Date of this Version
The awareness, if not the magnitude, of problems caused by sewer rats has increased in the United States in recent years. Thus, current concern with the more general problem of urban rats is leading many city agencies to incorporate plans for controlling sewer rats in budgets that are already severely strained. The most effective programs for controlling pests are those based on an intimate knowledge of the interactions between the target species and its environment. Some basic studies of sewer rat ecology were begun in St. Louis, Missouri, in February, 1969. Since the initial results have provided information that should be helpful in planning control operations in other cities, a brief account of the relevant findings will be presented here so that the information may become available before the study is completed and published in fuller detail. The most extensive studies of sewer rats in the United States have been conducted in California, where sanitary sewers are generally separate from storm systems and where roof rats (Rattus rattus) are often the dominant species (e.g., Rohe, 1966). Much work has also been done in Great Britain, where the sewer networks sometimes seem to defy simple description. Recent work there (e.g. Greaves, et al, 1968), as in California, has been mainly in evaluating methods of control, although some analyses of the systems from an ecological viewpoint have been made. Neither of these groups of studies has been in sewer systems that seem directly comparable to the combined storm and sanitary sewers of St. Louis and a need for more specific basic information on the characteristics of sewer rats was recognized. The most frequently cited paper on the rats of combined sewer systems in the United States (Beck and Rodeheffer, 1965) does not describe the methods used and thus, the results and conclusions are difficult to evaluate. In contrast to earlier studies, we started simply with the question, "What characteristics of the sewer system influence the numbers, distribution, and behavior of sewer rats?" R. norvegicus is probably the only vertebrate species that 1ives in our sewers.