Explore the vast range of titles available.

Migration is a striking behavioral strategy by which many animals enhance resource acquisition while reducing predation risk. Historically, the demographic benefits of such movements made migration common, but in many taxa the phenomenon is considered globally threatened. Here we describe a long-term decline in the productivity of elk ( Cervus elaphus ) that migrate through intact wilderness areas to protected summer ranges inside Yellowstone National Park, USA. We attribute this decline to a long-term reduction in the demographic benefits that ungulates typically gain from migration. Among migratory elk, we observed a 21-year, 70% reduction in recruitment and a 4-year, 19% depression in their pregnancy rate largely caused by infrequent reproduction of females that were young or lactating. In contrast, among resident elk, we have recently observed increasing recruitment and a high rate of pregnancy. Landscape-level changes in habitat quality and predation appear to be responsible for the declining productivity of Yellowstone migrants. From 1989 to 2009, migratory elk experienced an increasing rate and shorter duration of green-up coincident with warmer spring-summer temperatures and reduced spring precipitation, also consistent with observations of an unusually severe drought in the region. Migrants are also now exposed to four times as many grizzly bears ( Ursus arctos ) and wolves ( Canis lupus ) as resident elk. Both of these restored predators consume migratory elk calves at high rates in the Yellowstone wilderness but are maintained at low densities via lethal management and human disturbance in the year-round habitats of resident elk. Our findings suggest that large-carnivore recovery and drought, operating simultaneously along an elevation gradient, have disproportionately influenced the demography of migratory elk. Many migratory animals travel large geographic distances between their seasonal ranges. Changes in land use and climate that disparately influence such seasonal ranges may alter the ecological basis of migratory behavior, representing an important challenge for, and a powerful lens into, the ecology and conservation of migratory taxa.

Identifying the ecological dynamics underlying human-wildlife conflicts is important for the management and conservation of wildlife populations. In landscapes still occupied by large carnivores, many ungulate prey species migrate seasonally, yet little empirical research has explored the relationship between carnivore distribution and ungulate migration strategy. In this study, we evaluate the influence of elk ( Cervus elaphus ) distribution and other landscape features on wolf ( Canis lupus ) habitat use in an area of chronic wolf-livestock conflict in the Greater Yellowstone Ecosystem, USA. Using three years of fine-scale wolf ( n = 14) and elk ( n = 81) movement data, we compared the seasonal habitat use of wolves in an area dominated by migratory elk with that of wolves in an adjacent area dominated by resident elk. Most migratory elk vacate the associated winter wolf territories each summer via a 40-60 km migration, whereas resident elk remain accessible to wolves year-round. We used a generalized linear model to compare the relative probability of wolf use as a function of GIS-based habitat covariates in the migratory and resident elk areas. Although wolves in both areas used elk-rich habitat all year, elk density in summer had a weaker influence on the habitat use of wolves in the migratory elk area than the resident elk area. Wolves employed a number of alternative strategies to cope with the departure of migratory elk. Wolves in the two areas also differed in their disposition toward roads. In winter, wolves in the migratory elk area used habitat close to roads, while wolves in the resident elk area avoided roads. In summer, wolves in the migratory elk area were indifferent to roads, while wolves in resident elk areas strongly avoided roads, presumably due to the location of dens and summering elk combined with different traffic levels. Study results can help wildlife managers to anticipate the movements and establishment of wolf packs as they expand into areas with migratory or resident prey populations, varying levels of human activity, and front-country rangelands with potential for conflicts with livestock.

Wolf (Canis lupus) diets and potential effects on prey have been a prominent subject of interest to wildlife researchers and managers since reintroduction into Yellowstone National Park, Wyoming, USA, in 1995 and 1996. Post-reintroduction, wolves expanded south and recolonized areas in the southern Yellowstone ecosystem. Elk (Cervus elaphus) in this area are supplementally fed during winter (Dec–Mar) at state-managed feedgrounds, resulting in high-density congregations of elk. From December to March 2000–2007, we determined the winter predation patterns of wolves by examining the remains of 289 wolf kills on 3 state-managed feedgrounds and adjacent winter range near Jackson, Wyoming. During winters 2002–2005, we also monitored the movements of radio-collared elk on feedgrounds to describe the response of elk to the presence of wolf kills. Thirty-seven percent (n = 106) of kills were located on elk feedgrounds where elk composition included 49% calves, 42% adult females, 5% adult males, and 5% unknown. Sixty-three percent (n = 183) of kills were located on winter range adjacent to feedgrounds and prey species consisted of 90% elk (38% calves, 35% adult females, 24% adult males, 2% unknown), 9% moose (Alces alces; 13% calves, 69% adult females, 6% adult males, 1% unknown), 1% mule deer (Odocoileus hemionus; 1 fawn, 1 adult female), and 0.5% adult female bison (Bison bison). Mean age of elk killed on feedgrounds was 4.2 years (range = 0–20) and 4.6 years (range = 0–23) on winter range. Calves were selected more than available in most years with female elk killed less than expected. Adult males were killed more than expected in 2005–2007. Eighty-eight percent (n = 198) of the time elk remained on the feedground even when wolves made a kill. Less commonly, elk left the feedground, gathered in larger herds on adjacent feedgrounds absent of wolves, and returned within a few days (6%, n = 13) or left the feedground for another feedground and did not return for the rest of the winter (6%; n = 14). Elk were less likely to leave feedgrounds in the presence of a wolf kill when there were more elk on that feedground. Elk left feedgrounds with greater topography and tree cover (Alkali and Fish Creek) and gathered on the flat, open feedgrounds (Patrol Cabin) more frequently than they left flat, open feedgrounds for feedgrounds with greater topography and tree cover. Our results indicate wolves in our study area primarily preyed on elk and exhibited a strong preference for elk calves. High-density concentrations of elk on feedgrounds will continue to be an attractant for wolves. Although elk leave feedgrounds for reasons other than wolf presence, any displacement of elk from feedgrounds due to wolves will be temporary. State managers have the ability to alter management strategies (e.g., increasing wolf harvest, phasing out elk feeding, increasing the intensity of elk feeding) in an effort to affect predator-prey relationships.

Gray wolves (Canis lupus) were extirpated from the northern Rocky Mountains (NRM) of the United States by the 1930s. Dispersing wolves from Canada naturally recolonized Montana and first denned there in 1986. In 1995 and 1996, the United States Fish and Wildlife Service reintroduced 66 wolves into central Idaho and Yellowstone National Park. By 2008, there were ≥1,655 wolves in ≥217 packs, including 95 breeding pairs in the NRM. From 1993–2008, we captured and radio-collared 1,681 wolves and documented 297 radio-collared wolves dispersing as lone individuals. We monitored dispersing wolves to determine their pack characteristics (i.e., pack size and surrounding pack density) before and after dispersal, their reproductive success, and eventual fate. We calculated summary statistics for characteristics of wolf dispersal (i.e., straight-line distance, age, time of year, sex ratio, reproduction, and survival), and we tested these characteristics for differences between sexes and age groups. Approximately, 10% of the known wolf population dispersed annually. The sex ratio of dispersals favored males (169 M, 128 F), but fewer dispersed males reproduced (28%, n = 47) than females (42%, n = 54). Fifty-nine percent of all dispersers of known age were adults (n = 156), 37% were yearlings (n = 99), and 4% were pups (n = 10). Mean age at dispersal for males (32.8 months) was not significantly different (P = 0.88) than for females (32.1 months). Yellowstone National Park had a significant positive effect on dispersal rate. Pack density in a wolf’s natal population had a negative effect on dispersal rate when the entire NRM population was considered. The mean NRM pack size (6.9) from 1993 to 2008 was smaller than the mean size of packs (10.0) from which wolves dispersed during that time period (P < 0.001); however, pack size was not in our most supported model. Dispersals occurred throughout the year but generally increased in the fall and peaked in January. The mean duration of all dispersals was 5.5 months. Radio-collared wolves dispersed between Montana, Idaho, and Wyoming to other adjacent states, and between the United States and Canada throughout the study. Mean straight-line distance between starting and ending points for dispersing males (98.1 km) was not significantly different than females (87.7 km; P = 0.11). Ten wolves (3.4%) dispersed distances >300 km. On average, dispersal distance decreased later in the study (P = 0.006). Sex, survival rate in the natal population, start date, dispersal distance, and direction were not significant predictors of dispersal rate or successful dispersal. Wolves that formed new packs were >11 times more likely to reproduce than those that joined packs and surrounding pack density had a negative effect on successful dispersal. Dispersal behavior seems to be innate in sexually mature wolves and thereby assures that genetic diversity will remain high and help conserve the NRM wolf population.

Wolf (Canis lupus) predation on livestock and management methods used to mitigate conflicts are highly controversial and scrutinized especially where wolf populations are recovering. Wolves are commonly removed from a local area in attempts to reduce further depredations, but the effectiveness of such management actions is poorly understood. We compared the effects of 3 management responses to livestock depredation by wolf packs in Montana, Idaho, and Wyoming: no removal, partial pack removal, and full pack removal. We examined the effectiveness of each management response in reducing further depredations using a conditional recurrent event model. From 1989 to 2008, we documented 967 depredations by 156 packs: 228 on sheep and 739 on cattle and other stock. Median time between recurrent depredations was 19 days following no removal (n = 593), 64 days following partial pack removal (n = 326), and 730 days following full pack removal (n = 48; recurring depredations were made by the next pack to occupy the territory). Compared to no removal, full pack removal reduced the occurrence of subsequent depredations by 79% (hazard ratio [HR] = 0.21, P < 0.001) over a span of 1,850 days (5 years), whereas partial pack removal reduced the occurrence of subsequent depredations by 29% (HR = 0.71, P < 0.001) over the same period. Partial pack removal was most effective if conducted within the first 7 days following depredation, after which there was only a marginally significant difference between partial pack removal and no action (HR = 0.86, P = 0.07), and no difference after 14 days (HR = 0.99, P = 0.93). Within partial pack removal, we found no difference in depredation recurrence when a breeding female (HR = 0.64, P = 0.2) or ≥1-year-old male was removed (HR = 1.0, P = 0.99). The relative effect of all treatments was generally consistent across seasons (spring, summer grazing, and winter) and type of livestock. Ultimately, pack size was the best predictor of a recurrent depredation event; the probability of a depredation event recurring within 5 years increased by 7% for each animal left in the pack after the management response. However, the greater the number of wolves left in a pack, the higher the likelihood the pack met federal criteria to count as a breeding pair the following year toward population recovery goals. Published 2015. This article is a U.S. Government work and is in the public domain in the USA.

The role of predation by large carnivores in suppressing prey populations and structuring ecosystems is highly debated, calling for a detailed understanding of carnivore diets. Wolves (Canis lupus) roam across three continents and persist throughout widely different ecosystems. Their diet is flexible and may vary spatially as well as seasonally, which requires analysis of diet on different spatial and temporal scales. Few studies have investigated the summer diet of wolves, which is more variable, consists of smaller prey, and requires different methods than studying their winter diet. To better understand the summer diet of wolves, we combined three independently collected wolf scat data sets from three distinctly different portions of the Greater Yellowstone Ecosystem: Yellowstone National Park (2009), Grand Teton National Park (2003 – 2009), and the Absaroka-Beartooth Wilderness (2009 – 2010). These areas represent different ecological conditions and management regimes, which may impact wolf diet. We estimated relative biomass and compared occurrence of different prey species among packs, years, as well as the three regions. In total, we analyzed 1,906 wolf scats and found that neonate cervids, adult elk, and adult deer were the most important prey species in the summer diet of the wolves. We found dietary variation among packs residing in the same area, as well as across years. The occurrence of neonate cervids displayed the most variation, and low occurrence of this prey type often was associated with a more diverse diet. Wolf packs within the national parks had a higher occurrence of medium-sized prey (~ 50 – 70 kg) and lower occurrence of small-sized prey (≤ 20 kg) compared to wolves in the Absaroka-Beartooth Wilderness. These results demonstrate flexibility in summer diet across packs, years, and between regions within the Greater Yellowstone Ecosystem.

Managers of recovering wolf (Canis lupus) populations require knowledge regarding the potential impacts caused by the loss of territorial, breeding wolves when devising plans that aim to balance population goals with human concerns. Although ecologists have studied wolves extensively, we lack an understanding of this phenomenon as published records are sparse. Therefore, we pooled data (n = 134 cases) on 148 territorial breeding wolves (75 M and 73 F) from our research and published accounts to assess the impacts of breeder loss on wolf pup survival, reproduction, and territorial social groups. In 58 of 71 cases (84%), ≥1 pup survived, and the number or sex of remaining breeders (including multiple breeders) did not influence pup survival. Pups survived more frequently in groups of ≥6 wolves (90%) compared with smaller groups (68%). Auxiliary nonbreeders benefited pup survival, with pups surviving in 92% of cases where auxiliaries were present and 64% where they were absent. Logistic regression analysis indicated that the number of adult-sized wolves remaining after breeder loss, along with pup age, had the greatest influence on pup survival. Territorial wolves reproduced the following season in 47% of cases, and a greater proportion reproduced where one breeder had to be replaced (56%) versus cases where both breeders had to be replaced (9%). Group size was greater for wolves that reproduced the following season compared with those that did not reproduce. Large recolonizing (>75 wolves) and saturated wolf populations had similar times to breeder replacement and next reproduction, which was about half that for small recolonizing (≤75 wolves) populations. We found inverse relationships between recolonizing population size and time to breeder replacement (r = −0.37) and time to next reproduction (r = −0.36). Time to breeder replacement correlated strongly with time to next reproduction (r = 0.97). Wolf social groups dissolved and abandoned their territories subsequent to breeder loss in 38% of cases. Where groups dissolved, wolves reestablished territories in 53% of cases, and neighboring wolves usurped territories in an additional 21% of cases. Fewer groups dissolved where breeders remained (26%) versus cases where breeders were absent (85%). Group size after breeder loss was smaller where groups dissolved versus cases where groups did not dissolve. To minimize negative impacts, we recommend that managers of recolonizing wolf populations limit lethal control to solitary individuals or territorial pairs where possible, because selective removal of pack members can be difficult. When reproductive packs are to be managed, we recommend that managers only remove wolves from reproductive packs when pups are ≥6 months old and packs contain ≥6 members (including ≥3 ad-sized wolves). Ideally, such packs should be close to neighboring packs and occur within larger (≥75 wolves) recolonizing populations.

Increasingly, animals that migrate long distances to exploit seasonal habitats must traverse political boundaries capable of altering the very ecological gradients that promote migratory behavior. This transboundary aspect of migration presents many new challenges and opportunities for research and conservation (e.g., Bolger et al. 2008, Taillon et al. 2012). Work to date has often focused on physical barriers to movement (roads, fences, and housing and energy development) that can threaten migratory populations to varying degrees (Holdo et al. 2011, Sawyer et al. 2013). However, even in the absence of conspicuous barriers, political and jurisdictional boundaries can bring dramatic differences in land use and conservation policy. What happens to migratory populations when these boundaries alter the resources and refuges that they seek on their seasonal journeys? It was this subtler question we confronted as we tried to understand the divergent productivity of migratory and resident elk (Cervus elaphus) in a population that occupies relatively undeveloped habitats of the Greater Yellowstone Ecosystem, USA (GYE). Over two decades, the recruitment rate of migratory elk has declined, while that of resident elk has remained stable, and recently increased. Over the same period, resident elk have grown more abundant, and the population's winter distribution has shifted similar to 18 km further away from the wilderness core of the GYE (Fig. 1). These changes have emerged without any physical obstruction of migration, and without migratory individuals\"staying behind\" to remain resident (Middleton et al. 2013). Gaillard (2013) points out that (1) calf:cow ratios are an imperfect index of recruitment, (2) that we could have failed to detect a low rate of individual switching between the two subpopulations, and (3) that we could not account for the full suite of fitness components in this population. Nevertheless, our comparative approach revealed important contrasts that suggest the population's ongoing transition has been largely brought about by changes in calf recruitment (Middleton et al. 2013), with residents outperforming migrants. Similar patterns have emerged in and around Banff National Park in Alberta, Canada, where wolf (Canis lupus) recovery and agriculture (factors also at play in the GYE) have been associated with declines in the recruitment and abundance of migratory elk (Hebblewhite et al. 2005, 2006). These trends pose challenges for conservation and management. Migratory ungulates can be ecologically and economically important, but are broadly threatened (Bolger et al. 2008), whereas resident ungulates that commingle with domestic livestock can increase risks of disease transmission (Cross et al. 2009), crop damage, and human-carnivore conflict (Nelson et al. 2012).

Successful nonlethal management of livestock predation is important for conserving rare or endangered carnivores. In the northwestern United States, wolves (Canis lupus) have been translocated away from livestock to mitigate conflicts while promoting wolf restoration. We assessed predation on livestock, pack establishment, survival, and homing behavior of 88 translocated wolves with radiotelemetry to determine the effectiveness of translocation in our region and consider how it may be improved. More than one-quarter of translocated wolves preyed on livestock after release. Most translocated wolves (67%) never established or joined a pack, although eight new packs resulted from translocations. Translocated wolves had lower annual survival (0.60) than other radio-collared wolves (0.73), with government removal the primary source of mortality. In northwestern Montana, where most wolves have settled in human-populated areas with livestock, survival of translocated wolves was lowest (0.41) and more wolves proportionally failed to establish packs (83%) after release. Annual survival of translocated wolves was highest in central Idaho (0.71) and more wolves proportionally established packs (44%) there than in the other two recovery areas. Translocated wolves showed a strong homing tendency; most of those that failed to home still showed directional movement toward capture sites. Wolves that successfully returned to capture sites were more likely to be adults, hard (immediately) rather than soft (temporarily held in enclosure) released, and translocated shorter distances than other wolves that did not return home. Success of translocations varied and was most affected by the area in which wolves were released. We suggest managers translocating wolves or other large carnivores consider soft releasing individuals (in family groups, if social) when feasible because this may decrease homing behavior and increase release-site fidelity.

Gray wolf (Canis lupus) populations have persisted and expanded in northwest Montana since 1986, while reintroduction efforts in Idaho and Yellowstone have further bolstered the regional population. However, rigorous analysis of either the availability of wolf habitat in the entire region, or the specific habitat requirements of local wolves, has yet to be conducted. We examined wolf-habitat relationships in the northern Rocky Mountains of the U.S. by relating landscape/habitat features found within wolf pack home ranges (n = 56) to those found in adjacent non-occupied areas (n = 56). Logistic regression revealed that increased forest cover, lower human population density, higher elk density, and lower sheep density were the primary factors related to wolf occupation. Similar factors promoted wolf pack persistence. Further, our analysis indicated that relatively large tracts of suitable habitat remain unoccupied in the Rocky Mountains, suggesting that wolf populations likely will continue to increase in the region. Analysis of the habitat linkage between the 3 main wolf recovery areas indicates that populations in central Idaho and northwest Montana have higher connectivity than either of the 2 recovery areas to the Greater Yellowstone recovery area. Thus, for the northern Rocky Mountains to function as a metapopulation for wolves, it will be necessary that dispersal corridors to the Yellowstone ecosystem be established and conserved.