Rodents are among the most successful mammals on earth. They are highly adaptable, and thus are able to colonize many different types of land masses on the planet. When local conditions are favorable, rodents can reproduce quickly. Rodents can also utilize sophisticated behavior patterns to avoid dangers from predators - people included. Worldwide, the mammalian order Rodentia comprises the largest order of mammals, consisting of 1,700 species. In the family Muridae alone - the family to which the commensal rats and mice belong - approximately 500 species occur. The commensal (meaning: to share the table) rodents include the house mouse, the Norway rat and the black rat (or roof rat). Other rodents include voles, deer mice and pack rats. As gnawing and burrowing mammals, rodents inflict serious damage to structures, equipment, furniture, utilities and transportation vehicles. Rats and mice spend approximately 2% of their daily activities gnawing on various natural and man-made objects. Because of their behavior, biology and morphology, rodents have the potential to serve as exceptional disease "vehicles." Rodents have been responsible for some of the most devastating disease outbreaks of all time. More than 10 million people have died from rodent-borne diseases over the past century alone. Disease organisms may be transmitted directly through a rodent's bite, carried from a rodent by a flea, tick or mite that bites and then transfers the pathogen.