Parasites of Some Minnesota Cricetidae and Zapodidae, and a Host Catalogue of Helminth Parasites of Native American Mice

Abstract

The problem of parasites of the mice native to North America has been much neglected in the past despite the economic and ecological importance of these rodents. True, much has been written concerning the losses due to field mice; and their importance in human and animal disease has not been overlooked. The fact that they serve as key animals in the food chain and are, at the time of their cyclic high, preyed upon by the carnivores almost to the exclusion of other animals, has also been emphasized by various workers. Whether their cycles of abundance and dearth are influenced by the same force or forces as those which govern the snowshoe hare and the ruffed grouse populations, is a mooted question. The phenomenal increase of wild mice in the late summer and fall of certain years has been noted from times long past. In order to gain some information concerning these sudden outbreaks and die-offs of wild mice, Elton and his associate (1931) trapped large numbers of three species of field mice and examined them for ectoparasites, endoparasites, protozoa, and bacterial infections. They came to no definite conclusions concerning the role that these agents play in the cyclic phenomenon. In 1934, however, Findlay and Middleton, and in 1935, Elton, Davis, and Findlay found that epidemics among voles (Microtus agrestis) in Britain were due to a protozoan infection of the brain due to a Toxoplasma. In 1927 N. E. Wayson of the U. S. Public Health Service concluded that the epizootic among Microtus californicus in California was due to Bacillus murisepticus or Bacillus rhusiopathiae suis. In 1936 Harkema published a list of the external and internal parasites of the white-footed mouse (Peromyscus leucopus leucopus) of his region, North Carolina. Other investigators, but especially M. C. Hall, have added to our knowledge of parasites of rodents by compiling the published material. In the present work the chief emphasis has been placed on the parasites and parasitism of the various species of field mice, but the influence that these parasites might exert on the abundance and scarcity of the mice has been constantly kept in mind. At all times, too, the activities and habits of the mice have been studied. In order to make the recorded knowledge of the internal parasites of mice native to North America more accessible, a host-parasite catalogue has 575