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Editor’s Note: 1. Do Dogs Watch TV?
Do dogs watch TV?Many people contend their dogs watch TV. There are even DVDs designed to entertain dogs. These cinematic adventures are often filmed from the viewpoint of a dog, with the camera held about two feet from the ground. They include a variety of scenes, like running through fields with other dogs, racing up and down steps, going nose to nose with farm animals, chasing ducks, drinking from a bowl, taking a car ride and even a trip to the veterinarian’s office. Before you run out and buy these videos for your dog to watch, there are a few things you should know about the relationship between dogs and TV—specifically, about the way a dog’s eyes work. Dog’s-eye view A dog has the eyes of a night hunter. It is important to be able to detect surrounding movements, since things that move are most likely to be the things the dog (or at least its wild cousins) can hunt and eat. For this reason, a dog’s eyes are specially designed to pick out motion, more so than human eyes. At the level of a single cell in the eye, a moving target appears as a flicker, as it momentarily changes the light level. For this reason, behavioural researchers often use an individual’s ability to see a flickering target as a measure of the efficiency of motion perception. The researchers test how quickly they must flicker a target on and off until it looks the same as if it were continuously illuminated. The average human does not see flickering above a speed of 55 cycles per second (i.e. 55 Hz) of dark and light. This is why, for example, a fluorescent lamp seems to be continuously glowing with a uniform light, even though it is actually flickering, at a rate of some 120 Hz. When researchers tested Beagles, however, they found the dogs on average were able to see flicker rates up to 75 Hz, which is 50 per cent faster than humans can resolve. The fact dogs have better flicker perception than humans is consistent with the data that suggests they have better motion perception than humans. It can also help answer a common question: why do many dogs not seem interested in the images on TV, even when those images are designed specially for them? Screen flicker The image on a TV screen is redrawn at a rate of 60 Hz. To the best of a human’s resolution abilities, this flicker appears continuous. Changing images provide the illusion of movement, as characters on the screen advertise products or act out stories. However, because many dogs can resolve flickers at higher speed, the TV screen probably still appears to them as a rapid flicker, making the images appear less real. Thus, many dogs do not direct much—if any—of their attention to what is happening on the TV screen. Some dogs ignore the apparent flickering and will respond to interesting images on the TV screen. These dogs often ‘follow’ the images, even trying to look behind the screen to find out where something has gone after disappearing from their view. However, since a dog’s dominant sense is its nose and objects on the screen have no scent, most TV-watching dogs will quickly lose interest in the images and wander off to pursue other activities. —Dr. Stanley Coren The nose knowsNot only can dogs smell a hot dog a mile away, a new study suggests they can sniff out bladder cancer in people. In the study, urine from 36 bladder cancer patients and 108 comparison volunteers was used. Each dog had to sniff seven urine samples and lay down next to the one from the bladder cancer patient. The test was repeated eight times for each dog, with new samples each time. The dogs had an average success rate of 41 per cent, compared to 14 per cent by chance alone. The study was published by the British Medical Journal and carried out by researchers at Amersham Hospital in England. The idea came about after two London dermatologists described the case of a woman who asked that a mole be cut out of her leg because her dog would constantly sniff at it, even through her pants. One day, he tried to bite the mole off when she was wearing shorts. It turned out she had malignant melanoma. Perhaps even more intriguing, urine from one patient during the study had been deemed cancer-free, but the dogs identified it as a cancer case. Additional tests proved that, in fact, the patient had a life-threatening tumour in the right kidney. The truth about cats and dogs?The history of pets is being rewritten in the wake of new discoveries and theories. Until recently, the earliest domesticated cats were believed to be those in Egypt some 4,000 years ago. However, the journal Science published a paper in 2004 about the discovery of a kitten buried 9,500 years ago next to a human body. The bodies of the person and what was possibly its pet (though not in the contemporary sense of the term) were found in a Neolithic-era village on Cyprus, a Mediterranean island. Burial rites of the era and the way each body’s head pointed in the same direction suggest the two had a special friendship intended to continue in the afterlife. Meanwhile, that same year, dog researchers meeting at the American Association for the Advancement of Science discussed the theory that all domesticated dog breeds origninated from one species, which was likely a wolf in East Asia. Norine E. Noonan, a dog researcher at South Carolina’s College of Charleston, says domestication in that region began at least 100,000 years ago, with the wolves seeking food and warmth. These ‘proto-dogs’ helped humans hunt and in return received their protection. From there, they migrated with people to other parts of the world. Your dog smells!Dogs live in a different sensory world than humans do. What our canine companions may lack in colour vision and taste buds, they more than make up for in hearing and especially smell. Odours are everywhere, but for the most part, people do not notice them. For dogs, on the other hand, odours are the primary source of information about their environment and its other inhabitants. Physically, a dog’s olfactory system is actually very similar to a human’s, but it is many times more sensitive. The scent membrane is roughly four times the size of a human’s. The scent receptors in a dog’s nose number more than 200 million, while a human has only about five million. The moisture of a dog’s wet nose also helps capture and transmit scents more efficiently. As a result, it is estimated that the German Shepherd’s sense of smell, for example, is 1,000 times more powerful than a human’s, while a Bloodhound can recognize tiny flakes of human skin that were dropped several days before. Just how old is your cat?At a 2004 Nestle Purina Nutrition Forum in St. Louis, Mo., researchers announced a new way to look at feline aging. In the past, kittenhood was considered the growth phase in cats, ranging from their first seven to 10 years of life, depending on the breed. Cats over that age were considered to be senior or geriatric. However, feline nutritionists now believe a cat’s life should be measured in four major stages: growth (the first year); young adult (one to seven years); mature adult (seven to 12 years); and geriatric (over 12). And you thought your dog was accident-prone…A 2003 study in the U.K. has British German Shepherd owners shaking their heads. It seems the survey of one of the nation’s most popular breeds has found that despite their intelligence, German Shepherds appear to be accident-prone. Swallowing toys and getting their heads stuck in cat flaps topped owners’ lists of the most common mishpas plaguing their breed. My dog is how old?To this day, there is a commonly held belief that, in terms of aging, one human year equals seven dog years. This simple ratio, however, is far from accurate, particularly because dogs clearly reach their adulthood within the first few years of life. Furthermore, the aging process varies significantly between different canine breeds and sizes. One general formula put forth in recent years is that a dog’s age can be calculated as 10.5 dog years per human year for the first two years of life and then four years per human year thereafter. For example, a two-year-old dog is 21 in dog years, while a three-year-old dog is 25. Following this formula further, a 10-year-old dog is 53 in human years. Another similar formula suggests the first human year of a dog’s life is equivalent to 15 dog years. By the end of the second year, the dog is 24. Then it ages four years each human year thereafter. Following this formula, a three-year-old dog is 28 and 10-year-old dog is 56. However, these catch-all theories do not take into account different breeds and weights. Larger dogs tend to have shorter lives than smaller dogs. The largest breeds are often elderly by age six or seven, whereas a dog weighing less than 9 kg (20 lb.) may well be closer to 36 or 40 in dog years at that stage. Do cats have nine lives?It is widely believed that cats have nine lives, but rarely is any insight given into this idiom’s specific meaning. Theories suggest it dates back to ancient times, when nine was considered a lucky number because it was the Trinity of Trinities, a mystical quantity referred to in folklore and religion alike. In Egypt, where cats were revered, there were nine primary gods. The creator, a sun god named Atum-Ra, embodied nine lives in one entity and would transform into a cat when visiting the underworld. In other cultures, cats may not have been worshipped as divine beings, but they were seen as somehow magical in nature, particularly because of their physical resilience. And indeed, that is why the idea of cats having nine lives continues to be referenced today. Tail talesCats are one of the most expressive domesticated animals. Facially and vocally (cats can make over 100 different vocal sounds) they communicate their pleasures and displeasures to us. But what about their tails? With between 18 to 20 vertebrae, the tail can be used as a barometer into the feline mind. Take a look at your cat’s tail and learn to read its moods. If your cat’s tail is… • A curved, S-shaped tail; signifies relaxation and contentment. • A tail positioned straight up in the air, with a slight curve at the end, shows curiosity and excitement. • A fully erect tail with a slight sway indicates a casual greeting. • A hanging tail, swinging from side to side shows impatience or fury. • A curved tail with a twitching tip means it is annoyed. • A lowered tail that is tucked between the hind legs indicates total submission. • A bristled tail held down shows abject terror. • A curved tail puffed out to twice its size signifies aggressive fear—if provoked further, it will attack. • A fluffed out and erect tail indicates anger, which will likely lead to aggressive behaviour. • A tail that stands stiffly in the air signifies the cat is thrilled to see you. Do you see what I see?Dogs are like red-green colour-blind people. Red light appears as dark grey and green light appears practically white. They can see bluish-violet and yellow, with all other colours appearing as shades of grey. Much like a black and white movie, colourized with bits of violet and yellow. Canine colour blindness may sound alarming when you consider seeing-eye dogs have to decide whether it is safe for their sightless owners to cross the street, but guide dogs are actually quite capable of interpreting traffic signals as they look at the brightness and position of the stoplights. Dark light means stop and whitish light means go. They then watch for traffic flow and noise to make their decision. Cats see a bit more like humans, but do not have the same vibrancy of colour. Rather, they see a very soft pastel version of colour. The imperfect colour perception of both dogs and cats comes from rod and cone photoreceptor limitations in the retina, which is a thin layer of tissue over the eye that lets light in, allowing for sight. Incidentially, dogs are thought to have about 20/75 vision, indicating they are able to see clearly an object from 20 feet away that a person with normal vision would see at a 75-ft distance. Cats have about 20/100 vision, and horses 20/33, much closer to that of humans.
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