Having a history of dependence on man, living in human communities, and competing with man for food may have led, by natural selection, to changes in behavior related to coexistence with humans. Rattus rattus , for example, display avoidance of unfamiliar objects such as traps. Living in trees or roofs, R. rattus tend to flee upward. Social groups usually contain a single dominant male and sometimes a linear male heirarchy. There are also two or three top females, subordinate to the males but dominant to the rest of the group.
Females display more aggressive behavior than males.
The feeding territory is defended against outsiders by biting, jumping, and standing on hind legs and hitting with the front paws. Habitat Rattus rattus occupies cities, villages, cultivated fields, and many undisturbed habitats. They shelter in nests built in trees, roofs, or other elevated positions. The black rat is economically important in terms of damaging food stores and as a transmitter of diseases like the bubonic plague, typhus, food poisoning, and trichinosis. Rat-borne diseases are thought to have taken more human lives in the last ten centuries than all the wars and revolutions ever fought.