Douglas W. Smith

Trophic cascades among wolves, elk and aspen on Yellowstone National Park's northern range

Quaking aspen (Populus tremuloides) biomass has declined in Yellowstone National Park (YNP) in the past century. We installed permanent belt transects (plots) for long-term monitoring of aspen stands both within and outside of established wolf pack territories on YNP’s northern range to determine if reintroduced wolves are influencing elk browsing patterns and aspen regeneration through a trophic cascades interaction. Wolves may have an indirect effect on aspen regeneration by altering elk movements, browsing patterns, and foraging behavior (predation risk effects). Elk pellet groups, aspen sucker heights, and the percentage of browsed suckers were the variables used to measure differences in aspen stands in high and low wolf-use areas of the northern range. The aspen stands in the high wolf-use areas had significantly lower counts of elk pellet groups in the mesic upland steppe and the combined mesic upland steppe and riparian/wet meadow habitat types. Based on our pellet group results, it appears that elk foraging behaviors may have been altered by the increased risk of predation due to the reintroduction of the wolf. In the riparian/ wet meadow habitat type, mean aspen sucker heights were significantly higher in the high wolf-use areas than in the low wolf-use areas. The percentage of browsed suckers in high and low wolf-use areas showed no significant differences in any of the habitat types. Considering the high browsing pressure in YNP aspen stands, it is uncertain whether the taller aspen suckers measured in the high wolf-use areas will eventually join the aspen overstory. These permanent plots represent a valuable baseline data set to assess any current and future aspen regeneration responses to the reintroduction of wolves in YNP. # 2001 Elsevier Science Ltd. All rights reserved.

The genealogy and genetic viability of reintroduced Yellowstone grey wolves

The recovery of the grey wolf in Yellowstone National Park is an outstanding example of a successful reintroduction. A general question concerning reintroduction is the degree to which genetic variation has been preserved and the specific behavioural mechanisms that enhance the preservation of genetic diversity and reduce inbreeding. We have analysed 200 Yellowstone wolves, including all 31 founders, for variation in 26 microsatellite loci over the 10‐year reintroduction period (1995–2004). The population maintained high levels of variation (1995 H0 = 0.69; 2004 H0 = 0.73) with low levels of inbreeding (1995 FIS = –0.063; 2004 FIS = –0.051) and throughout, the population expanded rapidly (N1995 = 21; N2004 = 169). Pedigree‐based effective population size ratios did not vary appreciably over the duration of population expansion (1995 Ne/Ng = 0.29; 2000 Ne/Ng = 0.26; 2004 Ne/Ng = 0.33). We estimated kinship and found only two of 30 natural breeding pairs showed evidence of being related (average r = –0.026, SE = 0.03). We reconstructed the genealogy of 200 wolves based on genetic and field data and discovered that they avoid inbreeding through a wide variety of behavioural mechanisms including absolute avoidance of breeding with related pack members, male‐biased dispersal to packs where they breed with nonrelatives, and female‐biased subordinate breeding. We documented a greater diversity of such population assembly patterns in Yellowstone than previously observed in any other natural wolf population. Inbreeding avoidance is nearly absolute despite the high probability of within‐pack inbreeding opportunities and extensive interpack kinship ties between adjacent packs. Simulations showed that the Yellowstone population has levels of genetic variation similar to that of a population managed for high variation and low inbreeding, and greater than that expected for random breeding within packs or across the entire breeding pool. Although short‐term losses in variation seem minimal, future projections of the population at carrying capacity suggest significant inbreeding depression will occur without connectivity and migratory exchange with other populations.

Modeling Effects of Environmental Change on Wolf Population Dynamics, Trait Evolution, and Life History

Analysis of a 20-year data set on Yellowstone wolves reveals that environmental change generates eco-evolutionary responses. Environmental change has been observed to generate simultaneous responses in population dynamics, life history, gene frequencies, and morphology in a number of species. But how common are such eco-evolutionary responses to environmental change likely to be? Are they inevitable, or do they require a specific type of change? Can we accurately predict eco-evolutionary responses? We address these questions using theory and data from the study of Yellowstone wolves. We show that environmental change is expected to generate eco-evolutionary change, that changes in the average environment will affect wolves to a greater extent than changes in how variable it is, and that accurate prediction of the consequences of environmental change will probably prove elusive.

Survival of Colonizing Wolves in the Northern Rocky Mountains of the United States, 1982-2004

Abstract After roughly a 60-year absence, wolves (Canis lupus) immigrated (1979) and were reintroduced (1995–1996) into the northern Rocky Mountains (NRM), USA, where wolves are protected under the Endangered Species Act. The wolf recovery goal is to restore an equitably distributed metapopulation of ≥30 breeding pairs and 300 wolves in Montana, Idaho, and Wyoming, while minimizing damage to livestock; ultimately, the objective is to establish state-managed conservation programs for wolf populations in NRM. Previously, wolves were eradicated from the NRM because of excessive human killing. We used Andersen–Gill hazard models to assess biological, habitat, and anthropogenic factors contributing to current wolf mortality risk and whether federal protection was adequate to provide acceptably low hazards. We radiocollared 711 wolves in Idaho, Montana, and Wyoming (e.g., NRM region of the United States) from 1982 to 2004 and recorded 363 mortalities. Overall, annual survival rate of wolves in the recovery areas was 0.750 (95% CI  =  0.728–0.772), which is generally considered adequate for wolf population sustainability and thereby allowed the NRM wolf population to increase. Contrary to our prediction, wolf mortality risk was higher in the northwest Montana (NWMT) recovery area, likely due to less abundant public land being secure wolf habitat compared to other recovery areas. In contrast, lower hazards in the Greater Yellowstone Area (GYA) and central Idaho (CID) likely were due to larger core areas that offered stronger wolf protection. We also found that wolves collared for damage management purposes (targeted sample) had substantially lower survival than those collared for monitoring purposes (representative sample) because most mortality was due to human factors (e.g., illegal take, control). This difference in survival underscores the importance of human-caused mortality in this recovering NRM population. Other factors contributing to increased mortality risk were pup and yearling age class, or dispersing status, which was related to younger age cohorts. When we included habitat variables in our analysis, we found that wolves having abundant agricultural and private land as well as livestock in their territory had higher mortality risk. Wolf survival was higher in areas with increased wolf density, implying that secure core habitat, particularly in GYA and CID, is important for wolf protection. We failed to detect changes in wolf hazards according to either gender or season. Maintaining wolves in NWMT will require greater attention to human harvest, conflict resolution, and illegal mortality than in either CID or GYA; however, if human access increases in the future in either of the latter 2 areas hazards to wolves also may increase. Indeed, because overall suitable habitat is more fragmented and the NRM has higher human access than many places where wolves roam freely and are subject to harvest (e.g., Canada and AK), monitoring of wolf vital rates, along with concomitant conservation and management strategies directed at wolves, their habitat, and humans, will be important for ensuring long-term viability of wolves in the region.

People and Wildlife: Managing wolf–human conflict in the northwestern United States

INTRODUCTION The grey wolf ( Canis lupus ) is the most widely distributed large carnivore in the northern hemisphere (Nowak 1995) and has a reputation for killing livestock and competing with human hunters for wild ungulates (Young 1944; Fritts et al . 2003). Wolves rarely threaten human safety, but many people still fear them. In the western USA, widespread extirpation of ungulates by colonizing settlers, wolf depredation on livestock and negative public attitudes towards wolves resulted in extirpation of wolf populations by 1930 (Mech 1970; McIntyre 1995). By 1970, mule deer ( Odocoileus hemionus ), white-tailed deer ( O. virginianus ), elk ( Cervus elaphus ), moose ( Alces alces ) and bighorn sheep ( Ovis canadensis ) populations had been restored throughout the western USA while bison ( Bison bison ) were recovered only in Yellowstone National Park. However, grey wolves were still persecuted. In 1974, grey wolves were protected and managed by the US Fish and Wildlife Service under the federal Endangered Species Act of 1973. In 1986, the first recorded den in the western USA in over 50 years was established in Glacier National Park by wolves that naturally dispersed from Canada (Ream et al . 1989). Restoration of wolves in that region emphasized legal protection and building local public tolerance. Wolves from Canada were reintroduced to central Idaho and Yellowstone National Park in 1995 and 1996 to accelerate restoration (Bangs and Fritts 1996; Fritts et al . 1997). The Northern Rocky Mountains wolf population grew from 10 wolves in 1987 to 663 wolves by 2003 (US Fish and Wildlife Service et al . 2003) (Fig. 21.1, Table 21.1).

Influences of wolves and high-elevation dispersion on reproductive success of pronghorn (Antilocapra americana)

Abstract Mitigation of predation risk promotes high-elevation dispersion prior to birthing in many ungulate populations. Coyotes (Canis latrans) account for nearly 80% of pronghorn (Antilocapra americana) fawn mortality in Yellowstone National Park, but reintroduced gray wolves (Canis lupus) and factors associated with mountainous terrain can strongly influence space use by predators during summer and are likely to underlie significant spatial variation in survival rates of pronghorn fawns. We used generalized logit models paneled by maternal identity to assess the relative and interactive influences of summer wolf density, winter snow depth, and terrain slope on survival of pronghorn fawns in Yellowstone during 1999–2001 and 2004–2006. In this partially migratory population only migrant pronghorn accessed areas where wolves were numerous and winter snow depths were high. Survival of migrant fawns was higher in areas that experienced deep winter snow and had steeper slope. The influence of wolves on fawn survival was positive only in areas of low winter snowfall where coyotes were abundant, supporting predictions of a coyote-mediated effect of wolves and winter snowfall on pronghorn reproductive success. Our results suggest that deep winter snow, coupled with constraints on mobility imposed by reproduction in populations of social carnivores, can lead to the formation of high-elevation refugia for migrant ungulates. This research offers novel insights into the indirect effects of wolf restoration and climatic factors on the Yellowstone predator–prey complex and a conceptual framework for examining the ecological effects in other mountain communities of restoration of, and seasonal space use by, large carnivores.

Interactions between wolves and female grizzly bears with cubs in Yellowstone National Park

Gray wolves (Canis lupus) were extirpated from Yellowstone National Park (YNP) by the 1920s through predator control actions (Murie 1940,Young and Goldman 1944, Weaver 1978), then reintroduced into the park from 1995 to 1996 to restore ecological integrity and adhere to legal mandates (Bangs and Fritts 1996, Phillips and Smith 1996, Smith et al. 2000). Prior to reintroduction, the potential effects of wolves on the region’s threatened grizzly bear (Ursus arctos) population were evaluated (Servheen and Knight 1993). In areas where wolves and grizzly bears are sympatric, interspecific killing by both species occasionally occurs (Ballard 1980, 1982; Hayes and Baer 1992). Most agonistic interactions between wolves and grizzly bears involve defense of young or competition for carcasses (Murie 1944, 1981; Ballard 1982; Hornbeck and Horejsi 1986; Hayes and Mossop 1987; Kehoe 1995; McNulty et al. 2001). Servheen and Knight (1993) predicted that reintroduced wolves could reduce the frequency of winter-killed and disease-killed ungulates available for bears to scavenge, and that grizzly bears would occasionally usurp wolf-killed ungulate carcasses. Servheen and Knight (1993) hypothesized that interspecific killing and competition for carcasses would have little or no population level effect on either species. As a component of post-reintroduction wolf and grizzly bear monitoring programs, interspecific interactions between the species were recorded. We expected reintroduced wolves to occasionally kill grizzly bears, especially cubs-of-the-year (cubs). We also predicted that adult males, solitary adult females, and female grizzly bears accompanied by yearling or 2-year-old offspring would occasionally usurp wolf-killed ungulates and scavenge the remains. We hypothesized that these cohorts of grizzly bears would be more successful than subadults at usurping wolf-kills. We further hypothesized that due to potential danger to cubs, females with cubs would not attempt to displace wolf packs from their kills. Our monitoring of interspecific interactions between wolves and grizzly bears is ongoing. From wolf reintroduction in 1995 until January of 2003, 96 wolf– grizzly bear interactions have been recorded (Ballard et al. 2003; D. Smith, National Park Service, Yellowstone National Park, Wyoming, USA, unpublished data). Here we report observations of interactions between wolves and female grizzly bears with cubs and evidence of wolf packs killing grizzly bear cubs near carcasses. Due to grizzly bears’ low reproductive rate (Schwartz et al. 2003) and status as a threatened species (USFWS 1993), the effects of wolves on carcass availability and cub survival is an important consideration for wolf reintroduction and grizzly bear conservation efforts. YNP encompasses 891,000 ha in the states of Wyoming, Montana, and Idaho, USA. The park contains a variety of habitats from high elevation alpine to low elevation sagebrush grasslands (Despain 1990). YNP and the surrounding area (Greater Yellowstone Ecosystem, GYE) support an estimated 56,100 elk (Cervus elaphus), 29,500 mule deer (Odocoileus hemionus), 5,800 moose (Alces alces), 3,900 bighorn sheep (Ovis canadensis), 3,600 bison (Bison bison), and smaller numbers of whitetail deer (Odocoileus virginianus), mountain goat (Oreamnos americanus), and pronghorn antelope (Antilocapra americana) (U.S. Fish and Wildlife Service 1994). Large carnivores in the GYE include grizzly bears, American black bears (U. americanus), wolves, and mountain lions (Felis concolor). In 2002, the reintroduced wolf population in the GYE was estimated at 273 wolves in 31 packs (Smith et al. 2003a). More than 90% of the prey killed by wolves in the GYE is elk (Smith et al. 2003b). Other prey species killed by wolves include deer, bison, and moose, but individually none of these prey comprise .2% of GYE wolves’ diet. The GYE grizzly bear population is estimated at 280–610 bears (Eberhardt and Knight 1996). The GYE is unique among areas inhabited by grizzly bears in North America because kerry_gunther@nps.gov doug_smith@nps.gov

Environmental and Intrinsic Correlates of Stress in Free-Ranging Wolves.

Background When confronted with a stressor, animals react with several physiological and behavioral responses. Although sustained or repeated stress can result in severe deleterious physiological effects, the causes of stress in free-ranging animals are yet poorly documented. In our study, we aimed at identifying the main factors affecting stress levels in free-ranging wolves (Canis lupus). Methodology/Principal Findings We used fecal cortisol metabolites (FCM) as an index of stress, after validating the method for its application in wolves. We analyzed a total of 450 fecal samples from eleven wolf packs belonging to three protected populations, in Italy (Abruzzo), France (Mercantour), and the United States (Yellowstone). We collected samples during two consecutive winters in each study area. We found no relationship between FCM concentrations and age, sex or social status of individuals. At the group level, our results suggest that breeding pair permanency and the loss of pack members through processes different from dispersal may importantly impact stress levels in wolves. We measured higher FCM levels in comparatively small packs living in sympatry with a population of free-ranging dogs. Lastly, our results indicate that FCM concentrations are associated with endoparasitic infections of individuals. Conclusions/Significance In social mammals sharing strong bonds among group members, the death of one or several members of the group most likely induces important stress in the remainder of the social unit. The potential impact of social and territorial stability on stress levels should be further investigated in free-ranging populations, especially in highly social and in territorial species. As persistent or repeated stressors may facilitate or induce pathologies and physiological alterations that can affect survival and fitness, we advocate considering the potential impact of anthropogenic causes of stress in management and conservation programs regarding wolves and other wildlife.

Implications of Harvest on the Boundaries of Protected Areas for Large Carnivore Viewing Opportunities

The desire to see free ranging large carnivores in their natural habitat is a driver of tourism in protected areas around the globe. However, large carnivores are wide-ranging and subject to human-caused mortality outside protected area boundaries. The impact of harvest (trapping or hunting) on wildlife viewing opportunities has been the subject of intense debate and speculation, but quantitative analyses have been lacking. We examined the effect of legal harvest of wolves (Canis lupus) along the boundaries of two North American National Parks, Denali (DNPP) and Yellowstone (YNP), on wolf viewing opportunities within the parks during peak tourist season. We used data on wolf sightings, pack sizes, den site locations, and harvest adjacent to DNPP from 1997–2013 and YNP from 2008–2013 to evaluate the relationship between harvest and wolf viewing opportunities. Although sightings were largely driven by wolf population size and proximity of den sites to roads, sightings in both parks were significantly reduced by harvest. Sightings in YNP increased by 45% following years with no harvest of a wolf from a pack, and sightings in DNPP were more than twice as likely during a period with a harvest buffer zone than in years without the buffer. These findings show that harvest of wolves adjacent to protected areas can reduce sightings within those areas despite minimal impacts on the size of protected wolf populations. Consumptive use of carnivores adjacent to protected areas may therefore reduce their potential for non-consumptive use, and these tradeoffs should be considered when developing regional wildlife management policies.

Chapter 15 Wolf Recolonization of the Madison Headwaters Area in Yellowstone

Theme After decades of absence, large carnivores are being restored or recolonizing substantial portions of their historical ranges worldwide. The reintroduction of wolves (Canis lupus) to Yellowstone National Park in 1995 is one such example of this larger trend. While the Greater Yellowstone Area was rich in prey abundance and diversity, how wolves would respond to the varying prey assemblages within the park was an open question. Wolves were expected to readily adapt to the elk-rich (Cervus elaphus) area of northern Yellowstone, but restoration success and subsequent wolf population ecology was less certain in the central portion of the park, where formidable bison outnumber elk and prey density was more patchy and seasonal due to severe winters. We describe wolf reintroduction efforts in the central Yellowstone area and the population ecology of wolf packs in this system as it transitioned from no wolves to an established population. We focused on pack dynamics in this relatively small area that supports dense ungulate prey in winter, but dispersed prey in summer.