1. Dogs curl up in a ball when they sleep due to an age-old instinct to keep themselves warm and protect their abdomen and vital organs from predators.
2. In addition to sweating through their paw pads, dogs pant to cool themselves off. A panting dog can take 300-400 breaths (compared to his regular 30-40) with very little effort.
3. When dogs kick after going to the bathroom, they are using the scent glands on their paws to further mark their territory.
4. Dogs' ears are extremely expressive. It's no wonder! There are more than a dozen separate muscles that control a dog's ear movements.
5. Sound frequency is measured in Hertz (Hz). The higher the Hertz, the higher-pitched the sound. Dogs hear best at 8,000 Hz, while humans hear best at around 2,000 Hz.
6. Dogs have about 1,700 taste buds. Humans have approximately 9,000 and cats have around 473.
7. Dogs' noses secrete a thin layer of mucous that helps them absorb scent. They then lick their noses to sample the scent through their mouth.
8. 62% of U. S. Households own a pet, which equates to 72. 9 million homes
9. 45% of dogs sleep in their owner's bed (we're pretty sure a large percentage also hog the blankets!)
10. Dogs have three eyelids, an upper lid, a lower lid and the third lid, called a nictitating membrane or "haw," which helps keep the eye moist and protected.
11. A large breed dog's resting heart beats between 60 and 100 times per minute, and a small dog breed's heart beats between 100-140. Comparatively, a resting human heart beats 60-100 times per minute.
12. Dogs' eyes contain a special membrane, called the tapetum lucidum, which allows them to see in the dark.
13. Dogs do dream! Dogs and humans have the same type of slow wave sleep (SWS) and rapid eye movement (REM) and during this REM stage dogs can dream. The twitching and paw movements that occur during their sleep are signs that your pet is dreaming
14. Dalmatian puppies are pure white when they are born and develop their spots as they grow older.
15. Puppies have 28 teeth and normal adult dogs have 42.
Related: 33 Cool Facts About Dogs And Cats
16. It's rumored that, at the end of the Beatles song, "A Day in the Life," Paul McCartney recorded an ultrasonic whistle, audible only to dogs, just for his Shetland sheepdog.
17. Three dogs (from First Class cabins!) survived the sinking of the Titanic - two Pomeranians and one Pekingese.
18. Until the twentieth century dogs' teeth were used as money by Solomon Island natives.
19. Goethe couldn't stand the sound of barking dogs and could only write if he had an apple rotting in the drawer of his desk.
20. Jackals have one more pair of chromosomes than dogs or wolves.
21. Dogs and cats consume over $11 billion worth of pet food a year
22. Chinese Crested dogs can get acne.
23. "Lassie" was played by a group of male dogs; the main one was named Pal.
24. Dogs sweat only through their tongues.
25. Dogs and cats, like people, are either right-handed or left-handed-that is, these animals favor either right or left paws.
26. Dogs have 17 muscles in their ears so they can turn them in several directions to pick up sounds.
27. One million stray dogs and 500,000 stray cats live in New York city metropolitan area.
28. Dogs have four toes on their hind feet, and five on their front feet.
29. Cats can make over 100 individual vocal sounds, whereas dogs can only make 10.
30. Dogs' sense of smell is about 100,000 times stronger than humans', but they have just one-sixth our number of taste buds.
31. The most dogs ever owned by one person were 5,000 Mastiffs owned by Kubla Khan.
32. Dogs, nose prints are as unique as human fingerprints and can be used to identify them.
33. In 2003, Dr. Roger Mugford invented the 'wag-o-meter' a device that claims to interpret a dog's exact mood by measuring the wag of its tail.
34. A dog's shoulder blades are unattached to the rest of the skeleton to allow greater flexibility for running.
Related: 27 Little Known Facts About Dogs
35. The earliest European images of dogs are found in cave paintings dating back 12,000 years ago in Spain.
36. The dumbest dog in the world is the Afghan hounds.
37. Apple and pear seeds contain arsenic, which may be deadly to dogs.
38. It is much easier for dogs to learn spoken commands if they are given in conjunction with hand signals or gestures.
39. The only dog that doesn't have a pink tongue is the chow.
40. Dogs and cats, like humans, are either right or left handed.
41. Chocolate can kill dogs, as it contains theobromine, which affects their heart and nervous system.
42. A dog's sense of smell is 1,000 times more sensitive than a humans.
43. Cats have the largest eyes relative to their head size of any mammal.
44. Cats have an extra organ that allows them to taste scents on the air, which is why your cat stares at you with her mouth open from time to time.
45. A house cat's genome is 95.6 percent tiger, and they share many behaviors with their jungle ancestors.
46. Cats are believed to be the only mammals who don't taste sweetness.
47. Cats are nearsighted, but their peripheral vision and night vision are much better than that of humans.
Related: 27 Interesting Facts About Cats That Might Surprise You
48. Cats live longer when they stay indoors.
49. Cats are crepuscular, which means that they're most active at dawn and dusk.
50. Cats can spend up to a third of their waking hours grooming.
51. Certain cats go crazy for foods you wouldn't expect, like olives, potato chips, and the hops in beer.
52. For some reason, cats really dislike citrus scents.
53. Cats love to sleep in laundry baskets, too, because they're basically hiding places with peep holes.
54. Every Scottish Fold cat in the world can trace its heritage back to the first one, which was found in Scotland in the 1960s.
55. Cats were first brought to the Americas in colonial times to get rid of rodents.
56. A house cat could beat superstar runner Usain Bolt in the 200 meter dash.
57. About half of the cats in the world respond to the scent of catnip.
58. A group of kittens is called a "kindle."
59. In terms of development, the first year of a cat's life is equal to the first 15 years of a human life. After its second year, a cat is 25 in human years.
60. A female cat can be referred to as a molly or a queen, and a male cat is often labeled as a tom.
61. A cat's smell is their strongest sense, and they rely on this leading sense to identify people and objects; a feline's sense of smell is 14x better than a human's.
62. Cats only sweat through their paws and nowhere else on their body.
63. Cats can hear better than both humans and dogs.
Related: 47 Incredible Random Facts About Cats
64. Cats seek out boxes and enclosed spaces that offer cover for their predatory hunting instincts.
65. Cats don't see in black and white - but they are somewhat colorblind.
66. An entire ancient Egyptian city was founded to worship the feline deity Bastet.
67. A cat has a total of 24 whiskers, 4 rows of whiskers on each side. The upper two rows can move independently of the bottom two rows. Whiskers can also tell a cat whether the space they are entering is big enough for it.
68. Cats step with both left legs, then both right legs when they walk or run!
69. Cats can be trained to use the toilet as their litter box. Some can even be taught to flush when they're done.
70. Cats eat grass to keep their digestive systems clean. The regurgitation brings up hair and other irritants.
71. Cats will enjoy heat and sun exposure, often sleeping in a sunny area during the heat of the day. People will start to feel uncomfortable when their skin's temperature gets higher than about 44.5C (112F), but cats don't start to show of discomfort until their skin reaches about 52C (126F).
72. A steady diet of dog food may cause blindness in your cat - it lack taurine.
73. 21% of dogs and 7% of cats snore.
74. Cats can purr to express pain or fear in addition to expressing pleasure or contenment. Female cats often purr when they are in labor and when they are nursing their kittens. Purring also aids in the healing of bones, tendons, ligaments, and muscles along with providing pain relief.
75. Cats bites are more likely to become infected than dog bites - but human bites are the most dangerous of all.
76. Cats choose who they bond with, it cannot be forced. If you are the chosen one embrace it as a gift. You have your cat's love.
77. Talk about Facetime: Cats greet one another by rubbing their noses together.
78. A Selkirk slowly loses its naturally-born curly coat, but it grows again when the cat is around 8 months.
79. Because of widespread cat smuggling in ancient Egypt, the exportation of cats was a crime punishable by death.
80. Despite appearing like a wild cat, the Ocicat does not have an ounce of wild blood.
81. In the 1930s, two Russian biologists discovered that color change in Siamese kittens depend on their body temperature. Siamese cats carry albino genes that work only when the body temperature is above 98° F. If these kittens are left in a very warm room, their points won’t darken and they will stay a creamy white.
Related: 25 Weird Facts You Didn’t Know About Eyes
82. In contrast to dogs, cats have not undergone major changes during their domestication process.
83. Cat paws act as tempetature regulators, shock absorbers, hunting and grooming tools, sensors, and more
84. A cat’s heart beats nearly twice as fast as a human heart, at 110 to 140 beats a minute.
85. A cat has 230 bones in its body. A human has 206. A cat has no collarbone, so it can fit through any opening the size of its head.
86. A commemorative tower was built in Scotland for a cat named Towser, who caught nearly 30,000 mice in her lifetime.
87. Cats have about 130,000 hairs per square inch (20,155 hairs per square centimeter).
88. A cat lover is called an Ailurophilia (Greek: cat+lover).
89. A cat’s back is extremely flexible because it has up to 53 loosely fitting vertebrae. Humans only have 34.
90. A cat almost never meows at another cat, mostly just humans. Cats typically will spit, purr, and hiss at other cats.
91. Like humans, cats tend to favor one paw over another
92. On average, cats spend 2/3 of every day sleeping. That means a nine-year-old cat has been awake for only three years of its life.
Related: 101 Quick And Interesting Phobia Facts
93. A cat’s hearing is better than a dog’s. And a cat can hear high-frequency sounds up to two octaves higher than a human.
94. Eighty-eight percent of cats in the U.S. are spayed or neutered.
95. A cat's carbon footprint is similar to that of a VW Bug, whereas a dog's is more like a Hummer.
96. A cat's nose is ridged with a unique pattern, just like a human fingerprint.
97. Cats have scent glands along their tail, their forehead, lips, chin, and the underside of their front paws.
98. A cat has five toes on his front paws, and four on the back, unless he's a polydactyl.
99. A cat's cerebral cortex (the part of the brain in charge of cognitive information processing) has 300 million neurons, compared with a dog's 160 million.
100. Cats make more than 100 different sounds whereas dogs make around 10.
101. Cats are the most popular pet in the United States: There are 88 million pet cats and 74 million dogs.