The elk population in Rocky Mountain National Park has increased dramatically from the early 1970s, after active elk population management ended in 1969, to present time. Paradoxically, this increase in an important host for the Rocky Mountain wood tick does not seem to have lead to increased tick abundance in the park.

Data from Poudre Canyon and Rocky Mountain National Park are suggestive of an ecological cascade where overgrazing by elk in Rocky Mountain National Park in recent decades caused negative effects on vegetation followed by decreased tick abundance.

Values indicated by * are significantly (P < 0.05) higher than the value for the other area. Data for tick abundance should not be compared between 2006 and 2007 because a smaller drag size was used in 2007.

Data for abundance of rodents and larval and nymphal ticks infesting these animals in areas with differing elk grazing pressures are needed to test the hypothesis of an ecological cascade where overgrazing by elk leads to: (1) decreased vegetation cover, (2) suppression of rodent tick hosts, (3) decreased tick abundance and (4) decreased risk of human exposure to Rocky Mountain wood ticks and the disease agents they transmit.

From: Eisen, Ibarra-Juarez, Eisen and Piesman. 2008. Indicators for elevated risk of human exposure to host-seeking adults of the Rocky Mountain wood tick (Dermacentor andersoni) in Colorado. Journal of Vector Ecology: 117-128.