The most popular pets can vary from one country to the next, but on a worldwide basis, according to Pettable, house cats are generally thought to be more common than any other pets. Dogs are the second most popular pets, and these are generally followed by fish, rodents, birds and various reptiles. The method used to measure pets can cause this to vary because some studies look at households while others look at the actual number of animals. So, while a person may own only a single dog, some fish owners may have a dozen fish in one tank. An example of how this can skew statistics occurs in America, which has more households that own dogs, but has cat owners that collectively have so many individual animals that they still manage to outnumber the dogs on a country-wide basis.
Cats and dogs are both popular pets for similar reasons. They can offer personal affection for people, and they bond with their owners to varying extents. Dogs are naturally social animals that crave a pack environment, and this causes them to form an especially tight bond, while cats also form a bond that is slightly different, but still generally powerful. In addition, both animals have been useful to people from a practical perspective, with cats being used as rodent killers and dogs having many important uses, from hunting to security.
Fish are some of the most popular pets partly because people love to watch them. They're colorful and some people get a great sense of joy from seeing them swim inside their artificial environments. They're also generally low-maintenance pets that don't take up that much space.
People keep rodents as pets for slightly different reasons. Sometimes they're mostly kept in their cages, and people may purchase them for some of the same reasons they buy fish. Other people form very close bonds with their pet rodents and take them out of their cages often to pet them. Some types, like rabbits, are commonly allowed to roam a person's house without a cage much of the time, and people may treat them exactly like a cat or a dog.
Birds sing, and some types can even learn to speak. This, along with their colorfulness and easy maintenance, make them some of the most popular pets. Many bird species also have very long life spans, and this often appeals to people.
Exotic reptiles are some of the most popular pets for people with allergies because they have no fur. They also appeal to people who want to own an animal that's a little bit closer to being wild. Most of these animals aren't actually domesticated at all, and some of them can even be a little dangerous if they aren't handled exactly right. Maintenance for reptiles can sometimes be difficult because they may require very carefully controlled environments to avoid infections or problems with body temperature.