Males may roam, and may be larger. Older animals may be more reliable, a good match for small children and the elderly. Also consider how much exercise, space and grooming each breed require. Cats are independent, but they also need attention. They are healthier and happier living indoors and need less space than a dog.
Horses require a lot of exercise, space and time, but they can be good companions for active people.
Birds need a cage, and daily cleaning. They are great companions with little care and respond well to careful training. Small mammals tend to be clean and lively. Some, such as gerbils, hamsters, and ferrets sleep during the day and are active at night. Some may be prone to biting, and may not be a good pet for a small child.