Dog

The dog (Canis familiaris or Canis lupus familiaris) is a domesticated descendant of wolves. Also called the domestic dog, it was selectively bred during the Late Pleistocene by hunter-gatherers. Dogs and the modern gray wolf share a common ancestor. Dogs were the first species to be domesticated over 14,000 years ago, before the development of agriculture, though genetic studies suggest the domestication process may have begun over 25,000 years ago.

Dogs have been bred for desired behaviors, sensory capabilities, and physical attributes. Dog breeds vary widely in shape, size, and color. They have powerful jaws that house around 42 teeth, and well-developed senses of smell, hearing, and sight. Compared to humans, dogs possess a superior sense of smell and hearing, but inferior visual acuity.

Dogs perform many roles for humans, such as hunting, herding, pulling loads, protection, companionship, therapy, aiding disabled people, and assisting police and the military. Over the millennia, dogs have uniquely adapted to human behavior; this adaptation includes being able to understand and communicate with humans.

The global dog population is estimated at 700 million to 1 billion, distributed around the world. The dog is the most popular pet in the United States, present in 34–40% of households. Developed countries make up approximately 20% of the global dog population, while around 75% of dogs are estimated to be from developing countries, mainly in the form of feral and street dogs.

Taxonomy

Further information: Canis lupus dingo § Taxonomic debate – the domestic dog, dingo, and New Guinea singing dog

Dogs are members of the Canidae family and are classified as a subspecies of Canis lupus, which also includes wolves and dingoes. Scientists believe dogs and wolves separated between 27,000 and 40,000 years ago. Dogs were first domesticated from wolves at least 14,000 years ago by hunter-gatherers. One of the oldest known dogs was found buried with humans in Germany between 14,000 and 15,000 years ago.

Domestication

Main article: Domestication of the dog

The oldest known remains of a domesticated dog were found in Bonn-Oberkassel, Germany. This dog was buried with a man and a woman and had survived a serious illness as a puppy, showing that humans cared for it. This shows that dogs were the first animals to be domesticated, even before farming began. DNA studies suggest dogs were first domesticated over 25,000 years ago, possibly in Siberia, and later spread around the world with humans.

Breeds

There are about 450 official dog breeds, more than any other mammal. Most of these breeds developed during the Victorian era when people began carefully selecting dogs for specific traits. Today, dog breeds vary greatly in size, shape, fur, and behavior. These differences allow dogs to serve many roles, such as guarding, herding, hunting, and detecting scents.

Anatomy and physiology

Dogs come in many sizes, from very large like the Great Dane to very small like the Chihuahua. No matter their size, all healthy dogs have the same number of bones, though their skeletons can look quite different. Their bodies are built for running, with special bones and muscles that help them move quickly and efficiently.

Dogs can see, hear, smell, taste, and feel their way through the world. Their sense of smell is especially strong—much better than humans'. They can also see in colors, though not as many as we can. Dogs use their tails to show how they are feeling and to keep their balance. Their coats come in many types, from thick and double-layered to thin or even hairless.

Health

Dogs can suffer from many different health problems, both conditions they are born with and ones they develop later in life. Some common issues include diseases of the respiratory system, heart problems, blood disorders, digestive issues, liver disease, pancreatic problems, kidney disease, urinary tract infections, hormonal imbalances, nervous system disorders, muscle and bone issues, skin conditions, and eye problems. Dogs can also get infections from parasites like fleas, ticks, and worms, as well as from viruses such as distemper and parvovirus.

Vaccines are available to help protect dogs from many of these diseases. Unfortunately, dogs are also often exposed to harmful substances by accident, such as certain human medicines, chocolate, and cleaning products, which can make them very sick. The most common cause of death in older dogs is cancer, followed by heart and kidney problems.

Behavior

See also: Dog intelligence

See also: Dog behavior § Behavior compared with other canids

Dogs have been living with humans for thousands of years, which has shaped their behavior. They can understand and communicate with humans better than many other animals. Scientists think that dogs have special skills that help them connect with people, similar to how children learn and interact.

Dogs were bred to have friendly and helpful behaviors. Studies show that small changes in their genes affect how they feel and act. These changes help dogs be less fearful and more friendly. Some dogs can feel anxious or aggressive because of past experiences, but most are happy to be around people and other animals. Dogs also have natural instincts, like chasing after moving things, which can be used for hunting. They can swim, though not all dogs are natural swimmers.

Ecology

Dogs are the most common large carnivores living with humans. In 2020, there were between 700 million and 1 billion dogs in the world. In the United States, dogs were found in about one-third of all homes.

Dogs can sometimes face other wild animals. Wolves, coyotes, big cats like leopards, and even tigers can attack dogs. In places like New Zealand, where there were no native land animals before humans arrived, dogs have had a big impact on local wildlife.

Roles with humans

Main article: Human–canine bond

Dogs have lived with humans for a very long time. They started as predators and scavengers, which means they hunted and looked for food left behind. Dogs learned many useful behaviors from their ancestors, the wolves, such as bite inhibition and understanding body language. These skills make dogs easy to train and good companions.

Dogs can do many jobs for people. They help with hunting, herding animals, pulling heavy loads, protecting homes, and even helping police and the military. Dogs are also beloved pets and can help people who have disabilities. Because of all these roles, dogs are often called "man's best friend" in many parts of the world. In some cultures, dogs are also used for food, though this is less common today.

Terminology

The word Dog refers to the whole species or any male dog. A female dog is called a Bitch. Young dogs under 12 months old are known as Puppy or pup. The male parent of a group of puppies is called the Sire, and the female parent is called the Dam. All the puppies from one birth are called a Litter, and the act of a female dog giving birth is called Whelping. Puppies that still need their mother’s care are called Whelps.