Ecology and health of Rattus at Nome, Alaska

Schiller, Everett

A parasitological study of rats (Rattus norvegicus Berkenhout) was undertaken at Nome, Alaska, and some notes were made on the effect of winter conditions on this population. A high rate of reproduction during the summer results in a dense population by fall. Mortality among rats living under marginal conditions during the winter is especially high. Some principal manifestations of the adverse effect of low temperature on the surviving animals are: damage resulting from severe frost-bite ranging from slightly injured ears and tails to the loss of limbs; arrested reproductive activity during the winter; and a smaller maximum size than is usually found in similar population samples. Nome rats are parasitized by relatively few species. Of 393 rats examined for helminths, 51 (13 per cent) harbored the dwarf tapeworm, Hymenolepis nana (v. Siebold, 1852). The only other helminths found were the nematodes Trichosomoides crassicauda (Bellingham, 1840) and Trichinella spiralis (Owen, 1835). Fleas, Nosopsylla fasciatus (Bosc d'Antic), were highly prevalent on rats from one of the population centers located within the business district. These specimens constitute the most northerly record of this species from the New World. A hemoflagellate of the genus Trypanosoma, probably T. lewisi Kent, was also recorded. Several of the rats had severe pulmonary infections. This disease probably contributed significantly to the winter mortality. The following species of bacteria were identified from cultures inoculated with purulent material direct from the lesions: Micrococcus flavus Trevisan; Micrococcus aurantiacus Cohn; Micrococcus candidus Cohn; Micrococcus sp; Escherichia coli Castellani and Chalmers; Escherichia intermedium Vaughn and Levine; Alcaligenes faecalis Castellani and Chalmers; Aerobacter aerogenes Beijerinck; and a sporeforming Bacillus sp. None of these is believed to be the primary cause of the disease. Attempts to reproduce the disease in laboratory ani

Ecology and health of Rattus at Nome, Alaska

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