Fluctuations in Numbers of the Muskrat (Ondatra zibethica) in Canada

Abstract

Analysis of records, chiefly of the Hudson Bay Co. for fur sales and fur returns, together with a questionnaire sent to fur posts, shows that since about 1850 there has been a strongly marked cycle of about 10 yrs. in the numbers of muskrat. This cycle covers a wide geographic range across Canada and runs parallel with a similar cycle in numbers of various terrestrial animals, which would infer that some climatic factor controls these different population rhythms.