Monday, 22 de December de 2008

Tail

There are many different shapes for dog tails: straight, straight up, sickle, curled, cork-screw. In some breeds, the tail is traditionally docked to avoid injuries (especially for hunting dogs).[48] It can happen that some puppies are born with a short tail or no tail in some breeds.[49]

Behavior and intelligence

Many dogs, such as this American Water Spaniel, have had their natural hunting instincts suppressed or altered to suit human needs.
Many dogs can be trained to skillfully perform tasks not natural to canines, such as in this dog agility competition.

Dogs are very social animals, but their personality and behavior vary with breed as well as how they are treated by their owners and others who come in contact with them. It is not uncommon for dogs to attack humans and other animals; however, this is usually because of lack of care or improper upbringing by its owner.

Intelligence

Main article: Dog intelligence

Dogs are valued for their intelligence. This intelligence is expressed differently with different breeds and individuals, however. For example, Border Collies are noted for their ability to learn commands, while other breeds may not be so motivated towards obedience, but instead show their cleverness in devising ways to steal food or escape from a yard. Being highly adaptable animals themselves, dogs have learned to do many jobs as required by humans over the generations. Dogs are employed in various roles across the globe, proving invaluable assets in areas such as search-and-rescue; law enforcement (including attack dogs, sniffer dogs and tracking dogs); guards for livestock, people or property; herding; Arctic exploration sled-pullers; guiding the blind and acting as a pair of ears for the deaf; assisting with hunting, and a great many other roles which they may be trained to assume. Most dogs rarely have to deal with complex tasks and are unlikely to learn relatively complicated activities (such as opening doors) unaided. Some dogs (such as guide dogs for the visually impaired) are specially trained to recognize and avoid dangerous situations.

Evaluation of a dog's intelligence

The meaning of "intelligence" in general, not only in reference to dogs, is hard to define. Some tests measure problem-solving abilities and others test the ability to learn in comparison to others of the same age. Defining it for dogs is just as difficult. It is likely that dogs do not have the ability to premeditate an action to solve a problem.

A mirror test is one possible measure of self-awareness.

For example, the ability to learn quickly could be a sign of intelligence. Conversely it could be interpreted as a sign of a desire to please. In contrast, some dogs who do not learn very quickly may have other talents. An example is breeds that are not particularly interested in pleasing their owners, such as Siberian Huskies. Huskies are often fascinated with the myriad of possibilities for escaping from yards, catching small animals, and often figuring out on their own numerous inventive ways of doing both.

Assistance dogs are also required to be obedient at all times. This means they must learn a tremendous number of commands, understand how to act in a large variety of situations, and recognize threats to their human companion, some of which they might never before have encountered.

Many owners of livestock guardian breeds believe that breeds like the Great Pyrenees or the Kuvasz are not easily trained because their stubborn nature prevents them from seeing the point of such commands as “sit” or “down”. Hounds may also suffer from this type of ranking. These dogs are bred to have more of a "pack" mentality with other dogs and less reliance on a master's direct commands. While they may not have the same kind of intelligence as a Border Collie, they were not bred to learn and obey commands quickly, but to think for themselves while trailing game.

Human relationships

A U.S. Army Staff Sgt. and his military working dog wait at a safe house before conducting an assault against insurgents in Buhriz, Iraq on April 10, 2007.

Dogs are highly social animals. This can account for their trainability, playfulness, and ability to fit into human households and social situations. These attributes have earned dogs a unique position in the realm of interspecies relationships despite being one of the most effective, voracious, and potentially dangerous predators. Dogs and humans at times co-operate in some of the most effective hunting in the animal world; in that context, dogs are superpredators.

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Barking can be used as a form of communication amongst dogs.

The loyalty and devotion that dogs demonstrate as part of their natural instincts as pack animals closely mimics the human idea of love and friendship, leading many dog owners to view their pets as full-fledged family members. Conversely, dogs seem to view their human companions as members of their pack, and make few, if any, distinctions between their owners and fellow dogs. 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 and worked with humans in so many roles that their loyalty has earned them the unique sobriquet "man's best friend",[50] a term which is used in other languages as well as in Icelandic (“besti vinur mannsins&rdquoGuiño. However, some cultures consider dogs to be unclean. In some parts of the world, dogs are raised as livestock to produce dog meat for human consumption. In many places, consumption of dog meat is discouraged by social convention or cultural taboo.

Dog communication

Main article: Dog communication

Dog communication refers to body movements and sounds dogs use to send signals to other dogs, and other animals (usually humans). Dog communication comes in a variety of forms. Dogs use certain movements of their bodies and body parts and different vocalizations to send signals. There are a number of basic ways a dog can communicate. These are movements of the ears, eyes and eyebrows, mouth, head, tail, and entire body, as well as barks, growls, whines and whimpers, and howls.

Reproduction

Dogs develop their own societies. Puppies participate with their littermates in learning to relate to other dogs. Dogs learn to successfully relate to other dogs by keeping the peace, rather than by constantly fighting to reestablish this hierarchy.

Life cycle

Main article: Canine reproduction

In domestic dogs, sexual maturity (puberty) begins to happen around age 6 to 12 months for both males and females,[51] although this can be delayed until up to two years old for some large breeds. Adolescence for most domestic dogs is around 12 to 15 months, beyond which they are for the most part more adult than puppy. As with other domesticated species, domestication has selectively bred for higher libido and earlier and more frequent breeding cycles in dogs, than in their wild ancestors. Dogs remain reproductively active until old age.

An Australian Shepherd Puppy Red Merle

Most female dogs have their first estrous cycle between 6 and 12 months, although some larger breeds delay until as late as 2 years. Females experience estrous cycles biannually, during which her body prepares for pregnancy, and at the peak she will come into estrus, during which time she will be mentally and physically receptive to copulation.

Dogs bear their litters roughly 56 to 72 days after fertilization,[52] with an average of 63 days, although the length of gestation can vary. An average litter consists of about six puppies,[53] though this number may vary widely based on the breed of dog. Toy dogs generally produce from one to four puppies in each litter, while much larger breeds may average as many as 12 pups in each litter.

Spaying and neutering

Main article: Spaying and neutering

Neutering (spaying females and castrating males) refers to the sterilization of animals, usually by removal of the male's testicles or the female's ovaries and uterus, in order to eliminate the ability to procreate, and reduce sex drive. Neutering has also been known to reduce aggression in male dogs, but has been shown to occasionally increase aggression in female dogs.[54]

A wild dog from Sri Lanka nursing her four puppies.

Animal control agencies in the United States and the ASPCA advise that dogs not intended for further breeding should be neutered so that they do not have undesired puppies.[55]

Because of the overpopulation of dogs in some countries, puppies born to strays or as the result of accidental breedings often end up being killed in animal shelters. Neutering can also decrease or eliminate the risk of hormone-driven diseases such as mammary cancer, as well as undesired hormone-driven behaviors. However, certain medical problems are more likely after neutering, such as urinary incontinence in females[56] and prostate cancer in males.[57] The hormonal changes involved with sterilization are likely to somewhat change the animal's personality, however, and some object to neutering as the sterilization could be carried out without the excision of organs.

It is not essential 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 castration.

Female cats and dogs are seven times more likely to develop mammary tumors if they are not spayed before their first heat cycle.[58] Dog food containing soybeans or soybean fractions have been found to contain phytoestrogens in levels that could have biological effects when ingested longterm.[59]

Gender-preservative surgeries such as vasectomy and tubal ligation are possible, but do not appear to be popular due to the continuation of gender-specific behaviors and disease risks.

Overpopulation

United States

According to the Humane Society of the United States, 3–4 million dogs and cats are put down each year in the United States and many more are confined to cages in shelters because there are many more animals than there are homes. Spaying or castrating dogs helps keep overpopulation down.[60] Local humane societies, SPCAs and other animal protection organizations urge people to neuter their pets and to adopt animals from shelters instead of purchasing them. Several notable public figures have spoken out against animal overpopulation, including Bob Barker. On his game show, The Price Is Right, Barker stressed the problem at the end of every episode, saying: "Help control the pet population. Have your pets spayed or neutered." The current host, Drew Carey, makes a similar plea at the conclusion of each episode.

Working, utility and assistance dogs

Main article: Working dog

Dogs have traditionally been used for a variety of tasks since their domestication by early man. A classic example of the use of dogs for work is the sheep dog.[61] Dogs have also been used by hunters to flush out game.[62]

Show and sport (competition) dogs

Main article: Dog sports

Owners of dogs often enter them in competitions,[63] whether show (breed conformation shows) or sports, including dog racing & dog sledding. The winners garner much prestige and prize money. These dogs are often bred specifically for competition, which may not be entirely beneficial for the breeds due to the magnification of hereditary defects.

Health

Main article: Dog health

Morbidity

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. Dogs, like all mammals, are also susceptible to heat exhaustion when dealing with high levels of humidity and/or extreme temperatures.[64]

Diseases

Infectious diseases commonly associated with dogs include rabies (hydrophobia), canine parvovirus, and canine distemper. Inherited diseases of dogs can include a wide range from elbow or hip dysplasia and medial patellar luxation to epilepsy and pulmonic stenosis. Canines can get just about anything a human can get (excluding many infections which are species specific) like hypothyroidism, cancer, dental disease, heart disease, etc.

Two serious medical conditions affecting dogs are pyometra, affecting unspayed females of all types and ages, and bloat, which affects the larger breeds or deep chested dogs. Both of these are acute conditions, and can kill rapidly; owners of dogs which may be at risk should learn about such conditions as part of good animal care.

See also: Vaccination of dogs
First generation hybrids (such as this terrier mix) often are healthier than either parent due to the genetic phenomenon of heterosis or "hybrid vigor".

Parasites

Common external parasites are various species of fleas, ticks, and mites. Internal parasites include hookworms, tapeworms, roundworms, and heartworms. See also CVBD (Canine Vector-Borne Diseases).

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.

Mortality

Main article: Aging in dogs

The typical lifespan of dogs varies widely among breeds. Based on questionnaire surveys of owners in the UK, Denmark, USA, and Canada, the median longevity of most dog breeds is between 10 and 13 years.[65][66][67][68] The breed with the dubious distinction of the shortest lifespan (among breeds for which there is a questionnaire survey with a reasonable sample size) is the Dogue de Bordeaux with a median longevity of about 5.2 years, but several breeds, including Miniature Bull Terrier, Bulldog, Nova Scotia Duck Tolling Retriever, Bloodhound, Irish Wolfhound, Greater Swiss Mountain Dog, Great Dane, and Mastiff, are nearly as short-lived, with median longevities between 6 and 7 years.[68] On the other end of the spectrum, the longest-lived breeds, including Toy Poodle, Border Terrier, Miniature Dachshund, Miniature Poodle, and Tibetan Spaniel, have median longevities between 14 and 15 years.[68] The median longevity of mixed breed dogs (average of all sizes) is one or more years longer than that of purebred dogs (all breeds averaged).[67][66][68][69] As a rule of thumb, small breeds are longer-lived than large breeds, but some of the longest lived large breeds have median longevities nearly as long as those of the shortest lived small breeds, and some of the breeds with the shortest longevities are medium-sized.[70]

"Median longevity" refers to the age at which half the dogs in a population have died and half are still alive. Individual dogs, even in breeds with low median longevities, may live well beyond the median. The dog widely reported to be the longest-lived on record is "Bluey," purportedly born in 1910 in Australia. He died in 1939 at the age of 29.5 years. Bluey is usually identified as an Australian Cattle Dog, but the first Australian Cattle Dog breed standard was written in 1902,[71] only eight years before Bluey's birth. It is unclear how closely Bluey was related to the breed as it exists today. The Bluey record is anecdotal and unverified.[72] The longest verified records are of dogs living to 24 years.[72]

Predation

In some areas where dogs and wolves are sympatric, dogs can be a major food source for wolves. Reports from Croatia indicate that dogs are killed more frequently than sheep. Wolves in Russia apparently limit feral dog populations. In Wisconsin, more compensation has been paid for dog losses than livestock.[73] Some wolf pairs have been reported to predate on dogs by having one wolf lure the dog out into heavy brush where the second animal waits in ambush.[74] In some instances, wolves have displayed an uncharacteristic fearlessness of humans and buildings when attacking dogs, to an extent where they have to be beaten off or killed.[75] Coyotes have also been known to attack dogs. Approximately 3 to 5 pets attacked by coyotes, mostly dogs, are brought into the Animal Urgent Care hospital of South Orange County (California) each week.[76]

Big cats have been recorded to kill dogs. Leopards in particular are known to have a prediliction for dogs, and have been recorded to kill and consume them regardless of the dog's size or ferocity.[77] Unlike sympatric leopards, tigers in India seldom prey on dogs, though in Manchuria, Indochina, Indonesia and Malaysia, tigers are reputed to kill dogs with the same vigour as leopards.[78]

Striped hyenas are major predators of village dogs in Turkmenistan, India and the Caucasus.[79]

Diet

Nutrition

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There are a great quantity of commercial foods and treats marketed for dogs, and not all are recommended as part of a balanced, healthy diet.

There is some debate as to whether domestic dogs should be classified as omnivores or carnivores, by diet. 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 the cat family with its shorter small intestine, a dog is neither dependent on meat-specific protein nor a very high level of protein in order to fulfill its basic dietary requirements. Dogs are able to healthily digest a variety of foods including vegetables and grains, and in fact dogs can consume a large proportion of these in their diet. Wild canines not only eat available plants to obtain essential amino acids, but also obtain nutrients from vegetable matter from the stomach and intestinal contents of their herbivorous prey, which they usually consume. Domestic dogs can survive healthily on a reasonable and carefully designed vegetarian diet, particularly if eggs and milk products are included. Some sources suggest that a dog fed on a strict vegetarian diet without L-carnitine may develop dilated cardiomyopathy,[80] however, L-carnitine is found in many nuts, seeds, beans, vegetables, fruits and whole grains. In the wild, dogs can survive on a vegetarian diet when animal prey is not available. Observation of extremely stressful conditions such as the Iditarod Trail Sled Dog Race, and scientific studies of similar conditions has shown that high-protein (approximately 40%) diets including meat help prevent damage to muscle tissue in dogs and some other mammals. This level of protein corresponds to the percentage of protein found in the wild dog's diet when prey is abundant; higher levels of protein seem to confer no added benefit.

Dogs frequently eat grass, which is a harmless activity. Explanations abound, but rationales such as that it neutralizes acid, or that dogs eat grass to induce vomiting to remove unwanted substances from their stomachs,[81] are at best educated guesses. Dogs do vomit more readily than humans, as part of their typical feeding behavior of gulping down food then regurgitating indigestible material such as bones and fur. This behavior is typical of pack feeding in the wild, where the most important thing is to get as much of the kill as possible before others consume it all. Individual domestic dogs, however, may be very "picky" eaters, in the absence of this social pressure. Dogs may also appear to eat grass when they are just running the blades through their mouth to gather information. Their sense of smell and taste may act together to detect if other animals have walked through their area or urinated on the grass.[81]

Dangerous substances

  • Chocolate can contain high amounts of fat and caffeine-like stimulants known as methylxanthines which, ingested in significant amounts, can potentially produce clinical effects in dogs ranging from vomiting and diarrhea to panting, excessive thirst and urination, hyperactivity, abnormal heart rhythm, tremors, seizures and even death in severe cases. Typically, the darker the chocolate, the higher the potential for clinical problems from methylxanthine poisoning. As little as 20 oz (570 g) of milk chocolate—or only 2 oz (57 g) of baking chocolate—can cause serious problems in a 10-pound (4.5 kg) dog. White chocolate may not have the same potential as darker forms to cause a methylxanthine poisoning, the high fat content of lighter chocolates could still lead to vomiting and diarrhea, as well as the possible development of life-threatening pancreatitis, an inflammatory condition of the pancreas.[82]
  • The acute danger from grapes and raisins was discovered around 2000, and has slowly been publicized since then. The cause is not known. Small quantities will induce acute renal failure. Sultanas and currants may also be dangerous.[83][84]
  • Xylitol, a sugar substitute found in a variety of sugar-free and dietetic cookies, mints and chewing gum is proving highly toxic, even fatal, to dogs.[85]
  • A toxic dose of roasted macadamia nuts may be as little as one nut per kilogram of body weight in the dog.[86]
  • Alcoholic beverages pose comparable hazards to dogs as they do to humans, but due to low body weight and lack of alcohol tolerance they are toxic in much smaller portions. Signs of alcohol intoxication in pets may include vomiting, wobbly gait, depression, disorientation, and.or hypothermia (low core body temperature.) High doses may result in heart arrhythmias, seizures, tremors, and even death.[87]

Abuse

Main article: Cruelty to animals

Cruelty to dogs refers to treatment that causes unacceptable suffering or harm. What qualifies as unacceptable suffering varies among countries and cultures. Cruelty can be passive, typified by simple neglect, or active, with malicious intent.[92]

Malicious treatment of a dog can lead to dog attacks upon not only the abuser but also innocent people.

Dog meat for human consumption

Main article: Dog meat

In some countries, certain dog breeds, apart from being kept as pets, are raised on farms and slaughtered for consumption. In countries where dogs are popular as household pets, consumption of dog meat is generally considered abhorrent. There are exceptions, such as Korea and Vietnam, where dogs are popular as both pets and meat.[93][94]

Dog meat has been a source of food in China from at least the time of Confucius, and possibly even before. Ancient writings from the Zhou Dynasty referred to the 'three beasts' (which were bred for food), including pig, goat, and dog. Mencius, the philosopher, recommended dog as the tastiest of all meats.

Dogs in religion

Main article: Dogs in religion

Dogs have played a role in many religious traditions, including ancient Egyptian religion, Chinese religion, Hinduism, Christianity, and Islam.

See also


Tags: Dog, Domestic, canis, wild, wolf, world, evolution

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