Migratory Ungulates Research Articles

A Migratory Northern Ungulate in the Pursuit of Spring: Jumping or Surfing the Green Wave?

The forage-maturation hypothesis (FMH) states that herbivores migrate along a phenological gradient of plant development in order to maximize energy intake. Despite strong support for the FMH, the actual relationship between plant phenology and ungulate movement has remained enigmatic. We linked plant phenology (MODIS-normalized difference vegetation index [NDVI] data) and space use of 167 migratory and 78 resident red deer (Cervus elaphus), using a space-time-time matrix of "springness," defined as the instantaneous rate of green-up. Consistent with the FMH, migrants experienced substantially greater access to early plant phenology than did residents. Deer were also more likely to migrate in areas where migration led to greater gains in springness. Rather than "surfing the green wave" during migration, migratory red deer moved rapidly from the winter to the summer range, thereby "jumping the green wave." However, migrants and, to a lesser degree, residents did track phenological green-up through parts of the growing season by making smaller-scale adjustments in habitat use. Despite pronounced differences in their life histories, we found only marginal differences between male and female red deer in this study. Those differences that we did detect pointed toward additional constraints on female space-use tactics, such as those posed by calving and caring for dependent offspring. We conclude that whereas in some systems migration itself is a way to surf the green wave, in others it may simply be a means to reconnect with phenological spring at the summer range. In the light of ubiquitous anthropogenic environmental change, understanding the relationship between the green wave and ungulate space use has important consequences for the management and conservation of migratory ungulates and the phenomenon of migration itself.

Mechanisms of Coexistence in Vultures: Understanding the Patterns of Vulture Abundance at Carcasses in Masai Mara National Reserve, Kenya

Abstract. Because of the high, albeit seasonal, availability of carcasses, the Mara-Serengeti ecosystem, Kenya, has a high diversity of scavengers, leading to considerable competition between species. From patterns of occurrence of vultures at 163 carcasses over an 8-year period in the Masai Mara National Reserve, we were able to identify some mechanisms that may reduce competition. Species are associated on the basis of similar dietary needs and beak morphology, and they are highly interdependent, showing little evidence of disassociation. Social vultures (genus Gyps) dominated the vulture scene at the reserve; they were more abundant at carcasses when migratory ungulates were present in the dry season, when more carcasses are likely to be available, than when migratory ungulates were absent. In addition, regardless of the predator's identity, presence of a predator reduced the number of vultures, suggesting that vultures prefer carrion not killed by predators where available. Comparisons between past an...

Mitigating roadway impacts to migratory mule deer—A case study with underpasses and continuous fencing

AbstractWildlife–vehicle collisions pose a major safety concern to motorists and can be a significant source of mortality for wildlife. Additionally, roadways can impede movements and reduce habitat connectivity. For migratory ungulates, these problems can be exacerbated when roadways bisect migration routes, as is the case in Southwest Wyoming, USA, where a 21‐km section of U.S. Highway 30 overlaps with a critical winter range and migration route used by thousands of mule deer (Odocoileus hemionus). In an effort to reduce deer–vehicle collisions (DVC) and maintain migratory connectivity, the Wyoming Department of Transportation installed 7 concrete box‐culvert underpasses with continuous game‐proof fencing between each crossing structure. To evaluate the effectiveness of this mitigation project, we used remote cameras to quantify the number of mule deer that used the underpasses, estimate passage rates through time, and compare rates of DVCs before and after underpass construction. Through 3 years of monitoring (which encompassed autumn migration [2008, 2009, and 2010], winter use, and spring migration [2009, 2010, and 2011] for 3 migration cycles), we documented 49,146 mule deer move through the underpasses. Passage rates of deer approaching underpasses steadily increased from 54% in Year 1 to 92% in Year 3. Peak movements during the autumn migration occurred in mid‐December, while peak spring movements were in mid‐March and early May. Underpass and fence installation effectively reduced DVCs by 81%. Had fence gates remained closed and cattle guards clear of snow, DVCs could be eliminated altogether. Our results suggest that underpasses, combined with game‐proof fencing, can improve highway safety for motorists while providing safe and effective movement corridors for large populations of migratory mule deer. © 2012 The Wildlife Society.

Seasonal variation in breeding Rüppell’s Vultures Gyps rueppellii at Kwenia, southern Kenya and implications for conservation

SummaryVulture populations have been declining globally and regionally within Africa. Rüppell’s Vulture Gyps rueppellii is currently listed as ‘Near Threatened’ and numbers of the species, along with African White-backed Vultures G. africanus, have declined by 52% in and around the Mara-Serengeti ecosystem. A large breeding colony of Rüppell’s Vulture at Kwenia, southern Kenya, was monitored between 2002 and 2009. Around 150–200 adults were present on each visit, with up to 64 simultaneously active nests. The date of egg-laying differed considerably between years, with two discrete breeding attempts in some years. Nests were not positioned randomly across the cliff face and the number of active nests was related to rainfall in the previous year. The large ungulate migration of the Mara-Serengeti provides a vital foraging ground for the species. Conservation implications of the loss of vultures are discussed.

Wet season range fidelity in a tropical migratory ungulate

1. In migratory populations, the degree of fidelity and dispersal among seasonal ranges is an important population process with consequences for demography, management, sensitivity to habitat change and adaptation to local environmental conditions. 2. Characterizing patterns of range fidelity in ungulates, however, has remained challenging because of the difficulties of following large numbers of marked individuals across multiple migratory cycles and of identifying the appropriate scale of analysis. 3. We examined fidelity to wet season (i.e. breeding) ranges in a recently declining population of wildebeest Connochaetes taurinus Burchell in northern Tanzania across 3 years. We used computer-assisted photographic identification and capture-recapture to characterize return patterns to three wet season ranges that were ecologically discrete and topographically isolated from one another. 4. Among 2557 uniquely identified adult wildebeest, we observed 150 recaptures across consecutive wet seasons. Between the two migratory subpopulations, the probability of remaining faithful to wet season areas ranged between 0·82 and 1·00. Animals from a non-migratory segment of the population (near Lake Manyara National Park) were rarely observed in other wet season ranges, despite proximity to one of the migratory pathways. 5. We found no effect of sex on an individuals' probability of switching wet season ranges. However, the breeding status of females in year i had a strong influence on patterns of range selection in year i + 1, with surviving breeders over three times as likely to switch ranges as non-breeders. 6. Social-group associations between pairs of recaptured animals were random with respect to an individual's wet season range during the previous or forthcoming wet seasons, suggesting that an individual's herd identity during the dry season does not predict wet season range selection. 7. Examining fidelity and dispersal in terrestrial migrations improves our understanding of the constraints that migrants experience when they face rapid habitat changes or fluctuations in environmental conditions.

Shifting targets in the tundra: Protection of migratory caribou calving grounds must account for spatial changes over time

Industrial development, expansion of human populations and climate change increasingly affect habitats of migratory species. Effective protection of critical habitats is urgently required because several large migratory species have declined over the last decades. Protection of critical habitats, such as the calving grounds of migratory ungulates, may however require consideration of temporal shifts in spatial location. We assessed changes in the location of calving grounds used by migratory caribou over 35years by the Rivière-George (RG) herd and 15years by the Rivière-aux-Feuilles (RAF) herd, in Northern Québec and Labrador, Canada. We also evaluated the proportion of annual calving ground within protected Wildlife Habitats established to protect caribou calving grounds. The annual size and location of calving grounds changed substantially over time: calving ground size remained relatively stable for the RAF but it declined over 85% for the RG. Calving grounds moved 300km northward in the Ungava peninsula for the RAF and shifted over 230km back and forth to the Labrador coast for the RG. Despite recent modifications, legally designated Wildlife Habitats in Québec protected less than 20% of the RG and RAF calving grounds. Protection of calving grounds of migratory caribou must consider the dynamic use of space by adult females. We present recommendations on the use of available monitoring data to better protect calving grounds of migratory caribou and critical habitats of large migratory species.

Stopover ecology of a migratory ungulate

1. Birds that migrate long distances use stopover sites to optimize fuel loads and complete migration as quickly as possible. Stopover use has been predicted to facilitate a time-minimization strategy in land migrants as well, but empirical tests have been lacking, and alternative migration strategies have not been considered. 2. We used fine-scale movement data to evaluate the ecological role of stopovers in migratory mule deer Odocoileus hemionus- a land migrant whose fitness is strongly influenced by energy intake rather than migration speed. 3. Although deer could easily complete migrations (range 18-144 km) in several days, they took an average of 3 weeks and spent 95% of that time in a series of stopover sites that had higher forage quality than movement corridors. Forage quality of stopovers increased with elevation and distance from winter range. Mule deer use of stopovers corresponded with a narrow phenological range, such that deer occupied stopovers 44 days prior to peak green-up, when forage quality was presumed to be highest. Mule deer used one stopover for every 5·3 and 6·7 km travelled during spring and autumn migrations, respectively, and used the same stopovers in consecutive years. 4. Study findings indicate that stopovers play a key role in the migration strategy of mule deer by allowing individuals to migrate in concert with plant phenology and maximize energy intake rather than speed. Our results suggest that stopover use may be more common among non-avian taxa than previously thought and, although the underlying migration strategies of temperate ungulates and birds are quite different, stopover use is important to both. 5. Exploring the role of stopovers in land migrants broadens the scope of stopover ecology and recognizes that the applied and theoretical benefits of stopover ecology need not be limited to avian taxa.

Topographic and ungulate regulation of soil C turnover in a temperate grassland ecosystem

A major obstacle for predicting the effects of climate and land use changes on global soil carbon (C) stores is the very limited knowledge about the long timescale dynamics of the relatively stable fraction of soil C, which represents the bulk of soil C and the primary determinant of the long-term C balance of terrestrial ecosystems. In this study, we examined how variable topo-edaphic conditions and herds of native migratory ungulates influenced turnover of the stable pool (total minus active fraction) of soil C in grasslands of Yellowstone National Park (YNP). Soil C properties were determined for grasslands located inside and outside long-term ungulate exclosures established 1958-1962 at seven variable topographic positions. Active C pool sizes, estimated with soil laboratory incubations, and soil radiocarbon measures were used to parameterize a process-based model to determine turnover of the stable C pool at the sites. Stable C turnover ranged 37-653 and 89-869 years for 0-10 and 0-20 cm soils, respectively. Among ungrazed communities, there was a trend for stable soil C turnover to slow along topographic gradients of increasing soil moisture, soil C content, and shoot biomass from hilltop to slope-bottom positions. This was likely a result of an increasing amount of support tissue resulting in greater concentrations of lignin and cellulose as shoot biomass increased down slope. In contrast, across the grazed landscape, stable C turnover sped up from hilltop to slope-bottom positions, which was likely a consequence of grazer effects on plant species composition along the topographic gradient. These findings indicated that despite topography playing the primary role in controlling such important site characteristics as soil moisture, soil C content, and plant production in YNP grassland, the long-term turnover of the stable C pool was determined by herbivores. The results demonstrate the important regulatory role of herbivores in controlling the C balance of this semiarid grassland ecosystem.

Major declines in the abundance of vultures and other scavenging raptors in and around the Masai Mara ecosystem, Kenya

Vulture population declines have been noted in West and Southern Africa, but have not been assessed in East Africa. Roadside transects conducted in 1976 and 1988 were compared with surveys done from 2003–2005 in and around Masai Mara National Reserve, Kenya. Staggering declines in abundance were found for seven of eight scavenging raptors surveyed. No Egyptian vultures were seen during recent transects. We compared trends between the ungulate migration and non-migration season among three land use types (reserve, buffer, and grazed) and among the species surveyed to establish the causes of declines in scavenging raptors. Large declines during the ungulate migratory period suggest that most scavenging raptor species are declining well beyond the area of study. For all species, except Hooded vultures, substantial declines outside of the reserve indicate an important role of land use change in causing observed declines. In addition, significant declines of populations of Gyps species in the reserve itself, especially during the migration season, provide evidence that human activities occurring in other parts of the species’ range such as poisoning of carcasses may be causing their decline. Declines found in this study suggest that at a minimum African white-backed, Rüppell’s, and Hooded vultures should be relisted as Vulnerable. Management actions that limit land use change around the reserve combined with a countrywide ban on carbamate pesticides will be important for conserving keystone members of the scavenging guild. Future research should further examine possible causes of these declines and quantify the effect of reduced scavenging raptor abundance on scavenging efficiency.

Responses to alternative rainfall regimes and antipoaching in a migratory system

Migratory ungulates may be particularly vulnerable to the challenges imposed by growing human populations and climate change. These species depend on vast areas to sustain their migratory behavior, and in many cases come into frequent contact with human populations outside protected areas. They may also act as spatial coupling agents allowing feedbacks between ecological systems and local economies, particularly in the agropastoral subsistence economies found in the African savanna biome. We used HUMENTS, a spatially realistic socioecological model of the Greater Serengeti Ecosystem in East Africa, to explore the potential impacts of changing climate and poaching on the migratory wildebeest (Connochaetes taurinus) population, the fire regime, and habitat structure in the ecosystem, as well as changes in the size and economic activities of the human population outside the protected area. Unlike earlier models, the HUMENTS model predicted only moderate declines in the wildebeest population associated with an increasing human population over the next century, with a gradual expansion of agriculture, more poaching, and increases in fire frequency and reduced tree density. Changes in rainfall were predicted to have strong asymmetric effects on the size and economic activity of the human population and on livestock, and more moderate effects on wildlife and other ecological indicators. Conversely, antipoaching had a stronger effect on the ecological portion of the system because of its effect on wildebeest (and therefore on fire and habitat structure), and a weaker effect on the socioeconomic component, except in areas directly adjacent to the protected-area boundary, which were affected by crop-raiding and the availability of wildlife as a source of income. The results highlight the strong direct and indirect effects of rainfall on the various components of socioecological systems in semiarid environments, and the key role of mobile wildlife populations as agents of spatial coupling between the human-dominated and natural portions of ecosystems. They also underscore the fundamental importance of considering the spatial configuration of hunting refuges across the landscape in relation to human populations.

Possible causes of decreasing migratory ungulate populations in an East African savannah after restrictions in their seasonal movements

AbstractIn many areas in Africa, seasonal movements of migratory ungulates are restricted and their population numbers decline, for example in the Tarangire region, Tanzania. Here, agriculture restricts migration of ungulates to their wet season ranges. We investigated whether low forage quality or supply are possible causes of population decline of wildebeest and zebra when access to these wet season ranges is restricted and migratory herds have to reside in the dry season range year‐round. We simulated grazing through a clipping experiment in the dry season range during the wet season. Clipping negatively affected forage supply and had a positive effect on forage quality by increasing proportions of live and leaf biomass as well as nutrient concentrations in the leaves. However, increase in forage quality in the dry season range due to grazing was not as such that requirements of wildebeest during the wet season, when females are lactating, could be met. We conclude that low forage quality in the dry season range during the wet season could cause the decrease in migratory ungulate populations in the Tarangire region. With this study, the necessity of protecting wet season ranges from expanding human activities to safeguard migratory systems is supported.

Prey selection and prey preferences of spotted hyenas Crocuta crocuta in the Etosha National Park, Namibia

AbstractThe feeding ecology of the spotted hyena Crocuta crocuta was studied in the central and eastern part of the Etosha National Park, Namibia. Hyenas mainly hunted migratory ungulates such as springbok Antidorcas marsupialis, zebra Equus burchelli, and blue wildebeest Connochaetes taurinus, but also resident species such as the greater kudu Tragelaphus strepsiceros and gemsbok Oryx gazella. There were, however, major differences in the species most frequently killed by hyenas in central and eastern Etosha. The preferred prey species of spotted hyenas in central Etosha was springbok, whereas regarding the abundance of zebra and wildebeest, these two species were rather avoided. In contrast, the prey species preferred by hyenas in eastern Etosha was kudu. Zebra and gemsbok were taken in proportion to their abundance, whereas wildebeest and springbok seemed to be rather avoided. Differences in prey selection and preferences were also reflected in differences in hunting group sizes. In eastern Etosha, where spotted hyenas frequently hunted larger prey, hunting group sizes were significantly larger compared to those in the center of the park.

Trade‐offs between predation risk and forage differ between migrant strategies in a migratory ungulate

Trade-offs between predation risk and forage fundamentally drive resource selection by animals. Among migratory ungulates, trade-offs can occur at large spatial scales through migration, which allows an "escape" from predation, but trade-offs can also occur at finer spatial scales. Previous authors suggest that ungulates will avoid predation risk at the largest scale, although few studies have examined multi-scale trade-offs to test for the relative benefits of risk avoidance across scales. Building on previously developed spatial models of forage and wolf predation risk, we tested for trade-offs at the broad landscape scale and at a finer, within-home-range scale for migratory and non-migratory resident elk (Cervus elaphus) during summer in the Canadian Rockies in Banff National Park (BNP) and adjacent Alberta, Canada. Migration reduced exposure to wolf predation risk by 70% relative to residents at the landscape scale; at the fine scale, migrants used areas that were, on average, 6% higher in forage digestibility. In contrast, by forgoing migration, resident elk were exposed to higher predation risk, but they reduced predation risk at fine scales to only 15% higher than migrants by using areas close to human activity, which wolves avoided. Thus, residents paid for trying to avoid predation risk with lower forage quality. Residents may have been able to compensate, however, by using areas of abundant forage close to human activity where they may have been able to forage more selectively while avoiding predation risk. Human activity effectively decoupled the positive correlation between high forage quality and wolf predation, providing an effective alternate strategy for residents, similar to recent findings in other systems. Although ungulates appear capable of balancing risk and forage at different spatial scales, risk avoidance at large landscape scales may be more effective in the absence of human-caused refugia from predation.

Identifying and prioritizing ungulate migration routes for landscape‐level conservation

As habitat loss and fragmentation increase across ungulate ranges, identifying and prioritizing migration routes for conservation has taken on new urgency. Here we present a general framework using the Brownian bridge movement model (BBMM) that: (1) provides a probabilistic estimate of the migration routes of a sampled population, (2) distinguishes between route segments that function as stopover sites vs. those used primarily as movement corridors, and (3) prioritizes routes for conservation based upon the proportion of the sampled population that uses them. We applied this approach to a migratory mule deer (Odocoileus hemionus) population in a pristine area of southwest Wyoming, USA, where 2000 gas wells and 1609 km of pipelines and roads have been proposed for development. Our analysis clearly delineated where migration routes occurred relative to proposed development and provided guidance for on-the-ground conservation efforts. Mule deer migration routes were characterized by a series of stopover sites where deer spent most of their time, connected by movement corridors through which deer moved quickly. Our findings suggest management strategies that differentiate between stopover sites and movement corridors may be warranted. Because some migration routes were used by more mule deer than others, proportional level of use may provide a reasonable metric by which routes can be prioritized for conservation. The methods we outline should be applicable to a wide range of species that inhabit regions where migration routes are threatened or poorly understood.

A keystone predator at risk? Density and distribution of the spotted hyena (Crocuta crocuta) in the Etosha National Park, Namibia

For wildlife management and conservation biology, it is important to be able to estimate the status and distribution of animals and to monitor their population trends. In the Etosha National Park, Namibia, there is a lack of knowledge about numbers and distribution of spotted hyenas ( Crocuta crocuta (Erxleben, 1777)) and factors regulating their population. To estimate hyena density and distribution, tape-recorded vocalizations (call-ups) were performed to attract hyenas in the central and eastern parts of Etosha. Eighty-five adult and subadult hyenas responded to the calls, with most of them responding in an area with high density of migratory ungulates, principally springbok ( Antidorcas marsupialis (Zimmermann, 1780)), wildebeest ( Connochaetes taurinus (Burchell, 1823)), and Burchell’s zebra ( Equus burchelli (Gray, 1824)). These migratory species are the main prey of spotted hyenas in Etosha. There was a strong spatial relationship between hyena density and migratory prey biomass. Based on this mathematical correlation, I estimated 203 ± 79 hyenas, i.e., 2.7 ± 1.1 hyenas/100 km2, in the central and eastern parts of Etosha. Applying this correlation to the western part of the park, it was possible to estimate 339 ± 176 spotted hyenas, corresponding to an overall density of 2.1 ± 1.0 hyenas/100 km2, in the whole Etosha National Park.

The Status of Wildlife in Protected Areas Compared to Non-Protected Areas of Kenya

We compile over 270 wildlife counts of Kenya's wildlife populations conducted over the last 30 years to compare trends in national parks and reserves with adjacent ecosystems and country-wide trends. The study shows the importance of discriminating human-induced changes from natural population oscillations related to rainfall and ecological factors. National park and reserve populations have declined sharply over the last 30 years, at a rate similar to non-protected areas and country-wide trends. The protected area losses reflect in part their poor coverage of seasonal ungulate migrations. The losses vary among parks. The largest parks, Tsavo East, Tsavo West and Meru, account for a disproportionate share of the losses due to habitat change and the difficulty of protecting large remote parks. The losses in Kenya's parks add to growing evidence for wildlife declines inside as well as outside African parks. The losses point to the need to quantify the performance of conservation policies and promote integrated landscape practices that combine parks with private and community-based measures.

Global decline in aggregated migrations of large terrestrial mammals

ESR Endangered Species Research Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsSpecials ESR 7:55-76 (2009) - DOI: https://doi.org/10.3354/esr00173 REVIEW Global decline in aggregated migrations of large terrestrial mammals Grant Harris1,2,*, Simon Thirgood 3,4, J. Grant C. Hopcraft3,5, Joris P. G. M. Cromsigt6, Joel Berger7,8 1Center for Biodiversity and Conservation, American Museum of Natural History, Central Park West, 79th Street, New York, New York 10024, USA 2US Fish & Wildlife Service, PO Box 1306, Albuquerque, New Mexico 87103, USA 3Frankfurt Zoological Society, PO Box 14935, Arusha, Tanzania 4Aberdeen Centre for Environmental Sustainability, Macaulay Institute, Aberdeen AB34 5EL, UK 5Community and Conservation Ecology, University of Groningen, Postbus 72, 9700 AB Groningen, The Netherlands 6Mammal Research Institute, Polish Academy of Sciences, 17-230 Bialowieza, Poland 7Northern Rockies Field Office, Wildlife Conservation Society, University of Montana, Missoula, Montana 59812, USA 8Division of Biological Sciences (HS 4824), University of Montana, Missoula, Montana 59812, USA *Email: grant_harris@fws.gov ABSTRACT: Knowledge of mammal migrations is low, and human impacts on migrations high. This jeopardizes efforts to conserve terrestrial migrations. To aid the conservation of these migrations, we synthesized information worldwide, describing 24 large-bodied ungulates that migrate in aggregations. This synthesis includes maps of extinct and extant migrations, numbers of migrants, summaries of ecological drivers and threats migrants confront. As data are often lacking, we outlined steps for science to address and inform conservation actions. We evaluated migrants against this framework, and reported their status. Mass migrations for 6 species are extinct or unknown. Most remaining migrants (n = 9) occur from 6 locations in Africa, with Eurasia and North America containing 6 and 4 remaining mass migrants, respectively (with caribou/reindeer Rangifer tarandus occurring in both regions). All migrants declined in abundance, except wildebeest and other migrants in the Serengeti-Mara Ecosystem (SME), white-eared kob and tiang in Sudan, and some caribou populations. Protected areas only contain migrations for 5 species in the SME, chiru on the Tibetan Plateau, and some caribou populations in North America. Most mass migrants track the seasonal and shifting patterns of greening vegetation over expanses of savannahs, steppes, and grasslands. Principal threats include overhunting and habitat loss from livestock, agriculture, and fencing that excludes animals from forage or water. Conservation science overlooks numerous migrations, so many have already disappeared and continue to do so. Key principles for conserving migrants, exemplified by the SME and Greater Yellowstone Ecosystem (GYE), include securing seasonal ranges, resource protection, government support and minimizing fences. This review forms a baseline for initiating conservation action for many ungulate migrations needing attention. KEY WORDS: Mammals · Migration · Aggregation · Serengeti-Mara · Yellowstone · Ungulate · Global audit Full text in pdf format PreviousNextCite this article as: Harris G, Thirgood S, Hopcraft JGC, Cromsigt JPGM, Berger J (2009) Global decline in aggregated migrations of large terrestrial mammals. Endang Species Res 7:55-76. https://doi.org/10.3354/esr00173Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in ESR Vol. 7, No. 1. Online publication date: April 21, 2009 Print ISSN: 1863-5407; Online ISSN: 1613-4796 Copyright © 2009 Inter-Research.

Editor's choice: Where the buffalo roam – bison and brucellosis in Yellowstone

Kilpatrick, A.M., Gillin, C.M. & Daszak, P. (2009) Wildlife–livestock conflict: the risk of pathogen transmission from bison to cattle outside Yellowstone National Park. Journal of Applied Ecology, 46, 476–485. An enduring symbol of the American West, great migratory herds of bison Bison bison once roamed the Great Plains in their millions (Berger & Cunningham 1994). Sadly, this wildlife spectacle is no more, as in parallel with population declines and extirpation in other migratory ungulates (Bolger et al. 2008; Harris et al. 2009), bison are now restricted to a number of small remnant populations. The causes of population decline in bison and other migrants are well known – hunting, habitat loss, fencing – and their need for space makes the conservation of these wide ranging species a major challenge (Berger 2004; Thirgood et al. 2004). The only free-ranging herd of bison remaining in the United States is found in the Greater Yellowstone Ecosystem of Montana, Wyoming and Idaho. At the start of the 20th century, this population had been reduced to 23 individuals, but with protection it has increased to nearly 5000. Bison spend most of the year at higher altitudes in the Yellowstone National Park but during severe winters they graze at lower elevations outside the park. Here they come into conflict with cattle ranching because of the risk of transmission of brucellosis from bison to cattle. Brucellosis is a bacterial disease that causes weight loss, abortion and reduced milk yields in cattle. The maintenance of brucellosis-free status in cattle is economically important to the livestock industry, and as a result, culling bison is part of the Government interagency disease control strategy (Clarke et al. 2005). The conservation success of Yellowstone's bison indirectly led to the culling of 1600 bison during the 2007/08 winter. For this issue's Editor's Choice selection, Kilpatrick et al. (2009) develop a quantitative risk assessment integrating both ecological and epidemiological data to assess the spatio-temporal risk of transmission of brucellosis from bison to cattle. The model demonstrates that the risk of transmission is highly variable in space, time and frequency and can be predicted by climatic conditions and the abundance of bison. Critically, the model suggests that the risk of brucellosis transmission is very low in most years and is periodically high only in certain localized areas around the park. The authors suggest alternative management strategies, such as financially compensating ranchers for grazing rights in localized areas, would be more cost-effective than the current policy of culling bison to control population size. Another management proposal is to the consider the section of the Greater Yellowstone Ecosystem which occurs in Montana as a separate zone from the rest of the state in terms of brucellosis infection status and provide yearly testing of cattle in that zone. This would cost a fraction of the $2.5 million that the current management strategies cost per year. Similarly, compensating ranchers for the financial value of all the cattle that graze in the affected areas around the park would cost about half the current yearly amount. The results of Kilpatrick et al.'s study have generated considerable interest from scientists, managers and the general public – particularly in the United States. In the month since the paper was published online it has been picked up in the mainstream media more than 100 times. Perhaps this is a reflection of the iconic status of the bison in American popular culture – but it does highlight the critical role of good ecological research in influencing natural resource management decisions. The primary role of the Editor's Choice initiative is to showcase papers that we believe best fulfil the journal's mission of publishing ecological studies with management relevance. Kilpatrick et al.'s study is a particularly good example of the connection between good science and real-world problem solving and we expect that the paper will be both widely cited and highly influential.

Influence of Habitat Conditions and Predation Risk on Productivity and Behavior of a Partially-Migratory Elk Herd in the Absaroka Range

Ungulate migration is an important but increasingly rare ecological process. Although Yellowstone National Park (YNP) retains a rich assemblage of migratory ungulates, changing ecological conditions across its boundaries are posing new and complex challenges to our understanding of migratory populations. This study is focused on the Clarks Fork elk herd, a partially-migratory population whose migratory subpopulation spends it summers in high-elevation alpine and subalpine habitats inside YNP’s northeastern boundary. In the past decade, productivity of migratory elk has declined sharply while the non-migratory herd segment has remained stable or grown on private lands east of YNP. Early findings have revealed that pregnancy of migratory elk is exceptionally low, suggesting that YNP migrants are nutritionally stressed. Although fat gain in temperate ungulates is conventionally thought to be limited by summer forage quality, and the park has lately experienced prolonged drought, some have suggested that physiologically-costly, wolf-induced antipredator behaviors are reducing elk condition and reproductive performance. We are investigating the relative influence of habitat conditions versus antipredator behavior on the body-fat levels and reproduction of Clarks Fork elk. Our results will help YNP, the Wyoming Game and Fish Department (WGFD), the US Fish and Wildlife Service (USFWS), and other state and federal management agencies understand and manage elk populations and their migrations in the post-wolf reintroduction era.

Yellowstone Pronghorn Alter Resource Selection After Sagebrush Decline

Animals alter resource use as conditions change and these changes could have significant consequences on demography. We generated a logistic resource selection probability function for habitat use and estimated percent composition of diets by pronghorn (Antilocapra americana) in Yellowstone National Park during winter to assess if selection of sagebrush (Artemisia) has changed since the 1960s, corresponding with diminishing sagebrush and increasing seral species such as rabbitbrush (Chrysothamnus). We located 37 radiocollared adult females in 1,440 different groups during December 1999 through March 2005 and compared habitat attributes to 9,347 randomly selected points from the winter range. Pronghorn preferred greasewood (Sarcobatus vermiculatus) and selected grasslands in comparison to the sagebrush cover type. The relative selection against sagebrush may stem from a substantial decrease in this plant type on the winter range by the 1960s due to intense browsing by congregated ungulates. The percent composition of sagebrush in the winter diets of pronghorn decreased from 67% during 1985–1988 to <10% during 2000–2001, while rabbitbrush increased from 5% to 60%. These findings and the results of companion time-series analyses suggest the winter range for Yellowstone pronghorn may not support larger populations (>500) of pronghorn for sustained periods, as occurred historically. Similar effects from habitat fragmentation and degradation face managers of migratory ungulates worldwide.