Key points are not available for this paper at this time.
P. H. Leslie, R. M. Ranson, The Mortality, Fertility and Rate of Natural Increase of the Vole (Microtus agrestis) as Observed in the Laboratory, Journal of Animal Ecology, Vol. 9, No. 1 (May, 1940), pp. 27-52
Leslie et al. (Wed,) studied this question.