Eastern Montana Golden Eagle Movement Ecology
Several studies have recently indicated decreasing population estimates for migrant and wintering Golden Eagles in the western US. There is also concern over an increase in future threats, specifically the expansion of wind energy development in the region. To create an effective management strategy, we must understand the current migration routes, important stopover areas, winter range movements, and potential hazards within both summer and winter ranges. Movements and important use areas of the non-breeding portion of the population (i.e., sub-adults and floaters) are also critical to the perseverance of this long-lived species through maintained recruitment into the breeding population. Our goal for this collaborative project with the BLM was to provide the needed information so an effective management strategy can be developed for Golden Eagles in the western US. This multi-year project was designed to help determine the seasonal abundance and density of Golden Eagles across eastern Montana and to help determine important wintering areas for eagles. The project is currently transitioning from research to analysis and manuscript preparation.
Great Gray Owls are one of the most secretive, elusive raptors and much of the basic ecology of this species remains unknown. Jackson Hole is home to one of the only historic studies of this species in the US, offering an ideal opportunity to investigate any changes in the status of this state-sensitive species. In 2013, we began a multiyear investigation of the ecology of Great Gray Owls. We were focused on documenting nesting density, determining productivity estimates, investigating seasonal movements, modeling habitat use and needs, and understanding prey selection. We also surveyed small mammal densities in owl territories and installed nesting platforms across the study area to determine which habitats are preferred for nesting, and also if nest sites are limiting the population. In May of 2015, the Great Gray Owl Ecology project shifted from Craighead Beringia South to the Teton Raptor Center, where they hope to continue studying Great Grays for the next 5-10 years. With long-lived species, such datasets are critical to proper understanding of the species’ community dynamics and needs.
Bald Eagles & Energy Development
The anticline region of the Green River Valley has been receiving, and will continue to receive, high development pressure from energy extraction practices and the resulting infrastructure. These anthropogenic actions result in habitat alteration, loss, and increased disturbance levels, which raises serious concern for sensitive wildlife species like ungulates, Sage-Grouse, and Bald Eagles. With over 8,500 gas wells already drilled in the Green River Valley and an additional 10,000 – 15,000 forecast to be drilled over the next decade, the rate of anthropogenic change to this area will only increase. Although the physical footprint of oil and gas infrastructure comprises only a small portion of the valley, recent research has shown that the effects of this infrastructure on native wildlife species can be extensive. Human modification and increased presence in the valley, especially in riparian corridors, may influence a variety of sensitive species. The Bald Eagle is listed as a Level I Priority Bird Species in Wyoming, and it is sensitive to year-round disturbance at nest sites and quality foraging areas. For this study, we used GPS transmitters to better understand Bald Eagle movements in these areas and to address if energy development had an impact on the behavior of the tracked eagles.
Lead Ingestion in Mammals
Many years of research at CBS has led to the discovery that avian scavengers such as ravens and eagles have been ingesting large amounts of lead from gut piles remaining after the elk, deer, and bison hunts in Jackson Hole. The next logical question was if mammalian scavengers were also at risk of lead poisoning from this source of environmental lead. After working on the avian side of this research with CBS, Tom Rogers investigated this question for his Master’s thesis at the University of Montana. With the help of CBS, Tom found no evidence to suggest that lead ingestion from the hunting season was a problem for species such as Grizzly bears, black bears, wolves, or cougars.
Lead Exposure in Large Carnivores in the Greater Yellowstone Ecosystem. 2011. T.A. Rogers, B. Bedrosian, J. Graham, K.R. Foresman. The Journal of Wildlife Management. 9999:1-8; 2011; DOI: 10.1002/jwmg.277
Ravens and Sage-Grouse
In a large-scale collaborative project with Dr. John Marzluff at the University of Washington, this project was developed to help understand the potential risk ravens presented to nesting Sage-Grouse. As a potential nest robber, increasing populations of ravens in Sublette and Teton Counties may affect the perseverance of Sage-Grouse. With the help of CBS and our Sage-Grouse project, Vivian Bui was able to obtain her Master’s degree by showing that raven occupancy (and not density) was correlated with Sage-Grouse nesting success.
Red-tailed Hawk Migration
The Red-tailed Hawk is a fairly common raptor throughout North America, yet we know surprisingly little about its migratory behavior. Red-tailed Hawk migration, like the migration of other animals, presents a unique and potentially stressful endeavor that may result in negative impacts to the birds on their breeding grounds in Jackson Hole. Additionally, the locations the birds choose to winter may also present challenges such as habitat loss or degradation, and dangers such as shooting or poisoning. Identifying Red-tailed Hawk migratory patterns and wintering areas will allow us to assess if and how stresses away from the breeding grounds may be influencing patterns in reproductive performance here in Jackson Hole.
In 1999, we began capturing and outfitting Red-tailed Hawks with satellite transmitters which allowed us to track the birds for up to two years. In 2014, we are analyzing these data to assess migration routes, length of migration, duration of migration, weather influences on migration, and make an environmental assessment of wintering areas to better understand the stresses associated with migration.
Teton Cougar Project
Cougars are not only difficult to study due to their elusive nature and their residence in vast, rugged terrain; they are hard to manage because they impact wild prey and can threaten human safety. Moreover, human values toward cougars are diverse. They invoke feelings of adventure to feelings of fear. Issues concerning private and public land ownership in traditional lion habitat with a long established history of public advocacy for lions and lion hunting, intensify difficulties for cougar researchers.
The Teton Cougar Project (TCP) was initiated in 2000 by Maurice Hornocker and Derek Craighead and was a joint project with the Hornocker Wildlife Institute and Wildlife Conservation Society. In 2002, Howard Quigley joined the Beringia South team and the TCP was moved to CBS. A Craighead Beringia South project for the following 10 years, the TCP contributed greatly to the body of growing scientific information about cougars including insights into demographics, habitat use, and an understanding of predator-prey dynamics to clarify responses of these resident carnivores following wolf re-introduction in Yellowstone National Park and Idaho in 1995-1996. In 2012, Panthera assumed oversight of the project; however, CBS and Panthera continue to be collaborators.
The Teton Cougar Project (2000-2012) captured and radio-collared more than 80 individual cougars. We utilized VHF radio collars and GPS collars to track cougar movements, locate potential predation sites, identify cougar dens, and to monitor kittens. We assessed individuals’ home ranges, territories, predation rates, and a shift in cougar predation habits as wolf presence increased following the reintroduction of wolves in Yellowstone National Park. The approximately 2,300 km2 study area extends from the town of Jackson, WY, to the northern boundary of the Grand Teton National Park. The entire region contains an estimated 12-14 resident, adult cougars.
Carnivores in the southern Greater Yellowstone Ecosystem are comprised of cougars, wolves, black bears and grizzly bears. The region also contains one of the highest concentrations of elk in North America. Following the extirpation of wolves in Yellowstone, cougars presumably extended their hunting niche to include those areas once occupied by their competitor, wolves. However, after the reintroduction of wolves into Yellowstone National Park and Idaho, wolves recolonized their historic range and cougars presumably adjusted by returning to their former range. We found that while cougars and wolves overlap in areas of use and prey upon similar species, cougars hunted in the higher elevations with forested cover while wolves hunted the lower elevations and on more open terrain (Woodruff et al. 2006).
Over the course of our study we observed what appeared to be an increase in the ratio of mule deer to elk kills (composition) based on evidence collected at investigations of cougar predation sites. To investigate these observations, we looked at potential wolf effects at both a population level and the landscape level, during summer and winter months. While elk were still cougars’ primary prey species, we looked at variation in the habitat characteristics and prey composition at predation sites in response to increased wolf proximity and numbers. Utilizing predation site characteristics (slope, aspect, elevation, ruggedness, and canopy cover) and specified criteria for determining cougar predation at kill sites, we found evidence supporting that cougar predation sites occurred at higher elevation and more north facing slopes during summer, and in more rugged areas during winter. We also found evidence that the probability of encountering a mule deer versus an elk at cougar predation sites increased in association with increasing wolf presence (Bartnick et al. 2013).
In additional investigations, we found that the success of dispersing individuals (more commonly young males in search of new territories) is influenced by habitat features. Comparing our study area with two others, we examined habitat use areas for dispersing cougars. In all three studies, cougars preferred habitats similar to those of the residents: rugged forested areas with ample access to prey, and they typically avoided development. Identifying these important habitat use areas helps to define connectivity corridors, which is important for ongoing conservation efforts (Newby et al. 2012).
As one of the most field-intensive projects in the west (monitoring 7 days per week for 12 years), we also documented several cases of previously undocumented cougar behavior. It was assumed previously that cougars were solitary individuals, but we discovered otherwise. We have documented instances of cougar family groups converging to hunt and feed together and cases of orphaned kittens apparently adopted into other cougar families.
In 2010-2011, Craighead Beringia South’s TCP team hosted filmmakers and collaborated with National Geographic Television for the creation of a one-hour documentary about cougars that culminated in the film American Cougar.