A further contribution to the study of cycles in British voles (Microtus).

Abstract

In a preliminary survey of the data concerning the fluctuations in numbers of British voles, written in November 1929 (Middleton, 1), it was shown that the maximum periods of abundance during the past 40 years fall into a more or less regular cycle of about 4 years. Methods were evolved for the purpose of obtaining more reliable evidence regarding future fluctuations, including an annual trapping census carried out on a number of areas in Great Britain, and a system of reports from observers throughout the country. In the present paper will be given the results of the past year's investigation correlated with and extending the previous work.