Native Ungulates Research Articles

Cougar kill rates and prey selection in a multiple-prey system in northeast Oregon

Cougars (Puma concolor) are a primary predator of mule deer (Odocoileus hemionus) and elk (Cervus elaphus) throughout western North America. Effective management of predator-prey systems requires a solid understanding of kill rates, prey use, and selection. We implemented a 3-year study in northeast Oregon to investigate cougar diet, kill rates, and prey selection in a multiple-prey system to assess the degree to which patterns in cougar predation may be generalizable across systems and to identify selective predation patterns of cougars that may affect ungulate populations. We marked 25 adult cougars with global positioning system (GPS) collars and monitored predation sequences for 7,642 days to identify kill sites. In field investigation of kill sites, we identified remains of 1,213 prey items killed by cougars, of which 1,158 (95.4%) were native ungulates. On average, cougars killed 1.03 ungulates/week (95% CI = 0.92–1.14), but kill rates varied by season, sex, and reproductive status of cougars. Cougars killed ungulate prey 1.55 (95% CI = 1.47–1.66) times more frequently during summer (May–Oct) than winter (Nov–Apr). Kill rates were higher in summer because juvenile ungulates were the most frequently killed prey item and were smaller than prey killed in winter. Female cougars with kittens >6 months old killed prey more frequently than males, solitary females, and females with kittens <6 months old likely in response to the increased energetic burden of raising kittens. Male cougars killed larger prey than females, which likely explains why males killed at similar rates as solitary females, despite the larger body size of males. We documented patterns in prey selection influenced by season and demographic classification of cougars. Diets of male cougars included roughly equal amounts of elk (52.2%) and deer (47.8%), whereas diets of females were dominated by deer (74.6%). Male and female cougars displayed strong patterns of selection for elk calves during summer. During winter, female cougars selected deer fawns and males selected elk calves. Female cougars with kittens >6 months old demonstrated little selection for any age class or species of prey, highlighting an opportunistic foraging strategy to maximize energy gains while feeding young. Across all cougars, we observed a pattern of selection for adult male deer during winter but not summer and did not observe patterns of selection for adult elk according to sex. Our results strongly supported the hypothesis proposed by [Knopff et al. (2010) Journal of Wildlife Management, 74: 1435–1447] that cougar predation is influenced by season and demographic classifications of cougars and our results provide strong evidence that this hypothesis should be generalizable to other areas. The patterns of selection for juvenile elk and deer suggested wildlife managers should consider the potential negative effects of cougars on ungulate populations in areas where juvenile recruitment has been chronically low. © 2014 The Wildlife Society.

Final Gondwana breakup: The Paleogene South American native ungulates and the demise of the South America–Antarctica land connection

The biogeographic hypothesis more accepted today is that Antarctica (West Antarctica) and southern South America (Magellan region, Patagonia) were connected by a long and narrow causeway (Weddellian Isthmus) between the Antarctic Peninsula and South America since the Late Cretaceous (Campanian) until the Early Paleogene allowing terrestrial vertebrates to colonize new frontiers using this land bridge. Stratigraphically calibrated phylogenies including large, terrestrial native ungulates Litopterna and Astrapotheria taxa reveal long ghost lineages that extended into the Late Paleocene and provide evidence for the minimum times at which these “native ungulates” were present both on Antarctica and South America. Based on these results we estimate that the Weddellian Isthmus was functional as a land bridge until the Late Paleocene. Our data place the disconnection between Antarctica and South America in the Late Paleocene, indicating that the terrestrial faunistic isolation (Simpson's “splendid isolation”) in South America begun at the end of the Paleocene (~56 to 57m.y.). This faunistic isolation is documented to have occurred at least 25Ma before the existence of deep-water circulation conditions in Drake Passage (~30m.y.) based on the onset of seafloor spreading in the west Scotia Sea region. We hypothesize that in the early stages of extension (Late Paleocene, ~55m.y.) a wide and relatively shallow epicontinental sea developed between the Antarctic Peninsula and South America drowning the Weddellian Isthmus and preventing the faunal interchange for obligate cursorial terrestrial forms.

The oldest mammals from Antarctica, early Eocene of the La Meseta Formation, Seymour Island

AbstractNew fossil mammals found at the base of Acantilados II Allomember of the La Meseta Formation, from the early Eocene (Ypresian) of Seymour Island, represent the oldest evidence of this group in Antarctica. Two specimens are here described; the first belongs to a talonid portion of a lower right molar assigned to the sparnotheriodontid litoptern Notiolofos sp. cf. N. arquinotiensis. Sparnotheriodontid were medium‐ to large‐sized ungulates, with a wide distribution in the Eocene of South America and Antarctica. The second specimen is an intermediate phalanx referred to an indeterminate Eutheria, probably a South American native ungulate. These Antarctic findings in sediments of 55.3 Ma query the minimum age needed for terrestrial mammals to spread from South America to Antarctica, which should have occurred before the final break‐up of Gondwana. This event involves the disappearance of the land bridge formed by the Weddellian Isthmus, which connected West Antarctica and southern South America from the Late Cretaceous until sometime in the earliest Palaeogene.

Holistic Management: Misinformation on the Science of Grazed Ecosystems

Over 3 billion hectares of lands worldwide are grazed by livestock, with a majority suffering degradation in ecological condition. Losses in plant productivity, biodiversity of plant and animal communities, and carbon storage are occurring as a result of livestock grazing. Holistic management (HM) has been proposed as a means of restoring degraded deserts and grasslands and reversing climate change. The fundamental approach of this system is based on frequently rotating livestock herds to mimic native ungulates reacting to predators in order to break up biological soil crusts and trample plants and soils to promote restoration. This review could find no peer-reviewed studies that show that this management approach is superior to conventional grazing systems in outcomes. Any claims of success due to HM are likely due to the management aspects of goal setting, monitoring, and adapting to meet goals, not the ecological principles embodied in HM. Ecologically, the application of HM principles of trampling and intensive foraging are as detrimental to plants, soils, water storage, and plant productivity as are conventional grazing systems. Contrary to claims made that HM will reverse climate change, the scientific evidence is that global greenhouse gas emissions are vastly larger than the capacity of worldwide grasslands and deserts to store the carbon emitted each year.

A priori assessment of reintroduction strategies for a native ungulate: using HexSim to guide release site selection

Reintroduction of native species to unoccupied portions of their historical range is a common management strategy to enhance the future viability of animal populations. This approach has met with mixed success, due to unforeseen impacts caused by human or other factors. Some of these impacts could potentially be mitigated through the use of anticipatory modeling coupled with appropriate management strategies prior to release. As part of an ongoing restoration program, we evaluated a portion of the former range of the tule elk (Cervus elaphus nannodes) in the Central Valley of California for potential reintroduction of a free-ranging herd. We used a new spatially explicit population model (HexSim) to analyze four different elk release scenarios. Each scenario corresponded to a different release location, and the model was used to compare simulated elk movement and population dynamics 25 years into the future. We also used HexSim to identify likely locations of human–elk conflict. Population forecasts after the 25-year period were highest (mean female population size of 169.6 per iteration) and potentially harmful barrier interactions were lowest (mean 8.6 per iteration) at the East Bear Creek site. These results indicate the East Bear Creek site release scenario as the most likely to result in a successful elk reintroduction, producing the most elk and generating the fewest human conflicts. We found HexSim to be a useful tool for this type of reintroduction planning and believe that other reintroduction efforts could benefit from this type of anticipatory modeling.

Mule deer–cattle interactions in managed coniferous forests during seasonal grazing periods in southern British Columbia, Canada

Context In young forests of the Pacific North-west of North America, the potential impacts of domestic grazing by cattle (Bos taurus) on forest ecosystems and native ungulates such as mule deer (Odocoileus hemionus) are poorly understood. It is not clear how cattle and deer may interact in young forests used for summer range by both ungulates, and winter range used by deer, where pre-commercial thinning (PCT) and fertilisation enhance both timber and forage. Aims To test the following two hypotheses: (H1) that PCT and repeated fertilisation of young lodgepole pine (Pinus contorta var. latifolia) stands would increase relative habitat use by cattle; and (H2) that increased use of forested range by cattle would result in decreased use by mule deer. Methods Replicate study areas were located near Summerland, Kelowna, and Williams Lake in south-central British Columbia, Canada. Each study area had the following nine treatments: four pairs of stands thinned to densities of ~250 (very low), ~500 (low), ~1000 (medium), and ~2000 (high) stems ha–1 with one stand of each pair fertilised five times at 2-year intervals. Relative habitat use was measured by counting cowpies for cattle in summer and pellet groups for deer in summer and winter periods 1998–2003. Key results Relative habitat use by cattle was significantly enhanced by fertiliser treatments and heavy thinning, supporting H1. Relative habitat use by deer during summer periods was not affected by stand density, but was significantly higher in fertilised than unfertilised stands, with no difference in winter months, thereby not supporting H2. Conclusions Summer habitat use by mule deer appeared to be a function of forage opportunities and no significant correlations in relative habitat use between cattle and mule deer during the summer were detected. Negative correlations were better explained by the need for tree cover by deer during severe winter conditions than a negative response to cattle grazing. Implications Domestic grazing by cattle may be compatible with native ungulates such as mule deer, at least in those forest sites that are managed intensively for timber production. Fertilisation may result in sufficient forage production in the understorey vegetation of these forest ecosystems, to compensate for cattle grazing that reduces the live forage biomass.

Megafauna: giant beasts of Pleistocene South America

Megafauna: giant beasts of Pleistocene South America

Native ungulates of diverse body sizes collectively regulate long‐term woody plant demography and structure of a semi‐arid savanna

Summary Large mammalian herbivores are well recognized to play important roles in regulating woody cover and biomass in savannas, but the extent to which browsing ungulates are capable of regulating woody populations in the absence of other disturbances such as fire is unclear. Moreover, the degree to which browser effects on savannas operate through effects on woody plant recruitment vs. mortality has rarely been examined. We conducted a 10‐year, replicated herbivore exclusion experiment in a semi‐arid savanna in East Africa (mean annual rainfall = 514 mm), where fires have been actively suppressed for decades. Browsers dramatically influenced recruitment, growth and mortality of all size classes of woody vegetation. A decade of herbivore exclusion resulted in a sevenfold increase in recruitment, a 2.5‐fold decrease in mortality and a threefold increase in woody biomass inside exclosures, while biomass outside exclosures remained relatively unchanged. At the plant community level, extensive browsing of seedlings by small‐bodied ungulates suppressed woody recruitment in this semi‐arid system, generating a ‘browsing trap’ comparable to the ‘fire trap’ reported for mesic systems. Browsing by large‐ and medium‐bodied ungulates reduced both growth and survival of individuals in larger size classes. At the plant species level, browser impacts were variable. Although browsers negatively influenced recruitment of all species, they had little to no impact on the mortality of some dominant species, resulting in a long‐term, browser‐driven shift in woody species composition that was largely mediated via their differential effects on plant mortality rates rather than recruitment. Synthesis. Our results demonstrate unequivocally that, even in the absence of fire, native browsing ungulates can exert dramatic ‘top‐down’ controls in semi‐arid savannas, influencing all aspects of woody plant demography. Besides suppressing woody plant recruitment, browsers can also have substantial cumulative long‐term impacts on growth and mortality rates of woody plants, including adults, which can differ between species in ways that fundamentally alter the structure and function of woody vegetation. In semi‐arid rangelands, intact communities of native browsing ungulates thus provide a critical ecosystem service by regulating woody cover, and their removal (or extinction) from these systems can lead to rapid woody encroachment.

Conservation and management of ungulates in North America

The North American Model of Wildlife Conservation had its genesis, in part, with the conservation of native ungulates. Thus, it is important to understand what these species are and how they have been and are, currently, managed. Ungulates are hooved quadrupeds that include those that are odd-toed (e.g. tapirs [Tapirus bairdii]) and even-toed (e.g. deer). Contemporary management of the ungulates evolved through three stages: exploitation, concern for survival and conservation through wise use. The success of conservation of ungulates has been attributed to the merger of biology, an understanding of habitat and the role of human dimensions. This triad of wildlife management has been effective. Most ungulate populations in North America have been restored; viable populations exist. Challenges to the conservation of large mammals remain, however, including increased human population growth, climate change and sources of funding.

Disentangling herbivore impacts on Populus tremuloides: a comparison of native ungulates and cattle in Canada’s Aspen Parkland

Ungulates impact woody species' growth and abundance but little is understood about the comparative impacts of different ungulate species on forest expansion in savanna environments. Replacement of native herbivore guilds with livestock [i.e., beef cattle (Bos taurus)] has been hypothesized as a factor facilitating trembling aspen (Populus tremuloides Michx.) encroachment into grasslands of the Northern Great Plains. We used a controlled herbivory study in the Parklands of western Canada to compare the impact of native ungulates and cattle on aspen saplings. Native ungulate treatments included a mixed species guild and sequences of herbivory by different ungulates [bison (Bison bison subsp. bison), elk (Cervus elaphus) then deer (Odocoileus hemionus); or deer, elk, then bison]. Herbivory treatments were replicated in three pastures, within which sets of 40 marked aspen saplings (<1.8 m) were tracked along permanent transects at 2-week intervals, and compared to a non-grazed aspen stand. Stems were assessed for mortality and incremental damage (herbivory, leader breakage, stem abrasion and trampling). Final mortality was greater with exposure to any type of herbivore, but remained similar between ungulate treatments. However, among all treatments, the growth of aspen was highest with exposure only to cattle. Herbivory of aspen was attributed primarily to elk within the native ungulate treatments, with other forms of physical damage, and ultimately sapling mortality, associated with exposure to bison. Overall, these results indicate that native ungulates, specifically elk and bison, have more negative impacts on aspen saplings and provide evidence that native and domestic ungulates can have different functional effects on woody plant dynamics in savanna ecosystems.

Skull Geometric Morphometrics and Paleoecology of Santacrucian (Late Early Miocene; Patagonia) Native Ungulates (Astrapotheria, Litopterna, and Notoungulata)

Three orders of South American extinct native ungulates are recorded from the Santa Cruz Formation along the Atlantic coast of Patagonia: Notoungulata (Adinotherium Ameghino, Nesodon Owen, Interatherium Ameghino, Protypotherium Ameghino, Hegetotherium Ameghino, and Pachyrukhos Ameghino), Litopterna (Theosodon Ameghino, Anisolophus Burmeister, Tetramerorhinus Ameghino, Diadiaphorus Ameghino, and Thoatheriurn Ameghino), and Astrapotheria (Astrapotherium Burmeister). An ecomorphological study based on geometric morphometries of the masticatory apparatus was performed. The reference sample included 618 extant specimens of the orders Artiodactyla, Perissodactyla, Hyracoidea, and Diprotodontia. Thirty six cranial and 27 mandibular three-dimensional landmarks were digitized. Allometric scaling, principal component analyses, and phylogenetic generalized estimating equations on the cranium and mandible were preformed. Analyses of cranial shape show strong phylogenetic constraints, whereas the mandibular analyses show a functional pattern related to habitat/ diet and hypsodonty. The extant brachydont ungulates from closed habitats show a more elongated and narrower mandibular symphysis with a lower mandibular corpus, than hypsodont, open habitat species. The latter have short symphyses with a high, curved mandibular corpus. This morphological pattern was also present among Santacrucian ungulates, allowing characterization of notoungulates mainly as open habitats dwellers, with some taxa foraging on grass (Protypotherium, Interatherium), and others on grass and leaves {Hegetotherium, Pachyrukhos, and Adinotheriurn), depending on the availability. Nesodon may have dwelled in mixed habitats and had a mixed feeding behavior, while small proterotheriids {Anisolophus and Thoatheriurn) may have fed predominantly on dicotyledonous plants. The remaining litopterns {Tetramerorhinus, Diadiaphorus, and Theosodon) and Astrapotherium may have foraged in closed habitats and fed on dicotyledonous plants.

Range Management Affects Native Ungulate Populations in Península Valdés, a World Natural Heritage

Sheep rearing is the main productive activity in Patagonian rangelands, where guanacos are the only native ungulate. Ranchers perceive a decrease in range carrying capacity as guanaco numbers increase, therefore guanaco conservation within private lands becomes a considerable challenge. This issue is particularly evident in the World Natural Heritage Península Valdés (PV), where there is a need to harmonize livestock production and biodiversity conservation. While sheep rearing prevails as the primary land use in the area, some ecotourism initiatives have been implemented to complement livestock production. In order to study how land use affected guanaco distribution, we characterized PV's ranches in terms of land subdivision, primary productivity, stocking-rate and management type, and assess how these variables affected guanaco encounter rates. Smaller ranches were composed of smaller paddocks (mean size 4.8 km2), which showed higher values of the remote-sensing derived Enhance Vegetation Index (EVI) (mean 0.14) and held higher sheep densities (mean 108.0 sheep/km2), while larger management units (mean size 23.8 km2), showed lower EVI values (mean 0.12) and lower stocking-rates (mean 36.7 sheep/km2). This pattern suggests that primary productivity has been a decisive factor to determine the minimal paddock size set by ranchers in PV, apparently precluding excessive land-subdivision in less productive areas. Guanaco encounter rate, expressed as number of guanacos per travelled kilometre, was inversely related to EVI and stocking-rate. However, land subdivision was the better predictor of guanaco encounter-rate within only sheep ranches, finding more guanacos per kilometre as paddock size increased. In contrast, in ranches where ecotourism was implemented as a complementary activity, guanaco encounter-rates were greater, regardless of paddock size. Our results suggest that the implementation of an additional activity by which landowners derive benefits from wildlife has prompted a beneficial outcome for guanacos, presumably through a decrease in harassment intensity. Finally, we propose possible mechanisms by which land subdivision may affect guanaco distribution and potential alternatives for the inclusion of wildlife conservation in a context of extensive livestock production.

Habitat Selection and Diet Composition of Reintroduced Native Ungulates in a Fire-Managed Tallgrass Prairie Reconstruction

In an effort to understand native ungulate behavior in a fire-managed tallgrass prairie reconstruction effort, we conducted a two year habitat selection and diet composition study of reintroduced populations of elk ( Cervus elaphus ) and bison ( Bison bison ) in southern Iowa. Our study included intensive surveys of ungulate group locations throughout the growing season, fecal sample collections for microhistological diet analysis, and plant community surveys. Bison and elk use of the reconstructed grassland was spatially nonrandom. Available cover and farthest distance from the enclosure fence strongly influenced habitat selection by elk. Bison segregated into a small bull group consisting of older bulls and a larger mixed group that included cows, yearlings, calves, and young bulls. The bull group selected areas with high percent cover of native plants, steeper slopes, and older burn areas. The mixed group strongly selected for recently burned areas with high native plant cover and eastern aspects. Elk consumed mostly non-native forbs while over 90% of the bison diet consisted of graminoid species. Although bison did not consume significantly different proportions of native species compared to non-natives, their selection of habitat was strongly related to presence of native plants, especially in combination with burned areas. The reintroduced ungulates behaved as three functionally distinct groups. Based on behavioral and group size differences, the large mixed sex/age bison group is likely to have the greatest impact on the fire-managed reconstruction, while the effects of the bison bull groups and elk are likely to have more localized effects on the reconstructed prairie.

SKULL GEOMETRIC MORPHOMETRICS AND PALEOECOLOGY OF SANTACRUCIAN (LATE EARLY MIOCENE; PATAGONIA) NATIVE UNGULATES (ASTRAPOTHERIA, LITOPTERNA, AND NOTOUNGULATA)

Three orders of South American extinct native ungulates are recorded from the Santa Cruz Formation along the Atlantic coast of Patagonia: the Notoungulata (Adinotherium, Nesodon, Interatherium, Protypotherium, Hegetotherium and Pachyrukhos), the Litopterna (Theosodon, Anisolophus, Tetramerorhinus, Diadiaphorus and Thoatherium) and the Astrapotheria (Astrapotherium). This work is an ecomorphologic study of these taxa based on geometric morphometrics of the masticatory apparatus. As a reference sample, 618 extant specimens of the orders Artiodactyla, Perissodactyla, Hyracoidea and Diprotodontia were included. Thirty-six cranial and 27 mandibular three-dimensional landmarks were digitized. Allometric scaling, principal component analyses, and phylogenetic generalized estimating equations on the cranium and mandible were preformed separately. The cranial analyses show strong phylogenetic constrains, whereas the mandibular analyses show a functional pattern related to habitat-diet and hypsodonty. The extant brachydont and closed habitat ungulates show a more elongated and narrower mandibular symphysis with a lower mandibular corpus, than hypsodont, open habitat species. The latter have short symphyses with a high, curved mandibular corpus. This general pattern was was also present among Santacrucian ungulates, which permit characterization of the notoungulates mainly as open habitats dwellers, with some foraging on grass (Protypotherium, Interatherium), and others on grass and leaves (Hegetotherium, Pachyrukhos and Adinotherium), depending on the availability. Nesodon may have dwelled in mixed habitats and had a mixed feeding behavior, while small proterotheriids (Anisolophus and Thoatherium) may have fed predominantly on dicotyledonous plants. The remaining litopterns (Tetramerorhinus, Diadiaphorus and Theosodon) and Astrapotherium may have foraged in closed habitats and fed on dicotyledonous plants.

Elk herbivory alters small mammal assemblages in high‐elevation drainages

Heavy herbivory by ungulates can substantially alter habitat, but the indirect consequences of habitat modification for animal assemblages that rely on that habitat are not well studied. This is a particularly important topic given that climate change can alter plant-herbivore interactions. We explored short-term responses of small mammal communities to recent exclusion of Rocky Mountain elk (Cervus elaphus) in high-elevation riparian drainages in northern Arizona, where elk impacts on vegetation have increased over the past quarter century associated with climate change. We used 10-ha elk exclosures paired with unfenced control drainages to examine how browsing influenced the habitat use, relative abundance, richness and diversity of a small mammal assemblage. We found that the small mammal assemblage changed significantly after 5years of elk exclusion. Relative abundance of voles (Microtus mexicanus) increased in exclosure drainages, likely due to an increase in habitat quality. The relative abundances of woodrats (Neotoma neomexicana) and two species of mice (Peromyscus maniculatus and P.boylii) decreased in the controls, while remaining stable in exclosures. The decline of mice in control drainages was likely due to the decline in shrub cover that they use. Thus, elk exclusion may have maintained or improved habitat for mice inside the exclosures while habitat quality and mouse abundance both declined outside the fences. Finally, small mammal species richness increased in the exclosures relative to the controls while species diversity showed no significant trends. Together, our results show that relaxation of heavy herbivore pressure by a widespread native ungulate can lead to rapid changes in small mammal assemblages. Moreover, exclusion of large herbivores can yield rapid responses by vegetation that may enhance or maintain habitat quality for small mammal populations.

Adapting to Climate Change on Western Public Lands: Addressing the Ecological Effects of Domestic, Wild, and Feral Ungulates

Climate change affects public land ecosystems and services throughout the American West and these effects are projected to intensify. Even if greenhouse gas emissions are reduced, adaptation strategies for public lands are needed to reduce anthropogenic stressors of terrestrial and aquatic ecosystems and to help native species and ecosystems survive in an altered environment. Historical and contemporary livestock production-the most widespread and long-running commercial use of public lands-can alter vegetation, soils, hydrology, and wildlife species composition and abundances in ways that exacerbate the effects of climate change on these resources. Excess abundance of native ungulates (e.g., deer or elk) and feral horses and burros add to these impacts. Although many of these consequences have been studied for decades, the ongoing and impending effects of ungulates in a changing climate require new management strategies for limiting their threats to the long-term supply of ecosystem services on public lands. Removing or reducing livestock across large areas of public land would alleviate a widely recognized and long-term stressor and make these lands less susceptible to the effects of climate change. Where livestock use continues, or where significant densities of wild or feral ungulates occur, management should carefully document the ecological, social, and economic consequences (both costs and benefits) to better ensure management that minimizes ungulate impacts to plant and animal communities, soils, and water resources. Reestablishing apex predators in large, contiguous areas of public land may help mitigate any adverse ecological effects of wild ungulates.

A Bayesian Approach to Landscape Ecological Risk Assessment Applied to the Upper Grande Ronde Watershed, Oregon

ABSTRACT We present a Bayesian network model based on the ecological risk assessment framework to evaluate potential impacts to habitats and resources resulting from wildfire, grazing, forest management activities, and insect outbreaks in a forested landscape in northeastern Oregon. The Bayesian network structure consisted of three tiers of nodes: landscape disturbances, habitats, and the ecological resources or endpoints of interest to land managers. Nodes at each tier were linked to lower nodes if ecological and spatial relationships existed between them. All parameters had four potential discrete states: zero, low, medium, and high. Our model reliably predicted probable risk to habitats and endpoints from natural and anthropogenic disturbances. The disturbances most likely to transform habitats and effect ecological resources were forest management and wildfire. Of the six habitats, moist forest (characterized by Douglas fir and grand fir) was found to be at greatest risk of ecological impacts. The management endpoint with the highest likelihood of impact was historical range of variability (HRV) for salmon habitat, followed by recreation (hunting native ungulates) and HRV wildfire. We found that the Bayesian approach to ecological risk assessment was a useful method to assess potential impacts to ecological resources resulting from forest management and natural disturbances.

Modelación de la distribución potencial y el efecto del cambio de uso de suelo en la conservación de los ungulados silvestres del Bajo Balsas, México

White-tailed deer Odocoileus virginianus and collared peccary Pecari tajacu are the two native ungulates species present in the Bajo Balsas region. Both are very important from an ecological, social and economical perspective. Therefore, evaluate the effects of changes in land use on their distribution is basic for conservation and management proposes. In this paper we used the ecological niche modeling to generate an hypothetical scenario about the potential distribution of these two species in this region, then using geographic information systems we obtained some landscape metrics to evaluate how changes in land use affects these distributions; finally, we analyzed the protection provided by the Biosphere Reserve of Zicuiran-Infiernillo (RBZI) to these ungulates. The potential distribution of white-tailed deer covered an area of 5,321 km2 and the collared peccary of 5,762 km2. As a result of changes in land use both species lose in their potential distribution an area of 1,011 km2 and 1,303 km2, respectively. The RBZI protects approximately 36% of the distributions of these ungulates in Bajo Balsas. Considering the small patches sizes to maintain minimum viable populations, We suggest that the best strategy for the conservation of these species in this region is a scheme based on source-sink dynamics, taking as a source the RBZI and as a sink the management units (UMA) that are already established in the area.

Interactive effects of insects and ungulates on root growth in a native grassland

Insects and ungulates co‐occur in grasslands, often feeding on the same plants at the same time and potentially having interactive effects on plant growth. Further, ungulate–insect interactions may differ between native ungulate guilds and domesticated cattle. Despite the prevalence of insects and ungulates in native grasslands, experiments simultaneously manipulating the densities of both these groups are rare. Using large, replicated paddocks, as well as insecticide application, we restricted access to vegetation by each group of herbivores. We also manipulated the species identity of the ungulate assemblage, allowing us to determine whether there are differential effects between native ungulate guilds (bison, elk and deer) and cattle on plant biomass. We found interactive effects of insect and ungulate herbivores on root growth. When insects were suppressed, both native ungulates and cattle caused an approximate doubling of root biomass. However, this stimulatory effect of ungulate grazing was eliminated when insects were also present. In contrast, neither insects nor ungulates had significant effects on shoot biomass at these densities. As a result, the dominant effects of above‐ground herbivory was on belowground plant growth. We suggest the effects of insect and ungulate assemblages on root biomass appear important in regulating primary production in this grassland and may account for some of the contradictory plant responses to ungulate herbivory in the literature.

Can rare positive interactions become common when large carnivores consume livestock?

Livestock populations in protected areas are viewed negatively because of their interaction with native ungulates through direct competition for food resources. However, livestock and native prey can also interact indirectly through their shared predator. Indirect interactions between two prey species occur when one prey modifies either the functional or numerical responses of a shared predator. This interaction is often manifested as negative effects (apparent competition) on one or both prey species through increased predation risk. But indirect interactions can also yield positive effects on a focal prey if the shared predator modifies its functional response toward increased consumption of an abundant and higher-quality alternative prey. Such a phenomenon between two prey species is underappreciated and overlooked in nature. Positive indirect effects can be expected to occur in livestock-dominated wildlife reserves containing large carnivores. We searched for such positive effects in Acacia-Zizhypus forests of India's Gir sanctuary where livestock (Bubalus bubalis and Bos indicus) and a coexisting native prey (chital deer, Axis axis) are consumed by Asiatic lions (Panthera leo persica). Chital vigilance was higher in areas with low livestock density than in areas with high livestock density. This positive indirect effect occurred because lion predation rates on livestock were twice as great where livestock were abundant than where livestock density was low. Positive indirect interactions mediated by shared predators may be more common than generally thought with rather major consequences for ecological understanding and conservation. We encourage further studies to understand outcomes of indirect interactions on long-term predator-prey dynamics in livestock-dominated protected areas.