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Dog

Dog


Conservation status: DomesticatedCategory:Domesticated animals The dog is a canine mammal of the Order Carnivora that has been domesticated for at least 24,800 years and perhaps for as long as 150,000 years based on recent evidence. In this time, the dog has been developed into hundreds of breeds with a great degree of variation. For example, heights range from just a few inches (such as the Chihuahua) to nearly three feet (such as the Irish Wolfhound), and colors range from white to black, with reds, grays (usually called blue), and browns occurring in a tremendous variation of patterns. Dogs, like humans, are highly social animals and pack hunters; this similarity in their overall behavioral design accounts for their trainability, playfulness, and ability to fit into human households and social situations. Dogs fill a variety of roles in human society and are often trained as working dogs. For dogs that do not have traditional jobs, a wide range of dog sports provide the opportunity to exhibit their natural skills. In many countries, the most common and perhaps most important role of dogs is as companions. Dogs have lived with and worked with humans in so many roles that their loyalty has earned them the sobriquet "man's best friend." Conversely, some cultures consider dogs to be unclean. In other cultures, some dogs are used as food.

Terminology

unclean Dog, in common usage, refers to the domestic dog, Canis lupus familiaris (originally classified as Canis familiaris by Linnaeus in 1758, but reclassified as a subspecies of the wolf, Canis lupus, by the Smithsonian Institution and the American Society of Mammalogists in 1993). The word is sometimes used to refer collectively to any mammal belonging to the family Canidae (as in "the dog family"), such as wolves, foxes and coyotes.
- Dog is also a term used by breeders to specifically denote a male domestic dog.
- Bitch is a female dog who is capable of breeding or has bred.
- Pack is used to denote a group of dogs.
- Puppy is a juvenile dog.
- Pooch, Poochie, Dogay, Pup, Pupsie, Doggy or Doggie are all informal and affectionate terms for a dog often used by children. Many additional terms are used for dogs that are not purebred; see Terms for mixed-breed dogs.

Physical characteristics

Although selective breeding has changed the appearance of many breeds, all dogs retain the basic ingredients from their distant ancestors. Like most predatory mammals, the dog has powerful muscles, a cardiovascular system that supports both sprinting and endurance, and teeth for catching, holding, and tearing. Its skeleton provides the ability to run and leap. They have small, tight feet, walking on their toes. :For details about dog appearance and physical attributes, see dog anatomy.

Intelligence

Among dog lovers, dogs are generally valued for their intelligence. Anecdotal evidence suggests that dogs have a reasonably high intelligence. For a detailed discussion on what dog intelligence is, see dog intelligence.

Diet

dog intelligence Presently, there is academic discussion as to whether domestic dogs are omnivores or carnivores. The classification in the Order Carnivora does not necessarily mean that a dog's diet must be restricted to meat. Unlike an obligate carnivore, such as a cat, a dog is not dependent on meat protein in order to fulfill its dietary requirements. Dogs are able to healthily digest a variety of foods including vegetables and grains, and in fact can consume a large proportion of these in its diet. Wild canines not only eat available plants to obtain key amino acids, but may also obtain nutrients from vegetable matter from the stomach contents of their herbivorous prey. Domestic dogs can survive healthily on a reasonable and carefully designed vegetarian diet, particularly if eggs and milk products are included. In the wild these diets are typically pursued in the absence of available meat. It has also been noted that extremely stressful conditions, such as the Iditarod race and scientific studies of similar conditions, suggest that high-protein diets including meat help prevent damage to muscle tissue. This research is also true of other mammals.

Dangerous substances

Some foods commonly enjoyed by humans are dangerous to dogs, including chocolate, grapes and raisins, onions, Macadamia nuts, and hops. Dogs also may find some poisons attractive, including antifreeze and snail bait.

Reproduction

Among professional breeders, dogs are only allowed to mate for a specific purpose. Sometimes dogs are bred to create puppies to sell, or sometimes to carry on an award-winning purebred line. Breeders who do this are usually experienced in this process. Dog breeders have access to records which allow them to accurately guess which characteristics will "breed true" in a particular dog. Dog breeders also have accurate information on the complexities of the reproductive process for the breed of dog that they are accustomed to handling. Dog owners may accidently allow their pets to breed without regard to bloodlines.

Fertility

As with most domesticated species, one of the first and strongest effects seen from selective breeding is selection for cooperation with the breeding process as directed by humans. In domestic dogs, one of the behaviours that is noted is the abolition of the pair bond seen in wild canines. The ability of female domestic dog to come into estrus at any time of the year and usually twice a year is also valued. The amount of time between cycles varies greatly among different dogs, but a particular dog's cycle tends to be consistent through her life. This also called in season or in heat. Conversely, undomesticated canine species experience estrus once a year, typically in late winter.

Menarche

Most bitches come into season for the first time between 6 and 12 months, although some larger breeds delay until as late as 2 years. Like most mammals, the age that a bitch first comes into season is mostly a function of her current body weight as a proportion of her body weight when fully mature. The different rates of maturation are responsible for the menarche, not the chronological age.

Pregnancy and litters

menarche A general rule of thumb is that a mammal will produce half as many offspring as the number of teats on the mother. This rule is altered in domesticated animals since larger litters are often favoured for economic reasons. Dogs bear their litters roughly 9 weeks after fertilization. An average litter consists of about six puppies, though this number may vary wildly based on the breed of dog. Since a mother can only provide nutrients and care to a limited number of offspring, humans must assist in the care and feeding when the litter exceeds approximately eight puppies. Some breeds have been developed to emphasize certain physical traits beyond the point at which they can safely bear litters on their own. For example, the Bulldog often requires artificial insemination and almost always requires cesarean section for giving birth.

Spaying and neutering

Dog experts advise that dogs not intended for further breeding should be spayed or neutered so that they do not have undesired puppies. Unwanted puppies are abandoned, eaten, or sometimes disposed of in an inhumane fashion. It is also common for adult stray dogs who are placed in animal shelters to be euthanized due to lack of space and resources. Spaying and neutering can also help prevent hormone-driven diseases such as breast cancer and prostate cancer, as well as undesired hormone-driven behaviors. Contrary to myth, it is not required for a female dog to either experience a heat cycle or have puppies before spaying, and likewise, a male dog does not need the experience of mating before neutering; these myths are responsible for numerous unnecessary health problems and unwanted puppies. It should also be noted that a female dog may become pregnant prior to her first cycle and should be kept away from other male dogs, including littermates over the age of 4 months. Many veterinarians recommend that owners neuter/spay their pets around the age of 5 months.

Attributes

neutered Modern dog breeds show more variation in size, appearance, and behavior than any other domestic animal. Within the range of extremes, dogs generally share attributes with their wild ancestors, the wolves. Dogs are predators and scavengers, possessing sharp teeth and strong jaws for attacking, holding, and tearing their food.

Sight

Dogs were thought to be dichromats and thus, by human standards, color blind.1, 2 New research is now being explored that suggests that dogs may actually see some colour, but not to the extent that humans do. Because the lenses of dogs' eyes are flatter than humans', they cannot see as much detail; on the other hand, their eyes are more sensitive to light and motion than humans' eyes. Some breeds, particularly the best sighthounds, have a field of vision up to 270° (compared to 100° to 120° for humans), although broad-headed breeds with their eyes set forward have a much narrower field of vision, as low as 180°.1, 2

Hearing

Dogs detect sounds as low as the 20 to 70 Hz frequency range (compared to 16 to 20 Hz for humans) and as high as 70,000 to 100,000 Hz (compared to 20,000 Hz for humans)2, and in addition have a degree of ear mobility that helps them to rapidly pinpoint the exact location of a sound. They can identify a sound's location much faster than can a human, and they can hear sounds up to four times the distance that humans can.

Scenting

Dogs have nearly 220 million smell-sensitive cells over an area about the size of a pocket handkerchief (compared to 5 million over an area the size of a postage stamp for humans). Some breeds have been selectively bred for excellence in detecting scents, even compared to their canine brethren. Other than the oversimplified obvious, i.e. chemical compounds that affect chemical sensors in the nose, what a dog actually detects when he is scenting is not really understood; although once a matter of debate, it now seems to be well established that dogs can distinguish two different types of scents when trailing, an air scent from some person or thing that has recently passed by, as well as a ground scent that remains detectable for a much longer period. The characteristics and behavior of these two types of scent trail would seem, after some thought, to be quite different, the air scent being intermittent but perhaps less obscured by competing scents, whereas the ground scent would be relatively permanent with respect to careful and repetitive search by the dog, but would seem to be much more contaminated with other scents. In any event, it is established by those who train tracking dogs that it is impossible to teach the dog how to track any better than it does naturally; the object instead is to motivate it properly, and teach it to maintain focus on a single track and ignore any others that might otherwise seem of greater interest to an untrained dog. An intensive search for a scent, for instance searching a ship for contraband, can actually be very fatiguing for a dog, and the dog must be motivated to continue this hard work for a long period of time.

Direction and spatial sense

It has been observed that a lost dog can often find its way home, sometimes traveling over long distances.

Weather detection

Dogs also have the ability to sense inclement weather (mainly thunderstorms) many miles away. This is due to their keen ability to detect fluctuations in barometric pressure and can explain a dog's anxiety before and during a storm. The evolutionary ability of sensing weather can be traced back to when wolves used it to move the pack into proper shelter before a dangerous storm.

Diseases and ailments

Dogs are susceptible to various diseases, ailments, and poisons, some of which affect humans in the same way, others of which are unique to dogs. For additional information on these and other related topics, see dog health and :Category:Dog health.

Diseases

Diseases commonly associated with dogs include rabies (hydrophobia), canine parvovirus, and canine distemper, although there are many others.

Parasites

Common external parasites are various species of fleas, ticks, and mites. Internal parasites include hookworms, tapeworms, roundworms, and heartworms.

Common Physical Disorders

Some breeds of dogs are also prone to certain genetic ailments, such as hip dysplasia, luxating patellas, cleft palate, blindness, or deafness. Dogs are also susceptible to the same ailments that humans are, including diabetes, epilepsy, cancer, and arthritis. Gastric torsion and bloat is a dangerous problem in some large-chested breeds.

Behaviour

bloat All dogs have a tremendous capacity to learn complex social behavior and to interpret varied body language and sounds, and, like many predators, can react to and learn from novel situations. The requirements of coordinating complex social behavior requires that canines have the ability to sense and deliver a wide variety of cues via body language, more so than for even humans, who can use language for the same purpose. Physiologically, this correlates with such features as a large number of nerves innervating the facial muscles of dogs, allowing subtle control of a wide variety of facial expressions; in contrast to cats, for instance, who have many fewer nerves governing their facial muscles, resulting in a smaller repertoire or "vocabulary" of expressions. This ability to read and deliver nonverbal cues makes dogs expert at reading human beings, as well, often even more so than other humans are, who rely on language. Most dog owners have a large collection of stories about their dogs recognizing individuals by their footsteps outside the door, and so on.

Interactions between Dogs and Humans

:Main article: Dog society The relationship between dogs and humans is rooted in history and dogs coexist with humans in a variety of ways. Dogs thrive in small social groups or packs which, from their viewpoint, can include humans. Dog society can be thought of as dog packs characterized by a companionate hierarchy, in which each individual has a rank, and in which there is intense loyalty within the group. Dogs thrive in human society because their relationships with humans mimic their natural social patterns. The dog is always aware of its rank relative to other individuals in the group. An assertive dog may consider itself the alpha animal, considering its human master to be subordinate.

Treats

Many dogs consider anything given to them directly by hand to be a treat, even the food they are accustomed to at meal time. Special dog treats are not necessary for such animals. Care should also be taken to avoid dropping small but inedible objects (such as marbles, coins, rings, etc.) around such dogs. Some food considered as treats for humans, such as chocolate and raisins, are poisonous to dogs. If a dog has something valuable (rings, money, irreplaceable items), a treat should be used to "barter" with the dog to retrieve the stolen item. Chasing a dog will encourage play behavior, which may cause the item to be swallowed or destroyed.

Dogs as working partners

Many breeds of dogs, but not least German Shepherd, Labrador Retriever, and Border Collie are commonly used as working dogs. There are service dogs, guard dogs, hunting dogs, and herding dogs. Dogs have served as guides for the blind, as commandos, and have flown into outer space (see Laika and other Russian space dogs). Most modern working dogs are put in positions which capitalize on their sensory or strength and endurance advantages over normal humans. Dogs are also used for searching for or rescuing people and animals, such as in avalanches, at disaster sites, and for missing people or pets.

Dogs as hunting and sporting partners

Many people compete with their dogs in a variety of dog sports, including agility, flyball, and many others. This often strengthens the bond between human and dog, since they must trust one another in a variety of environments and must learn how the other works and thinks. Setters in particular have a long history as upland gun dogs. They have a native ability to discover and "hold" upland game birds; to freeze them momentarily on the ground with their silent, elongated pointing stance. Once the hunter approaches, at his command they will flush the birds to fly and for the hunter to shoot at. As water dogs, the retrievers are unsurpassed. They can spend long hours in a duck blind and, after the hunter has fired at multiple ducks or geese, they can visually spot and remember the location of downed birds. At command, they dive into the icy water, swim out and retrieve the birds one by one. They can follow hand, verbal, and whistle commands at great distance as the hunter directs them to the downed bird. They typically have large, gentle muzzles to mitigate any potential damage to the game. When trained, beagles are particularly adept at chasing through thick briars and brush after rabbits. Many hound breeds are excellent at treeing raccoons during hunting season. Hunters with dogs report the satisfaction that the dogs seem to exhibit. Excitement is evident as they see the hunters load weapons, take to the field, and begin the hunt.

Dogs as pets

hound make the best pets]] Relationships between humans and dogs are often characterized by strong emotional bonds. Consequently, dogs are popular as pets and companions, independent of any utilitarian considerations. Many dog owners consider having unconditional acceptance from a friend who is always happy to see them to be quite utilitarian, particularly if the dog also leads them to regular exercise. Empirically, dogs are quite dependent on human companionship and may suffer poor health in its absence. Many dogs are reported to have separation anxiety if its owner is away for an extended period of time. Some research demonstrates that dogs are able to convey a depth of emotion not seen to the same extent in any other animal; this is purportedly due to their closely-knit development with modern man, and the survival-benefits of such communication as dogs became more dependent on humans for sustenance. Nevertheless, it is often unwise to anthropomorphize the responses of dogs. Despite understandably positive interpretations by dog owners, it is questionable whether these animals are truly capable of feeling emotions on a human level. More research is needed to determine the intelligence level of dogs, and the motivations behind their responses to their masters.

Dogs as food

:Main article: Taboo food and drink In some countries, certain breeds of dogs are raised for their meat. Often times, this causes friction with societies that want a complete ban on consumption of dog meat. In times of great stress, such as when the Vikings of Greenland starved to death at the start of the Little Ice Age (14th century - 19th century), humans have been known to eat their pets. In some small Chinese provincial towns, there is a special breed of dog (called "Black Dogs" in Chinese language) mainly used for cuisine. However, almost any breed of dog is eaten all over China. Although some Western dog lovers may claim that dog is regarded as a "lower source of food," many Asians, in actuality, regard it as a luxury food, costing much more than other types of meat. The people of Korea have been known to eat certain breeds of dogs as well. This led to issues during the 2002 Football World Cup when South Korea was hosting the game with the local government keen to obscure this practice from visiting countries.

Attacks on humans and livestock

Humans have a tendency to anthropomorphize animals, particularly pets such as dogs, which are generally portrayed as being "man's best friend". Animals are often given attributes such as "loyal", "cute", and "guardian", but these all have the potential to lure people into a false sense of security. After thousands of years of domestication and selective breeding for dogs who do not show aggression towards humans, most dogs are unlikely to attack people. However, their sharp teeth and claws can inflict injury in an attack; a large dog can knock a human down. Provocation can range from something as seemingly innocuous as a toddler pulling a dog's tail, in which case the dog might nip to discourage the behavior, to something completely transparent to humans, such as an odor or a movement that sets a dog off, to blatant human aggression or violence towards a dog, causing it to defend itself. There are hundreds of shades of provocation that may or may not lead to an attack upon a human. Canine aggression upon humans is ordinarily not tolerated. With formidable skills and weapons as hunters as well as large and unfussy appetites, dogs often menace livestock and wildlife. In most jurisdictions, dogs are destroyed for killing other creatures, so dogs should be prevented from any encounter with livestock or wildlife that might lead to a predatory response. The same creatures that wolves, coyotes, and foxes attack as prey, especially sheep and poultry, are similarly attractive prey to dogs. For more information about attack provocations and attack behavior, see dog attacks.

Abandoned Dogs

Wild dogs are shot by farmers in an effort to protect livestock. Bodies are sometimes tied to fences as warning to other dogs, especially in rural United States and Canada. Abandoned domestic dogs who become feral are particularly dangerous; they lack the survival skills of wild canines, as well as the genetic and learned fear of the humans' world. Feral dogs often form predatory packs that attack livestock and occasionally also prove dangerous to humans.

Ancestry and history of domestication

feral Molecular systematics indicate that the domestic dog is descended from a wolf-like ancestor. As reflected in the nomenclature, dogs are a subspecies of wolf and are thus still able to interbreed. The relationship between man and canine is a long-standing tradition. Wolf remains have been found in association with hominid remains dating from 400,000 years ago. Dogs were, and are, valued for their aid in hunting. Dog burials at the Mesolithic cemetery of Svaerdborg in Denmark indicate that in ancient Europe dogs were valued companions. The molecular genetic data suggests that the domestic lineage separated from modern wolves around 150,000 years ago (Vilà et al, 1997). Conservative estimates propose that the domestication of the dog probably occurred at least 14,000 years ago. There is archaeological evidence of dog remains that are morphologically different from wolves from that time frame. However, in the early 2000s [http://www.amonline.net.au/archive.cfm?id=716 some research] indicated that domestication in fact had already begun to occur as early as 100,000 years ago.

Wolf ancestors

Some evidence suggests that several varieties of ancient wolves contributed genetically to the domestic dog. These contributions may have been deliberate or unintentional interbreeding. This means that various traits from one or more of the ancestral wolf lines were preserved in the domestic dog. Although all wolves belong to the species Canis lupus, there are (or were) many subspecies that had developed a distinctive appearance, social structure, and other traits. For example, the Japanese wolf and the Eastern Timber Wolf posses different distinctive colouration, hunting and social structures. The Indian Wolf is thought to have contributed to the development of more breeds of dogs than other subspecies. Many of today's wild dogs, such as the dingo, the dhole and pariah dogs, are descended from this wolf. Domestic dogs like sight hounds are also thought to have descended from this wolf according to [http://www.abc.net.au/rn/science/ss/stories/s728909.htm recent genetic evidence]. This hypothesis that modern dog breeds originated from Asia contradicts an earlier theory that dogs had evolved in Africa, much like humans. The Indian wolf is also thought to have bred with descendants of the European wolf to create the Mastiffs and eventually leading to the development of such diverse breeds as the Pug, the Saint Bernard, and the Bloodhound. The Tibetan Mastiff is an example of an ancient breed. The European wolf, in turn, may have contributed many of its attributes to the Spitz dog types, most terriers, and many of today's sheepdogs. The Chinese wolf is probably ancestor to the Pekingese and toy spaniels, although it is also probable that descendants of the Chinese and European wolves encountered each other over the millennia, contributing to many of the oriental toy breeds. The Eastern Timber Wolf is a direct ancestor to most, if not all, of the North American northern sled dog types. This interbreeding still occurs with dogs living in the Arctic region, where the attributes of the wolf that enable survival in a hostile environment are valued by humans. Additionally, unintentional crossbreeding occurs simply because dogs and wolves live in the same environment. The general reproductive isolation which is required to define dogs and wolves as separate species is purely a result of lack of opportunity, stemming from a general mutual unfamiliarity, suspicion, mistrust, and fear. The phenotypic characteristic that define a wolf from a dog are tenuous. Wolves typically have a "brush tail" and erect ears. While some dog breeds possess one of these characteristics, they rarely possess both.

Speed of domestication

Current research indicates that domestication, or the attributes of a domesticated animal, [http://www.amsci.org/amsci/articles/99articles/Trut.html#26879 can occur much more quickly] than previously believed. Domestication of a wild dog may occur within one or two human generations with deliberate selective breeding. It is also now generally believed that initial domestication was not attained solely by human desire intervention but through mutual desire. Wild canines who scavenged around human habitations received more food than their more skittish or fearful counterparts. Canines who attacked people or their children were likely killed or driven away, while those more friendly animals survived. Canines would have been beneficial by chasing away other vermin or scavengers. The relationship is theorized to have developed in this way.

Dog breeds

There are numerous dog breeds, over 800 being recognized by various kennel clubs worldwide. As all dog breeds have been derived from mixed-breed dog populations, the term "purebred" has meaning only with respect to a certain number of generations. Many dogs, especially outside the United States and Western Europe, belong to no recognized breed. A few basic breed types have evolved gradually during the domesticated dog's relationship with man over the last 10,000 or more years, but most modern breeds are of relatively recent derivation. Many of these are the product of a deliberate process of artificial selection. Because of this, some breeds are highly specialized, and there is extraordinary morphological diversity across different breeds. Despite these differences, dogs are able to distinguish dogs from other kinds of animal. The definition of a dog breed is a matter of some controversy. Some groups use a definition that ultimately requires extreme inbreeding to qualify due to the low gene pool. Dogs that are bred in this manner often end up with severe health or behavioural problems. Other organizations define a breed more loosely, such that an individual may be considered of one breed as long as 75% of its parentage is of that breed. These considerations come into play among breeders who enter their dogs in dog shows. Even prize-winning purebred dogs sometimes possess crippling genetic defects due to inbreeding. These problems are not limited to purebred dogs and can affect mixed-breed populations. The behavior and appearance of a dog of a particular breed can be predicted fairly accurately, while mixed-breed dogs show a broader range of innovative appearance and behavior. In February 2004, the Canine Studies Institute in Aurora, Ohio, arranged recognized breeds of dogs into ten categories. Mixed-breed dogs or Mongrels are dogs that do not belong to specific breeds, being mixtures of two or more in variant percentages. Mixed breeds, or dogs with no purebred ancestry, are not inherently "better" or "worse" than purebred dogs as companions, pets, working dogs, or competitors in dog sports. Sometimes mixed-breed dogs are deliberately bred, for example, the Cockapoo, a mixture of Cocker Spaniel and Miniature Poodle. Such deliberate crosses may display hybrid vigor and other desirable traits, but can also lack one or more of the desired traits of their parents, such as temperament or a particular color or coat. However, without genetic testing of the parents, the crosses can sometimes end up inheriting genetic defects that occur in both parental breeds. Deliberately crossing two or more breeds is also a manner of establishing new breeds.

Neoteny in the rapid evolution of diverse dog breeds

This rapid evolution of dogs from wolves is an example of neoteny or paedomorphism. As with many species, the young wolves are more social and less dominant than adults; therefore, the selection for these characteristics, whether deliberate or inadvertent, is more likely to result in a simple retention of juvenile characteristics into adulthood than to generate a complex of independent new changes in behavior. This is true of many domesticated animals, including human beings themselves, who have many characteristics similar to young bonobo. This paedomorphic selection naturally results in a retention of juvenile physical characteristics as well. Compared to wolves, many adult dog breeds retain such juvenile characteristics as soft fuzzy fur, round torsos, large heads and eyes, ears that hang down rather than stand erect, etc.; characteristics which are shared by most juvenile mammals, and therefore generally elicit some degree of protective and nurturing behavior cross-species from most adult mammals, including humans, who term such characteristics "cute" or "appealing". The example of canine neoteny goes even further, in that the various breeds are differently neotenized according to the type of behavior that was selected.
- Breeds that guard flocks, such as the various sheepdog breeds, retain the most juvenile characteristics: they stay close to home with their foster "litter" (which might include a flock of sheep), rather than going out hunting, they have almost no predatory behavior (which would be disastrous in the vicinity of such a natural prey stimulus as sheep), they respond to perceived threats with a lot of vocalization and attempts to alert and engage the dominant individuals in their "pack" (i.e. humans) whenever possible, engaging in actual combat only as a last resort. In addition, they retain very juvenile physical characteristics such as round bodies and heads, soft coats, ears that hang down, and so on, which do not elicit fear responses from the sheep in the way that an appearance similar to that of an adult wolf would. (Compare to the physical appearance of the border collie, a sheep herding dog, whose physical configuration is closer to that of an adult wild canine and who therefore has a greater capacity to frighten sheep into a desired pattern of movement, along with the more adult aggressive temperament to do so).
- Breeds that are hunting dogs—that is, pointers, setters, spaniels, retrievers, etc.—have an intermediate degree of paedomorphism; they are at the point where they share in the pack's hunting behavior, but are still in a junior role, not participating in the actual attack. They identify potential prey and freeze into immobility, for instance, but refrain from then stalking the prey as an adult predator would do next; this results in the "pointing" behavior for which such dogs are bred. Similarly, they seize dead or wounded prey and bring it back to the "pack", even though they did not attack it themselves, that is, "retrieving" behavior. Their physical characteristics are closer to that of the mature wild canine than the sheepdog breeds, but they typically do not have erect ears, etc.
- Scenthounds maintain an intermediate body type and behavior pattern that causes them to actually pursue prey by tracking their scent, but tend to refrain from actual individual attacks in favor of vocally summoning the pack leaders (in this case, humans) to do the job. This contrasts with sighthounds, who pursue and attack perceived prey on sight, and who maintain the mature canine body type with erect ears, lean bodies, and adult coats.
- Terriers similarly have adult aggressive behavior, famously coupled with a lack of juvenile submission, and display correspondingly adult physical features such as erect ears, although many breeds have also been selected for size and sometimes dwarfed legs to enable them to pursue prey in their burrows.
- The least paedomorphic behavior pattern may be that of the basenji, bred in Africa to hunt alongside humans almost on a peer basis; this breed is often described as highly independent, neither needing nor appreciating a great deal of human attention or nurturing, often described as "catlike" in its behavior. It too has the body plan of an adult canine predator. Of course, dogs in general possess a significant ability to modify their behavior according to experience, including adapting to the behavior of their "pack leaders"—again, humans. This allows them to be trained to behave in a way that is not specifically the most natural to their breed; nevertheless, the accumulated experience of thousands of years shows that some combinations of nature and nurture are quite daunting, for instance, training whippets to guard flocks of sheep.

See also


- Dog communication
- bark (dog)

References and further reading

References


- Kennel Club Books [http://www.kennelclubbooks.com Website] 400 titles on dogs.
- Abrantes, Roger (1999). Dogs Home Alone. Wakan Tanka, 46 pages. ISBN 0966048423 (paperback).
- 1A&E Television Networks (1998). Big Dogs, Little Dogs: The companion volume to the A&E special presentation, A Lookout Book, GT Publishing. ISBN 1-57719-353-9 (hardcover).
- 2Alderton, David (1984). The Dog, Chartwell Books. ISBN 0-89009-786-0.
- Brewer, Douglas J. (2002) Dogs in Antiquity: Anubis to Cerberus: The Origins of the Domestic Dog, Aris & Phillips ISBN 0856687049
- Donaldson, Jean (1997). The Culture Clash. James & Kenneth Publishers. ISBN 1888047054 (paperback).
- Fogle, Bruce DVM The New Encyclopedia of the Dog, 2000
- Milani, Myrna M. (1986). The Body Language and Emotion of Dogs: A practical guide to the Physical and Behavioral Displays Owners and Dogs Exchange and How to Use Them to Create a Lasting Bond, William Morrow, 283 pages. ISBN 0688128416 (trade paperback).
- Pfaffenberger, Clare (1971). New Knowledge of Dog Behavior. Wiley, ISBN 0876057040 (hardcover); Dogwise Publications, 2001, 208 pages, ISBN 1929242042 (paperback).
- Shook, Larry (1995). "Breeders Can Hazardous to Health",The Puppy Report: How to Select a Healthy, Happy Dog, Chapter Two, pp. 13–34. Ballantine, 130 pages, ISBN 0345384393 (mass market paperback); Globe Pequot, 1992, ISBN 1558211403 (hardcover; this is much cheaper should you buy).
- Shook, Larry (1995). The Puppy Report: How to Select a Healthy, Happy Dog, Chapter Four, "Hereditary Problems in Purebred Dogs", pp. 57–72. Ballantine, 130 pages, ISBN 0345384393 (mass market paperback); Globe Pequot, 1992, ISBN 1558211403 (hardcover; this is much cheaper should you buy).
- Thomas, Elizabeth Marshall (1993). The Hidden Life of Dogs (hardcover), A Peter Davison Book, Houghton Mifflin. ISBN 0395669588.
- Vilà, Caries; Savolainen, Peter; Maldonado, Jesus E.; Amorim, Isabel R.; Rice, John E.; Honeycutt, Rodney L.; Crandall, Keith A.; Lundeberg, Joakim; Wayne, Robert K. (1997). [http://www.mnh.si.edu/GeneticsLab/StaffPage/MaldonadoJ/PublicationsCV/Science_Dog_Paper.pdf Multiple and ancient origins of the domestic dog.] Science 276, pp. 1687–1689.

External links

;General info
- [http://news.nationalgeographic.com/news/2004/02/0209_040209_dogsdogsdogs.html National Geographic News] Many articles and photos about dogs ;Genetics and origins
- Lindblad-Toh, K., et. al. [http://www.nature.com/nature/journal/v438/n7069/abs/nature04338.html "Genome sequence, comparative analysis, and haplotype structure of the domestic dog"] Nature 438:803-819, December 2005.
- [http://www.idir.net/~wolf2dog/wayne1.htm "Multiple and Ancient Origins of the Domestic Dog"]
- [http://www.fiu.edu/~milesk/Genetics.htm Canid Genetics]
- [http://www.nhgri.nih.gov/11008069 "Dog Genome Sequencing"] - NHGRI
- [http://www.ananova.com/news/story/sm_713600.html "World's dogs are descended from Asian wolves"]
- [http://magma.nationalgeographic.com/ngm/data/2002/01/01/html/ft_20020101.1.html#know "From Wolf to Woof - The Evolution of Dogs"] ;Training and behavior
- [http://www.uwsp.edu/psych/dog/dog.htm Noncommercial site sponsored by the University of Wisconsin-Stevens Point]
- [http://www.greatcanine.com/ Puppy Training Information] ;Breed listings from major kennel clubs
- [http://www.akc.org/ American Kennel Club]
- [http://www.ckc.ca/ Canadian Kennel Club]
- [http://www.ukcdogs.com/breeds/ United Kennel Club] Breed lists for many breeds and types not recognized by the AKC--and for many that are (U.S.)
- [http://www.fci.be FCI]Fédération Cynologique Internationale - FCI
- [http://www.dogdomain.com/fci-1.htm FCI] International breed standards
- [http://www.ankc.aust.com/breed_list.html Australian National Kennel Club]
- [http://www.the-kennel-club.org.uk The Kennel Club (UK)]
- [http://www.nzkc.org.nz/dogselect.html New Zealand Kennel Club] Category:Animals kept as pets Category:Canines ko:개 ja:イヌ simple:Dog th:สุนัข

Wikipedia:Conservation status

These conservation status categories are used in Wikipedia articles. For threatened species and species believed to have become extinct after 1500, the categories are based on the IUCN (International Union for Conservation of Nature and Natural Resources) Red List 1994 categories. Species should be classified using the IUCN 1994 criteria directly; the criteria given here are only a summary.
- Lower Risk (LR): Has been evaluated but does not qualify for Vulnerable, Endangered, or Critically Endangered. Divided into three subcategories, cd (Conservation Dependent), where cessation of current conservation measures could result in it being classified at a higher risk level, nt (Near Threatened), close to qualifying for listing as Vulnerable but not fully meeting those criteria, and lc (Least Concern) where neither of cd or nt apply. Least Concern is thus a catch-all category which includes common species as well as those for which there may be conservation concern, but which do not warrant a higher category. Examples: LRnt: Bigcone Douglas-fir; LRcd: Coast Redwood; LRlc: Leopard, Orca.
- Vulnerable (VU): faces a high risk of extinction in the medium-term. Examples: Ring-tailed Lemur, Great White Shark.
- Endangered (EN): faces a very high risk of extinction in the near future. Examples: Blue Whale, Desert Bighorn Sheep, Giant Panda, Black-footed ferret (as of September 20, 2005, upgraded from Extinct in the Wild).
- Critical (Wikipedia's term) or Critically Endangered (IUCN's term) (CR): faces an extremely high risk of extinction in the immediate future. Examples: Slender-billed Curlew, Spanish Lynx, Red Wolf.
- Extinct in the Wild (EW): captive individuals survive, and/or the species has been reintroduced outside its former natural range, but the species otherwise matches the criteria for "Extinct", such that no free-living, natural population is believed to exist. "Extirpated" is used for species that still exist in the wild but not in a particular area where they were once common. Examples: Przewalski's Horse (in preliminary recovery).
- Extinct (EX): extensive and appropriate surveys have failed to record any living members. The last remaining member is believed to have died later than 1500. Examples: Thylacine, Dodo, Moa, Huia.
- Data Deficient (DD): a taxon is listed as Data deficient when there is inadequate information to make an assessment of its risk category, either through lack of knowledge of population size, threats to it, or to taxonomic uncertainty of the validity of the taxon. Examples: Scottish Crossbill (taxonomic uncertainty with respect to Parrot Crossbill), Yunnan Cypress (lack of knowledge of wild population size). The following additional categories are specific to Wikipedia and cover species that fall outside the scope of the IUCN Red List. The criteria are authoritative and should be used directly.
- Secure (SE) or Domesticated: no immediate threat to the survival of the species. This category overlaps Least Concern but has been applied to humans and domesticated animals, for which the IUCN criteria are not valid. Examples: Human, Cat, Dog, Llama.
- Prehistoric: somewhere between Extinct and Fossil: the species went extinct before 1500. At least one specimen of the species exists in a non-fossilized state. This is of particular use in human evolution, as molecular analysis of the specimens can be compared against that of other modern and prehistoric specimens. Examples: Mammuthus exilis, Cave lion.
- Fossil: not a conservation status as much as an indication that the species is only known from the fossil records. Examples: Tyrannosaurus rex, Ammonite.

External link


- [http://redlist.org/info/categories_criteria1994.html IUCN Red List Categories & Criteria (1994)] ko:위키백과:멸종위기등급

Canidae



- Alopex
- Atelocynus
- Canis
- Cerdocyon
- Chrysocyon
- Cuon
- Dusicyon
- Fennecus
- Lycalopex
- Lycaon
- Nyctereutes
- Otocyon
- Pseudalopex
- Speothos
- Urocyon
- Vulpes Canidae is the family of carnivorous and omnivorous mammals commonly known as canines. It includes dogs, wolves, foxes, coyotes, and jackals. These animals are all digitigrades, meaning they walk on their toes. When mating, male canines develop a distinctive knot (the bulbis glandis) at the base of the erect penis which tends to trap the phallus inside the female's vagina for some time after copulation, ensuring greater reproductive success. [http://arbl.cvmbs.colostate.edu/hbooks/pathphys/reprod/semeneval/dog.html]

A classification of dogs

Note that the subdivision of Canidae into "foxes" and "true dogs" may not be in accordance with the actual relations, and that the classification of several canines is disputed. Recent DNA analysis have shown, however, that Canini and Vulpini are valid clades, with the exception of two genera: Nyctereutes and Otocyon. These are canid "outgroups" and are not closely related to vulpines nor canines. Speothos and Chrysocyon are primitive members of Canini, but might be placed in their own clade. Cuon may in fact be part of Canis and there is evidence that Alopex and Fennecus are not valid clades, but are both part of Vulpes. The Domestic Dog is listed by some authorities as Canis familiaris and others (including the Smithsonian Institution and the American Society of Mammalogists) as a subspecies of the Wolf (i.e., Canis lupus familiaris); the Red Wolf may or may not be a full species; and the Dingo, which is variously classified as Canis lupus dingo, Canis dingo and Canis familiaris dingo.
- True dogs - Tribe Canini
  - Genus Canis
    - Coyote, Canis latrans
    - Wolf, Canis lupus
      - Domestic Dog, Canis lupus familiaris
      - Dingo, Canis lupus dingo
      - many other proposed subspecies
    - Red Wolf, Canis rufus
    - Ethiopian Wolf, Canis simensis (also called Abyssinian Wolf, Simien Fox and Simien Jackal)
    - Jackal
      - Golden Jackal, Canis aureus
      - Side-striped Jackal, Canis adustus
      - Black-backed jackal, Canis mesomelas
  - Genus Lycaon
    - African Hunting Dog, Lycaon pictus (also called African Wild Dog)
  - Genus Cuon
    - Dhole, Cuon alpinus
  - Genus Nyctereutes
    - Raccoon Dog, Nyctereutes procyonoides
  - Genus Atelocynus
    - Short-eared Dog, Atelocynus microtis
  - Genus Speothos
    - Bush Dog, Speothos venaticus
  - Genus Chrysocyon
    - Maned Wolf, Chrysocyon brachyurus
  - (Genus Dusicyon extinct)
    - (Falkland Island Fox, Dusicyon australis extinct)
  - Genus Pseudalopex
    - Culpeo, Pseudalopex culpaeus
    - Darwin's Fox, Pseudalopex fulvipes
    - Argentine Grey Fox, Pseudalopex griseus
    - Pampas Fox, Pseudalopex gymnocercus
    - Sechura Fox, Pseudalopex sechurae
    - Hoary Fox, Pseudalopex vetulus
  - Genus Cerdocyon
    - Crab-eating Fox, Cerdocyon thous
- Foxes - Tribe Vulpini
  - Genus Vulpes
    - Red Fox, Vulpes vulpes
    - Swift Fox, Vulpes velox
    - Kit Fox, Vulpes macrotis
    - Corsac Fox, Vulpes corsac
    - Cape Fox, Vulpes chama
    - Pale Fox, Vulpes pallida
    - Bengal Fox, Vulpes bengalensis
    - Tibetan Fox, Vulpes ferrilata
    - Blanford's Fox, Vulpes cana
    - Rueppel's Fox, Vulpes rueppelli
    - Steppe Fox, Vulpes corsac
    - Fennec, Vulpes zerda (former Fennecus zerda)
  - Genus Alopex
    - Arctic Fox, Alopex lagopus
  - Genus Otocyon
    - Bat-eared Fox, Otocyon megalotis
  - Genus Urocyon
    - Gray Fox, Urocyon cinereoargenteus
    - Island Fox, Urocyon littoralis ja:イヌ科

Mammal



- Subclass Multituberculata (extinct)
  - Plagiaulacida
  - Cimolodonta
- Subclass Palaeoryctoides (extinct)
- Subclass Triconodonta (extinct)
- Subclass Eutheria (includes extinct ancestors)/Placentalia (excludes extinct ancestors)
  - Afrosoricida
  - Artiodactyla
  - Carnivora
  - Cetacea
  - Chiroptera
  - Cimolesta (extinct)
  - Creodonta (extinct)
  - Condylarthra (extinct)
  - Dermoptera
  - Desmostylia (extinct)
  - Embrithopoda (extinct)
  - Hyracoidea
  - Insectivora
  - Lagomorpha
  - Litopterna (extinct)
  - Macroscelidea
  - Mesonychia (extinct)
  - Notoungulata (extinct)
  - Perissodactyla
  - Pholidota
  - Plesiadapiformes (extinct)
  - Primates
  - Proboscidea
  - Rodentia
  - Scandentia
  - Sirenia
  - Taeniodonta (extinct)
  - Tillodontia (extinct)
  - Tubulidentata
  - Xenarthra
- Subclass Marsupialia
  - Dasyuromorphia
  - Didelphimorphia
  - Diprotodontia
  - Microbiotheria
  - Notoryctemorphia
  - Paucituberculata
  - Peramelemorphia
- Subclass Monotremata
  - Monotremata The mammals are the class of vertebrate animals characterized by the presence of mammary glands, which in females produce milk for the nourishment of young; the presence of hair or fur; and which have endothermic or "warm-blooded" bodies. The brain regulates endothermic and circulatory systems, including a four-chambered heart. Mammals encompass some 5500 species, distributed in about 1200 genera, 152 families and up to 46 orders, though this varies depending on the classification scheme adopted. Phylogenetically, Mammalia is defined as all of the descendants of the last common ancestor of monotremes (e.g., echidnas) and therian mammals (placentals and marsupials).

Characteristics

While most mammals give birth to live young, there are a few mammals (the monotremes) that lay eggs. Live birth also occurs in a variety of non-mammalian species, such as guppies and hammerhead sharks; thus it is not a distinguishing characteristic of mammals. Although all mammals are endothermic, so are birds and so this is also not a main defining feature. While monotremes do not have nipples, they do have mammary glands, meaning that they meet all conditions for inclusion in the class Mammalia. It should be noted that the current trend in taxonomy is to emphasize common ancestry; the diagnostic characteristics are useful for identifying this ancestry, but if, for example, a cetacean were found that had no hair at all, it would still be classified as a mammal. Mammals have three bones in each ear and one (the dentary) on each side of the lower jaw; all other vertebrates with ears have one bone (the stapes) in the ear and at least three on each side of the jaw. A group of therapsids called cynodonts had three bones in the jaw, but the main jaw joint was the dentary and the other bones conducted sound. The extra jaw bones of other vertebrates are thought to be homologous with the malleus and incus of the mammal ear. All mammalian brains possess a neocortex. This brain region is unique to mammals. Mammals have integumentary systems made up of three layers: the outermost epidermis, the dermis, and the hypodermis. The epidermis is typically ten to thirty cells thick, its main function being to provide a waterproof layer. Its outermost cells are constantly lost; its bottommost cells are constantly dividing and pushing upward. The middle layer, the dermis, is fifteen to forty times thicker than the epidermis. The dermis is made up of many components such as bony structures and blood vessels. The hypodermis is made up of adipose tissue. Its job is to store lipids, and to provide cushioning and insulation. The thickness of this layer varies widely from species to species. Most mammals are terrestrial, but a number are aquatic, including sirenia (manatees and dugongs) and the cetaceans (dolphins and whales). Whales are the largest of all animals. There are semi-aquatic species such as seals which come to land to breed but spend the majority of the time in water. True flight has evolved only once in mammals, the bats; mammals such as flying squirrels and flying lemurs are actually gliding animals. No mammals have hair naturally blue or green in colour. Some cetaceans, along with the mandrills appear to have shades of blue skin. Many mammals are indicated as having blue hair or fur, but in all cases, it will be found to be a shade of grey. The two-toed sloth can seem to have green fur, however, this colour is caused by algae growths.

Origins

Mammals belong among the amniotes, and in particular to a group called the synapsids, distinguished by the shape of their skulls, in particular the presence of a single hole where jaw muscles attach, called temporal fenestra. In comparison, dinosaurs, birds, and most reptiles are diapsids, with two temporal fenestrae; and turtles, with no temporal fenestra, are anapsids. From synapsids came the first mammal precursors, therapsids, and more specifically the eucynodonts, 220 million years ago (mya) during the Triassic period. Pre-mammalian ears began evolving in the late Permian to early Triassic to their current state, as three tiny bones (incus, malleus, and stapes) inside the skull; accompanied by the transformation of the lower jaw into a single bone. Other animals, including reptiles and pre-mammalian synapsids and therapsids, have several bones in the lower jaw, some of which are used for hearing; and a single ear-bone in the skull, the stapes. This transition is evidence of mammalian evolution from reptilian beginnings: from a single ear bone, and several lower jaw bones (for example the sailback pelycosaur, Dimetrodon) to progressively smaller "hearing jaw bones" (for example the cynodont, Probainognathus), and finally (possibly with Morganucodon, but definitely with Hadrocodium), true mammals with three ear bones in the skull and a single lower jaw bone. Hence pelycosaurs and cynodonts are sometimes called "mammal-like reptiles", though this is strictly incorrect since in modern parlance these two are not reptiles, but rather synapsids. During the Mesozoic Period mammals diversified into four main groups: multituberculates, monotremes, marsupials, and placentals. Multituberculates went extinct during the Oligocene, about 30 million years ago, but the three other mammal groups are all represented today. Most early mammals remained small and shrew-like throughout the Mesozoic, but rapidly developed into larger more diverse forms following the Cretaceous-Tertiary extinction event 65 mya. The names "Prototheria", "Metatheria" and "Eutheria" expressed the theory that Placentalia were descendants of Marsupialia, which were in turn descendants of Monotremata, but this theory has been refuted. However, Eutheria and Metatheria are often used in paleontology, especially with regards to mammals of the Mesozoic. Mammal evolutionary progression is below:
- Jawless fish: Cambrian period to mid Ordovician periods
- Bony fish: mid-Ordovician period to late Devonian period
- Amphibians: late Devonian period to early Carboniferous period
- Reptiles: late Carboniferous period
- Pelycosaurs (synapsids, or "mammal-like reptiles"): late Carboniferous period to very early Triassic period
- Cynodonts: Permian-Triassic
- Mammals: mid-Triassic period to today

In the Mesozoic

Most early mammals were small shrew-like animals that fed on insects. However, in January 2005, the discovery was reported of two fossils of Repenomamus around 130 million years old, one more than a meter in length, the other having remains of a baby dinosaur in its stomach (Nature, Jan. 15, 2005 [http://www.nature.com/cgi-taf/DynaPage.taf?file=/nature/journal/v433/n7022/full/433116b_fs.html].) The earliest mammals include:
- Eozostrodon: Triassic and Jurassic
- Deltatheridium: Cretaceous
- Jeholodens: mid-Cretaceous
- Megazostrodon: late Triassic and early Jurassic
- Triconodont: Triassic to Cretaceous
- Zalambdalestes: late Cretaceous Although mammals existed alongside the dinosaurs, mammals only began to dominate after the mass extinction of the dinosaurs 65 mya, in the Cenozoic.

In the Paleocene

During the next 8 million years, the Paleocene period (64–58 mya), mammals exploded into the ecological niches left by the extinction of the dinosaurs. Small rodent-like mammals still dominated, but medium and larger-sized mammals evolved.
- Ptilodus: multituberculate
- Pucadelphys andinus: an opposum-like marsupial
- Purgatorius: a primate-like mammal, placental
- Ectoconus: an early hoofed mammal, placental

Classification

Main article: Mammal classification George Gaylord Simpson's classic "Principles of Classification and a Classification of Mammals" (AMNH Bulletin v. 85, 1945) was the original source for the taxonomy listed here. Simpson laid out a systematics of mammal origins and relationships that was universally taught until the end of the 20th century. Since Simpson's 1945 classification, the paleontological record has been recalibrated, and the intervening years have seen much debate and progress concerning the theoretical underpinnings of systematization itself, partly through the new concept of cladistics. Though field work gradually made Simpson's classification outdated, it remained the closest thing to an official classification of mammals.

Standardized textbook classification

A somewhat standardized classification system has been adopted by most current mammalogy classroom textbooks. The following taxonomy of extant and recently extinct mammals is taken from Vaughan et al. (2000). Class Mammalia
- Subclass Prototheria - monotremes: platypus and echidnas
- Subclass Theria - live-bearing mammals
  - Infraclass Metatheria - marsupials
  - Infraclass Eutheria - placentals

McKenna/Bell classification

In 1997, the mammals were comprehensively revised by Malcolm C. McKenna and Susan K. Bell, which has resulted in the "McKenna/Bell classification". McKenna and Bell, Classification of Mammals: Above the species level, (1997) is the most comprehensive work to date on the systematics, relationships, and occurrences of all mammal taxa, living and extinct, down through the rank of genus. The new McKenna/Bell classification was quickly accepted by paleontologists. The authors work together as paleontologists at the American Museum of Natural History, New York. McKenna inherited the project from Simpson and, with Bell, constructed a completely updated hierarchical system, covering living and extinct taxa that reflects the historical genealogy of Mammalia. The McKenna/Bell hierarchical listing of all of the terms used for mammal groups above the species includes extinct mammals as well as modern groups, and introduces some fine distinctions such as legions and sublegions (ranks which fall between classes and orders) that are likely to be glossed over by the layman. The published re-classification forms both a comprehensive and authoritative record of approved names and classifications and a list of invalid names. Click on the highlighted link for a [http://nasa.utep.edu/chih/chklist/mammals/keys/mammtab.htm table comparing the traditional and the new McKenna/Bell classifications of mammals] Extinct groups are represented by †. Class Mammalia
- Subclass Prototheria: monotremes: platypuses and echidnas
- Subclass Theriiformes: live-bearing mammals and their prehistoric relatives
  - Infraclass †Allotheria: multituberculates
  - Infraclass †Triconodonta: triconodonts
  - Infraclass Holotheria: modern live-bearing mammals and their prehistoric relatives
    - Supercohort Theria: live-bearing mammals
      - Cohort Marsupialia: marsupials
      -
- Magnorder Australidelphia: Australian marsupials and the monito-del-monte
      -
- Magnorder Ameridelphia: New World marsupials
      - Cohort Placentalia: placentals
      -
- Magnorder Xenarthra: xenarthrans
      -
- Magnorder Epitheria: epitheres
      -
  - Grandorder Anagalida: lagomorphs, rodents, and elephant shrews
      -
  - Grandorder Ferae: carnivorans, pangolins, creodonts, and relatives
      -
  - Grandorder Lipotyphla: insectivorans
      -
  - Grandorder Archonta: bats, primates, colugos, and tree shrews
      -
  - Grandorder Ungulata: ungulates
      -
    - Order Tubulidentata incertae sedis: aardvark
      -
    - Mirorder Eparctocyona: condylarths, whales, and artiodactyls
      -
    - Mirorder †Meridiungulata: South American ungulates
      -
    - Mirorder Altungulata: perissodactyls, elephants, manatees, and hyraxes

Molecular classification of mammals

Molecular studies based on DNA analysis have suggested new relationships among mammal families over the last few years. The most recent classification systems based on molecular studies have proposed four groups or lineages of placental mammals. Molecular clocks suggest that these clades diverged from early common ancestors in the Cretaceous, but fossils have not been found to corroborate this hypothesis. These molecular findings are consistent with mammal zoogeography: The first divergence was that of the Afrotheria 110–100 mya. The Afrotheria proceeded to evolve and diversify in the isolation of the African-Arabian continent. The Xenarthra, isolated in South America, diverged from the Boreoeutheria approximately 100–95 mya. The Boreoeutheria split into the Laurasiatheria and Euarchontoglires between 95 and 85 mya; both of these groups evolved on the northern continent of Laurasia. After tens of millions of years of relative isolation, Africa-Arabia collided with Eurasia, exchanging Afrotheria and Boreoeutheria. The formation of the Isthmus of Panama linked South America and North America, which facilitated the exchange of mammal species in the Great American Interchange. The traditional view that no placental mammals reached Australasia until about 5 million years ago when bats and murine rodents arrived has been challenged by recent evidence and may need to be reassessed. It should however be noted that these molecular results are still controversial because they are not reflected by morphological data and thus not accepted by many systematists.
- Group I: Afrotheria
  - Order Macroscelidea: elephant shrews (Africa).
  - Order Afrosoricida
  - Order Tubulidentata: aardvark (Africa south of the Sahara).
  - Clade Paenungulata
    - Order Hyracoidea: hyraxes, dassies (Africa, Arabia).
    - Order Proboscidea: elephants (Africa, Southeast Asia).
    - Order Sirenia
- Group II: Xenarthra
  - Order Xenarthra: sloths and anteaters (Neotropical) and armadillos (Neotropical and Nearctic)
- Clade Boreoeutheria
  - Group III Euarchontoglires
    - Superorder Euarchonta
      - Order Scandentia: tree shrews (Southeast Asia).
      - Order Dermoptera: flying lemurs or colugos (Southeast Asia).
      - Order Primates: lemurs, bushbabies, monkeys, apes (cosmopolitan).
    - Superorder Glires
      - Order Lagomorpha: pikas, rabbits, hares (Eurasia, Africa, Americas).
      - Order Rodentia: rodents (cosmopolitan)
  - Group IV: Laurasiatheria
    - Order Insectivora: eulipotyphlan insectivorans
    - Order Chiroptera: bats (cosmopolitan)
    - Order Cetartiodactyla: cosmopolitan; includes former orders Cetacea (whales, dolphins and porpoises) and Artiodactyla (even-toed ungulates, including pigs, hippopotamus, camels, giraffe, deer, antelope, cattle, sheep, goats).
    - Clade Zooamata
      - Order Perissodactyla: odd-toed ungulates
      - Clade Ferae
      -
- Order Pholidota: pangolins, scaly anteaters (Africa, South Asia).
      -
- Order Carnivora: carnivorans (cosmopolitan)

Classification system used in related articles

In light of all the options available, the following classification system has been adopted for use in related articles. Class Mammalia
- Subclass/Order Monotremata: egg-laying mammals
  - Order Monotremata: echidnas and platypus
- Subclass Marsupialia: marsupials
  - Order Didelphimorphia: New World opossums
  - Order Paucituberculata: shrew opossums
  - Order Microbiotheria: Monito del Monte
  - Order Dasyuromorphia: marsupial carnivores
  - Order Notoryctemorphia: marsupial mole
  - Superorder Syndactyla: syndactylous marsupials
    - Order Peramelemorphia: bandicoots and bilbies
    - Order Diprotodontia: koalas, wombats, kangaroos, possums, etc.
- Subclass Placentalia
  - Order Xenarthra: sloths, anteaters, armadillos
  - Order Pholidota: pangolins
  - Superorder Glires
    - Order Rodentia: rodents
    - Order Lagomorpha: rabbits, hares, and pikas
  - Order Macroscelidea: elephant shrews
  - Superorder Archonta:
    - Order Primates: primates
    - Order Scandentia: tree shrews
    - Order Chiroptera: bats
    - Order Dermoptera: colugos
  - Order Insectivora: shrews, tenrecs, moles, hedgehogs, etc.
  - Order Carnivora: dogs, cats, weasels, seals, etc.
  - Superorder Ungulata: ungulates
    - Order Tubulidentata: aardvark
    - Order Hyracoidea: hyraxes
    - Order Proboscidea: elephants
    - Order Sirenia: manatees, dugong
    - Order Perissodactyla: horses, tapirs, rhinoceroses
    - Order Artiodactyla: even-toed ungulates
    - Order Cetacea: whales

References


- McKenna, Malcolm C., and Bell, Susan K. 1997. Classification of Mammals Above the Species Level. Columbia University Press, New York, 631 pp. ISBN 0-231-11013-8
- Nowak, Ronald M. 1999. Walker's Mammals of the World, 6th edition. Johns Hopkins University Press, 1936 pp. ISBN 0-801-85789-9
- Simpson, George Gaylord. 1945. "The principles of classification and a classification of mammals". Bulletin of the American Museum of Natural History, 85:1–350.
- Springer, Mark S., Michael J. Stanhope, Ole Madsen, and Wilfried W. de Jong. 2004. "Molecules consolidate the placental mammal tree". Trends in Ecology and Evolution, 19:430–438. ([http://www.zi.ku.dk/evolbiology/courses/ME04/7_9/springer200-phyl.pdf pdf version])
- Vaughan, Terry A., James M. Ryan, and Nicholas J. Capzaplewski. 2000. Mammalogy: Fourth Edition. Saunders College Publishing, 565 pp. ISBN 0-030-25034-X (Brooks Cole, 1999)
- Wilson, Don E., and Deeann M. Reeder (eds). 1993. Mammal Species of the World. Smithsonian Institution Press, 1206 pp. ISBN 1-560-98217-9

See also


- List of mammals
- List of regional mammals lists
- List of prehistoric mammals
- Mammal classification

External links


- [http://www.nceas.ucsb.edu/~alroy/nafmsd.html North American Fossil Mammal Systematics Database.]
- [http://paleocene-mammals.de/ Paleocene Mammals], a site covering the rise of the mammals
- [http://www.enchantedlearning.com/subjects/mammals/Evolution.shtml Evolution of Mammals], a brief introduction to early mammals
- [http://home.arcor.de/ktdykes/mesomamm.htm The Evolution of Mesozoic Mammals, a Rough Sketch], an informal introduction
- [http://www.carnegiemnh.org/research/news.html Carnegie Museum of Natural History], some discoveries of early mammal fossils
- [http://www.geocities.com/mammal_taxonomy/index.html Mammal Taxonomy], database of mammals of the world, updated each month
- [http://nmnhgoph.si.edu/msw/ Mammal Species of the World], searchable online version of 2nd edition (1993) of Mammal Species of the World zh-min-nan:Chhī-leng tōng-bu̍t ko:포유류 ms:Mamalia ja:哺乳類 simple:Mammal th:สัตว์เลี้ยงลูกด้วยนม

Carnivora


Ailuridae
Amphicyonidae †
Canidae
Felidae
Herpestidae
Hyaenidae
Mephitidae
Miacidae †
Mustelidae
Nandiniidae
Nimravidae †
Odobenidae
Otariidae
Phocidae
Procyonidae
Ursidae
Viverravidae †
Viverridae The diverse order Carnivora includes over 260 placental mammals. While the Giant Panda is an herbivore, nearly all others eat meat as their primary diet item: some (like the cat family) almost exclusively, others (like the bears and foxes) are more omnivorous. Members of Carnivora have a characteristic skull shape, and their dentition includes prominent canines and carnassials.

Phylogeny

Older classification schemes divided the order into two suborders, Fissipedia, which included the families of primarily land carnivores, and suborder Pinnipedia, which included the true seals, eared seals, and walrus. Newer classification schemes have been able to integrate the findings from molecular techniques for discovering genetic relationships. They generally divide the Carnivora into the suborders Feliformia (cat-like) and Caniformia (dog-like), which includes the pinnipeds. The pinnipeds form a clade with the bears to form the Arctoidea superfamily. The arctoids form a clade that includes another superfamily, containing the mustelids, procyonids, skunks and Ailurus - the Musteloidea. The dogs form an outgroup to these two superfamilies, they were the first of the extant Caniforms to split from the others. The same studies finally resolve the exact position of Ailurus : the Red Panda is not a Procyonid nor an Ursid, but forms a monotypic family with the Musteloids as closest living relatives. The same study also shows that the Mustelids are not a primitive family, as was once thought. Their small bodysize is a secondairy trait - the primitive bodyform of the Arctoids was large, not small. Recent molecular studies suggest that the endemic Carnivora of Madagascar, including three genera classed with the civets and four genera of mongooses classed with the Herpestidae, are all descended from a single ancestor. They form a single sister taxon to the Herpestidae. The hyenas are also closely related to this clade. The exact position of the cats in relation to the other families is somewhat disputed. Nandinia seems to be the most primitive of all the Feliforms and the very first to split from the others. The genus Prionodon (of the Viverrids) might form a family of its own as well, as some studies show they are the closest living relatives to the cats. The position of extinct carnivore families is not clear. Recent studies suggest that the ancient families Miacidae and Viverravidae are not basal members of the Caniformia and Feliformia, so they are not the direct ancestors of any living carnivore family. The Miacidae is not even monophyletic, rather it appears to represent a paraphyletic array of stem taxa. The Nimravidae are seen as the most basal of all Feliforms, and the first to split from the others. Other studies, however, show that the Nimravids and Felids are closely related. The position of many extinct 'Felids' is not clear - they may or may not be true cats after all. The Amphicyonids are the first of the Caniforms to split off - they do not have the Ursids as closest relatives (as most scientists thought), bur are rather an outgroup to all other Caniforms. The results of the same study further suggest a much younger minimum age for the crown-clade Carnivora (the divergence age of the subclades Caniformia and Feliformia) than had been inferred in many previous studies: middle-Eocene (ca. 43 million years ago), rather than early Paleocene (60 Ma). It remains unknown if the Creodonta are the closest relatives of the Carnivora, but it seems they are. They are united with the Pholidota and some extinct orders in the clade Ferae.

Classification


- Order Carnivora
  - Suborder Feliformia ("Cat-like")
    - Family Felidae: cats; 37 species in 18 genera
    - Family Herpestidae: mongooses and allies; 35 species in 17 genera
    - Family Hyaenidae: hyenas and aardwolf; 4 species in 4 genera
    - Family Nandiniidae: African palm civets; 1 species in 1 genus
    - Family Nimravidae: false sabre-tooths (extinct)
    - Family Viverridae: civets and allies; 35 species in 20 genera
  - Suborder Caniformia ("Dog-like")
    - Family Ailuridae: red panda; 1 species in 1 genus.
    - Family Amphicyonidae: beardogs (extinct)
    - Family Canidae: dogs and allies; 35 species in 10 genera
    - Family Mephitidae: skunks and stinkbadgers; 10 species in 3 genera
    - Family Mustelidae: weasels, martens, badgers, and otters; 55 species in 24 genera
    - Family Odobenidae: Walruses; 1 species in 1 genus
    - Family Otariidae: sea lions, eared seals, fur seals; 14 species in 7 genera
    - Family Phocidae: true seals; 19 species in 9 genera
    - Family Procyonidae: raccoons and allies; 19 species in 6 genera
    - Family Ursidae: bears; 8 species in 4 genera

See also


- Cat-fox - new carnivore discovered on Borneo

References


- [http://home.uchicago.edu/~johnf/pdf/Flynn_etal_2005.pdf Flynn et al: Molecular Phylogeny of Carnivora]
- [http://journals.cambridge.org/action/displayFulltext?type=1&fid=285903&jid=SYP&volumeId=3&issueId=01&aid=285902 Wesley-Hunt: Phylogeny of the Carnivores] Category:Carnivores ja:ネコ目 ko:식육목

Chihuahua (dog)

The Chihuahua is the smallest breed of dog and is named for the Chihuahua region in Mexico.

Appearance

The standard recognized by the AKC (American Kennel Club) is only known as "Chihuahua", but they come in two varieties, the longcoat and the smoothcoat. A Chihuahua should not weigh more than six pounds. They come in many colors, and are known for their large erect ears. Chihuahua puppies are often mistaken for hamsters because of their scrunched faces, extremely small size, and light coats. hamsters

Temperament

Although they are prized for their personality and loyalty, chihuahuas are not well-suited as children's pets because of their size and physical fragility. However, their alertness, intelligence and size make them easily adaptable to a variety of environments, including the city and small apartments, and make for usually long lifetimes of 15 years or more of loving companionship.

History

They are thought to be descendants of an ancient, similar, but slightly larger breed associated with royalty in Aztec civilizations known as the Techichi. They are the oldest canine breed in North America.

Health

This breed requires expert veterinary attention in areas such as birthing and dental care. They are also prone to some genetic anomalies, often neurological ones, such as seizure disorders and patella luxation. They are also known for their moleras and sensivity to eye infections. Chihuahaus were brought to America by tourists who brought the small dogs from there travels in Mexico.

Miscellaneous

"Teacup" and "Deer-faced" Chihuahuas

In recent years there has been an increase in the use of the terms "teacup" (or tea cup) and "deer" (or deer-faced) to describe Chihuahuas. Along with "mini" and "tiny toy", "teacup" is sometimes used to describe Chihuahuas and other dogs that are very small. These and other terms are not officially used by any kennel club or reputable breeder. Chihuahuas naturally vary in size, and very small Chihuahuas are often runts, unhealthy, or undernourished, or, if otherwise healthy, may have shortened life spans and other health problems due to extreme dwarfing. They are not normally suitable for breeding, and may require special care. "Deer" or "deer-faced" are terms that are sometimes used to describe Chihuahuas that do not have the breed-standard apple-domed appearance. These terms are also unofficial and have no real meaning.

Famous Chihuahuas

moleras
- Tinkerbell, Paris Hilton's former pet
- Scab, John Gebhardt's pet
- Bit Bit, Britney Spears' pet
- Bruiser, Elle Woods' pet in the Legally Blonde movies
- Gidget, the Taco Bell mascot
- Ren Höek, of Ren and Stimpy fame
- Wheely Willy, a motivational "speaker"
- Tito from Oliver and Company
- Taquito, the University of Puerto Rico's School of Medicine volleyball mascot
- The Spooky Chihuahua from Invader Zim

External links


- [http://www.chihuahua-people.com Chihuahua owners site]
- [http://www.chihuahua-land.com Chihuahua Webcam and photos] Category:Dog breeds Category:Fauna of Mexico ja:チワワ

Irish Wolfhound

The Irish Wolfhound is a breed of hound (a sighthound), bred to hunt. The name originates from its purpose rather than from its appearance: To hunt wolves.

Appearance

These dogs are the tallest breed, with a swift pace and good sight. They have a rough coat (gray, brindle, red, black, pure white, or fawn), a large arrow-shaped head, and a long, muscular neck. The Irish Wolfhound is usually known as the tallest dog in the world, averaging up to 86 cm (34 inches) at the withers, a fact that sometimes is its biggest disadvantage when attracting owners who have no concern for its special needs. As with all breeds, the ideal and accepted measurements vary somewhat from one standard to another, and there will always be individuals whose size falls outside these standards. However, generally breeders aim for a height averaging 32 to 34 inches (81 cm to 86 cm) in male dogs, two to four inches (5 to 10 cm) less for bitches. Acceptable weight minimums range from 105 lb (48 kg) for bitches to 120 lb (54 kg) for males.

Temperament

In temperament, they are considered gentle and friendly, very calm in the house, enjoying long sleeps but energetic when taken for walks. Despite their great size and sometimes intimidating appearance, wolfhounds are sensitive and should be corrected firmly but without anger. They should be socialized from a young age so that they have a chance to gather experience. While historically Wolfhounds should show a strong guarding instinct, most modern Irish Wolfhounds are not temperamentally suited to be a guard dog. withers

Health

Wolfhounds should not receive additional supplements when a good dog chow is used. It is generally accepted that they should be fed a large breed puppy food until 18 months of age and then change to a large breed adult food. By the age of 8 months, the dogs appear adult, and many owners start stressing them too much. Outstretched limbs and irreparable damage are the result. Wolfhounds need at least 18 months to be ready for lure coursing, running as a sport, and other strenuous activities. Heart disease and bone cancer are the leading cause of death and like all deep-chested dogs, gastric torsion (bloat) is always a possibility. Otherwise they are generally a healthy dog with few if any breed specific illnesses. The average lifespan is around 6 to 7 years, though breeders are doing their best to increase this, with some animals now reaching 10 years or more.

History

The breed is very old, possibly from the 1st century BC or earlier, bred as war dogs by the ancient Celts, who called them Cú Faoil. The Irish continued to breed them for this purpose, as well as to guard their homes and protect their stock. Regular references of Irish Wolfhounds being used in dog fights are found in many historical sagas - Cuchulain's favourite, Luath was slain by a southern chief's hound, Phorp. While many modern texts state Irish wolfhounds were used for coursing deer, contemporary pre-revival accounts such as Animated Nature (1796) by Oliver Goldsmith are explicit that the original animal was a very poor coursing dog. Their astonishing size, speed, and intelligence made them ideal hunting animals for both wild boar and wolves, and many were exported for this purpose. They were perhaps too ideal, as the wolf is now extinct in Ireland. The Irish Wolfhound has been recorded as being exhibited in Ancient Rome to some excitement, and mention is made that they so amazed and terrified the Romans that it was seen fit to only transport them in cages. Due to a massive export into various countries as a gift for royalty and a ban that allowed only royalty to own such a dog, the breed almost vanished in the middle of the 19th century. Captain Graham rebred the Irish Wolfhound with the