Elk Harvest Research Articles

Sustainable elk harvests in Alberta with increasing predator populations

Large predators often are believed to cause declines in hunter harvests of ungulates due to direct competition for prey with hunters. In Alberta, predators of elk (Cervus elaphus), including grizzly bear (Ursus arctos), cougar (Puma concolor), and wolf (Canis lupus), have increased in recent years. We used trend analysis replicated by Wildlife Management Unit (WMU) to examine regional trends in elk harvest and hunter success. Over a 26-yr period, average harvest of elk increased by 5.46% per year for unrestricted bull and by 6.64% per year for limited-quota seasons. Also, over the same time frame, average hunter success increased by 0.2% per year for unrestricted bull and by 0.3% per year for limited-quota seasons, but no trend was detected in hunter effort (P>0.05). Our results show that increasing large-predator populations do not necessarily reduce hunter harvest of elk, and we only found evidence for this in Alberta's mountain WMUs where predation on elk calves has reduced recruitment. Furthermore, data indicate that Alberta's elk harvest management has been sustainable, i.e., hunting has continued while populations of elk have increased throughout most of the province. Wildlife agencies can justify commitments to long-term population monitoring because data allow adaptive management and can inform stakeholders on the status of populations.

Supporting adaptive management with ecological forecasting: chronic wasting disease in the Jackson Elk Herd

AbstractAdaptive management has emerged as the prevailing approach for combining environmental research and management to advance science and policy. Adaptive management, as originally formulated by Carl Walters in 1986, depends on the use of Bayesian models to provide a framework to accumulate knowledge. The emergence of ecological forecasting using the Bayesian framework has provided robust tools and supports a new approach to informing adaptive management, which can be particularly useful in developing policy for managing infectious disease in wildlife. We used the potential infection of elk populations with chronic wasting disease in the Jackson Valley of Wyoming and the National Elk Refuge as a model system to show how Bayesian forecasting can support adaptive management in anticipation of management challenges. The core of our approach resembles the sex‐ and age‐structured, discrete time models used to support management decisions on elk harvest throughout western North America. Our model differs by including stages for CWD‐infected and unaffected animals. We used data on population counts, sex and age classification, and CWD testing, as well as results from prior research, in a Bayesian statistical framework to predict model parameters and the number of animals in each age, sex, and disease stage over time. Initial forecasts suggested CWD may reach a mean prevalence in the population of 12%, but uncertainty in this forecast is large and we cannot rule out a mean forecasted prevalence as high as 20%. Using recruitment rates observed during the last two decades, the model predicted that a CWD prevalence of 7% in females would cause the population growth rate () to drop below 1, resulting in population declines even when female harvest was zero. The primary value of this ecological forecasting approach is to provide a framework to assimilate data with understanding of disease processes to enable continuous improvement in understanding the ecology of CWD and its management.

Primarily resident grizzly bears respond to late-season elk harvest

Autumn ungulate hunting in the Greater Yellowstone Ecosystem carries the risk of hunter–grizzly bear (Ursus arctos) conflict and creates a substantial challenge for managers. For Grand Teton National Park, Wyoming, USA, a key information need is whether increased availability of elk (Cervus canadensis) carcasses during a late autumn (Nov–Dec) harvest within the national park attracts grizzly bears and increases the potential for conflict with hunters. Using a robust design analysis with 6 primary sampling periods during 2014–2015, we tested the hypothesis that the elk harvest resulted in temporary movements of grizzly bears into the hunt areas, thus increasing bear numbers. We detected 31 unique individuals (6 F, 25 M) through genetic sampling and retained 26 encounter histories for analysis. Markovian movement models had more support than a null model of no temporary movement. Contrary to our research hypothesis, temporary movements into the study area occurred between the July–August (no hunt; N2014–2015 = 5) and September–October (no hunt; N2014–2015 = 24) primary periods each year, rather than during the transition from September–October (no hunt) to November–December (hunt; N2014–2015 = 15). A post hoc analysis indicated that September–October population estimates were biased high by detections of transient bears. Grizzly bear presence during the elk hunt was limited to approximately 15 resident bears that specialized in accessing elk carcasses. The late timing of the elk hunt likely moderated the effect of carcasses as a food attractant because it coincides with the onset of hibernation. From a population response perspective, the current timing of the elk harvest likely represents a scenario of low relative risk of hunter–bear conflicts. The risk of hunter–grizzly bear encounters remains, but may be more a function of factors that operate at the level of individual bears and hunters, such as hunter movements and bear responses to olfactory cues.

The geography of conflict between elk and agricultural values in the Cypress Hills, Canada

Complex ecological issues like depredation and its management are determined by multiple factors acting at more than one scale and are interlinked with complex human social and economic behaviour. Depredation by wild herbivores can be a major obstacle to agricultural community support for wildlife conservation. For three decades, crop and fence damage, competition with livestock for native rangeland and tame pasture, and depredation of stored feed by elk ( Cervus elaphus canadensis) have been the cause of conflict with agricultural producers in the Cypress Hills, Alberta and Saskatchewan. Tolerance of elk presence on private lands is low because few benefits accrue to private landowners; rather they largely perceive elk as a public resource produced at their expense. Government management actions have focused on abatement inputs (e.g., population reduction; fencing) and compensation, but incentives to alter land use patterns (crop choice and location) in response to damages have not been considered. Nor has there been information on spatial structure of the elk population that would allow targeted management actions instead of attempting to manage the entire population. In this study we analysed the spatial structure of the Cypress Hills elk population, the distribution of the elk harvest in relation to agricultural conflicts, developed models of the spatial patterns of conflict fields, and evaluated compensation patterns for damage by wild herbivores. We propose modifications to current abatement and compensation programs and discuss alternative approaches involving changes to agricultural land use patterns that may reduce the intensity of conflicts with elk, and increase the acceptance capacity of landowners.

Selection of Northern Yellowstone Elk by Gray Wolves and Hunters

We compared selection of northern Yellowstone elk (Cervus elaphus) by hunters in the Gardiner Late Hunt and northern Yellowstone wolves (Canis lupus) with regard to sex, age, and impacts to recruitment. We compared harvest data from 1996–2001 with wolf-killed elk data from 1995–2001. We assessed the effects of hunting and wolf predation on reproductive female elk by constructing a life table and calculating reproductive values for females in the northern Yellowstone herd. We devised an index of total reproductive impact to measure impacts to calf production due to hunting and wolf predation. The age classes of female elk selected by wolves and hunters were significantly different. Hunters selected a large proportion of female elk with the greatest reproductive values, whereas wolves selected a large proportion of elk calves and older females with low reproductive values. The mean age of adult females killed by hunters throughout the study period was 6.5 years, whereas the mean age of adult females killed by wolves was 13.9 years. Hunting exerted a greater total reproductive impact on the herd than wolf predation. The combined effects of hunters killing prime-aged females (2–9 yr old), wolves killing calves, and predation by other predators has the potential to limit the elk population in the future. Yellowstone is unique in this regard because multiple predators that occur sympatrically, including hunters, wolves, grizzly bears (Ursus arctos), black bears (Ursus americanus), cougars (Felis concolor), and coyotes (Canis latrans), all prey on elk. Using an Adaptive Harvest Management process the known female elk harvest during the Gardiner Late Hunt has been reduced by 72% from 2,221 elk in 1997 to 620 elk in 2004. In the future, hunting harvest levels may be reduced further to partially offset elk losses to wolves, other predators, and environmental factors.

Indirect Effects of Elk Harvesting on Ravens in Jackson Hole, Wyoming

Harvesting of marine and terrestrial animals by humans produces animal biomass byproducts that many scavenger species exploit. Effects of food byproducts from harvesting on the ecology of scavenger species has rarely been measured, especially in terrestrial systems. Such nutritional subsidization of scavengers needs to be monitored because increases in their populations may influence population dynamics of other species and alter natural community dynamics. I quantified effects of the distribution of elk (Cervus elaphus) gutpiles generated by an intensive harvest program in Jackson Hole, Wyoming, USA, on local raven (Corvus corax) foraging behaviors, daily and seasonal movements, and population distribution. During Jackson Hole's 2001 fall elk harvest, I found ravens to be the most abundant vertebrate species scavenging on monitored gutpiles, and the number of ravens I detected during fixed-width transect surveys positively correlated with concurrent, sympatric gutpile densities. I found raven abundance, estimated via point-count surveys in habitat-paired harvest zone and reference plots, to increase significantly in conjunction with the fall elk harvest only in the harvest zone plots. Furthermore, estimated raven abundance and nest density in the spring were significantly higher in the harvest zone plots than in the reference plots. Results indicate that in Jackson Hole, ravens exploit gutpiles provided by elk harvesting, daily raven distribution in the fall corresponds with the immediate distribution of gutpiles across the landscape, fall raven abundance is associated with the overall density of gutpiles in a given area in the fall, and spring raven abundance and nest density are associated with fall gutpile density. Collectively, these findings suggest that the high concentration of elk gutpiles in Jackson Hole is a significant supplemental food resource for ravens, and that wildlife harvesting in a terrestrial environment is capable of influencing the foraging behaviors, movements, and population dynamics of scavenger species. Wildlife managers must consider nontarget species when evaluating the efficacy of their regulatory programs and work to minimize unintended effects caused by wildlife management on the surrounding ecological community. Jackson Hole's elk population regulation program is a model for ungulate management due to its long-term success, while at the same time managers in Jackson Hole are continually addressing how their program may affect the surrounding ecological community and considering alternative management strategies to more effectively conserve the region's diversity. Results here provide baseline information on raven ecology in relation to Jackson Hole's current elk management program for comparison to other areas with intensive ungulate management programs, and for later comparison within Jackson Hole as strategies for managing its elk population change in the future. This study also draws attention toward monitoring effects of anthropogenic byproduct food resources that, despite their inconspicuousness in the literature, can substantially influence the ecology of opportunistic scavengers; and it points out several scavenger species other than ravens that also may be influenced by access to gutpiles or other anthropogenic foods that are abundant, reliable, and nutritious. Finally, having determined a clear link between elk harvesting and the population dynamics of ravens—an influential species in its ecological community—this study sets the stage for future research, testing the strength and extent of a trophic cascade that may be initiated by gutpile availability and propagated by increases in raven population density in Jackson Hole.

Adaptive management for reintroductions: Updating a wolf recovery model for Yellowstone National Park

Ecological models have their greatest potential for conservation in the context of adaptive management, but there are few examples where models have been updated as new data have become available. We update a predator–prey model built to anticipate the consequences of wolf ( Canis lupus) reintroduction into Yellowstone National Park, with new data accumulated since wolves were released in 1995. Observed response to wolf recovery allows us to evaluate our ability to predict system dynamics and thereby address concerns about future impacts of predation on elk ( Cervus canadensis) numbers and harvest by hunters. Structural assumptions of the model include a dynamic carrying capacity for elk, K elk( t), varying as a function of winter severity and summer forage production. During severe winters the aerial extent of Yellowstone's Northern Range gets smaller resulting in density-dependent migration of elk outside the park where they are subject to hunter harvest. The updated model predicts that hunter harvest of elk will cause a decline of mean herd size relative to that expected without harvest. Wolf predation results in a further 21% reduction in elk herd size with wolf consumption averaging approximately 1035 elk annually. Elk harvest is reduced by wolves yet annual hunter harvest was sustained at an average of 1089 elk. Predation and hunter harvest is density-dependent providing a stabilizing influence that reduces the risk of severe elk population decline. Using simulation models in adaptive management of the wolf–ungulate system in Yellowstone reinforces agency management policies, especially the density-dependent harvest quota for elk.

Simulating the effects of wolf-elk population dynamics on resource flow to scavengers

The reintroduction of gray wolves to Yellowstone National Park (YNP) provides a natural experiment regarding the effects of top predators on scavenger species. Fieldwork on the Northern Range of Yellowstone indicates that wolves facilitate carrion acquisition by scavengers, but it is unclear whether this represents a transient or permanent effect of wolf reintroduction. Here we present a wolf-elk model with human elk harvest and use it to investigate the long-term consequences of predator–prey dynamics and hunting on resource flow to scavengers. Our model shows that while wolves reduce the total amount of carrion, they stabilize carrion abundance by reducing temporal variation in the quantity of carrion and extending the period over which carrion is available. Specifically, the availability of carrion is shifted from reliance on winter severity and elk density to dependence on the strength of wolf predation. Though wolves reduce the overall abundance of carrion by lowering the elk population, this reduction is partially offset by increases in the productivity of an elk population invigorated by removal of the weakest individuals. The result of this is higher carrion production per elk in the presence of wolves. In addition, this yields an ecological explanation for the phenomena that predators increase the robustness of their prey: namely that by reducing the effect of density-dependent resource competition among elk, those that remain, even some of the older animals, are better fed and healthier as a result. Our model also suggests that human hunting has no effect on the distribution of carrion across the year but is crucial in determining the long-term abundance of carrion because of the effect of hunting on elk population levels. By reducing the proportion of cows in the annual hunt, which have historically been high in order to control the number of elk migrating north of the park, managers can allow an adequate supply of carrion without substantially reducing hunter take. The effects of a more tractable food resource is likely to benefit scavengers in Yellowstone and other areas of the world where wolves have been or are currently being considered for reintroduction.

Rationed Access and Welfare: The Case of Public Resource Lotteries

<i>Pressures on public lands and waterways are resulting increasingly in the rationing of public access by lottery. Upon accounting for the uncertainties of random rationing, discrete choice models lend themselves to analyzing participation in public resource lotteries and estimating welfare changes. Key to valuing lotteryrationed rights is accounting for changes in access probabilities that result from policy changes. The empirical application models the discrete choices of more than 18,000 participants in a New Mexico lottery system for elk harvest rights. Welfare estimates are obtained from simulated policy changes that affect, individually and jointly, the access probability and indirect utility.</i> (JEL Q20)

Survival and Harvest Vulnerability of Elk in the Cascade Range of Washington

We studied survival and vulnerability to hunting mortality among adult male subadult male, and adult female elk (Cervus elaphus; n = 78) in the Cascade Range of south-central Washington, USA, 1992-1999. Among several candidate survival models, the weight of evidence suggested that the data best supported a model wherein survival varied by sex, (S MALE = 0.65 [95% CI: 0.54 to 0.75], S FEMALE = 0.83 [95% CI: 0.70 to 0.91]). Thirty-nine (50%) of the radiomarked elk died during the study. All deaths among subadult (≤4 yr) males and all but 1 death among females were caused by hunting. Eleven of 17 (64.7%) deaths among adult (>5 yr) males were hunting-related, whereas 5 deaths (29.4%) were independent of hunting. We evaluated 12 candidate logistic regression models relating elk harvest risks to landscape features within summer-autumn home ranges, where most hunting mortalities occurred, using an information-theoretic approach. Akaike model weights indicated that 5 models represented a best-model subset using data from all radiomarked elk and 4 models represented a logical best-model subset when the analysis was limited to data from male elk, although collective Akaike weights differed between the 2 subsets. Several models in the best-model subsets contained road density (km/km 2 ) as an explanatory variable, but models using road density-as the only explanatory variable were not among the best-model subsets. Two additional variables appeared to be useful for modeling harvest risks. Aspect diversity, an index of topographic complexity (which influenced hunter effort), and percent of elk home ranges in managed forest were common to several models in the best-model subsets. The managed forest variable indexed the proportion of an elk's home range that was roaded. All models in the best-model subsets had either a road density or percent managed forest variable, suggesting that broadly defined road effects were important sources of harvest vulnerability. For all elk, the model with the highest Akaike weight (56%) used road density and 2 topographic variables to explain elk harvest risks. For male-only data the best-supported model (weight = 25%) used percent massaged forest and aspect diversity as explanatory variables. Our analysis supported the inference that harvest vulnerability in elk in the south-central Cascades was strongly affected by the presence and/or density of open roads, but that topographic complexity influenced the likelihood that elk were killed apart from roading effects.

Proximate Factors Affecting Male Elk Hunting Mortality in Northern Idaho

We studied the effect of habitat use, hunter density, and hunting season structure on male elk (Cervus elaphus) harvest mortality in the Coeur d'Alene Mountains of northern Idaho, USA. Proximate mortality causes were identified using odds ratios derived from logistic regression. The predictive ability of mortality models was quantified with receiver operating characteristic (ROC) curves. Mortality of elk during the hunting season increased when total road densities increased and when hunting seasons occurred during the rut. We observed a cumulative effect of increasing open and closed road density on elk mortality; thus, in the Coeur d'Alene Mountains, road closures alone may not always reduce the risk of mortality. None of our models had strong predictive abilities, but they provide a mechanism that can be used to judge the effectiveness of management activities and to generally predict survival, given habitat and hunting season changes. Because these models relate season structure and road access to elk harvest mortality, they provide an opportunity for improved management coordination between state and federal agencies.

Vehicle Restrictions Influence Elk and Hunter Distribution in Montana

Abstract Restricting vehicle use on portions of two areas in Montana led to contrasting results in overall hunting pressure, in seasonal distribution of hunters and of elk, and in elk harvest. The Judith River area of the Lewis and Clark National Forest was two-thirds forested with interspersed clearcuts and natural openings; here hunting pressure increased 26 percent, but distribution through the seasons was unchanged. Conversely, on the Ruby River area of the Beaverhead National Forest, essentially open grassland with scattered islands of timber, overall hunting pressure did not change significantly, but was more uniformly distributed through the seasons when travel was restricted. The numbers of elk seen and killed per hunter each increased 28 percent under vehicle restrictions on the Judith River area. However, the uniformity of sightings and kills through the seasons increased markedly on the Ruby but not on the Judith. Differing responses were believed due mostly to differences in total forest cover on the two areas. Hunters spent more time walking, and consequently saw more elk under restricted travel conditions than under unrestricted travel.