The American Curl is a breed of cat characterized by its unusual ears, which curl back from the face toward the center of the back of the skull. The American Curl is a medium sized cat (5-10 lbs), and does not reach maturity until 2-3 years of age. They are strong and healthy, remarkably free of the genetic defects that affect many purebred cats. American Curl kittens are born with straight ears, which begin to curl within ten days. After four months, their ears will not curl any longer.