When do animals become mutants?

Animals are said to be mutants when they show characteristicsdifferent from the rest of their species. Mutations are processes by which the hereditary properties of some of the reproductive cells in animals are altered. In nature these changes can take place spontaneously and unpredictably. But they are rare, and little is known about this cause, beyond the fact that the longer an animal takes to breed, the less likely it is to give birth to a mutant. Nowadays, the most common causes of animals reproducing mutants are chemical substances and radiation. Indeed, radiation is a rapidly increasing hazard.