9 Extreme Pets: The Smallest, Biggest and Fastest Dog and Cat Breeds

We all know that cats and dogs come in all shapes and sizes, but when you place a 6-inch-tall Chihuahua next to a nearly 3-foot-tall Irish Wolfhound, it becomes quite apparent just how dramatic those breed variations really are.

From the world's oldest dog breed to the least hairy cat breed, we rounded up nine of the most extreme feline and canine breeds.

The Chihuahua is one of the most popular breeds in AmericaSmallest Dog Breed - Chihuahua

Chihuahuas might be the tiniest dog breed, but they don't act like it. Don't be surprised when this feisty little dog tries to pick a fight with a Rottweiler at the dog park. Along with her spirited and fearless personality, the Chihuahua is exceedingly loyal to her favorite human.

Smallest Cat Breed - Singapura

The Singapura weighs a mere 4 to 6 pounds, but she has tons of energy. When the curious (and bossy) kitty isn't supervising everything that's going on in your home, you'll find her chasing toys and leaping to high places.

Tallest Dog Breed - Irish Wolfhound

It's hard to ignore the towering 30- to 35-inch-tall Irish Wolfhound - his giant size gives him quite a commanding appearance. Unfortunately, because the breed is so big, its lifespan is heartbreakingly short. The average life of the Irish Wolfhound is only 6 to 8 years.

Related: 13 Largest Dog Breeds: Towering and Commanding

Hide your valuables from this kitty.Shortest Cat Breed - Munchkin

Don't be fooled by the Munchkin's signature stubby legs; he's not a Dachshund in disguise. And if you're expecting a slow or laid-back feline, think again. The energetic breed is a true extrovert who's happy to play with other cats, dogs and kids.

Heaviest Dog Breed - Mastiff

Weighing in on average at a whopping 200 pounds, the Mastiff probably weighs more than you do. While he's a massive and extremely powerful dog, he's also a classic gentle giant who loves his family and will try his best to snuggle with you on the couch.

See Also: 10 Most High-Maintenance Dog Breeds

Least Hairy Cat Breed - Sphynx

With her wrinkly face, lemon-shaped eyes and huge ears, the Sphynx truly looks like she's out of this world. Instead of having fur, the breed's skin is covered in a fine down, like that of a peach. And though she is hairless, it doesn't mean you're off the hook for grooming her; the breed must be bathed frequently to prevent clogged pores from oily skin.

Fastest Dog Breed - Greyhound

It might not surprise you that a Greyhound can run up to 44 miles per hour, but did you know that he'd much rather curl up on the sofa than join you for a jog? If this speedy breed is going to race you to anything, it's to the comfiest spot on the couch.

The lithe Egyptian Mau is the model/actress of the cat worldFastest Cat Breed - Egyptian Mau

Considered the track star of the feline world, the Egyptian Mau can run up to 30 miles per hour. Not only is the breed incredibly speedy, but thanks to his long hind legs, he can also catapult himself to high places without a problem. So don't be surprised when this agile feline leaps up on your shoulder - or that high shelf you thought was cat-proof.

Oldest Dog Breed - Saluki

Lots of breeds claim to be thousands of years old, but analysis of the canine genome confirms that the Saluki is the world's oldest dog. The elegant sighthound is believed to have originated in Egypt around 329 B.C.

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