The ecology of the lone star tick, Amblyomma americanum (L.), in two contrasting habitats in Virginia (Acarina: Ixodidae).

Abstract

Aspects of the population dynamics and distribution of the lone star tick, Amblyomma americallum (L.), were studied in 2 contrasting, predominantly forest habitats in Virginia. The 17.6-ha Piedmont locality comprised old fields and mixed pine-deciduous forest in various stages of succession adjacent to a swamp, cultivated fields and pastures. The average adult tick density in this area at the time of peak host seeking activity was 627/ha (range, 421–833/ha); the average peak nymphal tick density was 1338/ha (range, 393–2283/ha). Radioisotope-tagged larvae of the lone star tick were released in this area in an attempt to estimate the population density of this stage, but none were recaptured on the various mammals sampled (raccoons, skunks, opossums, and gray squirrels). The contrasting coastal plain 59.5-ha Newport News study area was part of a very large expanse of unused mixed pinedeciduous forest containing extensive freshwater habitat. The average adult and nymphal tick densities at peak host seeking activity were 2273/ha and 3001/ha, respectively, or approximately 4.4 and 2.3 times the comparable densities at the Montpelier study area. Estimates of the larval tick population were obtained by release and recapture of radioisotopetagged individuals on raccoons. The estimated average larval density for the stream and swamp-edge habitat frequented by these animals was 10,859/ha. These results suggest that the very large subclimax lowland deciduous forest represented by the Newport News City Park had a much higher lone star tick support capacity than the small, frequently cut-over upland woodlots represented by the Piedmont plateau Montpelier study area. The results of studies on population dynamics, particularly changes in the relative frequency of adults versus nymphs between years, suggest that the life cycle in nature requires 3 activity seasons for completion, at least in this cooler, northern part of the geographic range. Statistical tests of the locations of tick captures in the 2 areas suggest that the distribution is essentially random. No consistent relationship between tick distribution and any of the dominant forest types was found. However, ticks were less abundant in the old fields than in the forest habitat. Possible explanations for the findings described above are discussed in the text.