Domestic dogs are found in association with humans worldwide and in a wide variety of habitats.
Domestic dogs come in a bewildering variety of shapes and sizes. They have been selectively bred for millenia for various behaviors, sensory capabilities, and physical attributes, including dogs bred for herding livestock (collies, sheperds, etc.), different kinds of hunting (pointers, hounds, etc.), catching rats (small terriers), guarding (mastiffs, chows), helping fishermen with nets (Newfoundlands, poodles), pulling loads (huskies, St. Bernard's), guarding carriages and horsemen (dalmatians), and as companion dogs. Some kinds were even bred simply as lap warmers (Pekingese). Their basic morphology though, no matter how modified, is that of their wild ancestors, gray wolves.
Reproduction in domestic dogs is generally manipulated by humans. Feral males tend to compete amongst themselves for access to receptive females. Some feral domestic dog populations have reverted to ancestral habits where a single male and female pair (the alpha animals) dominate mating in a small, family group, or pack. Other pack members help to care for the offspring of the dominant pair.
Domestic dogs have a gestation period of 9 weeks, after which anywhere from 1 to dozens of puppies can be born, depending on the breed and nutritional status of the mother. Average litter sizes are from 3 to 9 puppies. Male and female dogs usually reach puberty between 6 and 12 months of age; however, the time that a dog actually breeds depends on many social factors, ranging from size of breed (larger dogs need more time before they are ready to breed) and level of confidence a dog must attain before being ready to breed.
Most breeds are seasonally monocyclic, showing signs of heat every 6 months or so. The reproductive cycle has four stages: anestrus, proestrus, estrus, and diestrus. The anestrus period lasts about 2 to 4 months. Proestrus is the time when a bloody discharge first appears in a female. This is the beginning of "heat," a period that usually last 9 days but that can last up to 28 days. The end of this period is marked by the female's acceptance of a male partner. Estrus is the period when the female is sexually receptive and breeding can occur. Ovulation occurs about 24 hours after the acceptance of the male. Ova survive and are capable of being fertilized for about 4 days after ovulation; therefore it is possible for a female to mate with more that one male. Diestrus follows estrus in the nonpregnant cycle, characterized by a state of "pseudopregnancy", which is followed by a return of the uterus and ovaries to the anestrus, resting state.
Females nurse and care for their puppies until they are weaned at about 8 to 10 weeks of age. In feral domestic dog packs, puppies are cared for by all members of the pack.
Longevity in domestic dogs depends on the care they receive, their breed, and body size. In general, larger breeds have shorter lifespans. Well-cared for animals can live for 12 years or more.
Domestic dogs are similar to their ancestors, wolves, in that they are both pack animals with a complex set of behaviors related to determining the dogs position in the social hierarchy and their mood. There is only one leader in a pack, and often there is a struggle between members of the pack to determine who the leader is. The struggle ends with one animal on top of the other, with the submissive animal lying on its back. The dominant animal places its paw on the chest of the submissive one, and until the submissive animal looks away from the eyes of the dominant animal, the struggle continues. As soon as the submissive animal averts his eyes, he has admitted defeat and the leader of the pack has been determined. Dogs exhibit characteristic postures that reveal their states of mind. The neutral position is when a dog is calmly observing things in the environment. The mouth of a dog in this position may be open or closed. In the alert position, the dog's mouth may be open or closed, depending on the excitement level and environmental temperature. The hairs along the back and shoulders may raise without any intent of the dog to attack. The dog has simply focused his attention on some object and is curious about it. Offensive threat posture: hair raised, teeth showing, nose wrinkled, and growling may be heard. The tail is upright, although it may be wagging. A dog in this stance is ready to attack. Defensive threat: although the dog may be growling and snarling, the ears are laid back, which is a sign of submission in normal dogs, and the tail is hanging down. Greetings: relaxed face, mouth slightly open, loosely pulled back ears, tail wagging. This is the posture dogs assume when playing with family members or other dogs. Play invitation: lowered front part of body while keeping the rear end up. A dog may bark in this invitation to play, but it does not growl excessivly. Submission: body low to the ground, as compact as possible. Ears are drawn back, tail is tucked tightly under body. Submissive dogs pull the corners of their mouths back but do not show their teeth (submissive grin). Some submissive dogs assume the most vulnerable position known to dogs, lying on the backs, exposing their undersides. This position admits ultimate defeat in the struggle of dominance between dogs.
Domestic dogs use a complex set of communication modes to navigate their social environment. Chemical cues, such as pheromones, communicate information on reproductive status, social status, and mood. Body language is heavily used and various vocalizations are used as well. Social bonding and communication also occurs through touch.
Puppies have different feeding habits than older dogs. A puppy needs twice as much protein and 50% more calories per pound of body weight daily in order to meet its growth requirements. A rapid change in a puppy's diet may cause gastrointestinal upsets. Puppies must feed 4 times daily until the age of 3 months, 3 times daily until 6 months and twice daily for the rest of its life. Older dogs' feeding habits are different in a couple of ways. The average size dog requires about 30 calories per pound of body weight per day. Interestingly, larger breeds need only 20 calories per pound of weight, while smaller breeds need about 40 calories per pound of body weight. A dog's diet should consist of balanced porportions of proteins, carbohydrates, fats and, of course, water. A dog can go days without food and lose 30% to 40% of it's body weight without dying, but a 10% to 15% water loss could be fatal. All-meat diets are not recommended for dogs due to the lack of calcium and iron found in meat. Diet supplements should be avoided. Human foods that can be fatal to dogs include moldy cheese, onions, and chocolate. Feral domestic dogs will eat a variety of foods including animals and fruits.
Because of their association with humans, domestic dogs are not preyed upon by wild predators. However, feral domestic dogs may be preyed upon by any large predator. Often they are killed by other canids, such as wolves and jackals.
Feral domestic dogs impact ecosystems primarily through predation on native wildlife, often resulting in severe population declines, especially of island endemic species.
There are many species of parasites and disease organisms that infect dogs. Some of which can also infect humans.
If trained properly and treated well, dogs are loyal and protective animals. Domestic dogs have been bred to many purposes throughout the millenia, including as draft animals, guards, hunting, herding, and fishing aids, and as lap animals. More recently dogs are employed as guide dogs for the blind, deaf, and disabled, using their keen sense of smell to detect bombs or drugs, and as therapy animals.
Domestic dogs carry and transmit human diseases, including viral, bacterial, and parasitic diseases. Dogs are still one of the primary vectors for transmitting rabies to humans in undeveloped parts of the world. In addition, domestic dogs are responsible for attacks on adults and children, sometimes resulting in death.
Domestic dogs are not threatened, though some agencies try to protect rare breeds from disappearing.
Tanya Dewey (author), Animal Diversity Web.
Sheetal Bhagat (author), University of Michigan-Ann Arbor.
Living in Australia, New Zealand, Tasmania, New Guinea and associated islands.
living in sub-Saharan Africa (south of 30 degrees north) and Madagascar.
living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico.
living in the southern part of the New World. In other words, Central and South America.
living in the northern part of the Old World. In otherwords, Europe and Asia and northern Africa.
uses sound to communicate
living in landscapes dominated by human agriculture.
young are born in a relatively underdeveloped state; they are unable to feed or care for themselves or locomote independently for a period of time after birth/hatching. In birds, naked and helpless after hatching.
having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.
flesh of dead animals.
Found in coastal areas between 30 and 40 degrees latitude, in areas with a Mediterranean climate. Vegetation is dominated by stands of dense, spiny shrubs with tough (hard or waxy) evergreen leaves. May be maintained by periodic fire. In South America it includes the scrub ecotone between forest and paramo.
uses smells or other chemicals to communicate
helpers provide assistance in raising young that are not their own
having a worldwide distribution. Found on all continents (except maybe Antarctica) and in all biogeographic provinces; or in all the major oceans (Atlantic, Indian, and Pacific.
active at dawn and dusk
in deserts low (less than 30 cm per year) and unpredictable rainfall results in landscapes dominated by plants and animals adapted to aridity. Vegetation is typically sparse, though spectacular blooms may occur following rain. Deserts can be cold or warm and daily temperates typically fluctuate. In dune areas vegetation is also sparse and conditions are dry. This is because sand does not hold water well so little is available to plants. In dunes near seas and oceans this is compounded by the influence of salt in the air and soil. Salt limits the ability of plants to take up water through their roots.
ranking system or pecking order among members of a long-term social group, where dominance status affects access to resources or mates
animals that use metabolically generated heat to regulate body temperature independently of ambient temperature. Endothermy is a synapomorphy of the Mammalia, although it may have arisen in a (now extinct) synapsid ancestor; the fossil record does not distinguish these possibilities. Convergent in birds.
parental care is carried out by females
forest biomes are dominated by trees, otherwise forest biomes can vary widely in amount of precipitation and seasonality.
referring to animal species that have been transported to and established populations in regions outside of their natural range, usually through human action.
offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).
parental care is carried out by males
Having one mate at a time.
having the capacity to move from one place to another.
the area in which the animal is naturally found, the region in which it is endemic.
active during the night
generally wanders from place to place, usually within a well-defined range.
islands that are not part of continental shelf areas, they are not, and have never been, connected to a continental land mass, most typically these are volcanic islands.
an animal that mainly eats all kinds of things, including plants and animals
found in the oriental region of the world. In other words, India and southeast Asia.
the business of buying and selling animals for people to keep in their homes as pets.
chemicals released into air or water that are detected by and responded to by other animals of the same species
the regions of the earth that surround the north and south poles, from the north pole to 60 degrees north and from the south pole to 60 degrees south.
the kind of polygamy in which a female pairs with several males, each of which also pairs with several different females.
"many forms." A species is polymorphic if its individuals can be divided into two or more easily recognized groups, based on structure, color, or other similar characteristics. The term only applies when the distinct groups can be found in the same area; graded or clinal variation throughout the range of a species (e.g. a north-to-south decrease in size) is not polymorphism. Polymorphic characteristics may be inherited because the differences have a genetic basis, or they may be the result of environmental influences. We do not consider sexual differences (i.e. sexual dimorphism), seasonal changes (e.g. change in fur color), or age-related changes to be polymorphic. Polymorphism in a local population can be an adaptation to prevent density-dependent predation, where predators preferentially prey on the most common morph.
rainforests, both temperate and tropical, are dominated by trees often forming a closed canopy with little light reaching the ground. Epiphytes and climbing plants are also abundant. Precipitation is typically not limiting, but may be somewhat seasonal.
scrub forests develop in areas that experience dry seasons.
reproduction that includes combining the genetic contribution of two individuals, a male and a female
associates with others of its species; forms social groups.
living in residential areas on the outskirts of large cities or towns.
uses touch to communicate
Coniferous or boreal forest, located in a band across northern North America, Europe, and Asia. This terrestrial biome also occurs at high elevations. Long, cold winters and short, wet summers. Few species of trees are present; these are primarily conifers that grow in dense stands with little undergrowth. Some deciduous trees also may be present.
that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle).
Living on the ground.
defends an area within the home range, occupied by a single animals or group of animals of the same species and held through overt defense, display, or advertisement
the region of the earth that surrounds the equator, from 23.5 degrees north to 23.5 degrees south.
A terrestrial biome. Savannas are grasslands with scattered individual trees that do not form a closed canopy. Extensive savannas are found in parts of subtropical and tropical Africa and South America, and in Australia.
A grassland with scattered trees or scattered clumps of trees, a type of community intermediate between grassland and forest. See also Tropical savanna and grassland biome.
A terrestrial biome found in temperate latitudes (>23.5° N or S latitude). Vegetation is made up mostly of grasses, the height and species diversity of which depend largely on the amount of moisture available. Fire and grazing are important in the long-term maintenance of grasslands.
A terrestrial biome with low, shrubby or mat-like vegetation found at extremely high latitudes or elevations, near the limit of plant growth. Soils usually subject to permafrost. Plant diversity is typically low and the growing season is short.
living in cities and large towns, landscapes dominated by human structures and activity.
uses sight to communicate
reproduction in which fertilization and development take place within the female body and the developing embryo derives nourishment from the female.
breeding takes place throughout the year
American Kennel Club. 1992. The Complete Dog Book. Howeel Book House, New York, N.Y.
McGinnis, Terri. 1974. The Well Dog Book. Random House, New York
The Marshall Cavendish International Wildlife Encyclopedia.1989. V. 7. Marshall Cavendish Corporation. Freeport, Long Island. New York.