The cat is a small domesticated carnivorous mammal. It is valued by humans for its companionship and its ability to destroy vermin. A skilled predator, the cat is known to hunt over 1,000 species for food. Intelligent, the cat can be trained to obey simple commands, and has been known to teach itself to manipulate simple mechanisms. Cats have lived in close association with humans for at least 9,500 years. Legends and myths about the cat exist in many cultures, from the ancient Egyptians and Chinese to the Vikings. They have been both revered and vilified by different cultures.

Cats use more than one hundred vocalizations and types of body language for communication, including mewing, purring, hissing, growling, chirping, clicking, and grunting. Cats have even been observed mimicking the calls of birds. Like horses and other domesticated animals, cats can sometimes become feral, living effectively in the wild. Feral cats will often form small feral cat colonies. Animal welfare organizations note that few abandoned cats are able to survive long enough to become feral, most being killed by vehicles, or succumbing to starvation, predators, exposure, or disease.

The dog is a mammal in the order Carnivora. Dogs were domesticated from wolves as recently as 15,000 years ago, or perhaps as early as 100,000 years ago based upon recent genetic fossil and DNA evidence. Other research suggests that dogs have only been domesticated for a much shorter amount of time. Genetic research has identified 14 ancient dog breeds, with the oldest being the Chow Chow, Shar Pei, Akita Inu, Shiba Inu and Basenji. Because many of the 14 breeds are associated with China and Japan, the theory that the dog originated in Asia seems to be likely. Over time, the dog has developed into hundreds of breeds with a great degree of variation.
Dogs, like humans, are highly social animals and this similarity in their overall behavioral pattern accounts for their trainability, playfulness, and ability to fit into human households and social situations. This similarity has earned dogs a unique position in the realm of interspecies relationships. 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 with and worked with humans in so many roles that their loyalty has earned them the unique sobriquet "man's best friend". Conversely, some cultures consider dogs to be unclean.

The horse is a large odd-toed ungulate mammal, one of ten modern species of the genus Equus. Horses have long been among the most economically important domesticated animals; although their importance has declined with mechanization, they are still found worldwide, fitting into human lives in various ways. The horse is prominent in religion, mythology, and art; it has played an important role in transportation, agriculture, and war; it has additionally served as a source of food, fuel, and clothing.
Horses first evolved in the Americas, but went extinct there until reintroduced by Europeans. While isolated domestication may have occurred as early as 10,000 years ago, the first clear evidence dates to c. 5000 BC, and becomes widespread only after 2000 BC. Selective breeding since that time has produced numerous breeds. Some can be ridden, usually with a saddle, while other breeds can be harnessed to pull objects such as carriages or plows. In some societies, horses are a source of food, both meat and milk; in others it is taboo to consume them. In industrialized countries horses are predominantly kept for leisure and sporting pursuits, while they are still used as working animals in many other parts of the world.

Fish are aquatic vertebrates that are typically cold-blooded; covered with scales, and equipped with two sets of paired fins and several unpaired fins. Fish are abundant in the sea and in fresh water, with species being known from mountain streams as well as in the deepest depths of the ocean. They are of tremendous importance as food for people around the world, either collected from the wild or farmed in much the same way as cattle or chickens. Fish are also exploited for recreation, through angling and fishkeeping, and fish are commonly exhibited in public aquaria. Through the ages, many cultures have featured fish in their legends and myths, from the "great fish" that swallowed Jonah the Prophet through to the half-human, half-fish mermaid around which books and movies have been centred. Fish have been used as symbols in many different ways, from the ichthys used by early Christians through to the allegorical use of a marlin in Ernest Hemingway's novel, The Old Man and the Sea.