Elevated Arterial Blood Pressure in an Asymptotic Population of Meadow Voles (Microtus pennsylvanicus)

Abstract

THE factors regulating the growth and final size of mammalian populations include climatic conditions, availability of food, predation, disease, and intraspecific strife^1–3. In studies of the demography and organ weight changes in increasing animal numbers in freely growing confined populations of mice, Christian, Lloyd and Davis⁴ have observed that the population growth curve will reach an asymptote after which the population remains close to this size. The attainment of the upper asymptote is associated with cessation of rearing of all young animals. It is not known why reproduction fails at high density but it may involve behavioural changes, failure of lactation and increased intrauterine mortality.