How Cats Develop Kittens begin to crawl out of their nest when they are about a month old. The rate of growth and the ultimate size and weight depend greatly on inheritance and nutrition. They reach full skeletal development by the time they are about a year old. Female cats usually become sexually mature when they are six to eight months old, and males become sexually active a few months later. Like many other mammals, cats like to play.
Kittens stalk one another as make-believe enemies and have sham battles.
Even old cats enjoy short periods of play. Some scientists believe that in play the animals practice the skills and techniques important for their survival. Cats are hunters and stalkers. Many games they play show their ability to creep close to prey, then swiftly spring upon it. Most kinds of cats are skillful climbers, escaping into trees for safety or climbing to lie in wait for prey.