Rick Wallen

ABSTRACT Over a century of concerted conservation recovered the bison population in Yellowstone National Park from 23 animals in 1901 to 5000 by 2005. This conservation success led to societal conflicts and disagreements among various management entities regarding classic issues of overabundance (Garrott et al. 1993), combined with concerns over the risk of brucellosis transmission to domestic livestock when bison migrate out of the park (Cheville et al. 1998). As a result, more than 6700 bison have been culled since 1983 as they attempted to leave the park (Gates et al. 2005). These large‐scale removals are aimed at brucellosis risk management, but likely influence bison demographics and vital rates. The development of rigorously estimated vital rates that incorporate the effects of brucellosis and associated management actions is essential for formulating appropriate management strategies (e.g., vaccination, culling) for long‐term bison conservation. These estimates will also contribute to the growing scientific understanding of how climate, disease, and density affect managed ungulate populations. Fuller et al. (2007b) found high and consistent adult female survival and lower birth rates in brucellosis seropositive Yellowstone bison during 1995–2001. We focused on the central herd and incorporated additional information collected during 2002–2006 to extend those analyses by investigating density, climate, and brucellosis seroprevalence effects on age‐specific survival and fecundity.

Concerns over migratory bison (Bison bison) at Yellowstone National Park transmitting brucellosis (Brucella abortus) to cattle herds on adjacent lands led to proposals for bison vaccination. We developed an individual-based model to evaluate how brucellosis infection might respond under alternate vaccination strategies, including: (1) vaccination of female calves and yearlings captured at the park boundary when bison move outside the primary conservation area; (2) combining boundary vaccination with the remote delivery of vaccine to female calves and yearlings distributed throughout the park; and (3) vaccinating all female bison (including adults) during boundary capture and throughout the park using remote delivery of vaccine. Simulations suggested Alternative 3 would be most effective, with brucellosis seroprevalence decreasing by 66% (from 0.47 to 0.16) over a 30-year period resulting from 29% of the population receiving protection through vaccination. Under this alternative, bison would receive multiple vaccinations that extend the duration of vaccine protection and defend against recurring infection in latently infected animals. The initial decrease in population seroprevalence will likely be slow due to high initial seroprevalence (40-60%), long-lived antibodies, and the culling of some vaccinated bison that were subsequently exposed to field strain Brucella and reacted positively on serologic tests. Vaccination is unlikely to eradicate B. abortus from Yellowstone bison, but could be an effective tool for reducing the level of infection. Our approach and findings have applicability world-wide for managers dealing with intractable wildlife diseases that cross wildlife-livestock and wildlife-human interfaces and affect public health or economic well-being.

Background Yellowstone National Park (YNP) developed a plan to manage the abundance of bison during the winter of 2012 using population data, modeled forecasts of movement, and a suite of wildlife management tools, consistent with the 2000 Interagency Bison ...

Throughout the world, fragmentation of landscapes by human activities has constrained the opportunity for large herbivores to migrate. Conflict between people and wildlife results when migrating animals transmit disease to livestock, damage property, and threaten human safety. Mitigating this conflict requires understanding the forces that shape migration patterns. Bison Bos bison migrating from Yellowstone National Park into the state of Montana during winter and spring concern ranchers on lands surrounding the park because bison can transmit brucellosis (Brucella abortus) to cattle. Migrations have been constrained, with bison being lethally removed or moved back into the park. We developed a state-space model to support decisions on bison management aimed at mitigating conflict with landowners outside the park. The model integrated recent GPS observations with 22 years (1990-2012) of aerial counts to forecast monthly distributions and identify factors driving migration. Wintering areas were located along decreasing elevation gradients, and bison accumulated in wintering areas prior to moving to areas progressively lower in elevation. Bison movements were affected by time since the onset of snowpack, snowpack magnitude, standing crop, and herd size. Migration pathways were increasingly used over time, suggesting that experience or learning influenced movements. To support adaptive management of Yellowstone bison, we forecast future movements to evaluate alternatives. Our approach of developing models capable of making explicit probabilistic forecasts of large herbivore movements and seasonal distributions is applicable to managing the migratory movements of large herbivores worldwide. These forecasts allow managers to develop and refine strategies in advance, and promote sound decision-making that reduces conflict as migratory animals come into contact with people.

... Permissions & Reprints. Review. Carrying capacity, migration, and dispersal in Yellowstone bison. Glenn E. Plumb a , Corresponding Author Contact Information , E-mail The Corresponding Author , PJ White a , Michael B. Coughenour b and Rick L. Wallen a. ...

ABSTRACT Background/Question/Methods Conserving the Yellowstone bison represents one of the greatest success stories in the history of wildlife management in North America. However, success has not come without challenges. The most significant problem confronting those who manage the population today is conflict created by the risk of spread of brucellosis from bison to cattle. Modern, adaptive management aimed at minimizing this risk requires a model capable of forecasting the population’s dynamics and its disease status. We used a discrete time, stage structured model assimilated with time series of monitoring data and results of detailed process studies to forecast changes in abundance and diseases status of the Yellowstone bison population. A Bayesian, hierarchical approach allowed use of data from multiple sources, supported estimation of process variance and observation error, and provided true forecasts, that is, predictions with confidence envelopes. Results/Conclusions Model forecasts suggested changes in policy could enhance conservation of bison while reducing risks of transmission of brucellosis from bison to livestock. Episodic, large removals to regulate the size of the population could be replaced by culling a much smaller number of animals annually, thereby mimicking chronic, natural mortality. Targeting sero-negative animals for culling rather than sero-positive ones could reduce the probability of disease transmission. A forecasting model can enhance management and policy by allowing evaluation of alternative actions. These evaluations are made honest by comprehensive assessments of uncertainty.