During 1969-1970, crucial information was obtained concerning populations and responses of Microtus montanus. In summer and fall of 1969, Microtus montanus reached peak densities in excess of 200 mice per acre. Breeding continued into October of 1969. By May, 1970 the densities had decreased to minimum levels ( less than 10 per acre). Extremely low densities persisted through the summer and into the fall of 1970. Quite obvioulsy, the peak and crash of the microtine cycle occured in the winter of 1969-70. In contrast to 1969, breeding has ceased by the first week in September of 1970. Project Number 110.
Negus, Norman C.
"Population Dynamics of Microtine Rodents,"
Jackson Hole Research Station Annual Report: Vol. 1970
, Article 17.
Available at: https://repository.uwyo.edu/jhrs_reports/vol1970/iss1/17