A rat is a small rodent found on all continents except Antarctica. Rats are often considered to be pests. They are also often known to carry disease; notably, the spread of the bubonic plague is attributed to rats. The genus Rattus includes over 50 species.
Rats are capable of surviving in a wide range of different environments ranging from grasslands, forests, urban settlements, ships, and the unforgiving arctic. They tend to thrive around human beings.