Nutrition and Population Dynamics of the Prairie Vole, Microtus ochrogaster, in Central Illinois

Abstract

SUMMARY (1) Nutrition and demographic characteristics of three populations of prairie voles were compared in adjacent, but distinctly different, habitats in central Illinois. (2) Live trappings from 1972 to 1976 provided data for two cyclic fluctuations in density. Densities reached higher levels in all habitats during the first cycle (prairie-38/ha, bluegrass-128/ha and alfalfa-244/ha) than during the second cycle (10/ha, 60/ha and 102/ha, respectively). (3) Voles had greater reproduction and survival and higher body weights in the alfalfa than in the bluegrass or prairie habitats. Data obtained by snap-trapping indicated that litter sizes and fat reserves were also greater in the alfalfa habitat. (4) Examination of stomach contents showed that dicotyledons comprised a major portion of the vole diet in all habitats even though grasses dominated the vegetation in the bluegrass and prairie habitats. Voles in the latter habitats supplemented their diet with seeds and insects. (5) Analysis of nutrients in three common food items (alfalfa, clover and bluegrass) revealed that legumes not only contained more digestible energy than bluegrass but also higher levels of crude protein, calcium, phosphorus and sodium. Moreover, voles grew more rapidly, bred earlier and produced more young when fed alfalfa than when fed dandelions and bluegrass. (6) When released in enclosures, voles grew faster and reproduced sooner in the alfalfa than in the bluegrass or prairie habitats. (7) We conclude that the quality of available food can exert a strong influence on the density of herbivores. Higher forage quality accounted for greater peak densities of vole populations, but it did not prevent population declines.