As an animal matures, larger permanent teeth will appear on the lower jaw. A new pair of teeth will appear for each year of an animal's life. A total of four pairs of teeth can be found in the front and by comparing the size of the teeth, you can determine an animal's age. An animal less than a year of age will have all small baby teeth. As the animal approaches a year of age, the pair of teeth in the middle will fall out and be replaced by larger permanent teeth. At age two, the animal will have two pairs of teeth, at age three the animal will have three pairs and at age four the animal will have four pairs. Once the animal has reached four, it is considered mature.

Using teeth to determine age won't tell you the birth date of an animal, however it can give you a general idea of the age of an animal. Most animals will cut a new set of teeth within a month or two of their birth date, so it can be a useful tool for estimating the age of an animal