Small mammal communities in North American grasslands.

Abstract

Small mammal communities in North American grasslands usually contain 10 to 15 species, including carnivores, insectivores, lagomorphs and rodents. The most diverse group, the rodents, has species that primarily eat insects, monocotyledons, dicotyledons or seeds, as well as species that are omnivorous. Western grasslands have summer drought and many species found there, particularly heteromyid rodents, are also found in western deserts. The wetter eastern grasslands contain insectivores and rodents that also occur in eastern forest meadows The occurrence and relative abundance of particular species at any site depends upon at least three factors: vegetational characteristics (cover and food availability), abundance of predators and abundance of competing species. A literature review indicates that competitive effects have been particularly well documented among grassland rodents. These effects range from subtle habitat shifts to competitive exclusion and appear to be directly related to the amount of overlap in diet and to the density of the dominant competing species.