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.

Effects of migratory animals on resident parasite dynamics

Migratory animals can bring parasites into resident animal (i.e., non-migratory) home ranges (transport effects) and exert trophic effects that either promote or reduce parasite exposure to resident hosts. Here, we examine the importance of these transport and trophic effects and their interactions for resident parasite dynamics. We propose that migrant transport and trophic effects are impacted by the number of migratory animals entering a resident's home range (migration intensity), the amount of time that migrants spend within a resident's home range (migration duration), and the timing of migrant-resident interactions. We then incorporate migration intensity, duration, and timing into a framework for exploring the net impact of migrant trophic and transport effects on resident animal parasite prevalence.

Temperature and body size affect movement of juvenile Atlantic cod (Gadus morhua) and saithe (Pollachius virens) at nearshore nurseries

Seasonal migrations of marine fish between shallow summer feeding habitats and deep overwintering grounds are driven by fluctuations in the biotic and abiotic environment as well as by changes in the internal state. Ontogenetic shifts in physiology and metabolism affect the response to environmental drivers and may lead to changes in migration timing and propensity. In this study, we investigated the effect of temperature and body size on migration timing and depth distribution in acoustically tagged Atlantic cod, Gadus morhua, and saithe, Pollachius virens, during the period of seasonal migration from shallow summer habitats. The results from our study revealed a wide range of horizontal and vertical distribution of age 1 and 2 G. morhua within the fjord. Larger G. morhua inhabited deeper, cooler waters than smaller juveniles, likely reflecting size-dependent thermal preferences and predation pressure. Conversely, juvenile P. virens occupied primarily shallow waters close to land. The variation in depth distribution of G. morhua was mainly explained by body size and not, against our predictions, by water temperature. Conversely, the dispersal from the in-fjord habitats occurred when water temperatures were high, suggesting that seasonal temperature fluctuations can trigger the migration timing of P. virens and larger G. morhua from summer habitats. Partial migration of small juvenile G. morhua from in-fjord foraging grounds, likely influenced by individual body condition, suggested seasonal migration as a flexible strategy that individuals may use to reduce predation and energetic expenditure. Predation mortality rates of tagged juveniles were higher than previously suggested and are the first robust predation mortality rates for juvenile G. morhua and P. virens estimated based on acoustic transmitters with acidity sensors. The results have relevance for climate-informed marine spatial planning as under the scenario of increasing ocean temperatures, increasing summer temperatures may reduce the juveniles' resource utilization in the shallow summer nurseries, resulting in lower growth rates, increased predation pressure, and lower chances of juvenile winter survival.

Spatial overlap of gray wolves and ungulate prey changes seasonally corresponding to prey migration

BACKGROUND

Prey are more vulnerable during migration due to decreased familiarity with their surroundings and spatially concentrated movements. Predators may respond to increased prey vulnerability by shifting their ranges to match prey. Moose (Alces alces) and white-tailed deer (Odocoileus virginianus) are primary gray wolf (Canis lupus) prey and important subsistence species for Indigenous communities. We hypothesized wolves would increase use of ungulate migration corridors during migrations and predicted wolf distributions would overlap primary available prey.

METHODS

We examined seasonal gray wolf, moose, and white-tailed deer movements on and near the Grand Portage Indian Reservation, Minnesota, USA. We analyzed GPS collar data during 2012-2021 using Brownian bridge movement models (BBMM) in Migration Mapper and mechanistic range shift analysis (MRSA) to estimate individual- and population-level occurrence distributions and determine the status and timing of range shifts. We estimated proportional overlap of wolf distributions with moose and deer distributions and tested for differences among seasons, prey populations, and wolf sex and pack affiliations.

RESULTS

We identified a single migration corridor through which white-tailed deer synchronously departed in April and returned in October-November. Gray wolf distributions overlapped the deer migration corridor similarly year-round, but wolves altered within-range distributions seasonally corresponding to prey distributions. Seasonal wolf distributions had the greatest overlap with deer during fall migration (10 October-28 November) and greatest overlap with moose during summer (3 May-9 October).

CONCLUSIONS

Gray wolves did not increase their use of the white-tailed deer migration corridor but altered distributions within their territories in response to seasonal prey distributions. Greater overlap of wolves and white-tailed deer in fall may be due to greater predation success facilitated by asynchronous deer migration movements. Greater summer overlap between wolves and moose may be linked to moose calf vulnerability, American beaver (Castor canadensis) co-occurrence, and reduced deer abundance associated with migration. Our results suggest increases in predation pressure on deer in fall and moose in summer, which can inform Indigenous conservation efforts. We observed seasonal plasticity of wolf distributions suggestive of prey switching; that wolves did not exhibit migratory coupling was likely due to spatial constraints resulting from territoriality.

Interplay of competition and facilitation in grazing succession by migrant Serengeti herbivores

Competition, facilitation, and predation offer alternative explanations for successional patterns of migratory herbivores. However, these interactions are difficult to measure, leaving uncertainty about the mechanisms underlying body-size-dependent grazing-and even whether succession occurs at all. We used data from an 8-year camera-trap survey, GPS-collared herbivores, and fecal DNA metabarcoding to analyze the timing, arrival order, and interactions among migratory grazers in Serengeti National Park. Temporal grazing succession is characterized by a "push-pull" dynamic: Competitive grazing nudges zebra ahead of co-migrating wildebeest, whereas grass consumption by these large-bodied migrants attracts trailing, small-bodied gazelle that benefit from facilitation. "Natural experiments" involving intense wildfires and rainfall respectively disrupted and strengthened these effects. Our results highlight a balance between facilitative and competitive forces in co-regulating large-scale ungulate migrations.

Genomic correlates for migratory direction in a free-ranging cervid

Animal migrations are some of the most ubiquitous and one of the most threatened ecological processes globally. A wide range of migratory behaviours occur in nature, and this behaviour is not uniform among and within species, where even individuals in the same population can exhibit differences. While the environment largely drives migratory behaviour, it is necessary to understand the genetic mechanisms influencing migration to elucidate the potential of migratory species to cope with novel conditions and adapt to environmental change. In this study, we identified genes associated with a migratory trait by undertaking pooled genome-wide scans on a natural population of migrating mule deer. We identified genomic regions associated with variation in migratory direction, including FITM1, a gene linked to the formation of lipids, and DPPA3, a gene linked to epigenetic modifications of the maternal line. Such a genetic basis for a migratory trait contributes to the adaptive potential of the species and might affect the flexibility of individuals to change their behaviour in the face of changes in their environment.

Inferring spatially varying animal movement characteristics using a hierarchical continuous-time velocity model

Understanding the spatial dynamics of animal movement is an essential component of maintaining ecological connectivity, conserving key habitats, and mitigating the impacts of anthropogenic disturbance. Altered movement and migratory patterns are often an early warning sign of the effects of environmental disturbance, and a precursor to population declines. Here, we present a hierarchical Bayesian framework based on Gaussian processes for analysing the spatial characteristics of animal movement. At the heart of our approach is a novel covariance kernel that links the spatially varying parameters of a continuous-time velocity model with GPS locations from multiple individuals. We demonstrate the effectiveness of our framework by first applying it to a synthetic data set and then by analysing telemetry data from the Serengeti wildebeest migration. Through application of our approach, we are able to identify the key pathways of the wildebeest migration as well as revealing the impacts of environmental features on movement behaviour.

Fire, grazers, and browsers interact with grass competition to determine tree establishment in an African savanna

In savanna ecosystems, fire and herbivory alter the competitive relationship between trees and grasses. Mechanistically, grazing herbivores favor trees by removing grass, which reduces tree-grass competition and limits fire. Conversely, browsing herbivores consume trees and limit their recovery from fire. Herbivore feeding decisions are in turn shaped by risk-resource trade-offs that potentially determine the spatial patterns of herbivory. Identifying the dominant mechanistic pathways by which fire and herbivores control tree cover remains challenging, but is essential for understanding savanna dynamics. We used an experiment in the Serengeti ecosystem and a simple simulation driven by experimental results to address two main aims: (1) determine the importance of direct and indirect effects of grass, fire and herbivory on seedling establishment; and (2) establish whether predators determine the spatial pattern of successful seedling establishment via effects on mesoherbivore distribution. We transplanted tree seedlings into plots with a factorial combination of grass and herbivores (present/absent) across a lion kill-risk gradient in the Serengeti, burning half of the plots near the end of the experiment. Ungrazed grass limited tree seedling survival directly via competition, indirectly via fire, and by slowing seedling growth, which drove higher seedling mortality during fires. These effects restricted seedling establishment to below 18% and, in conjunction with browsing, resulted in seedling establishment dropping below 5%. In the absence of browsing and fire, grazing drove a 7.5-fold increase in seedling establishment. Lion predation risk had no observable impact on herbivore effects on seedling establishment. The severe negative effects of grass on seedling mortality suggests that regional patterns of tree cover and fire may overestimate the role of fire in limiting tree cover, with regular fires representing a proxy for the competitive effects of grass.

Increasing Anthropogenic Disturbance Restricts Wildebeest Movement Across East African Grazing Systems

The ability to move is essential for animals to find mates, escape predation, and meet energy and water demands. This is especially important across grazing systems where vegetation productivity can vary drastically between seasons or years. With grasslands undergoing significant changes due to climate change and anthropogenic development, there is an urgent need to determine the relative impacts of these pressures on the movement capacity of native herbivores. To measure these impacts, we fitted 36 white-bearded wildebeest (Connochaetes taurinus) with GPS collars across three study areas in southern Kenya (Amboseli Basin, Athi-Kaputiei Plains, and Mara) to test the relationship between movement (e.g., directional persistence, speed, home range crossing time) and gradients of vegetation productivity (i.e., NDVI) and anthropogenic disturbance. As expected, wildebeest moved the most (21.0 km day–1; CI: 18.7–23.3) across areas where movement was facilitated by low human footprint and necessitated by low vegetation productivity (Amboseli Basin). However, in areas with moderate vegetation productivity (Athi-Kaputiei Plains), wildebeest moved the least (13.3 km day–1; CI: 11.0–15.5). This deviation from expectations was largely explained by impediments to movement associated with a large human footprint. Notably, the movements of wildebeest in this area were also less directed than the other study populations, suggesting that anthropogenic disturbance (i.e., roads, fences, and the expansion of settlements) impacts the ability of wildebeest to move and access available resources. In areas with high vegetation productivity and moderate human footprint (Mara), we observed intermediate levels of daily movement (14.2 km day–1; CI: 12.3–16.1). Wildebeest across each of the study systems used grassland habitats outside of protected areas extensively, highlighting the importance of unprotected landscapes for conserving mobile species. These results provide unique insights into the interactive effects of climate and anthropogenic development on the movements of a dominant herbivore in East Africa and present a cautionary tale for the development of grazing ecosystems elsewhere.

Mechanistic movement models identify continuously updated autumn migration cues in Arctic caribou

BACKGROUND

Migrations in temperate systems typically have two migratory phases, spring and autumn, and many migratory ungulates track the pulse of spring vegetation growth during a synchronized spring migration. In contrast, autumn migrations are generally less synchronous and the cues driving them remain understudied. Our goal was to identify the cues that migrants use in deciding when to initiate migration and how this is updated while en route.

METHODS

We analyzed autumn migrations of Arctic barren-ground caribou (Rangifer tarandus) as a series of persistent and directional movements and assessed the influence of a suite of environmental factors. We fitted a dynamic-parameter movement model at the individual-level and estimated annual population-level parameters for weather covariates on 389 individual-seasons across 9 years.

RESULTS

Our results revealed strong, consistent effects of decreasing temperature and increasing snow depth on migratory movements, indicating that caribou continuously update their migratory decision based on dynamic environmental conditions. This suggests that individuals pace migration along gradients of these environmental variables. Whereas temperature and snow appeared to be the most consistent cues for migration, we also found interannual variability in the effect of wind, NDVI, and barometric pressure. The dispersed distribution of individuals in autumn resulted in diverse environmental conditions experienced by individual caribou and thus pronounced variability in migratory patterns.

CONCLUSIONS

By analyzing autumn migration as a continuous process across the entire migration period, we found that caribou migration was largely related to temperature and snow conditions experienced throughout the journey. This mechanism of pacing autumn migration based on indicators of the approaching winter is analogous to the more widely researched mechanism of spring migration, when many migrants pace migration with a resource wave. Such a similarity in mechanisms highlights the different environmental stimuli to which migrants have adapted their movements throughout their annual cycle. These insights have implications for how long-distance migratory patterns may change as the Arctic climate continues to warm.

Contrasting patterns of risk from human and non-human predators shape temporal activity of prey

Spatiotemporal variation in predation risk arises from interactions between landscape heterogeneity, predator densities and predator hunting mode, generating landscapes of fear for prey species that can have important effects on prey behaviour and ecosystem dynamics. As widespread apex predators, humans present a significant source of risk for hunted animal populations. Spatiotemporal patterns of risk from hunters can overlap or contrast with patterns of risk from other predators. Human infrastructure can also reshape spatial patterns of risk by facilitating or impeding hunter or predator movement, or deterring predators that are themselves wary of humans. We examined how anthropogenic and natural landscape features interact with hunting modes of rifle hunters and mountain lions Puma concolor to generate spatiotemporal patterns of risk for their primary prey. We explored the implications of human-modified landscapes of fear for Columbian black-tailed deer Odocoileus hemionus columbianus in Mendocino County, California. We used historical harvest records, hunter GPS trackers and camera trap records of mountain lions to model patterns of risk for deer. We then used camera traps to examine deer spatial and temporal activity patterns in response to this variation in risk. Hunters and mountain lions exhibited distinct, contrasting patterns of spatiotemporal activity. Risk from rifle hunters, who rely on long lines of sight, was highest in open grasslands and near roads and was confined to the daytime. Risk from mountain lions, an ambush predator, was highest in dense shrubland habitat, farther from developed areas, and during the night and crepuscular periods. Areas of human settlement provided a refuge from both hunters and mountain lions. We found no evidence that deer avoided risk in space at the scale of our observations, but deer adjusted their temporal activity patterns to reduce the risk of encounters with humans and mountain lions in areas of higher risk. Our study demonstrates that interactions between human infrastructure, habitat cover and predator hunting mode can result in distinct spatial patterns of predation risk from hunters and other predators that may lead to trade-offs for prey species. However, distinct diel activity patterns of predators may create vacant hunting domains that reduce costly trade-offs for prey. Our study highlights the importance of temporal partitioning as a mechanism of predation risk avoidance.

The sardine run in southeastern Africa is a mass migration into an ecological trap

The KwaZulu-Natal sardine run, popularly known as the “greatest shoal on Earth,” is a mass migration of South African sardines from their temperate core range into the subtropical Indian Ocean. It has been suggested that this represents the spawning migration of a distinct subtropical stock. Using genomic and transcriptomic data from sardines collected around the South African coast, we identified two stocks, one cool temperate (Atlantic) and the other warm temperate (Indian Ocean). Unexpectedly, we found that sardines participating in the sardine run are primarily of Atlantic origin and thus prefer colder water. These sardines separate from the warm-temperate stock and move into temporarily favorable Indian Ocean habitat during brief cold-water upwelling periods. Once the upwelling ends, they find themselves trapped in physiologically challenging subtropical habitat and subject to intense predation pressure. This makes the sardine run a rare example of a mass migration that has no apparent fitness benefits.

Predation landscapes influence migratory prey ecology and evolution

Migratory prey experience spatially variable predation across their life cycle. They face unique challenges in navigating this predation landscape, which affects their perception of risk, antipredator responses, and resulting mortality. Variable and unfamiliar predator cues during migration can limit accurate perception of risk and migrants often rely on social information and learning to compensate. The energetic demands of migration constrain antipredator responses, often through context-dependent patterns. While migration can increase mortality, migrants employ diverse strategies to balance risks and rewards, including life history and antipredator responses. Humans interact frequently with migratory prey across space and alter both mortality risk and antipredator responses, which can scale up to affect migratory populations and should be considered in conservation and management.

A hierarchical machine learning framework for the analysis of large scale animal movement data

BACKGROUND

In recent years the field of movement ecology has been revolutionized by our ability to collect high-accuracy, fine scale telemetry data from individual animals and groups. This growth in our data collection capacity has led to the development of statistical techniques that integrate telemetry data with random walk models to infer key parameters of the movement dynamics. While much progress has been made in the use of these models, several challenges remain. Notably robust and scalable methods are required for quantifying parameter uncertainty, coping with intermittent location fixes, and analysing the very large volumes of data being generated.

METHODS

In this work we implement a novel approach to movement modelling through the use of multilevel Gaussian processes. The hierarchical structure of the method enables the inference of continuous latent behavioural states underlying movement processes. For efficient inference on large data sets, we approximate the full likelihood using trajectory segmentation and sample from posterior distributions using gradient-based Markov chain Monte Carlo methods.

RESULTS

While formally equivalent to many continuous-time movement models, our Gaussian process approach provides flexible, powerful models that can detect multiscale patterns and trends in movement trajectory data. We illustrate a further advantage to our approach in that inference can be performed using highly efficient, GPU-accelerated machine learning libraries.

CONCLUSIONS

Multilevel Gaussian process models offer efficient inference for large-volume movement data sets, along with the fitting of complex flexible models. Applications of this approach include inferring the mean location of a migration route and quantifying significant changes, detecting diurnal activity patterns, or identifying the onset of directed persistent movements.

Relationships between resource availability and elevation vary between metrics creating gradients of nutritional complexity

Plant and animal community composition changes at higher elevations on mountains. Plant and animal species richness generally declines with elevation, but the shape of the relationship differs between taxa. There are several proposed mechanisms, including the productivity hypotheses; that declines in available plant biomass confers fewer resources to consumers, thus supporting fewer species. We investigated resource availability as we ascended three aspects of Helvellyn mountain, UK, measuring several plant nutritive metrics, plant species richness and biomass. We observed a linear decline in plant species richness as we ascended the mountain but there was a unimodal relationship between plant biomass and elevation. Generally, the highest biomass values at mid-elevations were associated with the lowest nutritive values, except mineral contents which declined with elevation. Intra-specific and inter-specific increases in nutritive values nearer the top and bottom of the mountain indicated that physiological, phenological and compositional mechanisms may have played a role. The shape of the relationship between resource availability and elevation was different depending on the metric. Many consumers actively select or avoid plants based on their nutritive values and the abundances of consumer taxa vary in their relationships with elevation. Consideration of multiple nutritive metrics and of the nutritional requirements of the consumer may provide a greater understanding of changes to plant and animal communities at higher elevations. We propose a novel hypothesis for explaining elevational diversity gradients, which warrants further study; the ‘nutritional complexity hypothesis’, where consumer species coexist due to greater variation in the nutritional chemistry of plants.

Differing physiological and behavioral responses to anthropogenic factors between resident and non-resident African elephants at Mpala Ranch, Laikipia County, Kenya

BACKGROUND

Heterogeneous landscapes like those of Laikipia County, Kenya consist of a mosaic of land-use types, which may exert differential physiological effects on elephants that occupy and traverse them. Understanding behavioral and physiological states of wild African elephants in response to the challenges of living in human-dominated landscapes is therefore important for conservation managers to evaluate risks imposed by elephants to humans and vice versa. Several conservation physiology tools have been developed to assess how animals respond to both natural and anthropogenic changes, and determine biological impacts. This study investigated how migratory and avoidance behavioral to vehicle presence, and vegetation quality affected fecal glucocorticoid (GC) metabolite (FGM) concentrations in African elephants at Mpala Ranch, Laikipia County, Kenya.

METHODS

The study compared adrenal glucocorticoid activity of resident elephants that live within Mpala (n = 57) and non-resident elephants whose space use patterns overlap several ranches (n = 99) in Laikipia County, Kenya. Fecal samples were collected for a 4-month period between April and August for analysis of FGM concentrations. Behavioral reactions to research vehicles and body condition also were assessed. Satellite images from Terra Moderate Resolution Imaging (MODIS MOD13Q1) were downloaded and processed using Google Earth Engine to calculate a Normalized Difference Vegetation Index (NDVI) as a measure of vegetation quality.

RESULTS

As expected, there was a positive correlation between avoidance behavior to vehicle presence and FGM concentrations in both resident and non-resident elephants, whereas there was an inverse relationship between FGM concentrations and NDVI values. Our study also found a positive influence of age on the FGM concentrations, but there were no relationships between FGM and sex, social group type, herd size, and body condition. However, contrary to our expectations, resident elephants had higher FGM concentrations than non-residents.

DISCUSSION

Findings reveal elephants with stronger avoidance responses to research vehicles and resident elephants with relatively smaller home ranges exhibited higher FGM concentrations within the Mpala Ranch, Kenya and surrounding areas. Higher vegetative quality within the ranges occupied by non-resident elephants in Laikipia may be one reason for lower FGM, and an indication that the non-residents are tracking better forage quality to improve energy balance and reduce overall GC output. Additionally, our study found a positive influence of age, but no other demographic variables on FGM concentrations. Finally, adrenal glucocorticoid activity was inversely related to vegetative quality. Our findings can help conservation managers better understand how behavior and environment influences the physiological states of African elephants, and how management intervention might mitigate negative human-elephant interactions.

Movement rules determine nomadic species' responses to resource supplementation and degradation

In environments that vary unpredictably, many animals are nomadic, moving in an irregular pattern that differs from year to year. Exploring the mechanisms of nomadic movement is needed to understand how animals survive in highly variable environments, and to predict behavioural and population responses to environmental change. We developed a network model to identify plausible mechanisms of nomadic animal movement by comparing the performance of multiple movement rules along a continuum from nomadism to residency. Using simulations and analytical results, we explored how different types of habitat modifications (that augment or decrease resource availability) might affect the abundance and movement rates of animals following each of these rules. Movement rules for which departure from patches depended on resource availability and/or competition performed almost equally well and better than residency or uninformed movement under most conditions, even though animals using each rule moved at substantially different rates. Habitat modifications that stabilized resources, either by resource supplementation or degradation, eroded the benefits of informed nomadic movements, particularly for movements based on resource availability alone. These results suggest that simple movement rules can explain nomadic animal movements and determine species' responses to environmental change. In particular, landscape stabilization and supplementation might be useful strategies for promoting populations of resident animals, but would be less beneficial for managing highly mobile species, many of which are threatened by habitat disruption and changes in climate.

Changes in aboveground locomotion of a scansorial opossum associated to habitat fragmentation

Habitat fragmentation may affect animal movement patterns due to changes in intra- and interspecific interactions as well as in habitat quality and structure. Although the effects of habitat fragmentation on terrestrial movements are relatively well-known, it is unclear whether and how they affect aboveground locomotion of individuals. We compared aboveground locomotion of a Neotropical small mammal, the gray four-eyed opossum, Philander quica, between two forest fragments and two areas of continuous forest in the Brazilian Atlantic Forest. We 1) quantified support availability and tested for active selection of different support diameters and inclinations by individuals; and 2) compared support diameters and inclinations used (observed values) among areas and between males and females. Both males and females selected supports based on diameters and inclinations in forest fragments. In continuous forests sites, females selected supports based on diameters and inclinations, but males selected only support diameters. Frequency of support diameter use differed significantly between forest fragments and continuous forest sites and between males and females. Frequency of support inclination use differed significantly between areas only for females, and between sexes only in continuous forest sites. Sex-related differences in support selection and use are likely related to differences in body size and conflicting energetic and behavioral demands related to use of arboreal space. Site-related differences in aboveground movements likely reflect the effects of forest edges that result in increased use of thinner supports in forest fragments. These results complement our previous findings that habitat fragmentation reduces daily home ranges and increases the total amount of aboveground locomotion of P. quica, and provide a more thorough picture of how forest-dependent species are able to use and persist in small forest fragments.

Mixed-species groups of Serengeti grazers: a test of the stress gradient hypothesis

Understanding the role of species interactions within communities is a central focus of ecology. A key challenge is to understand variation in species interactions along environmental gradients. The stress gradient hypothesis posits that positive interactions increase and competitive interactions decrease with increasing consumer pressure or environmental stress. This hypothesis has received extensive attention in plant community ecology, but only a handful of tests in animals. Furthermore, few empirical studies have examined multiple co‐occurring stressors. Here we test predictions of the stress gradient hypothesis using the occurrence of mixed‐species groups in six common grazing ungulate species within the Serengeti‐Mara ecosystem. We use mixed‐species groups as a proxy for potential positive interactions because they may enhance protection from predators or increase access to high‐quality forage. Alternatively, competition for resources may limit the formation of mixed‐species groups. Using more than 115,000 camera trap observations collected over 5 yr, we found that mixed‐species groups were more likely to occur in risky areas (i.e., areas closer to lion vantage points and in woodland habitat where lions hunt preferentially) and during time periods when resource levels were high. These results are consistent with the interpretation that stress from high predation risk may contribute to the formation of mixed‐species groups, but that competition for resources may prevent their formation when food availability is low. Our results are consistent with support for the stress gradient hypothesis in animals along a consumer pressure gradient while identifying the potential influence of a co‐occurring stressor, thus providing a link between research in plant community ecology on the stress gradient hypothesis, and research in animal ecology on trade‐offs between foraging and risk in landscapes of fear.

Rattlesnake migrations and the implications of thermal landscapes

BACKGROUND

The importance of thermal resources to terrestrial ectotherms has been well documented but less often considered in larger-scale analyses of habitat use and selection, such as those routinely conducted using standard habitat features such as vegetation and physical structure. Selection of habitat based on thermal attributes may be of particular importance for ectothermic species, especially in colder climates. In Canada, Western Rattlesnakes (Crotalus oreganus) reach their northern limits, with limited time to conduct annual migratory movements between hibernacula and summer habitat. We radio-tracked 35 male snakes departing from 10 different hibernacula. We examined coarse-scale differences in migratory movements across the region, and then compared the route of each snake with thermal landscapes and ruggedness GIS maps generated for different periods of the animals' active season.

RESULTS

We observed dichotomous habitat use (grasslands versus upland forests) throughout most of the species' northern range, reflected in different migratory movements of male snakes emanating from different hibernacula. Snakes utilizing higher-elevation forests moved further during the course of their annual migrations, and these snakes were more likely to use warmer areas of the landscape.

CONCLUSION

In addition to thermal benefits, advantages gained from selective migratory patterns may include prey availability and outbreeding. Testing these alternative hypotheses was beyond the scope of this study, and to collect the data to do so will require overcoming certain challenges. Still, insight into migratory differences between rattlesnake populations and the causal mechanism(s) of migrations will improve our ability to assess the implications of landscape change, management, and efficacy of conservation planning. Our findings suggest that such assessments may need to be tailored to individual dens and the migration strategies of their inhabitants. Additionally, local and landscape-scale migration patterns, as detected in this study, will have repercussions for snakes under climate-induced shifts in ecosystem boundaries and thermal regimes.

The benefit and strategy of spring movements in Mongolian gazelles

Animal movement is predicted to be nomadic in areas with low temporal predictability of environmental conditions, but it remains unclear whether the costs of nomadic movement outweigh the benefits received. To examine the spring movement strategy of Mongolian gazelles (Procapra gutturosa) in Mongolia, where predictability of vegetation conditions is relatively low, we identified the type of each movement, evaluated the preferred vegetation conditions for gazelles, and quantified the benefit achieved through each spring movement. The surveyed gazelles continuously preferred areas with intermediate normalized difference vegetation index (NDVI) values from May to July, and spatial and temporal shifts of the distribution of preferred areas explain the long-distance movements of many gazelles in spring. Three movement types, sedentary, linear, and nomadic movement, were identified. The period when benefit varied most greatly among individuals differed between the linear and nomadic movement types. During the spring movement period, the variance of benefit was larger for the nomadic movement type, whereas during the summer it was larger for the linear movement type, suggesting the existence of different movement strategies in the Mongolian gazelle. Linear long-distance movements over a short period in the linear movement type suggest the so-called jumper strategy, whereas other movement patterns might represent the searcher strategy. Benefit loss through movements of individuals in both strategies indicate low interannual predictability of vegetation conditions in the study area, and it would explain the co-existence of multiple movement types or strategies used by Mongolian gazelles in spring.

Long-term historical and projected herbivore population dynamics in Ngorongoro crater, Tanzania

The Ngorongoro Crater is an intact caldera with an area of approximately 310 km² located within the Ngorongoro Conservation Area (NCA) in northern Tanzania. It is known for the abundance and diversity of its wildlife and is a UNESCO World Heritage Site and an International Biosphere Reserve. Long term records (1963–2012) on herbivore populations, vegetation and rainfall made it possible to analyze historic and project future herbivore population dynamics. NCA was established as a multiple use area in 1959. In 1974 there was a perturbation in that resident Maasai and their livestock were removed from the Ngorongoro Crater. Thus, their pasture management that was a combination of livestock grazing and fire was also removed and 'burning' stopped being a regular occurrence until it was resumed in 2001 by NCA management. The Maasai pasture management would have selected for shorter grasses and more palatable species. Vegetation mapping in 1966–1967 recorded predominately short grasslands. Subsequent vegetation mapping in the crater in 1995 determined that the grassland structure had changed such that mid and tall grasses were dominant. After removal of the Maasai pastoralists from the Ngorongoro Crater in 1974, there were significant changes in population trends for some herbivore species. Buffalo, elephant and ostrich numbers increased significantly during 1974–2012. The zebra population was stable from 1963 to 2012 whereas population numbers of five species declined substantially between 1974 and 2012 relative to their peak numbers during 1974–1976. Grant’s and Thomson’s gazelles, eland, kongoni, and waterbuck (wet season only) declined significantly in the Crater in both seasons after 1974. In addition, some herbivore species were consistently more abundant inside the Crater during the wet than the dry season. This pattern was most evident for the large herbivore species requiring bulk forage, i.e., buffalo, eland, and elephant. Even with a change in grassland structure, total herbivore biomass remained relatively stable from 1963 to 2012, implying that the crater has a stable carrying capacity. Analyses of rainfall indicated that there was a persistent cycle of 4.83 years for the annual component. Herbivore population size was correlated with rainfall in both the wet and dry seasons. The relationships established between the time series of historic animal counts in the wet and dry seasons and lagged wet and dry season rainfall series were used to forecast the likely future trajectories of the wet and dry season population size for each species under three alternative climate change scenarios.

Causes and consequences of individual variation in animal movement

Animal movement comes in a variety of 'types' including small foraging movements, larger one-way dispersive movements, seasonally-predictable round-trip migratory movements, and erratic nomadic movements. Although most individuals move at some point throughout their lives, movement patterns can vary widely across individuals within the same species: differing within an individual over time (intra-individual), among individuals in the same population (inter-individual), or among populations (inter-population). Yet, studies of movement (theoretical and empirical alike) more often focus on understanding 'typical' movement patterns than understanding variation in movement. Here, I synthesize current knowledge of movement variation (drawing parallels across species and movement types), describing the causes (what factors contribute to individual variation), patterns (what movement variation looks like), consequences (why variation matters), maintenance (why variation persists), implications (for management and conservation), and finally gaps (what pieces we are currently missing). By synthesizing across scales of variation, I span across work on plasticity, personality, and geographic variation. Individual movement can be driven by factors that act at the individual, population, community and ecosystem level and have ramifications at each of these levels. Generally the consequences of movement are less well understood than the causes, in part because the effects of movement variation are often nested, with variation manifesting at the population level, which in turn affects communities and ecosystems. Understanding both cause and consequence is particularly important for predicting when variation begets variation in a positive feedback loop, versus when a negative feedback causes variation to be dampened successively. Finally, maintaining standing variation in movement may be important for facilitating species' ability to respond to future environmental change.

Assessing the importance of Isle of Man waters for the basking shark Cetorhinus maximus

Satellite tracking of endangered or threatened animals can facilitate informed conservation by revealing priority areas for their protection. Basking sharks Cetorhinus maximus (n = 11) were tagged during the summers of 2013, 2015, 2016 and 2017 in the Isle of Man (IoM; median tracking duration 378 d, range: 89-804 d; median minimum straight-line distance travelled 541 km, range: 170-10406 km). Tracking revealed 3 movement patterns: (1) coastal movements within IoM and Irish waters, (2) summer northward movements to Scotland and (3) international movements to Morocco and Norway. One tagged shark was bycaught and released alive in the Celtic Sea. Basking sharks displayed inter-annual site fidelity to the Irish Sea (n = 3), a Marine Nature Reserve (MNR) in IoM waters (n = 1), and Moroccan waters (n = 1). Core distribution areas (50% kernel density estimation) of 5 satellite tracked sharks in IoM waters were compared with 3902 public sightings between 2005 and 2017, highlighting west and south coast hotspots. Location data gathered from satellite tagging broadly correspond to the current boundaries of MNRs in IoM waters. However, minor modifications of some MNR boundaries would incorporate ~20% more satellite tracking location data from this study, and protective measures for basking sharks in IoM waters could further aid conservation of the species at local, regional and international scales. We also show the first documented movement of a basking shark from the British Isles to Norway, and the longest ever track for a tagged basking shark (2 yr and 2 mo, 804 d).

Habitat choices of African buffalo (Syncerus caffer) and plains zebra (Equus quagga) in a heterogeneous protected area

Abstract ContextAn understanding of large herbivore habitat choices in heterogeneous African protected areas is important for the better management of these key ecosystems. AimsTo determine habitat use of African buffalo (Syncerus caffer) and plains zebra (Equus quagga) in a heterogeneous protected area. MethodsZambezi National Park (ZNP), Zimbabwe, was divided into five vegetation types using an unsupervised classification on a Landsat satellite image that was classified into five land cover classes, using the K-means classification algorithm. African buffalo and plains zebra densities were then determined in each vegetation type using road transect surveys monthly between January 2013 and December 2015. Normalised difference vegetation index (NDVI), grass biomass, grass height and grass quality (nitrogen, calcium, phosphorus and acid detergent fibre content) were determined in each vegetation type during the wet (November to April) and dry (August to October) seasons to establish their quality as habitats for African buffalo and plains zebra. Key resultsBoth African buffalo and plains zebra mostly foraged in mixed and grassland areas, and avoided Zambezi teak vegetation type. Zambezi teak vegetation type had high NDVI due to the dense tree cover. Both African buffalo and plains zebra preferred vegetation types with intermediate grass biomass (approximately 300gm−2) and grass height (approximately 16cm). Grass nutritive value (in terms of nitrogen, phosphorus and acid detergent fibre) declined from wet to dry season in all vegetation types. ConclusionsAfrican buffalo and plains zebra in the ZNP confined their habitat use mostly to two vegetation types (mixed and grassland), which together covered 25% of the protected area. ImplicationsTeak (Baikiaea plurijuga) vegetation, which accounted for about 60% of the ZNP, was avoided by both African buffalo and plains zebra, suggesting that a significant part of the protected area was not used by the two herbivores.

Systematic review of equids and telemetry collars: implications for deployment and reporting

Abstract Data from animals equipped with global positioning system collars have advanced our understanding of vertebrates, but this technology has rarely been employed to study feral equids. Hesitation to equip feral equids with telemetry collars in the USA can often be attributed to safety concerns stemming from one study from the 1980s, where injuries were sustained by feral horses (Equus ferus caballus) equipped with radio-collars. Improvements in collar design over the ensuing quarter-century may have decreased risk of collar-related complications; however, telemetry-based studies on feral equids continue to be limited. In the present review, studies from wild and feral equids worldwide were systematically reviewed to better understand the mortality and injury risk in application of telemetry collars to equids. Our goals were to: (1) report the number of individual equids fitted with telemetry collars (1979–2017); and (2) document the number of individual equids that reportedly died or suffered injuries from collars or other sources. A comparative review of elk (Cervus canadensis), mule deer (Odocoileus hemionus) and pronghorn (Antilocapra americana) was also conducted to evaluate the relative risk of collar-related complications among equids and routinely collared North American ungulates. In total, 1089 wild and feral telemetered equids were identified across 48 studies. Of these, 87 (8.0%) were reported to have died, with only one (0.09%) mortality attributable to a collar. Comparatively, 23.0% (1095) of 4761 elk, mule deer and pronghorn fitted with telemetry collars were found to have died in the same number of studies, though no mortalities were reported to be related to the collar. Although wild and feral equids did not experience increased natural mortality compared with the other ungulates, studies have not provided sufficient information to assess relative risk of collar-related complications. Explicit reporting and discussion of telemetry collar impacts in future publications of all animal species are recommended, especially equids, to improve understanding of how telemetry collars can affect study individuals.

Migration and disturbance: impact of fencing and development on Western Rattlesnake (Crotalus oreganus) spring movements in British Columbia

Due to increasing anthropogenic pressures, including land-use transformation globally, the natural process of animal migration is undergoing alterations across many taxa. Small-scale migrants provide useful systems at workable scales for investigating the influence of disturbance and landscape barriers on natural movement patterns and migrations. The Western Rattlesnake (Crotalus oreganus Holbrook, 1840) in British Columbia, Canada, is a small, migrant predator that undertakes seasonal spring movements from its communal hibernaculum to summer hunting and mating grounds and reverses its movements in autumn. From 2011 to 2016, we examined changes to spring migration movements in 27 male Western Rattlesnakes encountering both mitigative fencing barriers and disturbed habitats. Individuals moving through disturbed habitats or intercepted by mitigative fencing demonstrated shorter migration distances and reduced spring path sinuosity compared with individuals migrating in undisturbed habitats. Specifically, individuals encountering a fence during spring movements completed shorter total spring migration path lengths and occupied smaller home ranges over the course of the entire active season. Total spring migration distance also was strongly associated with the distance that individuals traveled until they first encountered human disturbance. This study contributes significantly to our knowledge of how fencing barriers may impact normal behavioural patterns in smaller vertebrates.

Spatial ecology of male hippopotamus in a changing watershed

The obligate dependency of the common hippopotamus, Hippopotamus amphibius, on water makes them particularly vulnerable to hydrological disturbances. Despite the threats facing this at-risk species, there is a lack of information regarding H. amphibius spatial ecology. We used high-resolution tracking data of male H. amphibius to assess home range size, movement mode (e.g. residency and migratory movements), and resource selection patterns. We compared these results across seasons to understand how hydrological variability influences H. amphibius movement. Our study watershed has been severely impacted by anthropogenic water abstraction causing the river to stop flowing for prolonged periods. We observed H. amphibius movements to be highly constrained to the river course with grassy floodplains being their preferred habitat. Dominant and small sub-adult males displayed year-round residency in/near river pools and had smaller home ranges compared to large sub-adults. During the dry season, large sub-adult males made significant (~15 km) upstream movements. The larger home range size of large sub-adults can be attributed to the elevated levels of migratory and exploratory activities to limit conspecific aggression as the river dries. Our observations provide insight into how future changes in water flow may influence male H. amphibius movements and populations through density-dependent effects.

Longest terrestrial migrations and movements around the world

Long-distance terrestrial migrations are imperiled globally. We determined both round-trip migration distances (straight-line measurements between migratory end points) and total annual movement (sum of the distances between successive relocations over a year) for a suite of large mammals that had potential for long-distance movements to test which species displayed the longest of both. We found that caribou likely do exhibit the longest terrestrial migrations on the planet, but, over the course of a year, gray wolves move the most. Our results were consistent with the trophic-level based hypothesis that predators would move more than their prey. Herbivores in low productivity environments moved more than herbivores in more productive habitats. We also found that larger members of the same guild moved less than smaller members, supporting the ‘gastro-centric’ hypothesis. A better understanding of migration and movements of large mammals should aid in their conservation by helping delineate conservation area boundaries and determine priority corridors for protection to preserve connectivity. The magnitude of the migrations and movements we documented should also provide guidance on the scale of conservation efforts required and assist conservation planning across agency and even national boundaries.

Anthropogenic modifications to fire regimes in the wider Serengeti-Mara ecosystem

Fire is a key driver in savannah systems and widely used as a land management tool. Intensifying human land uses are leading to rapid changes in the fire regimes, with consequences for ecosystem functioning and composition. We undertake a novel analysis describing spatial patterns in the fire regime of the Serengeti-Mara ecosystem, document multidecadal temporal changes and investigate the factors underlying these patterns. We used MODIS active fire and burned area products from 2001 to 2014 to identify individual fires; summarizing four characteristics for each detected fire: size, ignition date, time since last fire and radiative power. Using satellite imagery, we estimated the rate of change in the density of livestock bomas as a proxy for livestock density. We used these metrics to model drivers of variation in the four fire characteristics, as well as total number of fires and total area burned. Fires in the Serengeti-Mara show high spatial variability-with number of fires and ignition date mirroring mean annual precipitation. The short-term effect of rainfall decreases fire size and intensity but cumulative rainfall over several years leads to increased standing grass biomass and fuel loads, and, therefore, in larger and hotter fires. Our study reveals dramatic changes over time, with a reduction in total number of fires and total area burned, to the point where some areas now experience virtually no fire. We suggest that increasing livestock numbers are driving this decline, presumably by inhibiting fire spread. These temporal patterns are part of a global decline in total area burned, especially in savannahs, and we caution that ecosystem functioning may have been compromised. Land managers and policy formulators need to factor in rapid fire regime modifications to achieve management objectives and maintain the ecological function of savannah ecosystems.

Cross-boundary human impacts compromise the Serengeti-Mara ecosystem

Protected areas provide major benefits for humans in the form of ecosystem services, but landscape degradation by human activity at their edges may compromise their ecological functioning. Using multiple lines of evidence from 40 years of research in the Serengeti-Mara ecosystem, we find that such edge degradation has effectively “squeezed” wildlife into the core protected area and has altered the ecosystem’s dynamics even within this 40,000-square-kilometer ecosystem. This spatial cascade reduced resilience in the core and was mediated by the movement of grazers, which reduced grass fuel and fires, weakened the capacity of soils to sequester nutrients and carbon, and decreased the responsiveness of primary production to rainfall. Similar effects in other protected ecosystems worldwide may require rethinking of natural resource management outside protected areas.

Joint species movement modeling: how do traits influence movements?

Joint species distribution modeling has enabled researchers to move from species-level to community-level analyses, leading to statistically more efficient and ecologically more informative use of data. Here, we propose joint species movement modeling (JSMM) as an analogous approach that enables inferring both species- and community-level movement parameters from multispecies movement data. The species-level movement parameters are modeled as a function of species traits and phylogenetic relationships, allowing one to ask how species traits influence movements, and whether phylogenetically related species are similar in their movement behavior. We illustrate the modeling framework with two contrasting case studies: a stochastic redistribution model for direct observations of bird movements and a spatially structured diffusion model for capture-recapture data on moth movements. In both cases, the JSMM identified several traits that explain differences in movement behavior among species, such as movement rate increasing with body size in both birds and moths. We show with simulations that the JSMM approach increases precision of species-specific parameter estimates by borrowing information from other species that are closely related or have similar traits. The JSMM framework is applicable for many kinds of data, and it facilitates a mechanistic understanding of the causes and consequences of interspecific variation in movement behavior.

From single steps to mass migration: the problem of scale in the movement ecology of the Serengeti wildebeest

A central question in ecology is how to link processes that occur over different scales. The daily interactions of individual organisms ultimately determine community dynamics, population fluctuations and the functioning of entire ecosystems. Observations of these multiscale ecological processes are constrained by various technological, biological or logistical issues, and there are often vast discrepancies between the scale at which observation is possible and the scale of the question of interest. Animal movement is characterized by processes that act over multiple spatial and temporal scales. Second-by-second decisions accumulate to produce annual movement patterns. Individuals influence, and are influenced by, collective movement decisions, which then govern the spatial distribution of populations and the connectivity of meta-populations. While the field of movement ecology is experiencing unprecedented growth in the availability of movement data, there remain challenges in integrating observations with questions of ecological interest. In this article, we present the major challenges of addressing these issues within the context of the Serengeti wildebeest migration, a keystone ecological phenomena that crosses multiple scales of space, time and biological complexity.This article is part of the theme issue 'Collective movement ecology'.

Landscapes of Fear: Spatial Patterns of Risk Perception and Response

Animals experience varying levels of predation risk as they navigate heterogeneous landscapes, and behavioral responses to perceived risk can structure ecosystems. The concept of the landscape of fear has recently become central to describing this spatial variation in risk, perception, and response. We present a framework linking the landscape of fear, defined as spatial variation in prey perception of risk, to the underlying physical landscape and predation risk, and to resulting patterns of prey distribution and antipredator behavior. By disambiguating the mechanisms through which prey perceive risk and incorporate fear into decision making, we can better quantify the nonlinear relationship between risk and response and evaluate the relative importance of the landscape of fear across taxa and ecosystems.

Resource landscapes explain contrasting patterns of aggregation and site fidelity by red knots at two wintering sites

BACKGROUND

Space use strategies by foraging animals are often considered to be species-specific. However, similarity between conspecific strategies may also result from similar resource environments. Here, we revisit classic predictions of the relationships between the resource distribution and foragers' space use by tracking free-living foragers of a single species in two contrasting resource landscapes. At two main non-breeding areas along the East-Atlantic flyway (Wadden Sea, The Netherlands and Banc d'Arguin, Mauritania), we mapped prey distributions and derived resource landscapes in terms of the predicted intake rate of red knots (Calidris canutus), migratory molluscivore shorebirds. We tracked the foraging paths of 13 and 38 individual red knots at intervals of 1 s over two and five weeks in the Wadden Sea and at Banc d'Arguin, respectively. Mediated by competition for resources, we expected aggregation to be strong and site fidelity weak in an environment with large resource patches. The opposite was expected for small resource patches, but only if local resource abundances were high.

RESULTS

Compared with Banc d'Arguin, resource patches in the Wadden Sea were larger and the maximum local resource abundance was higher. However, because of constraints set by digestive capacity, the average potential intake rates by red knots were similar at the two study sites. Space-use patterns differed as predicted from these differences in resource landscapes. Whereas foraging red knots in the Wadden Sea roamed the mudflats in high aggregation without site fidelity (i.e. grouping nomads), at Banc d'Arguin they showed less aggregation but were strongly site-faithful (i.e. solitary residents).

CONCLUSION

The space use pattern of red knots in the two study areas showed diametrically opposite patterns. These differences could be explained from the distribution of resources in the two areas. Our findings imply that intraspecific similarities in space use patterns represent responses to similar resource environments rather than species-specificity. To predict how environmental change affects space use, we need to understand the degree to which space-use strategies result from developmental plasticity and behavioural flexibility. This requires not only tracking foragers throughout their development, but also tracking their environment in sufficient spatial and temporal detail.

Habitat use by a mixed feeder: impala Aepyceros melampus in a heterogeneous protected area

Although large herbivore habitat use has been extensively studied, more information is still required on the use of heterogeneous vegetation types. Over 3 y we carried out monthly road transects in the Zambezi National Park (ZNP), Zimbabwe, to determine the impala density in each of five vegetation types. In addition we determined grass and browse chemical composition to test if at the time the impala switches from grass to browse, grass nutritive quality had declined below that of browse. Furthermore, grass height was measured in the five vegetation types. The impala used mixed, acacia and terminalia vegetation types, which constituted 37% of the protected area and avoided grassland and the predominant Zambezi teak (60% of ZNP) vegetation types. At the time of the diet switch by the impala from grass to browse, woody plant leaf nutritive quality was higher than grass in terms of nitrogen, calcium and acid detergent fibre content. The three vegetation types used by the impala had short to medium grass height. We concluded that when the impala switched from grass to browse the grass nutritive quality was lower than that of the browse.

Partial migration in savanna elephant populations distributed across southern Africa

Migration is an important, but threatened ecological process. Conserving migration requires the maintenance of functional connectivity across sufficiently large areas. Therefore, we need to know if, where and why species migrate. Elephants are highly mobile and can travel long distances but we do not know if they migrate. Here, we analysed the movement trajectories of 139 savanna elephants (Loxodonta africana) within eight clusters of protected areas across southern Africa to determine if elephants migrate, and if so, where, how and why they migrate. Only 25 of these elephants migrated. Elephants are a facultative partially migratory species, where only some individuals in a population migrate opportunistically, and not every year. Elephants migrated between distinct seasonal ranges corresponding to southern Africa’s dry and wet seasons. The timing of wet season migrations was associated with the onset of rainfall and the subsequent greening up of forage. Conversely, the duration, distance, and the timing of dry season migrations varied idiosyncratically. The drivers of elephant migration are likely a complex interaction between individual traits, density, and the distribution and availability of resources. Despite most migrations crossing administrative boundaries, conservation networks provided functional space for elephants to migrate.

A global comparison of the nutritive values of forage plants grown in contrasting environments

Forage plants are valuable because they maintain wild and domesticated herbivores, and sustain the delivery of meat, milk and other commodities. Forage plants contain different quantities of fibre, lignin, minerals and protein, and vary in the proportion of their tissue that can be digested by herbivores. These nutritive components are important determinants of consumer growth rates, reproductive success and behaviour. A dataset was compiled to quantify variation in forage plant nutritive values within- and between-plant species, and to assess variation between plant functional groups and bioclimatic zones. 1255 geo-located records containing 3774 measurements of nutritive values for 136 forage plant species grown in 30 countries were obtained from published articles. Spatial variability in forage nutritive values indicated that climate modified plant nutritive values. Forage plants grown in arid and equatorial regions generally contained less digestible material than those grown in temperate and tundra regions; containing more fibre and lignin, and less protein. These patterns may reveal why herbivore body sizes, digestion and migration strategies are different in warmer and drier regions. This dataset also revealed the capacity for variation in the nutrition provided by forage plants, which may drive consumer species coexistence. The proportion of the plant tissue that was digestible ranged between species from 2 to 91%. The amount of fibre contained within plant material ranged by 23-90%, protein by 2-36%, lignin by 1-21% and minerals by 2-22%. On average, grasses and tree foliage contained the most fibre, whilst herbaceous legumes contained the most protein and tree foliage contained the most lignin. However, there were individual species within each functional group that were highly nutritious. This dataset may be used to identify forage plant species or mixtures of species from different functional groups with useful nutritional traits which can be cultivated to enhance livestock productivity and inform wild herbivore conservation strategies.