Nature

YELLOWSTONE GRIZZLY BEARS ecology and conservation of an ICON OF WILDNESS Edited by P.J. White, Kerry A. Gunther, and Frank T. van Manen YELLOWSTONE GRIZZLY BEARS Yellowstone Grizzly Bears: Ecology and Conservation of an Icon of Wildness Editors P. J. White, Kerry A. Gunther, and Frank T. van Manen Contributing Authors Daniel D. Bjornlie, Amanda M. Bramblett, Steven L. Cain, Tyler H. Coleman, Jennifer K. Fortin-Noreus, Kevin L. Frey, Mark A. Haroldson, Pauline L. Kamath, Eric G. Reinertson, Charles T. Robbins, Daniel J. Thompson, Daniel B. Tyers, Katharine R. Wilmot, and Travis C. Wyman Managing Editor Jennifer A. Jerrett Yellowstone Forever, Yellowstone National Park and U.S. Geological Survey, Northern Rocky Mountain Science Center Yellowstone Forever, Yellowstone National Park 82190 Published 2017 Contents Printed in the United States of America All chapters are prepared solely by officers or employees of the United States government as part of their official duties and are not subject to copyright protection in the United States. Foreign copyrights may apply. National Park Service (NPS) photographs are not subject to copyright protection in the United States. Foreign copyrights may apply. However, because this work may contain other copyrighted images or other incorporated material, permission from the copyright holder may be Prefaceix Daniel N. Wenk, Superintendent, Yellowstone National Park Introductionxv P. J. White, Kerry A. Gunther, and Frank T. van Manen necessary. Cover and half title images: www.revealedinnature.com by Jake Davis. Chapter 1: The Population Library of Congress Cataloging-in-Publication Data Names: White, P. J. (Patrick James), editor. | Gunther, Kerry A., editor. | van Manen, Frank T., editor. | Bjornlie, Daniel D. Title: Yellowstone grizzly bears : ecology and conservation of an icon of 1 P. J. White, Kerry A. Gunther, and Travis C. Wyman Chapter 2: Historical Perspective 13 P. J. White and Kerry A. Gunther wildness / editors, P.J. White, Kerry A. Gunther, and Frank T. van Manen ; contributing authors, Daniel D. Bjornlie [and thirteen others] ; managing editor, Jennifer A. Jerrett. Chapter 3: Reproduction, Survival, and Population Growth 29 Frank T. van Manen and Mark A. Haroldson Description: Yellowstone National Park, [Wyoming] : National Park Service, Yellowstone National Park ; [Bozeman, Montana] : U.S. Geological Survey, Northern Rocky Mountain Science Center, 2017. | Includes bibliographical references and index. Chapter 4: Nutritional Ecology 47 Charles T. Robbins and Jennifer K. Fortin-Noreus Identifiers: LCCN 2016058699 | ISBN 9780934948463 (pbk. : alk. paper) Subjects: LCSH: Grizzly bear--Yellowstone National Park. | Grizzly bear--Habitat--Yellowstone National Park Region. | Grizzly Chapter 5: Movements and Occupied Range 63 Daniel D. Bjornlie and Mark A. Haroldson bear--Conservation--Yellowstone National Park Region. | Bear populations--Yellowstone National Park. | Yellowstone National Park. Classification: LCC QL737.C27 Y45 2017 | DDC 599.784--dc23 LC record available at https://lccn.loc.gov/2016058699 The authors gratefully acknowledge the generous contribution of Yellowstone Forever, whose publication grant enabled the production of this book. Chapter 6: Ecological Niche 75 Frank T. van Manen, Mark A. Haroldson, and Kerry A. Gunther Chapter 7: Genetics and Adaptive Capabilities Mark A. Haroldson, Pauline L. Kamath, and Frank T. van Manen 91 Chapter 8: Human-Bear Interactions 103 Kerry A. Gunther, Katharine R. Wilmot, Travis C. Wyman, and Eric G. Reinertson Chapter 9: Bear Viewing in Yellowstone and Grand Teton National Parks 117 Kerry A. Gunther, Katharine R. Wilmot, Steven L. Cain, Travis C. Wyman, Eric G. Reinertson, and Amanda M. Bramblett Chapter 10: Current Management Strategy 131 Kerry A. Gunther, Daniel B. Tyers, Tyler H. Coleman, Katharine R. Wilmot, and P. J. White Chapter 11: The Future 153 P. J. White, Kerry A. Gunther, Frank T. van Manen, Mark A. Haroldson, and Daniel J. Thompson Yellowstone Grizzly Bear Facts 169 Kerry A. Gunther, Mark A. Haroldson, and Frank T. van Manen History of Yellowstone Grizzly Bear Conservation and Management  177 Daniel B. Tyers, Kevin L. Frey, and Kerry A. Gunther Acknowledgments195 Glossary of Terms 197 Scientific Names  211 References215 Index255 Author Affiliations 274 Preface Daniel N. Wenk, Superintendent, Yellowstone National Park Grizzly bears are one of the most iconic wildlife species in Yellowstone National Park. They are the species that evokes the greatest emotions in visitors from great elation at seeing bears along roadsides to the awe of a surprise encounter in the backcountry. Grizzly bears are the species that, for many people around the world, best represents the wild natural history of the west. Photograph by Jake Davis My knowledge of grizzly bears and their management in Yellowstone National Park goes back almost 40 years. There were perhaps fewer than 250 grizzly bears in the Yellowstone area during 1975, when Grizzly bear in autumn. Grizzly bears go through a period of copious food consumption prior to entering their winter dens. Referred to as autumn hyperphagia, this stage allows bears to build up sufficient fat reserves before hibernation. they were protected as a threatened species under the Endangered Species Act. I worked in Yellowstone for Superintendents John Townsley and Bob Barbee from the fall of 1979 until the fall of 1984, and over that 5-year span I traveled the roads throughout the park on a near-daily basis. I observed only 5 grizzly bears in the wild during that entire 5-year period. In the early 1980s, the grizzly bear population was still declining following the high human-caused mortality associated with the x Yellowstone Grizzly Bears: Ecology and Conservation of an Icon of Wildness Preface closing of garbage dumps, both inside and outside of Yellowstone view, photograph, or simply enjoy bears that could be seen easily in National Park, where bears had fed for decades. The decisions by the roadside meadows. This new development had become both a bear National Park Service to take these actions were the subject of much management and people management challenge for the park, requiring discussion and heated debate among both advocates and critics of hundreds of staff hours to manage traffic, people, and bears. those decisions. It was rare for visitors to the area to see grizzly bears, Grizzly bear management had been so successful over the previous so it was difficult to understand why any bears—even problem bears— three decades that the Yellowstone population had been removed would be removed. At that time, the population seemed utterly at risk. from threatened species status in the spring of 2007 and contin- Much has changed since then. I believe Yellowstone is ecologically ued to expand in both numbers and range. However, in the fall healthier today than it was in the early 1980s. Many reasons have of 2009, they were returned to threatened species status by court contributed to this, including the reintroduction of wolves, manage- order due to uncertainty regarding the future of whitebark pine, a ment of fire on the landscape, and native fish restoration, but equally high-quality food source for grizzly bears. In 2013, the Interagency or more significant is the recovery of grizzly bears in this ecosystem. Grizzly Bear Study Team completed an analysis of the whitebark Thanks to the interdisciplinary efforts to restore a population of griz- pine issues and concluded that changes in food resources had not zly bears to this landscape, grizzly bears had increased significantly had a profound negative effect on grizzly bears at the population in numbers and range by the time I returned as Superintendent in or the individual level. The population, now numbering possibly 2011. What’s more, they had become a significant draw for tourism. as many as 1,000 bears, had continued to increase during a period I personally saw grizzly bears along the roadside on many occa- of marked whitebark pine mortality. Later that fall, the Yellowstone sions during that first spring back in Yellowstone. Over the Memorial Ecosystem Grizzly Bear Subcommittee voted to recommend that the Day weekend, I toured the park with my family and we saw 10 grizzly U.S. Fish and Wildlife Service once again consider removing grizzly bears just on one day. It was abundantly clear that this was a different bears from threatened species status. park than the one I left more than 25 years earlier. Grizzly bears had The science, well-articulated by the authors in this book, sug- become abundant enough that they were regularly observed forag- gests grizzly bears have recovered biologically. However, they will ing for natural foods in roadside meadows. Wildlife viewing, and likely always need careful management, warranting a conservative in particular viewing of grizzly bears, had become as important to approach strongly rooted in science-based decision making. The visitor experience as the thermal features or the incredible geology challenge for future management will be to maintain a viable popu- of the park. Yellowstone had become the premiere wildlife and griz- lation of grizzly bears within the Yellowstone ecosystem, including zly bear viewing opportunity in the contiguous 48 states and grizzly their ecological function on the landscape. Equally important will bear recovery contributed significantly to the visitor appreciation be managing the grizzly bear population to protect the values of and understanding of natural processes and healthy ecosystems. people, a great many of whom treasure the opportunity to experi- This is something I had never imagined back in the early 1980s, ence bears in their natural environment. This is going to be delicate but there was a tricky side to the recovery. An unintended conse- work, but we must find a way to preserve the bears’ role in ecosystem quence of this recovery was the development of large traffic jams, processes, while at the same time protecting multiple uses of these called “bear jams,” created by visitors that just wanted the chance to landscapes. Engendering public support across a spectrum of values will be critical for the continued survival of grizzly bears. xi xii Yellowstone Grizzly Bears: Ecology and Conservation of an Icon of Wildness Grizzly bears are the icon of wildness in Yellowstone National Park. The American people’s willingness to recover a species with such an intimidating reputation is a remarkable conservation achievement. This book outlines the fascinating history of the conservation of grizzly bears, from the early 1870s to the management challenges of today’s human-dominated landscape. The authors reveal the latest findings about the role grizzly bears play in Yellowstone National Park and the Greater Yellowstone Ecosystem, and contemplate the diverse stakeholder interests and issues in grizzly bear management. Most importantly, this book illustrates our collective commitment to sustain a viable population of wild grizzly bears on the landscape. Photograph by Ronan Donovan Grizzly bear walking toward a remote camera along Pelican Creek, Yellowstone National Park. Introduction P. J. White, Kerry A. Gunther, and Frank T. van Manen To many people , grizzly bears symbolize wildness because they dominate the landscape. Their intelligence, size, speed, strength, and resourcefulness evoke awe and wonder while, in certain situations, their explosive aggression in defense of food or young can create terror. As a result, grizzly bears remind us of an ancestral world filled with natural dangers and difficulties rarely experienced by most Photograph Photograph by Ronan byDonovan Drew Rush people today. Perhaps a few hundred grizzly bears survived Euro-American colonization and predator eradication efforts in the Yellowstone area This grizzly bear inspects a camera trap left at the site of a red squirrel midden in the mountains of Wyoming. during the mid-1800s to the mid-1900s, with the national park providing refuge to many of these bears after 1872. Early in the park’s history, black bears and grizzly bears were viewed as cute, though troublesome, garbage raiders whose begging along roadways, congregations at garbage dumps, and plundering through campgrounds and residential areas attracted people from around the world. Initially, managers tolerated and even facilitated these sideshows due to their popularity with visitors. Over time, however, increasing injuries to xvi Yellowstone Grizzly Bears: Ecology and Conservation of an Icon of Wildness Photograph by Drew Rush people and property damage from bears accustomed to obtaining to review details regarding data collection methods and statistical human foods led to changes in management to eliminate this depen- analyses. Similar wording was often maintained from these source dence and restore bears as wildlife. documents to preserve original intent and avoid misrepresentation. This transition took many decades and was not without conflict, but eventually reestablished grizzly bears as awe-inspiring symbols Also, a glossary of terms and a history of grizzly bear management are included for reference. of power and wildness, rather than conjuring images of Yogi Bear Chapters 1 and 2 provide background information on Yellowstone attempting to steal picnic baskets from campers in Jellystone Park. grizzly bears and the history of their management. Chapters 3 through Today, grizzly bear attacks on people (1 per year) and incidents of 5 discuss their demographics (reproduction, survival), nutrition, move- property damage (5 per year) in Yellowstone National Park are quite ments, and occupied range. Chapters 6 and 7 explore the ecological low, despite more than 4 million visits to the park annually. There are niche and genetic integrity of these bears, while Chapters 8 and 9 about 150 to 200 grizzly bears that primarily live in the park and at discuss human-bear interactions and bear viewing. Chapters 10 and least another 500 to 600 in surrounding portions of the Greater Yel- 11 address current strategies for reducing conflicts and provide man- lowstone Ecosystem, which encompasses portions of Idaho, Montana, agement considerations for the continued conservation of grizzly and Wyoming. These grizzly bears now occupy more than 22,000 bears in the ecosystem. We describe factors affecting grizzly bears and square miles (58,000 square kilometers), including many areas from opportunities for natural resource managers, wildlife ecologists, and which they were absent for numerous decades. The high visibility of others to enhance the conservation of grizzly bears. This information bears foraging for foods in roadside meadows has made Yellowstone should benefit professionals and students of wildlife conservation, National Park and other portions of the ecosystem some of the most as well as the millions of people that visit the Yellowstone area each popular bear viewing destinations in the world. year to observe bears or monitor their conservation and management Despite this success, there are lingering issues about how to via the Internet or other outreach avenues. conserve and manage grizzly bears into the future, including their Some information included in this book was originally presented in appropriate abundance and distribution, reducing human-induced a 2015 issue of Yellowstone Science. Also, much of the information in mortalities, access to (and protection of) available habitat, connec- Chapter 1 has been included in the Yellowstone Resources and Issues tivity and immigration of bears (gene flow) from other populations, Handbook, collaboratively written and edited by personnel from and protecting people and property. Also, there are new biological, the Yellowstone Center for Resources and the Division of Resource political, and social concerns about grizzly bear recovery, including Education and Youth Programs. In addition, portions of the glossary climate warming and its possible effects on key food resources, habitat of terms were adopted from previously published articles and texts. encroachment and increasing human-bear conflicts, and the possible References for definitions in the glossary are provided in the text. initiation and effects of sport harvests. (Morrison and Hall 2002, Hopkins et al. 2010, Gunther et al. 2015c, In this book, we provide updated information on grizzly bears in the Greater Yellowstone Ecosystem. This information was compiled from numerous published and unpublished sources and organized into a concise, readable format. The original sources of information are cited at the end of each paragraph. People can refer to these references xvii White et al. 2015, National Park Service 2016b) NPS Photo/Jim Peaco Chapter 1 THE POPULATION—ATTRIBUTES, BEHAVIOR, GENETICS, NUTRITION, AND STATUS P. J. White, Kerry A. Gunther, and Travis C. Wyman Attributes The species Ursus arctos is widely distributed across Asia and Europe, NPS Photo/Jim Peaco where it is called the brown bear. It is also found in portions of western North America, where it is called the grizzly bear (although coastal bears in Alaska and Canada are also called brown bears). Grizzly bear in the sagebrush, Yellowstone National Park. Grizzly bears move widely across the landscape, using a variety of habitats. Grizzly bears have a concave facial profile, long and slightly curving fore-claws (3 inches; 8 centimeters), and a prominent shoulder hump extending about 3 feet (1 meter) above-ground. They use their large shoulder muscles and long claws for digging foods such as bulbs, corms, roots, tubers, and rodents from the ground. Fur color can be brown, black, or blonde; often with white-colored tips that contribute to a silver or grayish sheen. Their dentition is characterized by large canines and other teeth with cusps in the front of the mouth 2 Yellowstone Grizzly Bears: Ecology and Conservation of an Icon of Wildness NPS Photo/Jim Peaco for cutting and tearing, coupled with flatter molar surfaces for chew- areas, meadows, river corridors, subalpine areas, talus slopes, and ing and grinding in the rear. (Herrero 1978, Schwartz et al. 2003b) valleys. Their movements are influenced by factors such as age and Grizzly bears are quadrupedal and walk with a lumbering gait on sex, breeding, changes in food availability and quality, disturbance the soles of all 4 feet. They have tremendous strength, can swim many by humans, denning, and the avoidance of larger, more dangerous miles, and can run 35 miles (45 kilometers) per hour. They have sen- bears. More information on the movements and occupied range of sitive hearing, vision similar to humans, and an incredible sense of Yellowstone grizzly bears is provided in Chapter 5. (Blanchard and smell due to millions of nerves in their large snout. They also have a Knight 1991, Keiter and Boyce 1991, Schwartz et al. 2003b, Coleman remarkable spatial memory, likely tied to smell, that enables them to et al. 2013b, Bjornlie et al. 2014a, Haroldson et al. 2015b) remember for decades the locations of key foods and other resources essential for survival. (Schwartz et al. 2003b, Peterson 2005) Yellowstone grizzly bears are primarily active from dusk to dawn, though they can be active at any time. When active, bears spend Yellowstone grizzly bears are large animals, with adult males most of their time feeding. Other activities include breeding, raising generally weighing more than females of similar age (males: 265 to young, resting, and interacting with other animals. Mating occurs 720 pounds [120 to 325 kilograms]; females: 200 to 440 pounds [90 during May through July, with males competing for females through to 200 kilograms]). Males and females are nearly full-grown by 5 displays and occasional fights. Dominant males attempt to isolate years of age, but continue to grow at a slower rate thereafter. Males females, but females often mate with multiple males and vice versa. reach their maximum size later in life than females. Cubs-of-the-year As a result, cubs in a single litter may be sired by 1 or more males. (hereafter cubs) weigh about 0.9 to 1.4 pounds (0.4 to 0.7 kilograms) (Schleyer 1983, Harting 1985, Craighead et al. 1995, Schwartz et al. at birth and 10 to 20 pounds (4.5 to 9.0 kilograms) by 10 weeks of 2003b, Coleman et al. 2013b) age. Yearlings weigh about 128 to 139 pounds (58 to 63 kilograms) Yellowstone grizzly bears enter dens from late October to Decem- in spring and 2-year-olds weigh about 187 to 217 pounds (84 to 98 ber as snow accumulates across the landscape, food becomes limited, kilograms). (Blanchard 1987, Schwartz et al. 2003b) and temperatures become frigid. Pregnant females usually den earliest, followed by females with cubs, subadults, and adult males. Dens generally consist of an entrance, a short tunnel, and a chamber with Behavior and Occupied Range some type of bedding material such as grass. Bears emerge from Yellowstone grizzly bears live in the Greater Yellowstone Ecosystem, hibernation in these dens after 4 to 6 months when temperatures which encompasses about 19 million acres (7.7 million hectares) of and food availability increase. Males emerge during early March, relatively undeveloped lands, including Grand Teton and Yellowstone followed by females without newborn cubs during late March to national parks, portions of 5 national forests, 3 national wildlife mid-April, and females with newborn cubs during mid-April to refuges, Bureau of Land Management and Bureau of Reclamation early May. (Craighead and Craighead 1972, Lindzey and Meslow lands, and private and state lands in Idaho, Montana, and Wyoming. 1976, Jonkel 1980, Judd et al. 1986, Linnell et al. 2000, Haroldson et Currently, grizzly bears occupy about two-thirds of this area, with al. 2002, Schwartz et al. 2003b) 150 to 200 of these bears having all or a significant portion of their The strongest relationship in grizzly bear society is between a home range inside Yellowstone National Park. Grizzly bears move mother and her cubs, which depend on her for food and protection. widely across the landscape, using forests, geothermal Cubs are born in the den during winter and spend up to 4 years 3 4 Today, there are at least 690 grizzly bears inhabiting more than 14.3 million acres (5.8 million hectares) of the Greater Yellowstone Ecosystem. Yellowstone Grizzly Bears: Ecology and Conservation of an Icon of Wildness NPS Photo/Jim Peaco with their mother before weaning and separation. Most offspring are The generalist diet of Yellowstone grizzly bears enables them weaned as 2-year-olds, though separation occasionally occurs as year- to feed across diverse habitats and adjust to variations in forage lings or 3-year-olds. Female grizzly bears aggressively protect their availability within and among seasons and years. Bears feed oppor- cubs from predators or other threats, including humans and adult tunistically on bison and elk carcasses left from accidents, injuries, male grizzly bears. Males do not help raise cubs and, in fact, some- starvation (winter-kill), and wolf predation. In spring, many bears times kill younger bears, which is referred to as infanticide. Most other hunt newborn elk calves, while some feed on spawning cutthroat grizzly bears are solitary, though aggregations of up to 2 dozen bears trout in the tributaries of Yellowstone Lake. Other food items eaten may occur near quality food sites such as carcasses of hoofed animals through summer and autumn include ants, army cutworm moths, (called ungulates). Large males dominate interactions with other bears, forbs, grasses and grass-like plants, and whitebark pine nuts from red sometimes driving them from quality habitats and food sources. As a squirrel caches. More information on the diet, nutritional ecology, result, subadult bears and females with young cubs may avoid areas and energetics of grizzly bears is provided in Chapter 4. (Mealey frequented by larger males. (Mattson et al. 1987, Schwartz et al. 2003b, 1980, Gunther and Renkin 1990, Reinhart 1990, Mattson et al. 1991a, Gunther and Wyman 2008, Gunther 2016) Green et al. 1997, Mattson 1997a, Jacoby et al. 1999, Koel et al. 2005, Barber-Meyer et al. 2008, Fortin et al. 2013, Middleton et al. 2013, Schwartz et al. 2013, Gunther et al. 2014) Nutritional Ecology Yellowstone grizzly bears have a generalist diet, which means they can eat a wide variety of foods. They have been documented eating Population Dynamics 175 different plants, 37 invertebrates, 34 mammals, 7 birds, and 4 Perhaps fewer than 250 grizzly bears remained in the Greater Yel- species of fish. Bears have a single stomach and a relatively short lowstone Ecosystem during the mid-1970s (Figure 1.1). Bear numbers intestinal tract to extract nutrients from this assortment of foods. were decreasing as many adult females were killed due to conflicts They do not have a cecum or rumen and, as a result, cannot digest with humans and, in turn, the recruitment of young bears into the plant fiber efficiently. To compensate, bears typically eat succulent population decreased. Grizzly bears have a low reproductive rate plants low in fiber and high in digestibility and nutrients. However, compared to other mammals and, as a result, higher survival was they cannot increase fat reserves solely by eating plants and, for this needed to increase numbers. In 1975, Yellowstone grizzly bears were reason, army cutworm moths, cutthroat trout, meat from ungulates, protected as threatened pursuant to the federal Endangered Spe- and whitebark pine nuts (seeds) are seasonally eaten due to their cies Act and managers began implementing measures to decrease high nutritional value. Grizzly bears in the Greater Yellowstone Eco- human-caused bear mortality, protect habitat on public lands, and system eat more meat than bears in most other populations, with a reduce conflicts between bears and people. These measures included diet that consists of about 40% meat and 60% plants. (Mealey 1975, preventing bears from getting human foods, reducing management Herrero 1978, Mattson et al. 1991a, Craighead et al. 1995, Mattson removals of bears, protecting undeveloped habitat, and educat- 1997a, Mattson 1997b, Jacoby et al. 1999, Herrero 2002, Schwartz et ing and managing people to ensure their safety. (Cowan et al. 1974, al. 2003b, Mowat and Heard 2006, Fortin et al. 2013, Schwartz et al. Craighead et al. 1974, U.S. Fish and Wildlife Service 1975, Knight and 2013, Gunther et al. 2014) 5 6 Yellowstone Grizzly Bears: Ecology and Conservation of an Icon of Wildness NPS Photo/Jim Peaco Today, there are at least 690 grizzly bears within the area monitored by the Interagency Grizzly Bear Study Team (called the Demographic Monitoring Area) inhabiting more than 14.3 million acres (5.8 million hectares) of the Greater Yellowstone Ecosystem. In reality, this estimate is probably much lower than the actual number of bears because it was derived from counts of unique females with cubs that may underestimate true bear numbers by 40% to 50% at the current population size. Bears continue to disperse into new areas, and abundance, reproduction, and survival are high enough that Figure 1.1. Counts or estimates of the number of grizzly bears in the Greater Yel- grizzly bears should continue to be well-distributed throughout lowstone Ecosystem, 1959-2016. Numbers were estimated from counts of bears at the ecosystem for the foreseeable future. However, conditions in open-pit garbage dumps during 1959 to 1974, extrapolated from the number of the ecosystem continue to change with increasing visitation and females with cubs observed in the ecosystem during 1978 to 2006, and estimated residential development, as well as recent decreases in some food using the Chao2 model during 2007 to 2016. (Craighead et al. 1974, Schwartz et resources that could increase human-bear interactions and compli- al. 2008, Haroldson et al. 2015b) cate bear conservation. Also, humans continue to be the primary source of mortality for grizzly bears, causing 87% of 61 deaths during 2015, primarily due to management removals for livestock depreda- Eberhardt 1985, Craighead et al. 1988, Craighead et al. 1995, Gunther tion or other conflicts and defensive shootings by ungulate hunters. 2008, Servheen and Shoemaker 2008) Therefore, public attitudes and their influence on future decisions There were signs of recovery starting in the late 1980s, with higher will have a tremendous impact on the further recovery of the Yel- adult female survival, population growth between 4% and 7% each lowstone grizzly bear population. More information on the historical year, and the recolonization of habitats outside Yellowstone National management and population trends of Yellowstone grizzly bears is Park. This recovery continued as managers focused on increasing provided in Chapter 2. (Cherry et al. 2007, Gunther 2008, Schwartz bear survival and recruitment by minimizing conflicts with humans. et al. 2008, Servheen and Shoemaker 2008, Bjornlie et al. 2014a, van By 2002, there were about 560 grizzly bears living across more than Manen et al. 2014, Haroldson et al. 2015b, Haroldson and Frey 2016, 8.1 million acres (3.3 million hectares) of the Greater Yellowstone van Manen et al. 2016a) Ecosystem. Also, the number of females producing cubs increased and then stabilized in the early 2000s, suggesting bear numbers in the core of the ecosystem were near the capacity of the environment Ecological Niche to support them. (Schwartz et al. 2002, Haroldson and Frey 2005, Grizzly bears influence the function and structure of the Greater Schwartz et al. 2006a, Schwartz et al. 2006b, Schwartz et al. 2006d, Yellowstone Ecosystem by limiting elk numbers in certain areas Harris et al. 2007, Haroldson and Frey 2008, Haroldson et al. 2008b, through predation on newborn calves, influencing the distribution Servheen and Shoemaker 2008, Servheen and Cross 2010, Schwartz of predators and scavengers through competition, and redistribut- et al. 2013, van Manen et al. 2016a) ing energy and nutrients across the landscape. Historically, as many 7 8 Yellowstone Grizzly Bears: Ecology and Conservation of an Icon of Wildness NPS Photo/Jim Peaco as 60 grizzly bears transferred energy and nutrients from aquatic 1978, Gunther et al. 2002, Schwartz et al. 2003b, Mattson et al. 2005, to terrestrial systems during spring foraging on spawning cutthroat Belant et al. 2006, Schwartz et al. 2013, Costello et al. 2016a) trout in tributaries of Yellowstone Lake, though this food source has decreased substantially in recent decades. (Reinhart and Mattson Adaptive Capabilities and Genetics 1990, Schwartz et al. 2003b, Barber-Meyer et al. 2008, Fortin et al. Yellowstone grizzly bears live in a challenging environment where 2013, Middleton et al. 2013, Schwartz et al. 2013, Center for Biologi- they compete for food, mates, and other resources. Consequently, cal Diversity 2014) they retain behaviors, capabilities, and traits that embody wildness. Ungulate carcasses from predation or starvation are an important However, the population has been geographically isolated from other food source for grizzly bears, particularly before and after hiberna- populations for about 100 years and may have experienced a bottle- tion, as well as during years when other important food sources such neck when numbers were reduced to less than 250 bears durin