Cats: Facts about our feline friends

Cats come in many breeds, though not with the same degree of diversity as dogs. The recognized number of cat breeds varies depending on the organization. The Cat Fanciers' Association recognizes 45 pedigreed breeds as well as the "companion cat," also known as "most regular cats," while the International Cat Association recognizes 73 breeds.

These breeds include relatively well-known varieties, like the slender Siamese cat and the fluffy Persian, as well as the leopard-spotted Bengal, the short-tailed American bobtail and the hairless Sphynx.

While dogs have been bred over centuries to carry out different tasks, leading to a variety of sizes and shapes of dog, domestic cats have only two jobs: controlling pests and being pets. This means that most pedigreed cats are bred for traits such as color and fur length rather than, say, a waterproof coat for swimming or a strong herding instinct for guarding sheep. Most cat breeds date to less than 100 years ago — although older breeds, like the Egyptian Mau or Persian, date back further.

Cats are intelligent, and the widely held belief that dogs are smarter than cats may not be supported by science. Felines display object permanence — or the ability to realize that something still exists when it's out of sight — which is an ability humans only develop when they are around 8 months old. Object permanence is an important skill to have when you're a hunter operating at night, listening for the telltale patter of tiny mice feet. Cats also recognize their owners' voices.

But cats don't always make their smarts easy to measure. "They're a nightmare to work with in the lab," said Julia Meyers-Manor, a psychologist at Ripon College in Wisconsin who studies animal cognition.

Compared with other animals, such as rats and dogs, few studies have been done on cat intelligence, Meyers-Manor told Live Science. Cats hate strangers and unfamiliar places, like labs, she said. They typically bury their faces in their owners' arms and refuse to cooperate with the task at hand.

Cats might not be the most socially savvy, but there is evidence that they form bonds with their humans. Cats can develop separation anxiety, often displayed by peeing or pooping somewhere they shouldn't, and studies also suggest that cats rely on emotional cues from their owners when responding to new situations. Cats also seem to recognize the emotions of both humans and other cats.

Cats have excellent nighttime vision. Their eyes are equipped with many rods, or special cells in the retina that are good at capturing dim light. This enables cats to see six to eight times better in the dark than humans can. A reflective layer in the eye also helps collect extra light at night. This layer is what makes cats' eyes shine green if a flashlight or headlight catches their eye in the dark.

Research suggests that cats can see ultraviolet light, which is blue light outside the range that humans can see. Cats likely don't see color as well as humans, though. They have two types of cells in their eyes that can detect short- and long-wavelength light, while humans have three. Their world probably looks more desaturated, or less colorful, and they also can't see long distances as well as humans. However, cats have a broader field of view than humans do: 200 degrees compared with 180 degrees for people.

Cats aren't particularly strong smellers, but their sense of hearing is very sensitive. Cats can hear frequencies between 55 hertz and 78 kilohertz. For comparison, the deepest sound a human can hear is 20 hertz, and the most piercing high sound is around 20 kilohertz.

Cats still work to control rats and mice around farms, nurseries and warehouses. But most of the time, a cat's job is to provide companionship for people.

Science suggests they do their job well. One study found that spending time with a cat reduced heart rate and blood pressure in both owners and volunteers who didn't own cats. Another study found that cats reduced their owners' negative moods. These effects may be tied to changes in brain activity. One study found that playing with, petting, training and feeding cats all activated a region of the brain called the prefrontal cortex that is linked to empathy and nonverbal communication.

The scientists said that cats' independence seemed to be key to making the cat-human relationship work. Getting a normally uncooperative cat to cooperate with play or training provided a big mood jolt, the researchers found. It turns out that for cats, playing hard to get pays off.