Large Herbivore Populations Research Articles

Morphological Traits Are Not Consistently Related to Population Size in Four Migratory Caribou Populations Across North America.

To develop effective management to maintain or restore populations of large herbivores, wildlife managers require sound empirical data on their variations in size and associated parameters. Many studies have highlighted links between morphological traits of individuals and population density; however, less attention has been devoted to whether or not morphological traits can reliably inform on population size in years when no population estimates are available. We evaluated the relationships between three morphological traits (hind foot length, body mass, and body fat) and population size interpolated over three decades, for four migratory caribou (Rangifer tarandus) herds in northern Canada and Alaska. Our sample included 8865 measurements of 4473 individuals. We used a Bayesian modeling approach to evaluate the relationships between morphology and population size across different sex and age classes, considering different temporal scales and, when possible, phases of population growth or decline. We found that morphological traits were not consistently linked to population size. Statistically significant relationships existed for some combinations of herd and age classes, but weak to absent relationships were more common. Our study suggests that morphological traits alone cannot replace data obtained from aerial surveys to approximate population size when population trends are unknown. We discuss the usefulness of morphological traits to explain population size, and recognize their role as complementary metrics to inform the management and conservation of large herbivores, but conclude that morphological data should not be used to predict population size without information on population trends.

The contribution of community-based conservation models to conserving large herbivore populations

In East Africa, community-based conservation models (CBCMs) have been established to support the conservation of wildlife in fragmented landscapes like the Tarangire Ecosystem, Tanzania. To assess how different management approaches maintained large herbivore populations, we conducted line distance surveys and estimated seasonal densities of elephant, giraffe, zebra, and wildebeest in six management units, including three CBCMs, two national parks (positive controls), and one area with little conservation interventions (negative control). Using a Monte-Carlo approach to propagate uncertainties from the density estimates and trend analysis, we analyzed the resulting time series (2011–2019). Densities of the target species were consistently low in the site with little conservation interventions. In contrast, densities of zebra and wildebeest in CBCMs were similar to national parks, providing evidence that CBCMs contributed to the stabilization of these migratory populations in the central part of the ecosystem. CBCMs also supported giraffe and elephant densities similar to those found in national parks. In contrast, the functional connectivity of Lake Manyara National Park has not been augmented by CBCMs. Our analysis suggests that CBCMs can effectively conserve large herbivores, and that maintaining connectivity through CBCMs should be prioritized.

Long-term data reveal fitness costs of anthropogenic prey depletion for a subordinate competitor, the African wild dog (Lycaon pictus).

Within carnivore guilds, dominant competitors (e.g., lions, Panthera leo) are limited primarily by the density of prey, while subordinate competitors (e.g., African wild dogs, Lycaon pictus) have been limited by the density of dominant competitors. Historically, the fitness and population density of subordinate competitors have not been tightly linked to prey density. However, populations of large herbivores have declined substantially across sub-Saharan Africa due to human impacts, and where prey depletion is severe, fitness costs for competitive subordinates may begin to outweigh the benefits of competitive release. Using long-term intensive monitoring of African wild dogs in Zambia's Luangwa Valley Ecosystem (LVE), we tested the effects of prey depletion on survival and reproduction. We hypothesized that African wild dog fitness would be lower in prey-depleted areas, despite lower lion densities. Our study area included four contiguous regions that varied in protection level, prey density, and lion density. We fit Bayesian Cormack-Jolly-Seber and closed-capture models to estimate effects on survival and population density, and generalized linear models to estimate effects on reproductive success. We found that the LVE is a stronghold for African wild dogs, with an estimated median density of 4.0 individuals/100 km2. Despite this high density, survival and reproduction differed among regions, and both components of fitness were substantially reduced in the region with the lowest prey density. Anthropogenic prey depletion is becoming an important limiting factor for African wild dogs. If prey depletion (or any other form of habitat degradation) becomes severe enough that its fitness costs outweigh the benefits of competitive release, such changes can fundamentally alter the balance between limiting factors for competitively subordinate species.

A general, resource‐based explanation for density dependence in populations of large herbivores

AbstractThe discipline of ecology seeks to understand how ecosystems, communities, and populations are regulated. A ubiquitous mechanism of population regulation of consumers is that capturing energy and nutrients in sufficient quantities for survival and reproduction becomes more difficult as population density increases. Extensive evidence has revealed that populations of large herbivores are often regulated by density dependence, defined as the reduction in the per‐capita population growth rate that occurs as populations grow large. Diminished body mass of individuals has been repeatedly observed in high‐density populations, implicating compromised nutrition as the primary cause of density dependence. However, there is no general explanation for why these nutritional deficiencies occur. Recent work demonstrated that reduced food intake rates resulting from the functional response of herbivores to depleted plant biomass does not provide a sensible explanation for density dependence because rates of food intake of herbivores are often insensitive to changes in plant biomass. A new model of feedbacks from plant biomass to herbivores shows how reduced nutrition of herbivores can result from increased dilution of nutrients in the plant tissue they consume as populations grow, even when their rate of consumption of plants remains constant. The model contains parameters that can be scaled to body mass, allowing unusually general predictions. The model shows that convex, concave, and linear relationships between the per‐capita growth rate and population density can arise from the effects of depletion of plant biomass by herbivore foraging. The model is the first to explicitly include spatial variance in the nutritional quality of plants as a general driver of herbivore population dynamics. I show how regulation of herbivore abundance by plant nutrients can occur, even when a large fraction of the consumable plant biomass remains uneaten, providing a simple, mechanistic explanation for bottom‐up control of population dynamics of primary consumers in a “green world.”

Predation risk drives long-term shifts in migratory behaviour and demography in a large herbivore population.

Migration is an adaptive life-history strategy across taxa that helps individuals maximise fitness by obtaining forage and avoiding predation risk. The mechanisms driving migratory changes are poorly understood, and links between migratory behaviour, space use, and demographic consequences are rare. Here, we use a nearly 20-year record of individual-based monitoring of a large herbivore, elk (Cervus canadensis) to test hypotheses for changing patterns of migration in and adjacent to a large protected area in Banff National Park (BNP), Canada. We test whether bottom-up (forage quality) or top-down (predation risk) factors explained trends in (i) the proportion of individuals using 5 different migratory tactics, (ii) differences in survival rates of migratory tactics during migration and whilst on summer ranges, (iii) cause-specific mortality by wolves and grizzly bears, and (iv) population abundance. We found dramatic shifts in migration consistent with behavioural plasticity in individual choice of annual migratory routes. Shifts were inconsistent with exposure to the bottom-up benefits of migration. Instead, exposure to landscape gradients in predation risk caused by exploitation outside the protected area drove migratory shifts. Carnivore exploitation outside the protected area led to higher survival rates for female elk remaining resident or migrating outside the protected area. Cause-specific mortality aligned with exposure to predation risk along migratory routes and summer ranges. Wolf predation risk was higher on migratory routes than summer ranges of montane-migrant tactics, but wolf predation risk traded-off with heightened risk from grizzly bears on summer ranges. A novel eastern migrant tactic emerged following a large forest fire that enhanced forage in an area with lower predation risk outside of the protected area. The changes in migratory behaviour translated to population abundance, where abundance of the montane-migratory tactics declined over time. The presence of diverse migratory life histories maintained a higher total population abundance than would have been the case with only one migratory tactic in the population. Our study demonstrates the complex ways in which migratory populations change over time through behavioural plasticity and associated demographic consequences because of individuals balancing predation risk and forage trade-offs.

Monitoring spatiotemporal dynamics of large herbivores across an African rangeland using hierarchical multi‐species distance sampling

AbstractA relative lack of standardised long‐term monitoring data often limits the ability of African conservancies to quantify their efficacy to protect wildlife. In this study, we combined eight 2‐km long transects surveyed monthly between October 2017 and March 2020 (total 240 transects sampled) with a hierarchical multi‐species and multi‐season distance sampling modelling framework to: (1) estimate monthly density of an ensemble of 10 different large herbivores and (2) understand how species respond to changes in vegetation productivity and time across the Naboisho Conservancy in the Greater Mara Ecosystem, Kenya. We documented a total of 55,298 individuals from 6830 animal groups. The median coefficient of variation for all density estimates was 27.67%. On average, number of groups was higher at intermediate levels of vegetation productivity. We found that in general, populations of large herbivores remained stable in the conservancy during the study period, except for wildebeest which decreased in density. We showed that multi‐species monitoring frameworks can be used to understand how species abundance changes across space and time, providing indications as to how they are responding to environmental dynamics or management prescriptions—both of which are valuable tools for under‐resourced wildlife conservancies.

Anthropogenic supply of nutrients in a wildlife reserve may compromise conservation success

In nutrient-poor wildlife reserves it has become common-practice to provide supplemental mineral resources for wildlife. Yet, the impacts of anthropogenic mineral supplementation on large herbivore nutrition, behaviour, and subsequent impact on ecosystem processes have received little attention. Here, we examine the contribution of anthropogenic mineral lick provision to wildlife nutrient intake across a community of mammalian herbivores (>10 kg) in the southern Kalahari Desert. Based on predicted daily nutrient intake and a faecal nutrient assessment, many large herbivore species appear deficient in phosphorus (P), sodium (Na), or zinc (Zn). For these nutrients, anthropogenic salt and mineral licks constitute an important source of nutrient intake helping to reduce or overcome requirement deficits. Larger-bodied species disproportionately consumed licks, acquiring more nutritional benefits. A comprehensive assessment of animal body condition indicated that, in general, large herbivores display good health. However, bulk grazers, non-ruminants and females displayed poorer body condition. We discuss how provisioning of anthropogenic mineral licks may inflate large herbivore populations beyond the long-term carrying capacity of the reserve by decoupling wildlife fecundity from nutrient-related feedbacks on population growth. Over time, this could compromise ecosystem integrity through habitat degradation, modified species interactions and trophic cascades. Based on results presented here, it is clear that anthropogenic provisioning of mineral licks should be considered cautiously by wildlife managers aiming to conserve natural processes in landscapes.

Functional adaptive resources for large herbivores in African savannas: an ecological-gradient based framework

The viability of large herbivore populations in the face of climate change, environmental variability, disease and predation will be determined by their freedom to assess and respond to these factors through access to a range of functional seasonal resources and habitats. Their responses will be contingent upon various organismal traits, such as body size, mouth and digestive anatomy, which also facilitate coexistence among sympatric species. In this paper we develop a functional adaptive forage resource framework based on plant biomass, quality and phenology responses on ecological productivity gradients. We show how large herbivores coexist and respond to environmental variability, disease and predation by their foraging responses in relation to functional adaptive resources, as mediated by their anatomical traits. Below a critical body size, where predation limits population size, large herbivores adopt a variety of predation avoidance strategies, which are linked to their anatomical traits and foraging strategies. Mouth anatomy, and its interaction with body size, appears to be the major anatomical trait determining large herbivore selection for grass height. Body size is the major trait determining vulnerability to predators. Ecological productivity gradients underlain by variation in soil moisture availability over the annual cycle support high quality forage in the least productive (driest) regions, which promote growth and reproduction (a fecundity resource). Reserves of adequate quality forage in moderate productivity regions and buffers of low-quality forage in wetter and more productive regions of the gradient prevent loss of body stores over the dry season and starvation during droughts. Fire and grazing contribute towards providing high quality forage by removing old, low-quality material and preventing forage maturation. Consuming a high diversity of plant species distributed across ecological gradients promotes phytochemical diversity in the diet, which functions as medicinal resources to promote health while combating disease and parasites. Large herbivores are becoming increasingly restricted by ecosystem fragmentation in their access to the full range of these functional resource classes. The negative consequences for large herbivore populations of reduced access to these resource classes is compounded by climate change, where conditions are hotter and drought frequency and intensity is expected to be higher.

Reconstructing Historical Distribution of Large Mammals and their Habitat to Inform Rewilding and Restoration in Central Tanzania

Backgroundand research aim: In the anthropogenic landscapes where historically wildlife existed, there can be a potential for rewilding to reverse extinction. However, there is limited literature providing approaches to achieve successful rewilding. The current study aimed at providing empirical based methodological procedures for successful rewilding of the University of Dodoma (UDOM) and nearby degraded landscape by assessing past and current vegetation and large mammal species’ occurrence. Methodology: The past occurrence of mega-herbivores and their habitat was assessed using systematic literature survey, past vegetation maps and key informant interviews. EBSCOhost database and Google Scholar search engine were used for literature searching. A survey was conducted at UDOM area which is one of the remaining habitat patches in central Tanzania to examine present plant diversity. Results: The baseline vegetation map of 1960 indicated that the study area was mainly Savanna woodland. Literature suggested that anthropogenic activities resulted into Land-Use Land-Cover Changes (LULCC) leading into wild animals’ extirpation leaving remnant populations in the surrounding protected areas. While the key informant interviews verified local loss of mega-herbivores, field data collected at UDOM campus in 2022 indicated the vegetation transformation to bushland dominated by Dichrostachys cinerea. The area’s past vegetation composition was 33% grasses, 29% herbs, 21% shrubs and 17% trees while the current was 18% grasses, 42% herbs, 30% shrubs and 10% trees. Conclusion: The study revealed that central Tanzania hosted spectacular large mammal populations that interacted with the savanna which has recently been transformed to bushland. However, observed evidence on past existence of large mammals and recent elephants’ sightings at UDOM area indicate great potential for rewilding. Implication for conservation: Reconstructing historical information of ecosystems is crucial for successful rewilding. Such information can guide conservation efforts aiming at reversing extinction and reestablishing connectivity of large herbivore population across ecosystems.

Maternal effects and the legacy of extreme environmental events for wild mammals.

Maternal effects and the legacy of extreme environmental events for wild mammals.

A 17-Year Study of the Response of Populations to Different Patterns in Antlerless Proportion of Imposed Culls: Antlerless Culling Reduces Overabundant Deer Population.

Increasing populations of large herbivores have caused environmental damage around the world, and it is necessary to improve population management strategies. Culling is a traditional management method. Antlerless deer proportions, consisting of adult female deer and fawn in Cervidae in wildlife statistics, are directly related to population increases; thus, the culling-based removal of individuals from habitats and the removal of these antlerless individuals by game hunting and nuisance control might be effective approaches for reducing population sizes. We evaluated the effectiveness of antlerless culling on 17-year density trends in the sika deer (Cervus nippon) population across an area of 1175 km2 in Fukuoka Prefecture (Japan). In 11 out of 47 grids (area measuring 5 by 5 km), the densities of sika deer tended to decline; meanwhile, in the remaining 36 grids, the densities increased. These density trends were explained by changes in the proportion of antlerless culling, as the densities declined with increasing proportions of antlerless deer. The results affirm the theory that antlerless culling is effective in population management; it is posited that antlerless-biased culling could be a crucial measure in managing overabundant populations of herbivores, contributing to more effective conservation of forest environments.

Rapid increase in sensitive indicator plants concurrent with deer management in an oak forest landscape

AbstractWildlife managers are implementing programs to reduce abundant populations of large herbivores, such as white‐tailed deer (Odocoileus virginianus) in eastern North America, with renewed research interest in understanding these programs' ecological effects. To examine plant community change following culling of white‐tailed deer in oak (Quercus spp.) forests in Ohio, USA, we measured browse severity on tree seedlings and cover of 43 deer‐sensitive, native indicator plant species across 20 years spanning pre‐ (2002–2015) and post‐ (2016–2021) deer culling periods. After culling halved deer abundance from 16.7 deer/km2 to 8.6 deer/km2, browse patterns on tree seedlings reversed from most seedlings exhibiting browse damage to most being undamaged. Cover of deer‐sensitive indicator plants increased 7‐fold in the 6 years after deer culling. Five of 6 indicator plant groups (e.g., Liliaceae) and 32 of 43 indicator species (74%) increased in cover after deer culling. Rhizomatous, clonally reproducing and early flowering (May–Jun) species were generally most responsive. The rapid increase in deer‐sensitive plants after deer culling in our study is among the fastest and largest reported among eastern North American studies. The plant community resilience observed in this study could partly relate to the relatively short duration (~10 yr) that deer populations were elevated before culling began, allowing persistence of local plant regeneration potential. Deer culling enabled a moderate deer population to coexist with a rising sensitive plant population.

Dynamics of Forage and Management Implications for Large Herbivore Habitat in Seasonally Dry Forest of Southeast Asia

Forage plants, as primary producers, play an essential role in maintaining populations of large herbivores. The availability and quality of these forage plants can affect the health and viability of these animals. Seasonally dry forests of Huai Kha Khaeng Wildlife Sanctuary and Huai Thab Salao-Huai Rabum Non-Hunting Area are recognized as one of the largest contiguous pieces of forests in mainland Southeast Asia and serve as a home to many large herbivore species, particularly banteng (Bos javanicus birmanicus). However, our understanding of forage plants and their dynamics is still limited. Therefore, the current study was undertaken to understand the dynamics of forage plants, prescribed burning effects, and the associated environmental factors. During 2018–2019, the results showed that the highest forage availability was in June after the prescribed burns at 156.2–252.6 kg ha−1 and the lowest in February before the burning at 16.8–39.8 kg ha−1. Environmental factors that impacted the forage availability include canopy cover, tree density, tree basal area, soil bulk density, soil pH, and topography. However, the impacts of these factors varied among the studied plant life forms, suggesting the importance of active habitat management through prescribed burns and stand improvement to maintain sufficient forage for large herbivores in the future.

Population and habitat connectivity of Grevy's zebra Equus grevyi, a threatened large herbivore in degraded rangelands

Land degradation, competition with livestock, infrastructure development, and climate change have reduced habitat availability and reduced population connectivity for many wildlife species. Large herbivores are particularly vulnerable, and approximately 90 % of global large herbivore diversity is in Africa. The endangered Grevy's zebra illustrates the decline and fragmentation of large mammalian herbivore populations, with extensive population loss across their range in northern Kenya and Ethiopia. A better understanding of the factors influencing population connectivity and movement patterns of Grevy's zebra, highlighted in national strategies, offers valuable insights for other threatened species.Using location and movement data for Grevy's zebra from GPS collars deployed between 2010 and 2017, seasonally-explicit landscape resistance was modelled as a function of water availability, vegetation, cattle density, topography and proximity to roads and settlements. Maximum entropy models identified habitat suitability during wet and dry seasons respectively. Population connectivity analyses using least-cost paths and circuit theory determined landscape resistance to movement and highlighted linkage pathways. Movement was modelled over a range of distances, using GPS data.Grevy's zebra reliance on water was confirmed, with an apparent trade-off between habitat suitability and proximity to people. Connectivity models highlighted potentially isolated populations, with reduced seasonal connectivity being most apparent between north to south distribution areas. These results can inform sustainable land management planning in northern Kenya and offer support for Grevy's zebra conservation actions. These results also provide insights that can be applied to other large herbivores occurring in this region and in arid or degraded environments elsewhere.

Forage availability, supplementary feed and ungulate density: Associations with ungulate damage in pine production forests

Populations of large herbivores, including members of the deer family Cervidae, are expanding across and within many regions of the northern hemisphere. Because their browsing on trees can result in economic losses to forestry and strongly affect ecosystems, it is becoming increasingly important to understand how best to mitigate resultant damage. Previous research has highlighted the importance of regulating deer density and the availability of alternative forage to reduce browsing damage levels in conifer production stands. However, often only one or two proxies of forage availability have been used instead of applying a broad foodscape approach and more knowledge is needed to understand which types of alternative forage best mitigate damage. We conducted field inventories of damage that occurred during the previous fall/winter in 112 production stands in southern Sweden, while also measuring forage availability and cervid faecal pellets in the surrounding landscape (16 ha). Local landowners provided data on supplementary feeding. We found that variation in cervid (Alces alces, Capreolus capreolus, Cervus elaphus and Dama dama) browsing damage to top shoots or stems of young Scots pine trees (Pinus sylvestris, hereon pine), was better explained by the availability of alternative natural forage (using several indices and species of trees and shrubs) than by supplementary feeding. The proportion of damaged pine trees was higher in stands with a lower density of pine stems; in landscapes with a lower density of key broadleaf tree species (genera Sorbus, Salix, Populus and Quercus); and in landscapes with more open land (agricultural fields and paddocks). Damage was also higher in stands where relatively large amounts of moose faeces was found, while not related to the amount of faeces from other cervid species. The amount of supplementary feed (silage or other types such as root vegetables) did not explain variation in pine damage, but the result was possibly affected by relatively few study areas supplying sufficient data on supplementary feeding. The results from our inventory illustrate the efficacy of using naturally growing forage to mitigate browsing damage to young pine trees in managed landscapes. Creation of such forage is also recommended over supplementary feeding because of co-benefits to forest biodiversity and ecosystem services.

Cretaceous Dinosaurs across Alaska Show the Role of Paleoclimate in Structuring Ancient Large-Herbivore Populations

The partially correlative Alaskan dinosaur-bearing Prince Creek Formation (PCF), North Slope, lower Cantwell Formation (LCF), Denali National Park, and Chignik Formation (CF), Aniakchak National Monument, form an N–S transect that, together, provides an unparalleled opportunity to examine an ancient high-latitude terrestrial ecosystem. The PCF, 75–85° N paleolatitude, had a Mean Annual Temperature (MAT) of ~5–7 °C and a Mean Annual Precipitation (MAP) of ~1250 mm/year. The LCF, ~71° N paleolatitude, had a MAT of ~7.4 °C and MAP of ~661 mm/year. The CF, ~57° N paleolatitude, had a MAT of ~13 °C and MAP of ~1090 mm/year. The relative abundances of the large-bodied herbivorous dinosaurs, hadrosaurids and ceratopsids, vary along this transect, suggesting that these climatic differences (temperature and precipitation) played a role in the ecology of these large-bodied herbivores of the ancient north. MAP played a more direct role in their distribution than MAT, and the seasonal temperature range may have played a secondary role.

Do trait responses to simulated browsing in Quercus robur saplings affect their attractiveness to Capreolus capreolus the following year?

With the rise of large herbivore populations in most northern hemisphere forests, browsing is becoming an increasingly important driver of forest regeneration dynamics. Among other processes affecting the regeneration, the concept of plant-herbivore feedback loops holds that browsed saplings are more subject to subsequent herbivory. This phenomenon is interpreted as a consequence of compensatory growth following browsing since fast growth is generally associated with higher digestibility and lower defense against herbivores. However, studies linking browsing-induced trait variations to subsequent attractiveness to herbivores are still lacking, especially in the forest context. In this study, we experimentally examine the existence of a feedback loop between oak ( Quercus robur L.) and roe deer ( Capreolus capreolus ) and investigate its underlying morphological and chemical traits. We simulated single and repeated roe deer browsing on nursery-grown oak saplings and measured the changes in sapling height growth, lateral branching, leaf traits and winter shoot traits over two years. We conducted winter feeding trials with tame roe deer one year after the first treatment to test the effect of simulated browsing on sapling attractiveness. Simulated browsing reduced sapling height growth but had no effect on branching. Simulated browsing had no effect on leaf traits after half a year, but decreased the phenolic content and increased the fiber content of winter shoots the following winter. Contrary to our predictions, roe deer preferentially browsed control saplings over saplings previously browsed. After two years, repeated browsing promoted fast carbon acquisition leaf traits (high chlorophyll, high specific leaf area and low fiber content), reduced leaf phenolic content and increased leaf digestibility. We showed that a reduction in 1-year-old oak sapling height growth following browsing, combined with increased structural defense at the expense of chemical defense in winter shoots the following winter, was correlated with reduced browsing pressure, thereby challenging the feedback loop hypothesis. However, we also demonstrated that repeated browsing promoted fast carbon acquisition leaf traits in 2.5-year-old saplings, which tend to support the existence of a feedback loop on older and more intensively browsed saplings. As such, our study provides empirical evidence that morphological and physiological trait responses to browsing influence oak sapling attractiveness, but that the direction and magnitude of this effect depend on the ontogenic stage of the sapling and on the number of browsing events. • We examine the morphological and chemical response of oak saplings to browsing. • Browsing reduces sapling height growth and modifies shoots chemical composition. • We show with feeding trials that roe deer prefers unbrowsed saplings. • Oak trait responses to browsing decrease the probability of subsequent herbivory.

Seasonal strategies differ between tropical and extratropical herbivores.

Seasonal diet shifts and migration are key components of large herbivore population dynamics, but we lack a systematic understanding of how these behaviours are distributed on a macroecological scale. The prevalence of seasonal strategies is likely related to herbivore body size and feeding guild, and may also be influenced by properties of the environment, such as soil nutrient availability and climate seasonality. We evaluated the distribution of seasonal dietary shifts and migration across large-bodied mammalian herbivores and determined how these behaviours related to diet, body size and environment. We found that herbivore strategies were consistently correlated with their traits: seasonal diet shifts were most prevalent among mixed feeding herbivores and migration among grazers and larger herbivores. Seasonality also played a role, particularly for migration, which was more common at higher latitudes. Both dietary shifts and migration were more widespread among extratropical herbivores, which also exhibited more intermediate diets and body sizes. Our findings suggest that strong seasonality in extratropical systems imposes pressure on herbivores, necessitating widespread behavioural responses to navigate seasonal resource bottlenecks. It follows that tropical and extratropical herbivores may have divergent responses to global change, with intensifying herbivore pressure in extratropical systems contrasting with diminishing herbivore pressure in tropical systems.

Conservation overstretch and long-term decline of wildlife and tourism in the Central African savannas.

When in 2010 the world's governments pledged to increase protected area coverage to 17% of the world's land surface, several Central African countries had already set aside 25% of their northern savannas for conservation. To evaluate the effectiveness of this commitment, we analyzed the results of 68 multispecies surveys conducted in the seven main savanna national parks in Central Africa (1960-2017). We also assembled information on potential drivers of large herbivore population trends (rainfall and number of rangers) and on tourist numbers and revenues. In six out of the seven parks, wild large herbivore populations declined dramatically over time, livestock numbers increased severalfold, and tourism, the pillar under a once thriving local wildlife industry, collapsed. Zakouma National Park (Chad) stood out because its large herbivore populations increased, an increase that was positively correlated with rainfall and number of rangers (a proxy for management inputs). With increasing insecurity and declining revenues, governments find themselves confronted with too few resources to protect vast areas. To deal with this conversation overstretch, we propose to extend the repeatedly promoted solutions--scaled up funding, enhanced management--with a strategic retreat, focusing scarce resources on smaller areas to save wildlife in the Central African savannas.

Mixed-severity wildfire shapes habitat use of large herbivores and carnivores

Ecological disturbance is a driving force that structures ecosystems and shapes landscape pattern. Wildfire is a widespread form of ecological disturbance, and in some vegetation communities fires are increasing in extent and severity. Across the gradient of fire severity, fire can have both positive and negative effects on animals, where some species require mature climax vegetation conditions and other species select for early successional stages. However, further work is necessary to understand how large mammalian herbivore and carnivore populations respond to the gradient of fire severity. The overall objective of this research was to understand the relative roles of fire, landscape, and human factors across the gradient of fire severity on occupancy and/or relative habitat use of large herbivores (i.e., elk and mule deer) and carnivores (i.e., black bear, mountain lion, and gray wolf) seven years post fire. We predicted that animals would increase use of areas characterized by higher fire severity (moderate, moderate/high, or high fire severity) and heterogeneity, where food resources were expected to be greatest. In addition, road density could either increase or decrease animal use of areas, where some animals might increase use near roads due to increased forage along roadsides or decrease use due to higher human activity. Remote wildlife (RW) cameras sampled the gradient of fire severity seven years post a large mixed-severity wildfire (Wallow Fire, year 2011, 2,177 km2) in the White Mountains of Arizona, USA. We evaluated RW camera data using single-species occupancy and Royle-Nichols (relative habitat use) models. As predicted, large mammals (black bear, elk, mountain lion, mule deer, and wolves) exhibited high occupancy and/or habitat use in relation to higher levels of fire severity and/or fire heterogeneity, which was likely related to bottom-up factors related to increased food resources. Some species (black bear and elk) also exhibited relatively high use of unburned forest. Elk reduced use of areas with higher road density, likely to avoid human activity, whereas mule deer increased use of areas with high road density. Mixed-severity wildfire may provide important resources, including pulses of food in early successional forests. Thus, allowing fire-adapted forests to experience mixed-severity wildfire is predicted to benefit some large herbivore and carnivore populations. If high occupancy and/or habitat use by wildlife in areas experiencing higher fire severity and heterogeneity translates into increased populations of animals, wildfire might be beneficial to humans, focal wildlife populations, and fire-adapted ecosystems.