Rodents are mammals, which are characterized by having a single pair of continuously growing incisors in both the upper and lower jaws. Approximately forty percent of all mammalian species are rodents and they are found in every continent except Antarctica. Rats and mice are rodents. The Roof rat, Norway rat and house mouse are referred to as commensal rodents, because of their intimate relationships with people. They live in close associations with humans and are dependent upon people for the essential elements of food, water and shelter. None of the commensal rodents are native to the United States. The house mouse, Norway rat and roof rat were all brought to the United States on European ships in the 17th and 18th centuries. House mice have a small, slender body with a pointed muzzle, and adult mice usually weigh less than an ounce. Mice are gray or brown in color with slightly lighter underbellies, but color can vary from black to white. The mouse has an almost hairless tail, that is approximately the length of its head and body combined. A young rat can be distinguished from a mouse by the fact that the rat's head and feet are much larger, in proportion to the body, than that of a mouse. Additionally, a rat's tail is not as long as the head and body combined. House mice damage consists primarily of the consumption and contamination of food. As with all commensal rodents, there is a potential for the transmission of disease to humans from rodent bites, droppings, or from the parasites that they harbor. Long Island is inhabited by both Norway rats and Roof rats. Norway rats are generally brown in color. Roof rats are smaller than Norway rats and tend to be black in color.