Supplemental feeding grounds of Wyoming

Funding Sources: USGS, Wyoming Livestock-Wildlife Initiative, WY Game and Fish, US Fish and Wildlife Service, Wyoming Game and Fish Department.

Collaborators: Mark Taper and Scott Creel (Montana State University), Brandon Scurlock, Eric Maichak, Jared Rogerson and Hank Edwards (Wyoming Game and Fish Department).

Students: Vicki Patrek and Tyler Creech

My research on brucellosis in the GYE began around the supplemental feedgrounds of Wyoming. We found that over 50% of the spatial variation in prevalence was associated with the length of artificial feeding season and in particular when the feeding season ends. Elk population size and density, measured at one point in time, were relatively unimportant. Our subsequent work, however, showed that contact rates with fetuses (the primary mode of transmission for B. abortus) were related to elk density within and among feedgrounds. These two studies show that a host density by time interaction determines the cumulative exposure rate of elk on the feedgrounds. Subsequently, my collaborators at WY Game and Fish and I have begun examining the impacts of changing the feedground system in two ways: (1) on some feedgrounds we have experimented with spreading the feed over larger areas, and (2) we are ending the feeding seasons prior to spring green-up on eight sites with the expectation that shortening the feeding season by 30 days should result in a 2/3rd reduction in prevalence. My collaborators and I also found that supplemental feeding resulted in higher stress levels (Master Thesis expected May 2009) and increased prevalence of some parasitic worms known as helminths.

Disease researchers often assume that increased densities translate into increased contact rates, and as a result increased transmission. By the same logic, reducing host densities may be a useful management tool. Our work suggests a slightly different perspective is necessary. When host density and transmission fluctuate over time, transmission is likely to be more related to the cumulative density during the period of transmission than a single point estimate. In addition, the additional stress of dense aggregations may be an alternative mechanism by which increased host densities translate into increased disease.

Citations:
Creech, T, PC Cross, S Creel, E Maichak, & B Scurlock. Accepted pending revision. Altered feeding styles dramatically reduces elk contact rates. Journal of Wildlife Management.

Patrek, VE, S Creel, ML Taper, B Scurlock & PC Cross. Accepted pending revision. Effects of supplemental feeding and aggregation on stress hormone concentrations in elk. Journal of Wildlife Management.

Maichak, EJ, BM Scurlock, JD Rogerson, LL Meadows, AE Barbknecht, WH Edwards, and PC Cross. 2009. Effects of management, behavior, and scavenging on risk of brucellosis transmission in elk of western Wyoming. Journal of Wildlife Diseases 45:398-410.

Cross, PC, WH Edwards, B Scurlock, E Machaik, & J Rogerson, 2007. Management and climate impacts on brucellosis in elk of the Greater Yellowstone Ecosystem. Ecological Applications 17(4):957-964.



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