Animal sense: Do they hear (and see and smell and taste) what we hear?

Robin Roberts

There’s a cat named Oscar living in a Rhode Island nursing home who displays a mysterious bedside manner: He jumps up on the beds of patients who are about to die. Does Oscar have a sixth sense, or is he simply smelling the chemicals the dying release as they slip away?

In addition to a highly tuned olfactory system, cats — and dogs — out-rank us in sight, sound, taste and sense. But since they refuse to explain exactly why that is, we turn to the experts for insight.

Seeing the Light

Where we go bump in the night, bashing into furniture and stubbing our toes, cats and dogs move easily through the dark. “The cat’s cornea allows five times more light in compared to humans,” says feline specialist Dr. Elizabeth O’Brien, DVM, DABVP, owner of Hamilton’s Cat Clinic and Ancaster’s Village Cat Clinic. “Cats [and dogs] have a tapetum lucidum [layer of tissue] under the retina which gives that yellow-green reflection when you shine light in their eyes.”

Cats need one-sixth the light we do to see in the dark, dogs need one-fifth. But we trump their vision in daylight: they actually see worse than we do. They can, however, focus better and for longer, since they don’t need to blink as much to lubricate their eyes.

Cats also have better binocular vision — overlapping fields of view — of about 140 degrees (humans have 120), which gives them great depth perception. This allows them to easily gauge the distance from floor to countertop without coming up short or over-shooting. And their peripheral vision is wider than ours, 200 degrees compared to 180. Dogs’ binocular vision isn’t as good, with only 60 degrees. But, since their eyes are closer to the side of their head, they trump us all in peripheral vision, with a 250-degree radius.

As for colour, cats (and dogs) were once thought to only see black and white, but it’s now generally agreed that cats can see purple, blue, green and yellow, while other colours are varying shades of gray. Dogs’ colour vision, on the other hand, has been described as similar to a person with red-green colour blindness. Where we have three different cone cells — red, green and blue — dogs have two — yellow and blue. So if you think Fido favours the red ball, he can’t distinguish it from the green or yellow one.

Dogs are also more nearsighted than us: what we can see clearly at 75 feet, they have to be closer, about 20 feet. Cats are worse: what we can see at 200 feet, they have to be 20 feet away. But cats can detect movement much quicker than we can, which comes in handy for mouse trapping. It’s also why they’re fascinated by the television, whose signal appears jumpy to them.

Wall of Sound

Cats and dogs have us beat with their exterior, cone-shaped ears, called pinnae, that catch and amplify sound waves, allowing them to hear up to five times better than us. Although we share the same lower audio limit of about 20 hertz with cats, their higher frequency is much greater. Ours reaches as high as 20,000 Hz, dogs about 45,000, and cats up to a whopping 65,000 Hz.

Both can rotate these pinnae independently, like satellite dishes — cats up to180 degrees — to localize sound. And while dogs can hear ultra-high frequencies, like dog whistles, that we can’t, cats can actually hear even higher tone and pitch. This helps them zero in on that mole underground, the squeals from their kittens, or the whir of a moth at the window.

“Rodents vocalize way up into the ultrasonic range and cats can hear those,” says Dr. Lee Niel, assistant professor and animal behaviour expert at the University of Guelph’s Ontario Veterinary College. “They hear those very high-pitch sounds that we have no idea about.”

Floppy-eared dogs aren’t as aurally disadvantaged as you’d think, although all dogs are not as adept as cats or humans at locating sound direction. “You’ll see when they’re really listening, they’ll pull their ear up to open it more,” says Dr. Niel.

With such super-sensitive ear drums, it’s amazing most dogs and cats can sit serenely while their owners blast the radio or TV without seeming the least bit bothered. “It’s not necessarily that they’re more sensitive to sound, it’s that they have a broader range of sounds they can hear,” says Dr. Niel. “They may be sensitive to certain ranges that we’re not.”

Shatter a glass or plate on the floor, for example, and they’ll hear a wide range of high-frequency sounds in the clatter that we don’t.

What’s That Smell?

A cat’s nose has around 200 million nerve cells while ours clock in around five or six million, making their sense of smell 15 times stronger than ours. Every cat also has tiny lines that run across its nose that is said to be as unique as a human fingerprint.

Dogs are tops, however, with some 300 million olfactory receptors in their noses. Which explains why you won’t find a calico sniffing your luggage at the airport. “Their sense of smell is not as good as a dog’s, but their ability to detect a very subtle change in temperature over their nose is better,” says Dr. O’Brien.

As an added advantage over humans, both dogs and cats have a secondary set of olfactory devices, called the Jacobson’s organ, on the roof of their mouth. Some researchers believe the information it processes lies between taste and smell. “I see it a lot in the clinic,” says Dr. O’Brien, who describes cats who come in and intently check out the previous patient’s presence with their high-res sniffers. “They suck in air over that gland in the roof of their mouth, and go into a flehmen response,” or lip curl, which they use to dissect a smell. Cats do it, dogs do it, rhinos, rams and giraffes do it, and it looks pretty hilarious. “It looks like they’re stunned, like they’re not breathing, with their mouth open, eyes dilated. They’re picking up the pheromones, those odorless chemicals, from the cat that was here earlier,” left behind by its paw pads or cheek glands.

A dog’s sense of smell is 1,000 times sharper than ours — some experts claim its millions times better. So why doesn’t he high tail it out of the kitchen when you burn the toast? “He probably still thinks it smells delicious!” says Dr. Niel.

Rover can also differentiate up to 100,000 smells, which is why he prefers to wolf his food rather than savour the flavour. His nostrils can move independently of one another to pinpoint where that succulent steak is grilling.

Taste Test

Humans and dogs top cats in taste, since cats have fewer taste buds — a mere 475 compared to a dog’s 1,700 and our 9,000. Because they’re carnivores, cats prefer fats and proteins and can’t actually taste sweet flavours. They can, however, taste bitterness, according to a recent study at the Monell Chemical Senses Center in Philadelphia. Apparently, cats have at least seven bitter receptors on their tongue (humans have 24). These help them determine whether or not what they’re about to chow down on is poisonous, since most toxins are bitter.

Dogs are basically omnivores (pizza, pasta, socks), but in the wild they were predominantly meat eaters, and still prefer it. Since meat is naturally salty, they get all they need and therefore don’t crave it.

Touchy-Feely

Cats’ paws are so sensitive they can sense insect or rodent movement under the ground. Their whiskers, about 12 on each side of their face, contain delicate nerve endings to detect the slightest touch — and the narrowest openings. They’re also loaded with sensory cells that notice the subtlest change in air movement.

“The skin around the nasal area is incredibly sensitive to changes in temperature, which helps in locating prey,” says Dr. O’Brien. “Cats have specialized hairs called vibrissae on their faces and forelegs. Facial vibrissae are ‘whiskers’, which help with tactile recognition, locating prey, food, water. The upper rows of whiskers actually move independently.”

Dogs also rely on their whiskers for spatial awareness, wind speed, level of water from their face when they’re swimming. Cats and dogs will both point their whiskers forward when threatened.

Sixth Sense

Although both Dr. Niel and Dr. O’Brien say there is no scientific evidence to support the theory that cats and dogs can predict earthquakes, tsunamis, hurricanes or other natural disasters, they do say there’s plenty of anecdotal evidence.

“I can tell you that often if a storm is coming or there’s a weather change, my feline patients are more reactive and tense,” says Dr. O’Brien.

Dr. Niel muses, “I wonder if that goes back to their paws being more sensitive,” that they can feel an impending disaster through those little cat feet.

As for seeing dead people, again, there’s no scientific evidence that ghosts exist, so there’s no evidence pets can sense them. But if your cat has ever suddenly fixated on a spot above your head and there’s nothing there, it can give you the chills. Dr. Niel explains the behaviour this way: “Cats and dogs are more sensitive to motion, so it could be that there’s a small beam of light, fleck of dust, or some other movement that we’re not tuned into that they are.”

Tell that to Oscar . . .