The Structure of a Colorado Tick Fever Ecosystem

Abstract

The habitat hyperspace of a south—facing slope ecosystem in Rocky Mountain National Park, Colorado, USA was characterized by two major gradients, soil depth and soil moisture. Richardson's ground squirrels (Spermophilus richardsonii) were limited in their distribution by areas of shallow soil, and excluded golden—mantled ground squirrels (S. lateralis) from areas of deep soil. The habitat hypervolume of the golden—mantled ground squirrel included that of the least chipmunk (Eutamias minimus); the golden—mantled ground squirrels suppressed the population of least chipmunks. Deer mice (Peromyscus maniculatus), least chipmunks, and golden—mantled ground squirrels were the principal hosts of larval wood ticks (Dermacentor andersoni). The golden—mantled ground squirrels and least chipmunks were the principal hosts of nymphal wood ticks. The circulation of Colorado tick fever virus was maintained through the interactions of the wood ticks, least chipmunks, and golden—mantled ground squirrels. Areas of wood tick abundance were accurately described by a discriminant function of five easily measured habitat hyperspace variables, areas of virus activity with seven variables.