Annual Timing of Elk Abortions and Potential Brucellosis Risk

The transmission of Brucella abortus, the bacteria causing brucellosis, occurs through abortion events. In this study, we investigated the timing of those abortion events using vaginal implant transmitters (VITs) in pregnant elk (Cervus elaphus) from the Jackson and Pinedale regions of Wyoming. From 2006 to 2013, we captured 463 pregnant female elk and 136 of those were seropositive (29%, 95% CI = [25, 34]). We had a total of 29 abortion events with 20 percent (95%CI = [13, 29]) of seropositive elk aborting compared to 2.2 percent (95% CI =[0.8, 4.5]) of seronegative elk aborting. VIT data are left-truncated, right and interval censored. We analyzed these data in a Bayesian framework borrowing from the survival analysis literature to estimate the baseline hazard and how it changes during the year. When we conducted a joint analysis of both abortions and births our preliminary results indicated that elk abortions are concentrated in March and April. Only three abortions occurred after 20 May  and one may have occurred as late as 10 July. These results are relevant to mitigating the risk of transmission between elk and cattle. Future work can build upon these results to assess the amount of brucellosis transmission risk during the winter on private land compared to public grazing allotments, which are used later in the year

Geo-Statistical Methods for Detecting Elk Parturition Sites from GPS Collar Data

There is an increasing awareness of the importance of juvenile survival in ungulate population dynamics, and the accurate prediction of parturition habitat may allow for more effective management. Detecting birth sites in a statistically rigorous way, however, often requires intensive field efforts that may not be possible for all studies. We developed a hierarchical two-stage clustering analysis for identifying elk parturition locations, which can be conducted retrospectively using only GPS location data. We validated our approach using a dataset of 59 adult female elk ( Cervus elaphus) fitted with both a Global Positioning System (GPS) collar (30-minute sampling interval) and vaginal implant transmitter (VIT) For the top parameter set, approximately 80% of estimable parturition sites were within 1 km of their respective VIT location. Roughly 10 % of our predicted birthing locations were over 2 km away from the VIT location, but many of these events could be filtered from the analyses due to their clustering attributes. Designed to minimize Type II errors this filtering also removes a subset of birthing sites that close to VIT locations, and magnitude of this effect varied across parameter sets. Sub-sampling of the GPS dataset from 30 min to 1, 2, 3, and 6 hour intervals resulted in modest reductions in the efficacy of our approach. With the use of GPS collars in ungulate studies on the rise, our approach provides managers with additional information on birth site locations at no additional cost over and above a typical GPS study

Adaptive Management of Winter Elk Feedgrounds in Western Wyoming as a Long-Term Strategy for Reducing Brucellosis in Elk While Maintaining Separation from Cattle: A Work in Progress

Brucellosis is of large economic and management concern in the Greater Yellowstone Ecosystem (GYE) where wildlife remain the last reservoir of the disease in the United States. Wyoming Game and Fish Department (WGFD) management of brucellosis has focused on separation of elk (Cervus elaphus) and cattle (Bos taurus) through operation of 22 winter feedgrounds, which originated to prevent elk starvation and elk damage. Although feedgrounds perpetuate the spread of brucellosis among elk, they are largely maintained to prevent disease spillover to cattle. Despite efforts, recent brucellosis occurrences in Wyoming cattle during 2004-2008 were linked to feedground elk. Therefore, numerous research projects conducted during 2006-2008 were aimed at developing feedground management strategies that lead to long-term brucellosis reductions in elk. Major research results lead the WGFD to development of the Target Feedground Project, which manipulates feeding management to reduce brucellosis in elk. This project was first implemented in winter 2007-08 and is conducted exclusively at target feedgrounds, where perceived elk-cattle commingling risk is low and there is a high potential for elk to free range in late winter/early spring. The first objective is to reduce elk densities while on feedgrounds by using low-density feeding. The second objective is to reduce duration of high elk concentration by manipulating end-feeding season date through systematic reductions in hay rations in late winter and early spring, with the goal of ending an average of 3-4 weeks earlier than long-term means. Advantages of this project, if successful, are sustainable reductions in elk brucellosis and decreased risk to cattle, lower elk feeding costs, and continued operation of feedgrounds to minimize elk-cattle commingling, elk damage, and sustain elk numbers that meet public expectation. Disadvantages are that the project is not suitable for all feedgrounds and elk on target feedgrounds remain susceptible to new diseases that may arise

Appendix C. Parameter estimates from the general linear model using all main effects to explain the end of the supplemental feeding season.

Parameter estimates from the general linear model using all main effects to explain the end of the supplemental feeding season

Appendix B. Parameter estimates from the best AIC logistic regression model of elk brucellosis status.

Parameter estimates from the best AIC logistic regression model of elk brucellosis status

Appendix A. A table of summmary statistics on the feeding and disease testing data at each of the 23 Wyoming elk feedgrounds and the covariates used in the statistical analyses.

A table of summmary statistics on the feeding and disease testing data at each of the 23 Wyoming elk feedgrounds and the covariates used in the statistical analyses

Appendix D. A photo of the elk feeding ground at Soda Lake in northwestern Wyoming, USA.

A photo of the elk feeding ground at Soda Lake in northwestern Wyoming, USA