The domestic dog (Canis lupus familiaris, considered by some scientists as the species Canis familiaris), or simply the dog, is a domesticated canine. It is sometimes considered a unique species, but has also been considered a subspecies of wolf. It is the world’s most abundant terrestrial carnivorous mammal, due almost entirely to its ancient partnership with the human species. The dog is one of the most common domestic animals and has been bred into a wide variety of forms, each one depending on what tasks its human caretakers intended for its lineage to carry out.
The first dogs were probably domesticated in Eurasia sometime between 40,000 and 20,000 years ago by bands of nomadic hunter-gatherers. They are believed to be the first animals which humans domesticated.
There are hundreds of breeds of dog, each with a particular appearance based on its genetic heritage, but some features are universal. The dog is a quadrupedal mammal similar in anatomy to the wolf, which it shares a common ancestor with. In most breeds, there is a pronounced snout called a muzzle with a large nose, and the jaws are typically strong with sharp canine teeth. The tongue is pink, typically long and strong, rounded in shape. Domestic dogs have upturned tails, which are unique among canines and can be used to immediately distinguish the domestic dog from wild dog species. However, some have very short tails, and the shape may be straight, vertical, sickle-shaped, or curled.
Dogs are covered in coats of hair; breeds suited to colder climates possess a double-layer of coarse guard hair and softer down hair, while other breeds have only the down hair. Coloration is often piebald, though entirely brown, black, gray, white, and blond dogs are common. Many have a white stripe or spot on the chest, called a blaze or star. Most breeds are powerfully muscled with fused wrists, evolutionary adaptations that suit their predatory lifestyle. The dog walks on four of its toes; the fifth toe is a dewclaw. Some dogs are double dewclawed. On the underside of the foot is a patch of tough skin called a footpad.
Size and shape are immensely variable because of the many types and breeds of dog that exist. The smallest known dog was a Yorkshire terrier which grew to 2.5 inches (6.3 centimeters) tall at the shoulder and weighing four ounces (113 grams), while the largest was an English mastiff weighing 343 pounds (155.6 kilograms) and the tallest was a Great Dane measuring 42 inches (106.7 centimeters) tall at the shoulder.
The dog’s senses are highly tuned, with its ability to hear and smell far exceeding that of the human. Its ears are particularly sensitive to high-pitched sounds, though floppy-eared domestic breeds have less sensitive hearing than pointy-eared breeds. In some dog breeds, the sense of smell can be up to forty times as sensitive as a human’s. Its nose is wet, which is used to determine temperature as the liquid evaporates off the nose. The nostrils are mobile, allowing the dog to more accurately determine where a smell is coming from. On the sides of the snout are whiskers which are used for tactile sensing. The dog has a less powerful sense of sight; humans can see more colors than dogs. The dog is primarily capable of seeing yellow, blue, and gray, with other colors being harder to distinguish. However, the dog is adept at seeing in low-light conditions, since its ancestors were crepuscular predators. Its pupils are round and quite large, and in many dogs the sclerae are only visible when it rotates its eyes.
The baby dog is called a pup or puppy. During this stage, its fur is generally softer and its head is proportionally large, while its legs are proportionally shorter. Similarly to the human baby, the puppy’s eyes and ears are large for its head size. These features give the puppy a vulnerable appearance which encourages adults to care for them.
Most dogs become physically mature over the course of 16 to 18 months, though their behavior may remain puppylike for a few years. Maturation varies based on breed.
As the dog grows older, its fur may begin to gray and colors fade. Dog lifespans vary based on breed, with the shortest-lived breeds reaching only five to six years while the longest-lived breeds may live to be fifteen years old.
The high degree of variability in the dog’s physiology mostly precludes the existence of prominent secondary sexual characteristics. As a result, there is little real sexual dimorphism in the dog.
Most of the world’s dogs are domesticated, living in or around human homes for all of their lives. Their ancestral home was in Eurasia, where their wolf-like ancestors were well adapted to temperate and cold conditions. Modern dogs with two-layer coats can survive and thrive in fairly cold environments, but most breeds are highly adaptable; they can acclimate to a wide variety of environment types.
The dog was not native to Isla Nublar. Humans on the island included Costa Rican peoples such as the Bribri, who did not introduce dogs, and neither is there any evidence that Europeans brought dogs to the island after locating it in the 1500s.
In fact, there is no evidence for dogs on Isla Nublar at all until 2005, when Jurassic World was opened on the island. The park was compliant with the Americans with Disabilities Act, and therefore service dogs would have been permitted in park facilities. It is not currently known what the park’s policy was on non-service dogs, but most public attractions do not permit dogs on the premises for purposes other than service or emotional necessity. It is possible that some Jurassic World employees may have been allowed to keep service dogs or emotional support dogs at their residences on the island.
Because disabled people are often deprived of the means to visit places like Jurassic World, there were probably only a few dogs on the island per visitor. None were seen during the 2015 incident. When the park closed, any service dogs belonging to tourists or employees would have been evacuated along with their owners. It is extremely unlikely that any were left behind.
It is unknown if any of the plantation workers who formerly lived on Isla Sorna owned dogs, but these would probably have been taken with them when they left the island. Similarly, it is not known if any InGen employees kept dogs on the island during operations from 1986 to 1993, but they probably would have taken them off the island with them during the 1993 evacuation.
Dogs are domesticated around the world, living in and around human homes in virtually every country. They spread around the world as humans migrated across continents in prehistory. Due to unplanned breeding, escapes, and intentional releases, there are also feral dogs living in many countries. Depending on their breed, dogs may be adapted to various climates, but most can adjust to multiple types of environment. Smaller dogs are better suited to life in urban areas where there are fewer predators and more humans to provide them with food, while larger dogs may be able to survive in the wild. However, even larger feral dogs will venture into cities to obtain food, as this is easier than hunting it down.
Behavior and Ecology
In the wild, the dog is a crepuscular hunter, active mainly at dawn and dusk when its low-light vision is of best use to it. They are equally capable during the day and night, though they may choose to sleep during the middle of the day or night.
In domestic life, dogs are typically diurnal because their owners are. The domestic dog in a home will often sleep when its owner sleeps, though the dog’s sleep schedule may differ slightly from its owner. In these cases, the owner will typically have to adapt to the dog’s sleep schedule rather than the other way around, because the dog will require assistance getting outside to defecate and urinate and then getting back in the home afterward. The dog may also request exercise or play during a time at which its owner would otherwise sleep, and the dog and human must find ways to resolve these disagreements.
Diet and Feeding Behavior
Voracious omnivores, dogs will eat virtually anything they perceive as food; in the wild, adult dogs will teach their offspring what foods are safe and which are not, but when dogs are raised by humans, it is the responsibility of the human to stop the dog from eating dangerous substances. Many substances found around human homes, including onions and garlic, chocolate, aloe and other domestic plants, grapes, xylitol, and cigarettes are harmful to the dog if consumed. The dog’s natural diet should include protein-based foods; it will happily eat most meats, but commercial dog foods are typically provided in the form of kibble.
In the wild, the dog preys on herbivorous mammals such as deer, and also scavenges carcasses. It hunts in packs, coordinating to bring down prey. The dog tracks food sources using its incredible sense of smell. It can excavate food using its claws, or tear it up using its powerful jaws and teeth. However, most feral dogs live in or near cities and will scavenge garbage or obtain food from humans. Some feral dogs will act similarly to domestic dogs and beg humans for handouts, but others take a more aggressive approach or try to steal food. The dog is a strategic hunter and scavenger, quickly learning what approaches work best and which do not.
Dogs are ancestrally carnivorous, but can also consume some fruits and vegetables. They have a preference for fruits that contain furaneol, such as tomatoes. On the other hand, they cannot abide bitter or spicy flavors. They have taste buds that respond to water, a feature that is found in many mammals but not humans; after eating sugary or salty foods, these water-sensing taste buds become more active and give the dog great pleasure when drinking water.
Like all canines, dogs are social animals and benefit from the presence of other dogs. Groups of dogs are called packs. They should be socialized when in the puppy stage to ensure that they are comfortable interacting with members of their own kind. Even adult dogs will happily engage in play behavior with one another, jumping on or racing one another, and can easily identify familiar dogs through scent. The nose and anus are the primary regions that dogs will scent one another. If interactions become too energetic or otherwise stressful, the dog will bite to announce that it is uncomfortable or upset.
Because its sense of smell is so powerful, dogs will use scent to interact as well. A dog will urinate on a particular object to announce its presence; its unique scent can be recognized by other dogs, and even those who have never met it before can discern details about its identity. Dogs will often urinate on communal objects, using these as a form of communication in the same way that humans utilize public bulletin boards.
Dog packs often have a form of hierarchy in place with parental figures leading their offspring and other younger dogs. The parents, sometimes called “alpha” dogs, are responsible for teaching and protecting the others. In domesticity, humans will assume the role of the parental alpha figure, which necessitates maintaining a sense of authority the dog will respect. Dogs rarely respond well to aggressive authority figures, instead respecting those with good parental traits. Sometimes, a dog that is used to being the center of attention can become jealous of newcomers. Jess Harding‘s dog Patchie became jealous of a new puppy her family adopted in the early 1990s.
Both male and female dogs are sexually mature at around six months to a year in most breeds, though in some it can be delayed to two years. The female experiences semiannual estrous cycles, meaning she can breed twice a year. She may mate with more than one male, bearing puppies from different fathers in the same litter. The male will court the female by sniffing her reproductive organs, at which point the female will either accept or reject him. The mating process itself takes five to twenty minutes, during which the dogs will be anatomically unable to separate. After fertilization, the gestation period lasts fifty-eight to sixty-eight days, after which the female will give birth to a litter of puppies. There are usually five or six in a litter, but this can vary with breed and age. Mated dogs will sometimes remain a pair, developing emotional bonds with one another.
Parent dogs are often highly protective of their offspring and will nurse them until they are capable of feeding themselves. Once they are weaned, it is still common for the mother (and father, if he is present) to provide food for them as they are not yet skilled at hunting or foraging. In natural conditions, the parents will teach their offspring how to obtain food and survive in the world; humans will often assist with this, or take over the process entirely, in domestic situations.
The dog is considered an adult by the time it reaches one or two years old, though the maturation rate varies by breed.
The best-known communication used by the dog is its bark, a loud call which it uses to get the attention of its fellows. Dogs use this sound to communicate to humans, typically to express a desire for the human to amend a troubling situation (though the human and dog may disagree over the definition of “troubling”). Depending on the size of the dog, the bark may sound like a high-pitched “yip” or a low, booming “woof.” Dogs will also make other sounds, such as a whining noise to express distress or growling to express anger.
When happy, the dog will communicate mostly through body language. A wagging tail is a sure sign that a dog is pleased, excited, or otherwise in a good mood. Panting is often considered a sign of excitement or happiness, though this is actually how the dog regulates its temperature as it cannot sweat. Still, an elevated temperature may indicate the dog is in an excited state. Other signs of joy in the dog include jumping or tapping the feet, licking a friendly human or other animal, or physically touching a friendly companion. To suggest play or other cooperative behavior, a dog may crouch down with its head near its paws and its tail in the air in preparation for a lunge forward. Submissive behavior is shown by lowering the whole body, while sadness or fear is indicated by tucking the tail between the legs. The dog’s eyes and face are expressive, which can be used to indicate its mood as well; for example, if the dog rolls its eyes so that the white sclerae show, this may mean that it is excited, afraid, or otherwise emotionally stimulated.
Dogs also communicate to one another using scent. The dog’s sense of smell is highly acute, and its brain’s olfactory cortex is extremely large. It can remember a multitude of different scents, which it uses to recognize fellow dogs, human companions, and other animals. Dogs can quickly recognize the smell of another dog’s urine, using this to discern information about that dog’s age, sex, health, and status. Taste can be used in a similar way to learn about other animals.
The long history of dogs and humans as companions means that dogs can also recognize and respond to specific human commands. Some dogs are capable of recognizing up to a thousand different words, phrases, and visual communications. Unlike many animals, the dog is capable of not only recognizing and responding to these commands but actually understanding the meaning.
In its ancestral state, the dog is a hunter and forager, coordinating with intelligent pack behavior to bring down prey in its environment. It is capable of out-maneuvering other predators with its speed, endurance, and strategy. Because it is intelligent, the dog is also a curious animal and may attempt to interact with other species in play. This is more common in domesticity, where the dog has less need to hunt and is therefore more likely to be friendly. If socialized properly, dogs can be taught to get along with other species of domestic animals. For example, Claire Dearing was able to socialize an adult dog she adopted in high school to be friendly with her pet skink, which she had owned since the age of eight.
However, even domestic dogs can have an impact on their environment if their human caretakers permit it. Dogs are naturally predator animals, and if permitted to do so, they may chase after and harass wild animals as a form of play. This can disturb some species, such as shorebirds that nest on beaches where humans permit their dogs to run free.
Dogs are also affected by numerous parasites. Some are internal, such as hookworms and the rabies virus, while others are external, such as ticks. These parasites can bring diseases; some, such as rabies, are fatal. In the wild, dogs have little to protect them from disease other than their own immune systems, so dogs that live in domestic homes are often better protected; their human companions can remove ectoparasites and provide them with medicine to prevent or cure disease caused by endoparasites.
Relationship to Humans
The dog was among the first animals to be domesticated by humans. It is believed that wolf-like canines began living near human settlements in Eurasia, taking scraps of food that were left over from the humans’ hunts. For thousands of years, this relationship developed; dogs learned how to communicate with humans more than any other animal, and humans brought dogs into their homes and bred them for specific traits. Modern dogs show the clear signs of this relationship; they are capable of understanding human communication and body language to a degree not seen in other species, even those that are more intelligent than the dog. For example, if a human points to an object, a dog can learn to look in the direction the human is pointing; other intelligent animals such as chimpanzees and dolphins will instead look at the human’s finger.
As of 2018, about nine hundred million dogs lived in homes around the world. this is an almost two hundred percent increase from the 2012 dog population. Of these, roughly ninety million live in the United States, where they are one of the most popular pets. Dogs have been bred for many purposes including physical work, competitive sports, personal protection, hunting, emergency rescue, companionship, and dog shows focused on beauty or talent. In the modern day, the dog’s intelligence and ability to read body language have made it an ideal service animal, providing assistance to disabled people in a wide variety of ways.
Not all human uses of dogs are positive; some have turned the physical strength of certain dogs to train them to fight or attack. Dogs have also been used as food, though this is taboo in many countries and is generally declining around the world. The use of dogs as military animals is also controversial, and has partially inspired projects such as I.B.R.I.S. and military bioengineering. Animal rights activists have worked together to advocate and provide for the welfare of dogs and other animals around the world, greatly improving their well-being.
Some geneticists, such as Henry Wu, consider the selective breeding of domestic dogs from wolves to be a precursor to the modern process of genetic engineering.
Patchie – male, owned by Jess Harding before 1993
Jess’s Second Dog – puppy adopted by the Harding family before 1993
Roo – male Pyrenees mix rehabilitated by Claire Dearing and adopted in approximately 1997
Earhart – female lab-rottweiler mix, former feral dog adopted by the Dearing family around 1999
Gray – owned by Paul Kirby, had reached an advanced age by 2001