Nebraska Academy of Sciences


Date of this Version



Published in Transactions of the Nebraska Academy of Science, Volume 4 (1977).


Copyright 1977 by the Authors; used by permission of the NAS


These questions are becoming more controversial in recent debates which have emerged from new realizations of rodent impact on health, conservation, and economy. The controversy, coupled with widespread evidence of genetic resistance, bait aversion, and other modes of adaptive behavior and physiology displayed by rodent pests, represents a new appreciation for one of man's most persistent problems. Old World rodents live in commensal association with man and his domestic animals. These rodents include black rats (sometimes called roof rats), Norway rats (sometimes called brown rats, sewer rats, wharf rats), and Old World (house) mice. Of the three types of Old World rodents, the most feared and successful are Norway rats, which are eminently bound by the habits of man and which have been well provided for by man. An interesting and readable account of rat association with man (Zinsser's Rats' Life and History) relates the episode of disease and destruction which began when these pests adopted their commensal association with man and moved from Central Asia to all regions of the earth, except the Arctic, sub-Arctic, and Antarctic zones. Since about the time of the Crusades, man has made a considered effort to wage war against house mice, roof rats, and alley rats. Still, these species maintain healthy populations throughout the world, despite human efforts to eradicate them by trapping, release of predators, shooting, poison baiting, bacteriological warfare, and the use of poison gas. Thus far, only destruction of the harborage that provides housing for rats and the storing of food supplies in rat proof containers have denied rats their cohabitation with man. Unfortunately, total elimination of rat harborage is rarely possible so that there are always large reservoir populations of the pests nearby. They invade and infest wide areas whenever conditions become favorable. Better sanitation, food and debris storage, and disposal and clean-up campaigns are essential to rat control. Yet, some situations cannot be corrected for economic reasons. Even in the United States we have the persistent problem of broken storm and sanitary sewers and a lack of rat-proof grain storage in many areas. In the United States there is probably at least one rat for every human being; in other parts of the world where grain storage and sanitation are not as sophisticated as ours, there may be 25 to 50 rats for every human being. Portions of Asia and Africa undoubtedly have huge reservoirs of rats; the most troublesome of these is the Norway rat because of his aggressive and adaptive behavior.