of an upcoming seizure.
• Wolves are strong animals capable of tearing off poorly fastened bars, sheets of iron, and mesh.
• Unlike many other predators, wolves often return to uneaten remains of their prey, especially during lean times of the year.
• Wolves in cold climates are larger than those in warmer regions, according to Bergmann's rule. This is because larger bodies retain heat more effectively.
• The wolf may have initiated living near humans on its own. Its pioneers may have been very rare individuals with unique behavior and high tolerance to humans.
• Friendliness and loyalty in dogs are linked to a pathological gene causing Williams syndrome in humans. In people with this syndrome, kindness and loyalty are present, but also mental retardation is observed.
• Mesolithic dogs were large with strong jaws. In the Volga-Oka interfluve, they were the only domestic animals of that time.
• Stray dogs lack pathological genes causing anomalies, especially in individuals up to the "seventh generation".
• Dogs have mutations that allow them to eat carbohydrate-rich food — their genome contains up to 34 copies of the Amy2B gene. Most modern dogs have more than 8 copies of this gene.
• Dogs can detect cancer by the smell of human breath. In an experiment, they correctly identified lung and breast cancer in 83 people.
• The origin of the word "dog" is not precisely established, but it is linked to Iranian languages, for example, the similar word spaka in the Median language. In ancient Indian languages, there is the word svaka, meaning "wolf.
• In Siberia, individual wolves may weigh more than 92 kg, exceeding average values.
• Dogs and humans share a gene that causes similar facial anomalies. In pugs and bulldogs, this gene forms a flat face, while in humans it causes brachycephaly with a flat profile and bulging eyes.
• A dog's field of vision is 240–250°, which is 60–70° wider than in humans. Dogs' eye axes diverge by about 20°, unlike the parallel arrangement in humans.
• Flat-faced dogs suffer from impaired vision. They inherited these genes from wolves, but in the wild, carriers of such mutations did not survive.
• Dingo dogs carry a unique Y-chromosomal haplogroup H60, which originated from the Y-chromosomal haplogroup H5. This haplogroup is not found in other domestic dogs.
• Dogs perceive moving images at a frequency of about 80 Hz, which is higher than in humans — 50–60 Hz. Therefore, a film with an insufficient frame rate for dogs appears to them as a flickering image.
• Wolves move by placing weight on their toes rather than the entire paw, making them "digitigrade" walkers.
• Proto-dogs and wolf-like dogs had different diets. Proto-dogs' diet included more bones, which they picked up near human settlements.
• Leucism is a breed characteristic in white spitzes, white bull terriers, and some sled dog breeds.
• Dogs do not distinguish some colors, for example, blue-green may appear white. Their retinas have more rods, so they see shades of gray better.
• The longevity record among dogs is 31 years and 165 days, set by a Rafirão do Alentejo dog named Bobi in 2023. This record had been held for almost 20 years.
• Dogs show a high level of rational activity, second only to primates, dolphins, and some corvid birds. In tests, they successfully solve tasks involving extrapolating the direction of object movement.
• Dogs chase small animals, making them less controllable and dangerous to local wildlife — such as squirrels, cats, and small dog breeds. Victims adopt a submissive posture instead of fleeing, but this does not stop the attack driven by hunting behavior.
• Dogs could accurately distinguish a living person from a deceased one. Many injured were unconscious, and dogs licked them to bring them back to consciousness. In such cases, they licked unconscious injured people.
• The genomes of different dog breeds differ by 0.15%, which provides all the breed diversity. Differences between clusters of dog breeds turned out to be much greater than differences between humans from different continents.
• The Boseron has dewclaws on both hind legs, and there may be 2 or more on each foot. In some breeds, dewclaws are located so high on the foot that they are useless.
• Dogs hear sounds up to 40 kHz, which is ultrasound for humans. Humans distinguish sounds with a frequency up to 20 kHz.
• Changes in a dog's diet led to changes in the genes of starch metabolism. This happened when starch from agricultural products entered a dog's diet.
• Dogs pulled weights from 25 to 35 puds, running up to 80 versts per day. On light harness, the same dogs ran up to 140 versts per day.
• Play together shapes social behavior in dogs and is characteristic only of social animal species. Such games are often performed without using objects.
• A team of 12–14 dogs can transport up to 1 ton of cargo on a good road. On rough terrain, it cannot transport more than 500 kg.
• Dogs in the North are irreplaceable as draft animals because they are endurance and can move on ice and loose snow where large animals sink. In blizzards, they find the way to shelter using sense and instinct.
• Greenery — a source of crude fiber — contains phytonutrients, potassium, and chlorophyll, thus being a natural source of digestive enzymes. Plants bitten by a dog’s front teeth provide enzymes necessary for digestion.
• A dog’s tail reflects its psychological state. When scared or uncertain, it tucks its tail between its legs, a behavior called passive-defensive reaction by dog experts. When excited, the tail lifts upward.
• Dogs do not like being petted on the head, back, or hugged. Petting and scratching bring them pleasure, but only under certain conditions.
• A puppy cannot see objects or their movement until 21 days, although its pupils already react to light. On the 13th day of life, its eyes open, but the retina is not yet developed.
• City residents are called “black dogs.” Every day, the dog swam from the city to the island, bringing him food.
• Stray dogs have excellent social adaptability and good topographical memory. They orient themselves by background noises, smells, and time intervals, and accurately identify their stop in public transport.
• Smell is one of the most important senses of a dog. It is used for finding food, mates, and in numerous social communication situations.
• Pepper spray is effective against dogs and can be freely purchased and carried discreetly. One such means is a pepper gas canister.
• By 2 months, male dogs surpass females in height and strength and usually occupy a dominant position in the group. At this age, sexual differences already affect status within the litter.
• The Brabant bulldog is faster and more endurance than the Danzig. It is smaller than the Danzig but surpasses it in agility.
• Hierarchy among dogs is cooperative, not linear. In recent years, with scientific development and new research, many experts firmly reject linear hierarchy.
• Ideas about strict hierarchy in dog packs arose from observations of wolves in captivity. These observations were conducted under inadequate living conditions.