Ecology of the American Dog Tick, Dermacentor variabilis,1 in a Study Area in Virginia. 2. Distribution in Relation to Vegetative Types2.

Abstract

The relationship between distribution of Dermacentor variabilis (Say) and vegetation was studied. Average tick capture frequency was compared with vegetation classified by 2 different methods. Immature tick capture frequency was highly aggregated with greatest numbers in the old field-forest ecotone. Adult tick distribution was much less aggregated, though these ticks also were collected more frequently in the field-forest ecotone. Comparisons of tick distribution with forest vegetation (exclusive of the ecotone) classified according to density of various height categories revealed little difference between low and medium height deciduous types, though both of these had more ticks than other forest types. In a comparison of tick distribution with forest vegetation classified according to tree species composition, immature tick capture frequency was greatest in the moist-mesic mixed pine-deciduous and mixed lowland types (3-year average) while adult tick capture frequency was greatest in the drier mixed upland and hickory dominant forest areas. The mixed oak type, which was in the most advanced stage of succession, i.e., approaching climax, had low yields of all D. variabilis life stages. Hypotheses to explain the reasons for these differences are discussed. The results of comparisons of capture frequencies of radioisotope-tagged ticks in relation to vegetation were similar to those for unmarked (wild ticks) with respect to the field forest ecotone, but not among the forest types. The use of radioisotope-tagged ticks to study the relationship between tick distribution and vegetation appears to have been useful where adequate samples were obtained (e.g., field-forest ecotone) and is of interest because the results can be related to the number of individuals released.