The purpose of an animal's skull is to protect the life centre or brain and sensory organs. Because animals are uniquely adapted for the particular environmental stresses they face, identification of animals is possible. Unique characteristics are often found in the shape and size of a skull. Teeth are another indicator of species. With more than 400 species of mammals alone in North America, identification can prove challenging.
Determine the class of vertebrate. Simply, vertebrates are animals with backbones. There are seven living classes of vertebrates. Generally speaking, amphibian bones like those of a frog are hollow, lightweight and have a smooth surface. Likewise, bird bones are also hollow and light but will have a hard outer surface. Mammal bones are dense and hard.
Use a key to determine the order of the animal. Keys are basically a systematic process of elimination. With each step, you are typically given two choices to describe the skull. Based on your observation, you will have identified the order to which the animal belongs or you will proceed to the next point. Keys are usually in that you focus on a single characteristic at a time.
Identify the family. Teeth are often the next characteristic under consideration. A key may indicate choices based on the dental formula, that is, the arrangement of teeth, or a choice based on actual tooth structure such as the presence of a cusp or projection or point on a tooth. Birds, however, do not have teeth. Characteristics of the bill will aid further identification.
Identify the species. At this point, the key will have more specific choices such as the length of the skull, comparison of skull structures or surface markings on a specific type of tooth. A ruler and magnifying glass are useful tools to make determinations, especially when dealing with smaller specimens. Some species such as opossums are easily identified upon sight without use of a key because of the unique nature of the skull or tooth structure. In this case, there is only one family present in North America.
Additional information about animals can be gleaned from skulls. For example, an examination of tooth wear can be a general indicator of age. A general picture of the health of the animal and possible cause of death can also possible. Using a systematic approach to identification by using a key is an easier way to identify animal skulls.
Use a ruler with millimetres. Millimetres are preferred because more precise measurements are possible.
Be aware of game laws in your area. All migratory birds, for example, are federally protected. Possession of any bird parts is prohibited.