Reproduction and demography of brucellosis infected bison in the southern Greater Yellowstone Ecosystem.

Authors(s): S. L. Cain

Publication:

Publisher:

Publication Date: 0000-00-00

Type: annual report

Location:

Abstract: Objectives Our objectives are: 1)to evaluate the relationship between the incidence of prematurely terminated pregnancies and brucellosis serology in brucellosis-infected and non-infected bison; 2)to assess the potential risk of disease transmission by examining spatial areas of overlap between bison and cattle, especially during high risk periods (e.g. calving); 3)to determine effects of disease exposure and maternal traits on calf growth rates and age at puberty; and 4)to determine effects of female age on pregnancy, birth, and calf survival. Findings and Status Preliminary but interesting results are emerging. We have documented a significant range expansion into the eastern portion of the park. Used rarely in the early 1990's when the herd numbered about 100, this area now contains bison year-round and increasing numbers remain through the winter. With the current herd size at about 550 animals, we have also detected that the primary calving period is about 3 weeks longer than it was 10 years ago. Furthermore, even though brucellosis does reduce the reproductive potential of the herd (abortion rates are being documented), the population continues to grow at an average rate of 15 percent a year, perhaps the fastest rate of any know wild bison herd. All of these results have a significant bearing on development of management strategies, including the interagency elk/bison EIS that is now in progress. Our intent is to continue this study until an active management plan can be put into place. Until then, the herd will continue to grow rapidly, which could change important parameters associated with minimizing brucellosis transmission risk. Reports have been produced annually since the onset of the study and publications will be forthcoming.

Keywords: animal, mammal, ungulate, bison, B ison bison, disease, brucellosis, Greater Yellowstone Ecosystem, Grand Teton National Park, livestock, population, habitat, management