The Greyhound is a very old breed of dog, a sighthound which has been historically bred for coursing game and latterly Greyhound racing. Since the rise in large scale adoption of retired racing Greyhounds, particularly in North America from the end of the 20th century, it has seen a resurgence in popularity as a family pet.
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History:
The breed's origin has in popular literature often romantically been connected to Ancient Egypt, in which it is believed "that the breed dates back about 4,000 years " a belief for which there is no scientific evidence. While similar in appearance to Saluki (Persian Greyhound) or Sloughi (tombs at Beni Hassan c. 2000 BCE), analyses of DNA reported in 2004 suggest that the Greyhound may not be closely related to these breeds, but is a close relative to herding dogs. Historical literature on the first sighthound in Europe (Arrian), the vertragus, the probable antecedent of the Greyhound, suggests that the origin is with the ancient Celts from Eastern Europe or Eurasia. Greyhound-type dogs of small, medium, and large size, would appear to have been bred across Europe since that time. All modern, pure-bred pedigree Greyhounds are derived from the Greyhound stock recorded and registered, firstly in the private 18th century, then public 19th century studbooks, which ultimately were registered with coursing, racing, and kennel club authorities of the United Kingdom. [Source1, Source 2, Source 3]Appearance:
The greyhound has a graceful, strong muscled, deep-chested, narrow-waisted, streamlined body. While running its long tail acts as a keel and the ears can fold toward the neck. Males can measure between up to 30”, weighing up to 70 lbs.The greyhound has his eyes well positioned at the sides of his head giving him a far wider field of view than other dogs (270 degrees versus 180 degrees.) They are sight hounds and can spot movement up to half a mile away.
Behavior:
Greyhounds are calm and social indoors and are often referred to as couch potatoes. Although greyhounds are possibly the most athletic of all domestic dogs they do not necessarily need a lot of exercise. Two 20 minute walks a day will usually suffice. A high fenced garden is advised as they are great jumpers. Greyhounds are fairly easy to train and can learn almost all commands. However, they must never be allowed off leash in public places, as it is in their natures to chase anything that moves and may choose to totally ignore you if they have their eyes set on a prey.They are affectionate with their families although can be aloof with strangers. They normally get on well with other dogs in the household but cat owners should exercise caution although many are said to tolerate or even take to cats or small dogs. Because of their nature as sprinters, greyhounds have relatively low endurance and their conditioning need to be slowly build up if you’d like to take him jogging.
Greyhounds rarely bark. The joke goes that greyhounds are good watchdogs: they watch thieves carry your stuff away. They are relatively small eaters and will therefore not cost a lot to feed. Grooming is very easy, a good brush once a week is enough. They don’t have much body odor but like most short haired dogs do shed a little.
I always had a thing for eyes. Cat eyes always fascinated me. I always wondered what the cats were thinking. Dog eyes were the best of all. My first dog, Tango, had dancing eyes. My Doberman, Ariel, possessed the saddest eyes I had ever seen. Then the first pair of greyhound eyes came along. Sultan had big “Bambi” eyes and classic greyhound eyeliner. His eyes said, “Love me.” Those eyes communicated better than any spoken words over the years.
Here I am, an owner of sight hounds. I got to thinking: what makes sight hounds sight hounds? They are hounds that hunt by sight. That means their gorgeous eyes are pretty important.
The eye is an organ with several parts
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| GreyHounds |
The eyeball rests in a cushion of fat that protects it in its bony socket. Seven muscles attach to the eyeball. They stabilize the eye and govern its movements. When you look at a dog’s eye, one of the first parts you will notice is the sclera. The sclera is the white area that rims most of the eye’s surface. The dog’s sclera is much less evident then a human’s sclera. Most of the dog’s eye has pigment. The pigment is in the iris, which is a layer of smooth muscle that controls the size of the pupil. Both the iris and the pupil have a cover that is a layer of thick transparent cells. These transparent cells are the cornea, or “window of the eye.”
The eye’s anatomy is similar in mammals. However, its functional capabilities vary greatly among the species. A dog’s eyes are towards the front of its head and are unable to see behind it. This is true of most predatory species. Prey species such as deer and antelopes have their eyes fixed on the sides of their heads. In some breeds, such as the sighthound breeds, the total field of vision is 270 degrees. This is 70 degrees greater than that of humans whose visual field is about 180 degrees. The average dog has a visual field of about 250 degrees. Flat faced breeds such as pugs have a little less. Therefore, sighthounds with their narrow heads can detect small movements over a much greater slice of landscape. If we are out walking and a cat is running some distance away, sighthounds will react and notice it much more quickly than a person would.
We can be walking on the road and see a squirrel sitting quietly — almost frozen, if you will. Yet, the dogs are completely oblivious to that. Although sighthounds have the ability to detect movement at great distances, their binocular vision is only about 70 degrees. Flat-faced breeds such as the pug or boxer have a binocular field of about 80 degrees. In humans the binocular field is 140 degrees; therefore humans have an advantage in depth perception. Both humans and dogs have binocular vision: we see the landscape through both eyes. When looking straight ahead, the images found by the eyes overlap to some extent. Because of the distance between the right and left eye, they will record slightly different images, which allows the brain to estimate distance shape, and texture. The greater this overlap, the greater is the capability for depth perception to evaluate and recognize objects. Without it, the landscape would look almost flat. The canine eye is smaller than the human eye although the cells in both retinas are of equal size. The image formed on the dog’s retina is only about 75 percent of the image in the human eye. This covers a smaller number of cells; we lose detail but gain sharpness and depth perception.
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Cones register fine detail in bright light. Rods in the eye are sensitive to light and are useful for black and white vision. Dogs also have a light reflecting layer called the tapetum lucidum at the back of their eyes, which acts as an image-intensifying device allowing them to utilize what little bit of illumination is available. Dog eyes that are in the process of adapting to seeing in dim light go through a few modifications. Finger-like projections of the tapetum move forward. They line the inner surface of the choroid to form a reflective layer behind the retina. The light passes through the retina in the dark-adapted eye, instead of being absorbed. The choroid reflects straight back through the retina by the tapetum twice and has a greater chance of activating the light-sensitive rods. In the dog, the tapetum is usually green or yellowish green. Hence the weird dog eyes that greet you when you are shining a flashlight in the middle of a power outage. Cats have this same advantage. Wild dogs tend to become active at dusk. That is the reason why nature allowed this adaptation to occur. Human vision has a higher cone and rod ratio and accounts for us having better color vision than dogs do. The evidence does point to the fact that dogs do perceive some colors. Perhaps they look at the world with rose-colored spectacles. This may not be a bad way to live, eh?
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The inner eye has two chambers.
The anterior chamber is between the cornea and the lens. The posterior contains a clear jelly and is the larger central cavity of the eye between the lens and the retina. Light enters the eye by passing first through the cornea and anterior chamber and then through the pupil and the lens. The iris expands and contracts, depending upon the brightness of the light. Light then traverses the posterior chamber and the retina receives it. The light converts into nerve impulses that pass via the optic nerve to the brain.The eye’s anatomy is similar in mammals. However, its functional capabilities vary greatly among the species. A dog’s eyes are towards the front of its head and are unable to see behind it. This is true of most predatory species. Prey species such as deer and antelopes have their eyes fixed on the sides of their heads. In some breeds, such as the sighthound breeds, the total field of vision is 270 degrees. This is 70 degrees greater than that of humans whose visual field is about 180 degrees. The average dog has a visual field of about 250 degrees. Flat faced breeds such as pugs have a little less. Therefore, sighthounds with their narrow heads can detect small movements over a much greater slice of landscape. If we are out walking and a cat is running some distance away, sighthounds will react and notice it much more quickly than a person would.
We can be walking on the road and see a squirrel sitting quietly — almost frozen, if you will. Yet, the dogs are completely oblivious to that. Although sighthounds have the ability to detect movement at great distances, their binocular vision is only about 70 degrees. Flat-faced breeds such as the pug or boxer have a binocular field of about 80 degrees. In humans the binocular field is 140 degrees; therefore humans have an advantage in depth perception. Both humans and dogs have binocular vision: we see the landscape through both eyes. When looking straight ahead, the images found by the eyes overlap to some extent. Because of the distance between the right and left eye, they will record slightly different images, which allows the brain to estimate distance shape, and texture. The greater this overlap, the greater is the capability for depth perception to evaluate and recognize objects. Without it, the landscape would look almost flat. The canine eye is smaller than the human eye although the cells in both retinas are of equal size. The image formed on the dog’s retina is only about 75 percent of the image in the human eye. This covers a smaller number of cells; we lose detail but gain sharpness and depth perception.
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When It’s Dark
Human eyes and dog eyes work differently in the dark. One night someone had forgotten to put on the hallway light. When I arrived home with the dogs I had a lot of difficulty finding the keyhole. I finally got the key in the lock. I was at the bottom of the stairs with Feather and Tauren. Here I am with my arms full. I can barely see in the dark and I knew the dogs had to get up the stairs. So I just let them lead the way and, sure enough, they got me safely to the top of the darkened stairs. These animals can see and navigate quite well in the dark.They have a significantly higher rod and cone ratio than we humans.What are rods and cones?
They are two different types of cells that exist in the retina of the eye. The name comes from their shape. Rods will record shapes and general outlines even in very low light levels.Cones register fine detail in bright light. Rods in the eye are sensitive to light and are useful for black and white vision. Dogs also have a light reflecting layer called the tapetum lucidum at the back of their eyes, which acts as an image-intensifying device allowing them to utilize what little bit of illumination is available. Dog eyes that are in the process of adapting to seeing in dim light go through a few modifications. Finger-like projections of the tapetum move forward. They line the inner surface of the choroid to form a reflective layer behind the retina. The light passes through the retina in the dark-adapted eye, instead of being absorbed. The choroid reflects straight back through the retina by the tapetum twice and has a greater chance of activating the light-sensitive rods. In the dog, the tapetum is usually green or yellowish green. Hence the weird dog eyes that greet you when you are shining a flashlight in the middle of a power outage. Cats have this same advantage. Wild dogs tend to become active at dusk. That is the reason why nature allowed this adaptation to occur. Human vision has a higher cone and rod ratio and accounts for us having better color vision than dogs do. The evidence does point to the fact that dogs do perceive some colors. Perhaps they look at the world with rose-colored spectacles. This may not be a bad way to live, eh?
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References:
Dog Owner’s Home Veterinary Handbook, Delbert G. Carlson D.V.M and James M. Giffen M.D.,Howell Book House, New York, 1992.
DogWatching, Desmond Morris, Three Rivers Press, New York, 1986.
Dog Behaviour, Dr. Ian Dunbar, TFH Publications, New Jersey, 1979.
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