Education: Bachelor of Science in education (biological science) and fisheries and wildlife biology (May 2000)
McNair Project: The Effects of Grazing and Burning on Populations of Lone-Star Ticks (Amblyomma americanum) in Tallgrass Prairie (1996)
Mentor: Jack Cully, Jr., Ph.D.
Ticks are parasites of wild ungulates such as bison (Bos bison) and white-tailed deer (Odocoileus virginianus). These parasitic arachnids can be problematic for humans, as certain species can carry diseases such as Lyme Disease (Borrelia burgdorferi). It would seem logical that studies of habitat manipulation on populations of tick species would allow us to use the most appropriate and effective methods of control to minimize harmful levels of these populations. A study was conducted under the supervision of Dr. Jack Cully during the summer of 1996 (June-August) near Manhattan, Kansas investigating the effects of fire and grazing on populations of lone-star ticks (Amblyomma americanum) in a grassland ecosystem. We hypothesized that ticks should be more plentiful in areas burned less frequently and grazed by native ungulates.
Our study site in this experiment was the Konza Prairie Research Natural Area. It is an 8600-acre grassland Long-Term Ecological Research (LTER) study area which provides habitat for a variety of mammals and birds. The Konza LTER is divided into study watersheds, each with its own burning and grazing regimes; the two major grazing ungulates are O. virginianus and B. bison. This study area is very useful in studying A. americanum for two major reasons: First, this is the most abundant grassland tick species in the area. This allows for easy data collection. Second, the study site allows for controlled burning and grazing treatments on a large-scale area.
The study involved a total of twelve watersheds, variously scattered over the study site. Of these, five were ungrazed and seven were grazed. Grazing by native ungulates allowed ticks to aquire blood meals and either mature themselves or nourish their eggs. Each of the twelve watersheds were subject to 1, 4, or 20 year burn intervals. The removal of understory vegetation by fire acts to reduce humidity available for ticks, thus creating a saturation deficit and ultimately causing dessication.
The sampling technique for the watersheds involved transect dragging. This technique consisted of dragging a white cotton-flannel cloth (approximately 1m square in size) over vegetation in 1 km transects divided into ten 100m subsections, with distances being measured via a hand-held meter wheel. Ticks caught on the cloth were pulled off with tweezers and placed in a solution of 70% ethanol.
Results showed that of the 1852 ticks collected during the study, 1847 were A. americanum and five were Dermacentor variabilis. The 4-year burn interval produced the most ticks, 1295 (1251 of which were A. americanum larvae). Two-way analysis of variance (ANOVA) showed that only larval A. americanum populations showed significant responses to burn intervals (F=6.08, P<.01). The 20-year burn unit produced 563 ticks. Lower numbers in this watershed as compared to that of the 4-year seems to disagree with our hypothesis; it should be noted, however, that one of the 20- year burn watersheds was consumed in a wildfire during the summer of 1995, thus possibly incorporating some bias into the final results. Only four ticks were found in the 1-year burn units during the entire study. A total of 1124 ticks were found in native grazed pasture throughout the study period. Two-way ANOVA showed no significant response to grazing regime at any life stage of tick (larvae, nymph, adult). It seems that burning does have an effect on tick populations, especially those in their larval life stage, and is a viable tool when manipulating habitat for tick control.