Sighthounds, also called gazehounds, are breeds of hunting dogs that primarily hunt by sight and speed, rather than by scent and endurance as scent hounds do.
These dogs specialize in pursuing prey, keeping it in sight, and overpowering it by their great speed and agility. They must be able to detect motion quickly, so they have keen vision. Sighthounds must be able to capture fast, agile prey such as deer and hare, so they have a very flexible back and long legs for a long stride, a deep chest to support an unusually (compared to other dogs) large heart, very efficient lungs for both anaerobic and aerobic sprints, and a lean, wiry body to keep their weight at a minimum. Sighthounds have unique anatomical and physiological features likely due to intentional selection for hunting by speed and sight; laboratory studies have established reference intervals for hematology and serum biochemical profiles in sighthounds, some of which are shared by all sighthounds and some of which may be unique to one breed. 
The typical sighthound type has a light, lean head, which is dolichocephalic in proportion. This shape can create the illusion that their heads are longer than usual. Wolves and other wild dogs are dolichocephalic or mesaticephalic, but some domesticated dogs have become brachycephalic (short-headed) due to artificial selection by humans over the course of 12,000 years. Dolichocephalic breeds have a wider field of vision but smaller overlap between the eyes and therefore possibly poorer depth perception in some of their field of view than brachycephalic breeds; most, if not all, dog breeds have less visual acuity than their antecedent the wolf.
There is no science-based evidence to confirm the popular belief that sighthounds have a higher visual acuity than other types of dogs. However, there is increasing evidence that dolichocephalic breeds, thanks to a higher number of retinal ganglion cells in their “visual streak”, retain more heightened sensitivity than other breeds to objects and rapid movement in the horizontal field of vision.
Sighthounds such as the saluki/sloughi type (both named after the Seleucid Empire) have existed for at least 5,000 years, with the earliest presumed sighthound remains appearing in the excavations of Sumer dated approximately 7000–6000 BC. The earliest description of a sighthound in European recorded history comes from Arrian's Cynegeticus, of the 2nd century AD. Although today most sighthounds are kept primarily as pets, they have been bred for thousands of years to detect movement, chase, capture, and kill prey primarily by speed. They thrive on physical activity. Some have mellow personalities, others are watchful or even hostile towards strangers, but the instinct to chase running animals remains strong.
List of sighthounds
- Borzoi (Russian Wolfhound)
- Chart Polski (Polish Greyhound)
- Galgo Español
- Hortaya Borzaya
- Irish Wolfhound
- Italian Greyhound
- Magyar agár (Hungarian Greyhound)
- Old Croatian Sighthound
- Saluki (Persian Greyhound)
- Scottish Deerhound
- Silken Windhound
Debate about breed inclusion
There has been considerable debate in many quarters about what breeds are considered to be sighthounds. This is partially due to the fact that most Anglophone kennel clubs such as The Kennel Club and American Kennel Club do not have a "Sighthound" group per se, instead including them in the larger "Hound" group. Nonetheless, the Old World (FCI) understanding of the sighthound is quite clear and well documented: sighthounds are gräoid- (greyhound-) shaped dogs, which owe their specific build to their recorded function of speed hunting.
While this debate may simply appear to be a matter of semantics, it is of deeper importance when classifying breeds based on a thorough understanding of their true history and function. The original, authentic, and documented use of a breed is paramount in deciding its category as a hound, sighthound, or working breed. It is also of practical concern where the sport of lure coursing is concerned, typically only open to breeds that may be considered sighthounds by their national breed club, and where, particularly in North America, breeds from the Hound Group are increasingly finding their way into the informal sighthound group because they are recognized as "lure coursing breeds" by ASFA and the American Kennel Club.
For instance, the Canadian Kennel Club (CKC), the American Kennel Club (AKC) and the American Sighthound Field Association (ASFA) consider the Basenji, originally a breed that tracks and drives game, to be eligible for the purpose of lure coursing even though the Fédération Cynologique Internationale (FCI) does not. The Basenji is far from alone in this. The Rhodesian Ridgeback, was actually classified as a gun dog by its founding parent club for several decades, only to be changed much later. Since that time the Ridgeback has been mired in a perpetual "classification conundrum", and is considered to be a scent hound by the FCI.
Other breeds that fall into varyingly gray areas include the Ibizan Hound, Pharaoh Hound, Cirneco dell'Etna – all originally warren rabbit hunting and retrieving scent hounds not recognized as true sighthounds in their countries of origin – as well as the Portuguese Podengo, Peruvian Inca Orchid, and the Thai Ridgeback. All of these breeds are recognized as eligible to compete in lure coursing trials by either the American Kennel Club and/or the American Sighthound Field Association, but may not be by the Fédération Cynologique Internationale.
Purebred "breed" status in question
Many hunting dog types capable of hunting by speed and sight are not recognized as sighthounds, either informally or formally by a major kennel club. These include the following which all work as sighthounds:
- American Staghound, a crossbreed
- Kangaroo Dog, a crossbreed
- Khalag Tazi
- Levriero Italiano
- Longdog, a crossbreed
- Lurcher, a crossbreed
- Mudhol Hound
- Old Croatian Sighthound
- Rampur Greyhound
Breeds considered to be controversial, not having by origin a sighthound function
A number of breeds, or types of dogs, which do not hunt solely by speed and sight, as well as a number of non-hunting breeds, are currently being recognized as sighthounds, either informally  or formally by kennel clubs, or lure and live coursing clubs. These include:
- Canary Islands Hound Podenco Canario
- Cirneco dell'Etna
- Ibizan Hound (Podenco Ibicenco)
- Pharaoh Hound (Kelb tal-fenek)
- Portuguese Podengo
- Rhodesian Ridgeback
- Peruvian Inca Orchid
- Thai Ridgeback
|Wikimedia Commons has media related to Sighthounds.|
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