Dogs are able to see much better in dim light than humans are. This is due to the tapetum lucidum, a light-reflecting layer behind the retina. Because it functions like a mirror, it also accounts for the strange shine or glow in a dog's eyes at night.
All dogs, from the German Shepherd to the tiny Poodle, are direct descendants of wolves. They can all breed together and produce fertile offspring. Technically they are of the same species.
Dogs can very easily regurgitate. In fact, after eating wolves can travel significant distances back to their dens and regurgitate the food at will to feed their pups!
Dogs can see color but it is not as vivid a color scheme as we see. It is much like our vision at twilight.
Some authorities estimate that some dogs sense of olfaction (smelling) is as high as 1 million times greater than ours.
Canis Major or The Great Dog: - The great dog follows his master, Orion, as he makes his annual journey through the sky. Sirius, also known as the Dog Star, is located on the shoulder of Canis Major. It is the brightest in the heavens, and its name means sparkling and scorching, as it is nearest to the sun during the height of summer.
The hot, summer days - Dog Days - which Sirius was thought to cause, run from July 3 to August 11th. The three stars of Orion's Belt point at the Dog Star, Sirius, in Canus Major at Orion's heels. It is best seen in the northern hemisphere during winter, between December and March.
Argos or Argus, Ulysses' hunting dog, was the only creature to recognize the Greek hero when he returned home disguised as a beggar after 20 years of adventure.
Cerberus, the three-headed dog of Greek mythology, guarded the gates to the underworld.
Laika became the world's first space traveler. Russian scientists sent the small animal aloft in an artificial earth satellite in 1957.
The basenji, an African wolf dog, is the only dog that cannot bark.
A dog can hear sounds 250 yards away that most people cannot hear beyond 25 yards. The human ear can detect sound waves vibrating at frequencies up to 20,000 times a second. But dogs can hear sound waves that vibrate at frequencies of more than 30,000 times a second.