Yellowstone Bison Research Articles

New perspectives on managing wildlife diseases

New perspectives on managing wildlife diseases

Editor's choice: Where the buffalo roam – bison and brucellosis in Yellowstone

Kilpatrick, A.M., Gillin, C.M. & Daszak, P. (2009) Wildlife–livestock conflict: the risk of pathogen transmission from bison to cattle outside Yellowstone National Park. Journal of Applied Ecology, 46, 476–485. An enduring symbol of the American West, great migratory herds of bison Bison bison once roamed the Great Plains in their millions (Berger & Cunningham 1994). Sadly, this wildlife spectacle is no more, as in parallel with population declines and extirpation in other migratory ungulates (Bolger et al. 2008; Harris et al. 2009), bison are now restricted to a number of small remnant populations. The causes of population decline in bison and other migrants are well known – hunting, habitat loss, fencing – and their need for space makes the conservation of these wide ranging species a major challenge (Berger 2004; Thirgood et al. 2004). The only free-ranging herd of bison remaining in the United States is found in the Greater Yellowstone Ecosystem of Montana, Wyoming and Idaho. At the start of the 20th century, this population had been reduced to 23 individuals, but with protection it has increased to nearly 5000. Bison spend most of the year at higher altitudes in the Yellowstone National Park but during severe winters they graze at lower elevations outside the park. Here they come into conflict with cattle ranching because of the risk of transmission of brucellosis from bison to cattle. Brucellosis is a bacterial disease that causes weight loss, abortion and reduced milk yields in cattle. The maintenance of brucellosis-free status in cattle is economically important to the livestock industry, and as a result, culling bison is part of the Government interagency disease control strategy (Clarke et al. 2005). The conservation success of Yellowstone's bison indirectly led to the culling of 1600 bison during the 2007/08 winter. For this issue's Editor's Choice selection, Kilpatrick et al. (2009) develop a quantitative risk assessment integrating both ecological and epidemiological data to assess the spatio-temporal risk of transmission of brucellosis from bison to cattle. The model demonstrates that the risk of transmission is highly variable in space, time and frequency and can be predicted by climatic conditions and the abundance of bison. Critically, the model suggests that the risk of brucellosis transmission is very low in most years and is periodically high only in certain localized areas around the park. The authors suggest alternative management strategies, such as financially compensating ranchers for grazing rights in localized areas, would be more cost-effective than the current policy of culling bison to control population size. Another management proposal is to the consider the section of the Greater Yellowstone Ecosystem which occurs in Montana as a separate zone from the rest of the state in terms of brucellosis infection status and provide yearly testing of cattle in that zone. This would cost a fraction of the $2.5 million that the current management strategies cost per year. Similarly, compensating ranchers for the financial value of all the cattle that graze in the affected areas around the park would cost about half the current yearly amount. The results of Kilpatrick et al.'s study have generated considerable interest from scientists, managers and the general public – particularly in the United States. In the month since the paper was published online it has been picked up in the mainstream media more than 100 times. Perhaps this is a reflection of the iconic status of the bison in American popular culture – but it does highlight the critical role of good ecological research in influencing natural resource management decisions. The primary role of the Editor's Choice initiative is to showcase papers that we believe best fulfil the journal's mission of publishing ecological studies with management relevance. Kilpatrick et al.'s study is a particularly good example of the connection between good science and real-world problem solving and we expect that the paper will be both widely cited and highly influential.

Allonursing and Cooperative Birthing Behavior in Yellowstone Bison, <em>Bison bison</em>

We document allonursing and cooperative birthing behavior in wild Bison near Yellowstone National Park in the western United States. During spring 2007, two female Bison nursed each other’s newborn calves and mutually cleaned both calves and consumed expelled birth material. Intensive cooperative birthing behavior has never been documented in wild Bison before. This observation of allonursing might be explained by kin selection and reciprocal altruism.

Reproduction and Survival of Yellowstone Bison

ABSTRACT The conservation of bison (Bison bison) from near extinction to >4,000 animals in Yellowstone National Park has led to conflict regarding overabundance and potential transmission of brucellosis (Brucella abortus) to cattle. We estimated survival and birth rates from 53 radiocollared adult female bison during 1995–2001, and we used calf:adult (C:A) ratios to estimate reproduction with the combined effects of pregnancy, fetal loss, and neonatal mortality during 1970–1997. Annual survival of adult females was high (0.92; 95% CI = 0.87‐0.95) and constant. Birth rates differed by brucellosis status and age. Birth rates were 0.40 calves per female (95% CI = 0.15‐0.65) for brucellosis‐positive 3 year olds, 0.63 (95% CI = 0.39‐0.87) for individuals testing negative, and 0.10 (95% CI = 0.00‐0.24) for individuals contracting brucellosis that birth year (sero‐converters). Birth rates were 0.64 (95% CI = 0.52‐0.76) for brucellosis‐positive individuals ≥4 years old, 0.81 (95% CI = 0.73‐0.89) for brucellosis‐negative individuals, and 0.22 (95% CI = 0.00‐0.46) for sero‐converters. Spring C:A ratios were negatively correlated with snow pack (β = −0.01 to −0.03, R2 = 0.26‐0.60, P < 0.05). Growth rate was highly elastic to adult survival (0.51), and juvenile survival (0.36) was 3 times more elastic than fecundity (0.12). Simulations suggested brucellosis eradication via vaccination would result in increased birth rates and a 29% increase in population growth (γ = 1.09), possibly leading to more bison movements outside the park. Our results will help park managers evaluate bison population dynamics and explore consequences of management actions and disease control programs.

Emigration and Density Dependence in Yellowstone Bison

Abstract: Understanding the relative importance of density‐dependent and density‐independent feedback on population growth is essential for developing management strategies to conserve wildlife. We examined a 99‐year time series of annual counts and removals for 2 bison (Bison bison) herds occupying northern and central Yellowstone National Park in the western United States. Yellowstone's aggressive management intervention effectively recovered bison from 46 animals in 1902 to > 1,500 animals in 1954. Supplemental feeding of the northern herd facilitated rapid growth (r = 0.16) during 1902 to 1952. Augmentation of the central herd with 71 animals also led to rapid growth over 1936 to 1954 (r = 0.10). In 1969, manipulative management ceased in the park, and we detected evidence of density‐dependent changes in population growth rates for both herds during 1970 to 2000 as numbers increased to >3,000 animals. The central herd showed evidence of a constant density‐dependent response over 1970 to 2000. In contrast, density dependence had a stronger effect on the northern herd's growth rate during 1970 to 1981 than during 1982 to 2000. We found evidence to suggest that these trends resulted from pulses of emigration from the central herd to the northern range beginning in 1982 in response to resource limitation generated by an interaction between density and severe snow pack. Corroborative evidence supporting this interpretation included 1) the annual growth of the central herd was negatively correlated with snow pack but that of the northern herd was not, 2) growth rates of the central and northern herds were uncorrelated during 1970 to 1981 but significantly and negatively correlated during 1982 to 2000, and 3) the northern herd could not have sustained the high removals experienced during 1984 to 2000 without immigration. Density‐related emigration from the central herd to the northern range may be fueling bison emigration onto private and public lands where large‐scale removals occur, exacerbating the brucellosis controversy for natural resource managers.

Spatial Population Structure of Yellowstone Bison

Abstract: Increases in Yellowstone National Park, USA, bison (Bison bison) numbers and shifts in seasonal distribution have resulted in more frequent movements of bison beyond park boundaries and development of an interagency management plan for the Yellowstone bison population. Implementation of the plan under the adaptive management paradigm requires an understanding of the spatial and temporal structure of the population. We used polythetic agglomerative hierarchical cluster analysis of radiolocations obtained from free‐ranging bison to investigate seasonal movements and aggregations. We classified radiolocations into 4 periods: annual, peak rut (15 Jul‐15 Sep), extended rut (1 Jun‐31 Oct), and winter (1 Nov‐31 May). We documented spatial separation of Yellowstone bison into 2 segments, the northern and central herds, during all periods. The estimated year‐round exchange rate (4.85‐5.83%) of instrumented bison varied with the fusion strategy employed. We did not observe exchange between the 2 segments during the peak rut and it varied during the extended rut (2.15‐3.23%). We estimated a winter exchange of 4.85‐7.77%. The outcome and effectiveness of management actions directed at Yellowstone bison may be affected by spatial segregation and herd affinity within the population. Reductions based on total population size, but not applied to the entire population, may adversely affect one herd while having little effect on the other. Similarly, management actions targeting a segment of the population may benefit from the spatial segregation exhibited.

TLR4 variation in Yellowstone bison

<i>TLR4</i> variation in Yellowstone bison

YELLOWSTONE BISON FETAL DEVELOPMENT AND PHENOLOGY OF PARTURITION

Abstract Knowledge of Yellowstone bison (Bison bison) parturition patterns allows managers to refine risk assessments and manage to reduce the potential for transmission of brucellosis between bison and cattle. We used historical (1941) and contemporary (1989–2002) weights and morphometric measurements of Yellowstone bison fetuses to describe fetal growth and to predict timing and synchrony of parturition. Our method was supported by agreement between our predicted parturition pattern and observed birth dates for bison that were taken in to captivity while pregnant. The distribution of parturition dates in Yellowstone bison is generally right-skewed with a majority of births in April and May and few births in the following months. Predicted timing of parturition was consistently earlier for bison of Yellowstone's northern herd than central herd. The predicted median parturition date for northern herd bison in the historical period was 3 to 12 days earlier than for 2 years in the contemporary period, respe...

Incisor wear and age in Yellowstone bison

Abstract Biologists commonly use tooth eruption and wear patterns or cementum annuli techniques to estimate age of ungulates. However, in some situations the accuracy or sampling procedures of either approach are undesirable. We investigated the progression of several quantitative measures of wear with age, using permanent first incisors from Yellowstone bison (Bison bison), and tested for differences between sexes and herds. We further investigated the relationship of wear and age to explore an age-estimation method. Labial-lingual width (LLW) correlated best with assigned age (r2=0.66, males; r2=0.76 females). Labial-lingual width differed between sexes, with females showing ∼0.2 mm more wear than males. Additionally, differences in rate of wear existed between bison of the northern and central Yellowstone herds (1.2 and 0.9 mm/year, respectively). We developed a regression formula to test the power of LLW as an estimator of Yellowstone bison age. Our method provided estimated ages within 1 year of the ...

EFFICACY OF SINGLE CALFHOOD VACCINATION OF ELK WITH BRUCELLA ABORTUS STRAIN 19

Brucellosis has been eradicated from cattle in the states of Wyoming, Montana, and Idaho, USA. However, free-ranging elk (Cervus elaphus) that use feedgrounds in the Greater Yellowstone Area (GYA) and bison (Bison bison) in Yellowstone and Grand Teton national parks still have high seroprevalence to the disease and have caused loss of brucellosis-free status in Wyoming. Management tools to control or eliminate the disease are limited; however, wildlife vaccination is among the methods currently used by wildlife managers in Wyoming. We conducted a controlled challenge study of single calfhood vaccination. Elk calves, caught in January and February of 1999 and 2000 and acclimated to captivity for 3 weeks, were randomly assigned to control or vaccinate groups. The vaccinate groups received Brucella abortus vaccine strain 19 (S19) by hand-delivered intramuscular injection. Calves were raised to adulthood and bred at either 2.5 or 3.5 years of age for 2000 and 1999 captures, respectively. Eighty-nine (44 controls, 45 vaccinates) pregnant elk entered the challenge portion of the study. We challenged elk at mid-gestation with pathogenic B. abortus strain 2308 by intraconjunctival instillation. Abortion occurred in significantly more (P = 0.002) controls (42; 93%) than vaccinates (32; 71%), and vaccine protected 25% of the vaccinate group. We used Brucella culture of fetus/calf tissues to determine the efficacy of vaccination for preventing infection, and we found that the number of infected fetuses/calves did not differ between controls and vaccinates (P = 0.14). Based on these data, single calfhood vaccination with S19 has low efficacy, will likely have only little to moderate effect on Brucella prevalence in elk, and is unlikely to eradicate the disease in wildlife of the GYA.

Stabilizing the Herd: Fixing the Identity of Nonhumans

Supported by scientific modes of representation, wildlife-management agencies commonly adopt policies that subordinate nonhuman species and resubstantiate human–nonhuman hierarchies. In this paper I illustrate the inadequacy of current management policies by drawing upon Deleuzian notions of immanence and movement and applying them to the specific case of Yellowstone bison. Modes of representation that define nonhuman ontology in terms of genetics are shown to be inadequate for they separate essence from experience and facilitate the removal and exclusion of nonhumans. In contrast, a Deleuzian theory of wildlife accentuates the importance of movement, contact, and contingency in the constitution of nonhuman ontology, thus outlining an approach that can also lead to a revision of human–nonhuman relations. In particular, movement provides a physical mechanism to bridge the theoretical gap that separates human from nonhuman, and suggests a means to link together ethical and evolutionary concerns regarding nonhumans. With the distinctions between Deleuzian theory and common wildlife-management practices in mind, the paradigm of sustainability is criticized for prioritizing demographic and genetic stability over spatial transgression, thereby minimizing the developmental capacities of nonhumans and legitimizing existing spatial structures of exclusion and control.

Bison and Elk: Brucellosis Seroprevalence on a Shared Winter Range

An increase in the population of Yellowstone bison (Bison bison) and changes in their winter distribution have prompted concerns about the potential for bison to transmit brucellosis to cattle. Elk (Gervus elaphus) also are hosts for the disease organism and could play a role as reservoirs for the disease. Environmental conditions on the Madison-Firehole winter range promote a high degree of range overlap between bison and elk (53% in Dec to 76% in May). Radiocollared elk were located within 100 m of bison 18% of the time, and commingling between species was positively correlated with snowpack. We investigated the seroprevalence of elk of the Madison-Firehole winter range and made comparisons to other elk populations in the region as an indicator of potential for interspecies transmission of brucellosis in the wild. We found that the seroprevalence rate in the Madison-Firehole elk (3%; n = 73) was consistent with elk that do not commingle with bison (0-1%) and lower than in elk associated with supplemental feeding programs (25-37%). Despite high levels of commingling, the seroprevalence rate in the Madison elk herd suggests that interspecies transmission from bison to elk in the Madison-Firehole is low.

Postmodern Policy Analysis in the Premodern West: Problem Definition in the Yellowstone Bison Case

Responding to calls for revised pedagogical strategies this article highlights the use of postmodern techniques in applied policy analysis. Focusing on the crucial role of problem definition in the Yellowstone National Park bison controversy of 1996-97, a postmodern approach is briefly examined and then applied in the form of a narrative analysis. An analysis of original survey data, newspaper articles, letters to the editors, public speeches, and public texts producedfive narratives: 1) “Hidden Agendas and Heroes,” 2) “Winter Ghost Towns and a Hobson’s Choice,” 3) “Two Goliaths and Little (David) Montana,” 4) “Blue Ribbons, a Mercy Harvest, and Anti-Recreationist Conspirators,” and 5) “Wild Bison and Wild Bureaucrats.” The article touches on language, power, democracy, and the relationship between positivism and postmodemism. It is argued that postmodem techniques can move from the realm of theory to the realm of practice and make significant contributions to applied policy analysis.

EFFECTS OF ELEVATED CO2AND DEFOLIATION ON GRASSES: A COMPARATIVE ECOSYSTEM APPROACH

Three plant species from each of three grassland ecosystems were grown under elevated (700 mL/m3) and ambient (350 mL/m3) CO2 and were defoliated or left undefoliated to test whether species response to elevated CO2 and grazing is related to evolutionary grazing history or to mode of photosynthesis. The three ecosystems represented a tropical grassland dominated by C4 species (the Serengeti of Africa), a temperate grassland dominated by a mixture of C3 and C4 species (Flooding Pampa of South America), and a northern temperate grassland dominated by C3 species (Yellowstone National Park of North America). Plants were grown in growth chambers under common conditions to compare relative responses to grazing and elevated CO2. Elevated CO2 caused an increase in total biomass and total productivity (biomass + clippings) only in Yellowstone species, and increases in growth occurred primarily in crowns and roots (storage organs). There were no significant CO2 effects on biomass or productivity in Serengeti or Flooding Pampa species, and no CO2 effects on aboveground biomass or productivity (aboveground biomass + clippings) in species from any of the three ecosystems. Since aboveground plant parts are the portions that are available to grazing mammals, this suggests that increased atmospheric CO2 may not affect food quantity in these three grasslands. There was no interaction between CO2 and defoliation for any species; thus, it appears that herbivores will not affect how grasses respond to elevated CO2 (at least under average nutrient conditions). Elevated CO2 caused a reduction in leaf percentage of N in species from Yellowstone and Flooding Pampa (especially the C3 species, Briza subaristata), but not in Serengeti species. Because the quantity of food was unaffected by the CO2 treatments and forage N was reduced, grazing mammals in Yellowstone (elk, Cervus elaphus, and bison, Bison bison) and the Flooding Pampa (cattle) may be negatively affected. Responses to defoliation were fairly consistent among ecosystems in aboveground productivity, which did not differ between defoliated and undefoliated plants, and in leaf water potentials and percentage of N, both of which increased in response to defoliation. However, differences among ecosystems were found for crown and root biomass in response to defoliation: Serengeti species, on average, had higher crown and similar root biomasses after defoliation, whereas defoliated species from the other two ecosystems had reduced crown and root biomass. We suggest that the lower intensity and increased temporal variance in grazing pressure in Yellowstone vs. the Serengeti, selected for plants that shift allocation away from roots and crowns in order to compensate for aboveground herbivory.

Research at Last for Yellowstone Bison

Ever since the harsh winter of 1989, bison from the burgeoning herd in Yellowstone National Park have been wandering out of the park in search of forage. That has been raising fears among neighboring Montana ranchers that bison-borne disease could infect their cattle, and has led to controversial shootings of hundreds of errant bison by park and state officials.

Greater Yellowstone's Bison: Unraveling of an Early American Wildlife Conservation Achievement

The Greater Yellowstone region's bison-brucellosis controversy has triggered troublesome proposals giving federal and state agriculture agencies jurisdiction over wildlife to eradicate a domestic livestock disease. Many of the region's bison (Bos bison) and elk (Cervus elaphus) carry the bacterium Brucella abortus, which can cause brucellosis. Local livestock officials fear bison and elk could transmit brucellosis to domestic livestock. jeopardizing state brucellosis class-free status. However, no cases of such transmission in an open range setting have been verified scientifically. Various federal and state agencies have jurisdiction over the region's wildlife and livestock; these agencies are having real difficulty reaching consensus on how to address brucellosis in the wildlife populations. Montana and Idaho recently vested state livestock officials with jurisdiction over bison leaving Yellowstone National Park (YNP), and the U.S. Department of Agriculture's Animal, Plant, and Health Inspection Service (APHIS) has indicated it may propose regulations asserting jurisdiction over bison. An interim bison management plan, the result of a recent court settlement, provides for the National Park Service (NPS) to participate in capturing, testing, and slaughtering Yellowstone's bison, but makes no provision for addressing brucellosis in elk. The region's brucellosis problem could be adequately addressed through a risk management disease control policy rather than a costly and perhaps fruitless eradication effort. Such an approach can be implemented without the unwelcome precedent of livestock officials taking jurisdiction over wildlife.

The Population Dynamics of Brucellosis in the Yellowstone National Park

The role that pathogens play in structuring ecological communities needs to be examined from both a theoretical and empirical perspective. This paper provides a brief introduction to the ecology and epidemiology of brucellosis in Yellowstone National Park. Observed patterns of infection for brucellosis in bison in national parks in the United States suggest that Brucella has a relatively sharply defined threshold for establishment and that the proportion of the host population infected increases as a relatively simple function of population density. Unfortunately, the threshold population for Brucella establishment in bison is low, a herd of at least 200 individuals; this makes it very hard to eradicate Brucella from wild populations. Simple calculations based on observed prevalence and recruitment data for the Yellowstone bison herd suggest that unacceptably high levels of culling would be required to eradicate brucellosis in the park. A simple mathematical model is used to describe aspects of the population dynamics of Brucella. The analyses suggest that an understanding of infectious disease dynamics is crucial to the management and conservation of wild and domestic ungulate species in and around national parks and other nature reserves. The consequences of disease control for the maintenance of biodiversity in other natural and captive communities need to be better understood.

On the Origin of Brucellosis in Bison of Yellowstone National Park: A Review

Brucellosis caused by Brucella abortus occurs in the free‐ranging bison (Bison bison) of Yellowstone and Wood Buffalo National Parks and in elk (Cervus elaphus) of the Greater Yellowstone Area. As a result of nationwide bovine brucellosis eradication programs, states and provinces proximate to the national parks are considered free of bovine brucellosis. Thus, increased attention has been focused on the wildlife within these areas as potential reservoirs for transmission to cattle. Because the national parks are mandated as natural areas, the question has been raised as to whether Brucella abortus is endogenous or exogenous to bison, particularly for Yellowstone National Park. We synthesized diverse lines of inquiry, including the evolutionary history of both bison and Brucella, wild animals as Brucella hosts, biochemical and genetic information, behavioral characteristics of host and organism, and area history to develop an evaluation of the question for the National Park Service. All lines of inquiry indicated that the organism was introduced to North America with cattle, and that the introduction into the Yellowstone bison probably was directly from cattle shortly before 1917. Fistulous withers of horses was a less likely possibility. Elk on winter feedgrounds south of Yellowstone National Park apparently acquired the disease directly from cattle. Bison presently using Grand Teton National Park probably acquired brucellosis from feedground elk.

Physiological Responses of Yellowstone Bison to Winter Nutritional Deprivation

Because nutrition is critically related to other aspects of bison (Bison bison) ecology, and the winter ranges inhabited by bison in Yellowstone National Park (YNP) are ecologically diverse, it was important to determine if nutritional deprivation differences occurred among winter ranges. We used chemistry profiles of urine suspended in snow to compare nutritional deprivation of bison from january to April 1988 on 4 sampling areas of 3 winter ranges in YNP. Declining (P < 0.001) trends of urinary potassium: creatinine ratios in bison on all 4 sampling areas indicated progressive nutritional deprivation through late March. Concurrent increases (P ≤ 0.001) in mean urea nitrogen: creatinine ratios from late February through late March in 3 of 4 areas suggested that increased net catabolism was occurring

Remote Monitoring of Ovulation and Pregnancy of Yellowstone Bison

The physiological mechanisms that control reproductive success of wild bison (Bison bison) are not known, and the relatively small scattered herds prevent intensive study. Environmental, demographic, and physiological factors all play major interrelated roles in reproductive self-regulation. Thus, we validated the use of urinary and fecal steroid analysis as a means of detecting ovulation and pregnancy in uncaptured free-roaming ungulates, and identified the physiologic mechanisms that govern reproductive success in wild bison. Free-roaming bison of 2 subpopulations of the Yellowstone National Park herd were observed during 1989-91