Foraging theory upscaled: the behavioural ecology of herbivore movement

DNA Metabarcoding Illuminates Seasonal Dietary Pattern and Niche Partitioning by Three Sympatric Herbivores

Diet composition is among the most critical dimensions of animal ecology, yet seasonal dietary diversity has rarely been investigated in sympatric herbivores. This study used DNA metabarcoding to conduct an analysis of seasonal variations in diet composition and trophic niches for sympatric sika deer, Reeves' muntjac, and Chinese hare in Taohongling National Nature Reserve (TNNR). The results showed that Smilax china (11.79%) was the leading food eaten by sika deer in summer, whereas dominated by Rubus spp. (36.42%) and Loropetalum chinense (25.48%) in winter; Rubus spp. accounted for the majority of Reeves' muntjac's diet throughout the year. In comparison, the Chinese hare primarily consumed Smilax china from winter to spring but changed to Poa annua (10.81%) and Setaria viridis (23.05%) in summer and fall. Compared to other seasons, significant differences (Shannon index, p < 0.05) occurred in spring and summer, showing higher diversity of food items across the three herbivorous. Nonmetric multidimensional scaling (NMDS) analysis suggested significant partitioning in the food items of Chinese hares compared to the two ruminants. Both sika deer and Reeves' muntjac occupied a wider niche breadth and dietary diversity in summer, reflecting generalised feeding habits (Sd: Ba = 0.06; Rm: Ba = 0.04) and lower in fall (Ba = 0.01) with stronger selectivity and specialization, which was consistent with the optimal foraging theory. Notably, no significant difference was indicated in seasonal niche breadth for Chinese hare (p > 0.05). The niche overlap indices were 0.989 (fall) and 0.831 (winter) between sika deer and Reeves' muntjac, indicating a higher dietary similarity and overlap. However, differences in foraging plant taxa and abundance ratios may facilitate dietary niche partitioning. The diet of herbivores reflected plant-herbivore interactions and seasonal diet differences were correlated with feeding strategies, which facilitate coexistence and reduce competition of co-occurring species in the food dimension.

Drivers of spring migration phenology in Rocky Mountain elk

By migrating, ungulates take advantage of cyclical fluctuations in resources, which allows them to persist at greater population numbers than they would in the absence of these seasonal movements. We sought to identify the drivers of spring elk (Cervus canadensis) migration and evaluate how well individuals were able to optimize access to forage prior to departure, while migrating, and upon arrival on summer range. Specifically, we investigated the timing and duration of spring migration in four Colorado elk herds to test how forage quality and snow dynamics pre-, during, and post-migration influenced elk departure from winter range and the length of time spent migrating. Our analyses revealed significant heterogeneity among and within herds. Overall, spatiotemporal dynamics in forage and snow emerged as critical drivers influencing migratory phenology, but the discrete covariates associated with forage and snow were herd-specific. We did not find marked sub-strategies wherein some herds or individuals optimized a specific component of migration, but rather found that elk varied in their ability to optimize access to forage at all times analyzed. Our findings suggest that elk exhibit a flexible response to environmental cues, adjusting migration timing and duration in accordance with local conditions. These results contribute to a deeper understanding of the mechanisms driving ungulate migration and emphasize the importance of considering dynamic environmental factors in studies of migration phenology. Further, they emphasize the importance of forage conditions not just on the migratory route, but also on winter and summer range. Additionally, they provide baseline knowledge of elk migrations in Colorado, useful information for ensuring the conservation and persistence of these migratory routes and the productivity they facilitate.

The energetics of movement, from exercise to ecology and evolution

Movement is energetically costly, requiring muscle activity to support and propel the animal as it walks, runs, climbs, swims or flies. In this Review, I examine the metabolic impact of locomotion over different timescales. During locomotion, whole-body energy expenditure can rise by more than an order of magnitude above resting, and these costs arise from activating muscle to exert force as well as the work that muscles perform. Over hours or days, locomotion can dominate daily energy expenditure (i.e. field metabolic rate), particularly when provisioning young, migrating, or during other periods of intense activity. The relationship between muscle force and metabolic cost means that locomotor costs and daily expenditures can be tracked using wearable accelerometers. Over longer timescales, however, the relationship between locomotion and daily expenditure becomes more tenuous. Compensatory trade-offs with other physiological activity, including thermoregulation, growth, maintenance and reproduction, obscure the relationship between daily locomotor activity and daily energy expenditure. Over evolutionary timeframes, variation in daily locomotor activity does not predict variation in daily expenditure. The apparent trade-offs between locomotor expenditure and other physiological tasks suggests that, over long timescales, the cost of locomotion might be best measured by its effects on other systems. The impact of locomotion on growth, reproduction and maintenance should be incorporated into ecological and evolutionary assessments of the costs of movement.

A Functional Response in Resource Selection Links Multiscale Responses of a Large Carnivore to Human Mortality Risk

Theory suggests that animals make hierarchical, multiscale resource selection decisions to address the hierarchy of factors limiting their fitness. Ecologists have developed tools to link population-level resource selection across scales; yet, theoretical expectations about the relationship between coarse- and fine-scale selection decisions at the individual level remain elusive despite their importance to fitness. With GPS-telemetry data collected across California, USA, we evaluated resource selection of mountain lions (Puma concolor; n = 244) relative to spatial variation in human-caused mortality risk. With hierarchical resource selection, coarse-scale selection determines availability at finer scales. This simple relationship allowed us to demonstrate that functional responses in resource selection explicitly link individual-level resource selection decisions across scales. We show that individuals proactively avoiding risk when selecting home ranges are freed to relax this avoidance when making decisions within home ranges. However, individuals also exhibit reactive avoidance of risk at the finest scales along movement paths.

Habitat selection ecology of the aquatic beetle community using explainable machine learning

The aim of our work is to determine the importance of habitat features for the selection of the aquatic beetle community. Insects are represented by their general ecological traits such as body size, ecological element and trophic type, which are categorised into four body size ranges, four ecological groups and four trophic types. To determine the importance of habitat selection of the studied insects, we analysed the relationships between the above categories and the set of habitat features of the lake and its surroundings. Ensemble machine learning modelling (XGBoost-SHAP) revealed the mechanism of habitat feature selection in relation to the general ecological traits. We found strong interactions between the body size, ecological element and trophic type of beetles, suggesting that these general traits control the structure and functioning of the beetle community studied. The area of the lake and the features of beetle occurrence in the aquatic environment play an important but secondary role, and the importance of the characteristics of the lake's riparian zone was minimised. We found several categories of beetles as they select the number of the same habitat features. The study can provide valuable information for the practical conservation and management of lake ecosystems.

Faithful pals and familiar locales: differentiating social and spatial site fidelity during reproduction

Site fidelity-the tendency to reuse familiar spaces-is expected to improve fitness. Familiarity with the local environment is particularly crucial when resource demands or predation risk are high. Consequently, site fidelity often peaks during reproduction when energetic costs are high and offspring are vulnerable. For many species, the environment they experience is not solely a function of geography but also of the social environment. Social fidelity, the selection for familiar social environments, could constitute an independent or parallel strategy to spatial fidelity when considering behaviour at the spatial-social interface. Using global positioning system locations from caribou across Newfoundland, we tested whether females selected calving sites based on proximity to familiar conspecifics, in addition to geographical (spatial) fidelity. These strategies were synergistic, not alternative, and correlated across the population but more variable within individuals. We also tested whether either form of fidelity affected reproductive success. We failed to detect an effect of spatial or social fidelity on reproductive success in this population. Nevertheless, given the association between social and spatial fidelity and the demonstrated fitness consequences of site fidelity in other systems, familiar conspecifics and the potential benefits these social partners provide may be an underappreciated component driving site fidelity.This article is part of the theme issue 'The spatial-social interface: a theoretical and empirical integration'.

Sirenian (manatees and dugongs) reproductive endocrinology

Reproductive hormones are essential to mating systems, behavior, fertility, gestation, parturition, and lactation in mammals and understanding the role of hormones in these processes is essential for species conservation. Sirenia is a unique order of marine mammals that include manatees, dugongs, and the extinct Steller's sea cow. Extant Sirenian species are all listed as vulnerable due to habitat loss, cold stress, boat strike trauma, harmful algal bloom toxicity, entanglements, and illegal hunting. Therefore, successful reproduction is essential to maintaining and increasing Sirenian populations. Understanding Sirenian reproductive behavior, endocrinology, and mating strategies will aid conservation and management efforts to protect and provide the proper conditions for successful reproduction. The objectives of this review were to synthesize the current knowledge regarding reproductive cycles and endocrinology of Sirenians and identify knowledge gaps for future investigation. The current literature on Sirenian reproductive physiology reports reproductive seasonality, sexual maturation, estrous cyclicity and acyclicity, pregnancy, and sex differences. However, there remain significant knowledge gaps on the cyclicity and pulsatile release of gonadotropins, maturation in females, and characterization of pregnancy hormone profiles throughout gestation. To date, there is no explanation for confirmed pattern for ovarian acyclicity, nor understanding of the function of the numerous accessory corpus luteum described in manatees. Research including a greater number of longitudinal and postmortem studies on a wider variety of wild manatee populations are important first steps. Taken together, understanding the reproductive endocrinology of these vulnerable and threatened species is critical for policy and management decisions to better inform protection initiatives.

Effects of the social environment on movement-integrated habitat selection

BACKGROUND

Movement links the distribution of habitats with the social environment of animals using those habitats. Despite the links between movement, habitat selection, and socioecology, their integration remains a challenge due to lack of shared vocabulary across fields, methodological gaps, and the implicit (rather than explicit) historical development of theory in the fields of social and spatial ecology. Given these challenges can be addressed, opportunity for further study will provide insight about the links between social, spatial, and movement ecology. Here, our objective was to disentangle the roles of habitat selection and social association as drivers of movement in caribou (Rangifer tarandus).

METHODS

To accomplish our objective, we modelled the relationship between collective movement and selection of foraging habitats using socially informed integrated step selection function (iSSF). Using iSSF, we modelled the effect of social processes, i.e., nearest neighbour distance and social preference, and movement behaviour on patterns of habitat selection.

RESULTS

By unifying social network analysis with iSSF, we identified movement-dependent social association, where individuals took shorter steps in lichen habitat and foraged in close proximity to more familiar individuals.

CONCLUSIONS

Our study demonstrates that social preference is context-dependent based on habitat selection and foraging behaviour. We therefore surmise that habitat selection and social association are drivers of collective movement, such that movement is the glue between habitat selection and social association. Here, we put these concepts into practice to demonstrate that movement is the glue connecting individual habitat selection to the social environment.

How do productivity gradient and diffusion shape patterns in a plant-herbivore grazing system?

Natural systems show heterogeneous patchy distributions of vegetation over large landscapes. Reaction-diffusion systems can demonstrate such heterogeneity of species distributions. Here, we analyse a reaction-diffusion model of plant-herbivore interactions in two-dimensional space to illustrate non-homogeneous distributions of plants and herbivores. The non-spatial system shows bottom-up control, where herbivore density is low under low and high primary productivity but increased at intermediate productivity. In addition, the non-spatial system provides bistability between a dense vegetation state devoid of herbivores and a coexisting state of plants and herbivores. In the spatiotemporal model, we give analytical conditions of occurring diffusion-driven (Turing) instability, where a novel point in our model is the relative dispersal of herbivores, which represents the movement of herbivores from a higher to a lower vegetation state in addition to the self-diffusion of both species. It is shown that heterogeneity in the population distribution does not occur if the relative dispersal of herbivores is low, but it appears in the opposite case. Due to bistability in the underlying non-spatial system, the spatiotemporal model produces initial value-dependent patterns. The two initial values make different patterns despite having the same primary productivity and relative dispersal rate. As productivity increases with a given relative herbivore dispersal, pattern transition occurs from a blend of stripes and spots of low vegetation state to a predominantly low-density vegetation state with smaller patches of densely vegetated states with one initial value. On the contrary, a discernible change in vegetation patterns from cold spots in the dense vegetation to hot stripes in the primarily low-vegetated state is noticed under the other initial population value. Furthermore, the population distributions of plants and herbivores in the entire domain after a long period are heterogeneous for both initial values, provided the relative herbivore dispersal is substantial. We estimated mean population densities to observe species fitness in the whole domain under variable productivity. When productivity is high, the mean population density of plants may go up or down, depending on the herbivore's relative dispersal rate. In contrast to the bottom-up control dynamics of the non-spatial system, the system exhibits a top-down control under high relative dispersal, where the herbivore regulates vegetation growth under high productivity. On the other hand, herbivores are extinct under high productivity if the relative dispersal is low.

The role of memory-based movements in the formation of animal home ranges

Most animals live in spatially-constrained home ranges. The prevalence of this space-use pattern in nature suggests that general biological mechanisms are likely to be responsible for their occurrence. Individual-based models of animal movement in both theoretical and empirical settings have demonstrated that the revisitation of familiar areas through memory can lead to the formation of stable home ranges. Here, we formulate a deterministic, mechanistic home range model that includes the interplay between a bi-component memory and resource preference, and evaluate resulting patterns of space-use. We show that a bi-component memory process can lead to the formation of stable home ranges and control its size, with greater spatial memory capabilities being associated with larger home range size. The interplay between memory and resource preferences gives rise to a continuum of space-use patterns-from spatially-restricted movements into a home range that is influenced by local resource heterogeneity, to diffusive-like movements dependent on larger-scale resource distributions, such as in nomadism. Future work could take advantage of this model formulation to evaluate the role of memory in shaping individual performance in response to varying spatio-temporal resource patterns.

Seasonal activity patterns of a Kalahari mammal community: Trade-offs between environmental heat load and predation pressure

Mammals in arid zones have to trade off thermal stress, predation pressure, and time spent foraging in a complex thermal landscape. We quantified the relationship between the environmental heat load and activity of a mammal community in the hot, arid Kalahari Desert. We deployed miniature black globe thermometers within the existing Snapshot Safari camera trap grid on Tswalu Kalahari Reserve, South Africa. Using the camera traps to record species' activity throughout the 24-h cycle, we quantified changes in the activity patterns of mammal species in relation to heat loads in their local environment. We compared the heat load during which species were active between two sites with differing predator guilds, one where lion (Panthera leo) biomass dominated the carnivore guild and the other where lions were absent. In the presence of lion, prey species were generally active under significantly higher heat loads, especially during the hot and dry spring. We suggest that increased foraging under high heat loads highlights the need to meet nutritional requirements while avoiding nocturnal activity when predatory pressures are high. Such a trade-off may become increasingly costly under the hotter and drier conditions predicted to become more prevalent as a result of climate change within the arid and semi-arid regions of southern Africa.

Patterns of Animal Rabies Prevalence in Northern South Africa between 1998 and 2022

Rabies is endemic in South Africa and rabies cycles are maintained in both domestic and wildlife species. The significant number of canine rabies cases reported by the World Organization for Animal Health Reference Laboratory for Rabies at Onderstepoort suggests the need for increased research and mass dog vaccinations on specific targeted foci in the country. This study aimed to investigate the spatiotemporal distribution of animal rabies cases from 1998 to 2017 in northern South Africa and environmental factors associated with highly enzootic municipalities. A descriptive analysis was used to investigate temporal patterns. The Getis-Ord Gi statistical tool was used to exhibit low and high clusters. Logistic regression was used to examine the association between the predictor variables and highly enzootic municipalities. A total of 9580 specimens were submitted for rabies diagnosis between 1998 and 2022. The highest positive case rates were from companion animals (1733 cases, 59.71%), followed by livestock (635 cases, 21.88%) and wildlife (621 cases, 21.39%). Rabies cases were reported throughout the year, with the majority occurring in the mid-dry season. Hot spots were frequently in the northern and eastern parts of Limpopo and Mpumalanga. Thicket bush and grassland were associated with rabies between 1998 and 2002. However, between 2008 and 2012, cultivated commercial crops and waterbodies were associated with rabies occurrence. In the last period, plantations and woodlands were associated with animal rabies. Of the total number of municipalities, five consistently and repeatedly had the highest rabies prevalence rates. These findings suggest that authorities should prioritize resources for those municipalities for rabies elimination and management.

A multistate Langevin diffusion for inferring behavior-specific habitat selection and utilization distributions

The identification of important habitat and the behavior(s) associated with it is critical to conservation and place-based management decisions. Behavior also links life-history requirements and habitat use, which are key to understanding why animals use certain habitats. Animal population studies often use tracking data to quantify space use and habitat selection, but they typically either ignore movement behavior (e.g., foraging, migrating, nesting) or adopt a two-stage approach that can induce bias and fail to propagate uncertainty. We develop a habitat-driven Langevin diffusion for animals that exhibit distinct movement behavior states, thereby providing a novel single-stage statistical method for inferring behavior-specific habitat selection and utilization distributions in continuous time. Practitioners can customize, fit, assess, and simulate our integrated model using the provided R package. Simulation experiments demonstrated that the model worked well under a range of sampling scenarios as long as observations were of sufficient temporal resolution. Our simulations also demonstrated the importance of accounting for different behaviors and the misleading inferences that can result when these are ignored. We provide case studies using plains zebra (Equus quagga) and Steller sea lion (Eumetopias jubatus) telemetry data. In the zebra example, our model identified distinct "encamped" and "exploratory" states, where the encamped state was characterized by strong selection for grassland and avoidance of other vegetation types, which may represent selection for foraging resources. In the sea lion example, our model identified distinct movement behavior modes typically associated with this marine central-place forager and, unlike previous analyses, found foraging-type movements to be associated with steeper offshore slopes characteristic of the continental shelf, submarine canyons, and seamounts that are believed to enhance prey concentrations. This is the first single-stage approach for inferring behavior-specific habitat selection and utilization distributions from tracking data that can be readily implemented with user-friendly software. As certain behaviors are often more relevant to specific conservation or management objectives, practitioners can use our model to help inform the identification and prioritization of important habitats. Moreover, by linking individual-level movement behaviors to population-level spatial processes, the multistate Langevin diffusion can advance inferences at the intersection of population, movement, and landscape ecology.

Monitoring the Effect of Weed Encroachment on Cattle Behavior in Grazing Systems Using GPS Tracking Collars

Weed encroachment on grasslands can negatively affect herbage allowance and animal behavior, impacting livestock production. We used low-cost GPS collars fitted to twenty-four Angus crossbred steers to evaluate the effects of different levels of weed encroachment on animal activities and spatial distribution. The experiment was established with a randomized complete block design, with three treatments and four blocks. The treatments were paddocks free of weeds (weed-free), paddocks with weeds established in alternated strips (weed-strips), and paddocks with weeds spread throughout the entire area (weed-infested). Animals in weed-infested paddocks had reduced resting time and increased grazing time, distance traveled, and rate of travel (p < 0.05) compared to animals in weed-free paddocks. The spatial distribution of the animals was consistently greater in weed-free paddocks than in weed-strips or weed-infested areas. The effects of weed encroachment on animal activities were minimized after weed senescence at the end of the growing season. Pasture weed encroachment affected cattle behavior and their spatial distribution across the pasture, potentially impacting animal welfare. Further long-term studies are encouraged to evaluate the impacts of weed encroachment on animal performance and to quantify the effects of behavioral changes on animal energy balance.

Behavioral-dependent recursive movements and implications for resource selection

Within home ranges, animals repeatedly visit certain areas. Recursive movement patterns are widespread throughout the animal kingdom, but are rarely considered when developing resource selection models. We examined how behavioral state-dependent recursive movements influenced reource selection of eastern wild turkey (Meleagris gallopavo silvestris) broods as they aged from day 1 to 28. Because broods become more plastic in behaviors once they begin roosting off the ground, we separated data into broods that were ground roosting (1-13 days) and tree roosting (14-28 days). We used Hidden Markov Models to identify 2 behavioral states (restricted and mobile). We extracted state-specific recursive movements based on states and specific step lengths, which we integrated into a step selection analysis to evaluate resource selection. We found that in a restricted state, ground roosting broods spent less time in areas of mixed pine-hardwoods and more time in areas with greater vegetation density. Tree roosting broods revisited areas closer to shrub/scrub landcover types, and areas with greater vegetation density. Tree roosting broods also spent less time near mixed pine-hardwoods, while spending more time in areas with greater vegetation density. We found that in a mobile state, ground roosting broods revisited areas closer to secondary roads and mixed pine-hardwoods, but farther from hardwoods. Tree roosting broods revisited areas farther from secondary roads and with greater vegetation density. Tree roosting broods also spent more time in areas closer to pine. Resource selection varied depending on behavioral state and recursive movements. However, revisitation and residence time impacted selection in both ground and tree roosting broods. Our findings highlight the need to consider how behaviors can influence movement decisions and ultimately resource selection.

Seasonal resource selection of free-ranging Zhongwei goats in the semi-arid grassland

Goats rarely move and forage randomly. They tend to move in ways generally influenced by biotic and abiotic factors, respectively. However, few studies have explored the foraging behaviour of goats in the absence of predation and human disturbance. Based on step selection function modelling framework, Normalised Difference Vegetation Index, vegetation surveys, and Global Positioning System tracking of 124 free-ranging domestic adult male Zhongwei goats over one year (2016-2017) were used to assess how biotic and abiotic environmental factors affected their spatiotemporal distribution, and developed a conceptual model to represent the goats' trade-off between forage quantity and preference at different seasons, in the semi-arid grassland of Loess Plateau of 1 178 hectare. The results showed that spatial distributions of goats responded to spatiotemporal variation of biotic factors rather than abiotic factors of elevation, slope and solar radiation, which indicated that biotic factors were of priority to abiotic factors in the foraging process for the goats. According to the season changing, the goats positively used areas with higher forage quantity in the spring and winter, areas of higher forage quantity and preferred species in summer, and areas of abundance of preferred species in autumn. We developed a model to describe the phenomenon that the goats selected areas with higher preferred species only when the forage quantity was plentiful, otherwise they selected areas with higher forage quantity. Better understanding of the patterns and drivers of spatiotemporal distribution of the goats can improve our ability to predict foraging behaviour of livestock in heterogeneous environment and lead to better management practices and policies for the sustainability of these semi-arid landscapes and associated ecosystem services.

Trophic Position of the Species and Site Trophic State Affect Diet Niche and Individual Specialization: From Apex Predator to Herbivore

Intra-species variability in isotopic niches, specifically isotopic total niche width (ITNW), isotopic individual niche width (IINW), and isotopic individual specialization (IIS), was studied using an innovative approach without sacrificing the vertebrates. Stable isotopes (δ13C, δ15N) in four body tissues differing in isotopic half-life were analyzed from four freshwater fish species representing different trophic positions. ITNW was widest for the apex predator (European catfish) and narrowest for the obligate predator (Northern pike). IINW exhibited a polynomial trend for the European catfish, Northern pike, and Eurasian perch (mesopredator), decreasing with body mass and increasing again after exceeding a certain species-dependent body mass threshold. Thus, for ectotherms, apex predator status is linked rather to its size than to the species. In herbivores (rudd), IINW increased with body mass. The IIS of predators negatively correlated with site trophic state. Therefore, eutrophication can significantly change the foraging behavior of certain species. We assume that the observed trends will occur in other species at similar trophic positions in either aquatic or terrestrial systems. For confirmation, we recommend conducting a similar study on other species in different habitats.

Hidden Markov movement models reveal diverse seasonal movement patterns in two North American ungulates

Animal movement is the mechanism connecting landscapes to fitness, and understanding variation in seasonal animal movements has benefited from the analysis and categorization of animal displacement. However, seasonal movement patterns can defy classification when movements are highly variable. Hidden Markov movement models (HMMs) are a class of latent-state models well-suited to modeling movement data. Here, we used HMMs to assess seasonal patterns of variation in the movement of pronghorn (Antilocapra americana), a species known for variable seasonal movements that challenge analytical approaches, while using a population of mule deer (Odocoileus hemionus), for whom seasonal movements are well-documented, as a comparison. We used population-level HMMs in a Bayesian framework to estimate a seasonal trend in the daily probability of transitioning between a short-distance local movement state and a long-distance movement state. The estimated seasonal patterns of movements in mule deer closely aligned with prior work based on indices of animal displacement: a short period of long-distance movements in the fall season and again in the spring, consistent with migrations to and from seasonal ranges. We found seasonal movement patterns for pronghorn were more variable, as a period of long-distance movements in the fall was followed by a winter period in which pronghorn were much more likely to further initiate and remain in a long-distance movement pattern compared with the movement patterns of mule deer. Overall, pronghorn were simply more likely to be in a long-distance movement pattern throughout the year. Hidden Markov movement models provide inference on seasonal movements similar to other methods, while providing a robust framework to understand movement patterns on shorter timescales and for more challenging movement patterns. Hidden Markov movement models can allow a rigorous assessment of the drivers of changes in movement patterns such as extreme weather events and land development, important for management and conservation.

Ranging behaviours across ecological and anthropogenic disturbance gradients: a pan-African perspective of giraffe (Giraffa spp.) space use

Animal movement behaviours are shaped by diverse factors, including resource availability and human impacts on the landscape. We generated home range estimates and daily movement rate estimates for 149 giraffe (Giraffa spp.) from all four species across Africa to evaluate the effects of environmental productivity and anthropogenic disturbance on space use. Using the continuous time movement modelling framework and a novel application of mixed effects meta-regression, we summarized overall giraffe space use and tested for the effects of resource availability and human impact on 95% autocorrelated kernel density estimate (AKDE) size and daily movement. The mean 95% AKDE was 359.9 km2 and the mean daily movement was 14.2 km, both with marginally significant differences across species. We found significant negative effects of resource availability, and significant positive effects of resource heterogeneity and protected area overlap on 95% AKDE size. There were significant negative effects of overall anthropogenic disturbance and positive effects of the heterogeneity of anthropogenic disturbance on daily movements and 95% AKDE size. Our results provide unique insights into the interactive effects of resource availability and anthropogenic development on the movements of a large-bodied browser and highlight the potential impacts of rapidly changing landscapes on animal space-use patterns.

Joint use of location and acceleration data reveals influences on transitions among habitats in wintering birds

Quantifying relationships between animal behavior and habitat use is essential to understanding animal decision-making. High-resolution location and acceleration data allows unprecedented insights into animal movement and behavior. These data types allow researchers to study the complex linkages between behavioral plasticity and habitat distribution. We used a novel Markov model in a Bayesian framework to quantify the influence of behavioral state frequencies and environmental variables on transitions among landcover types through joint use of location and tri-axial accelerometer data. Data were collected from 56 greater white-fronted geese (Anser albifrons frontalis) across seven ecologically distinct winter regions over two years in midcontinent North America. We showed that goose decision-making varied across landcover types, ecoregions, and abiotic conditions, and was influenced by behavior. We found that time spent in specific behaviors explained variation in the probability of transitioning among habitats, revealing unique behavioral responses from geese among different habitats. Combining GPS and acceleration data allowed unique study of potential influences of an ongoing large-scale range shift in the wintering distribution of a migratory bird across midcontinent North America. We anticipate that behavioral adaptations among variable landscapes is a likely mechanism explaining goose use of highly variable ecosystems during winter in ways which optimize their persistence.

Mechanisms of individual variation in large herbivore diets: Roles of spatial heterogeneity and state-dependent foraging

Many populations of consumers consist of relatively specialized individuals that eat only a subset of the foods consumed by the population at large. Although the ecological significance of individual-level diet variation is recognized, such variation is difficult to document, and its underlying mechanisms are poorly understood. Optimal foraging theory provides a useful framework for predicting how individuals might select different diets, positing that animals balance the "opportunity cost" of stopping to eat an available food item against the cost of searching for something more nutritious; diet composition should be contingent on the distribution of food, and individual foragers should be more selective when they have greater energy reserves to invest in searching for high-quality foods. We tested these predicted mechanisms of individual niche differentiation by quantifying environmental (resource heterogeneity) and organismal (nutritional condition) determinants of diet in a widespread browsing antelope (bushbuck, Tragelaphus sylvaticus) in an African floodplain-savanna ecosystem. We quantified individuals' realized dietary niches (taxonomic richness and composition) using DNA metabarcoding of fecal samples collected repeatedly from 15 GPS-collared animals (range 6-14 samples per individual, median 12). Bushbuck diets were structured by spatial heterogeneity and constrained by individual condition. We observed significant individual-level partitioning of food plants by bushbuck both within and between two adjacent habitat types (floodplain and woodland). Individuals with home ranges that were closer together and/or had similar vegetation structure (measured using LiDAR) ate more similar diets, supporting the prediction that heterogeneous resource distribution promotes individual differentiation. Individuals in good nutritional condition had significantly narrower diets (fewer plant taxa), searched their home ranges more intensively (intensity-of-use index), and had higher-quality diets (percent digestible protein) than those in poor condition, supporting the prediction that animals with greater endogenous reserves have narrower realized niches because they can invest more time in searching for nutritious foods. Our results support predictions from optimal foraging theory about the energetic basis of individual-level dietary variation and provide a potentially generalizable framework for understanding how individuals' realized niche width is governed by animal behavior and physiology in heterogeneous landscapes.

Resource-dependent foraging behaviour of grazers enhances effects of nutrient enrichment on algal biomass

Both the quantity and nutritional quality of food resources can strongly influence the foraging movements of herbivores, which in turn determine the strength of top-down control on primary producer biomass. Nutrient enrichment can alter the biomass and nutritional quality of primary producers, but the consequences for the foraging of herbivores and hence for top-down control are still poorly understood. In this study, we combined a two-factorial experiment (two nutrient levels × grazing by the freshwater gastropod Ancylus fluviatilis) with video analyses tracking grazers' movements to investigate nutrient enrichment effects on spatial ranges of grazing activity and algal biomass removal. Natural stream biofilms were grown in phosphorus-enriched (P+) and phosphorus-poor flumes (P-) for two weeks before A. fluviatilis were added to the flumes and allowed to graze on biofilm for an additional 2 weeks. Total periphyton biomass was enhanced by P+ and reduced by grazer presence. However, the total grazer effect depended on the nutrient level: at the end of the experiment, on average 95% of algal cover were removed by grazing in the P- flumes versus 26% in the P+ flumes. Fast movements of A. fluviatilis were detected significantly more often in the P- treatment, whereas grazers were detected resting more often in the P+ treatment. Our results demonstrate that nutrient enrichment can increase primary producer biomass both directly and indirectly by limiting the foraging ranges of herbivores. The resulting feedback loop between reduced grazing activity and increased plant biomass might in turn exacerbate eutrophication effects on habitat structure.

Foraging in heterogeneous landscapes: variation in movement patterns of a tropical sand-bubbler crab

Acquiring food in heterogeneous landscapes presents a challenge to many foragers, as searching for food in an optimal manner is difficult in spatially and temporally variable environments. Investigating individual foraging patterns can elucidate how environmental variations at different scales constrain or select for energy-optimizing movements, which can inform conservation and management strategies by identifying spatio-temporal variations in species’ habitat use. To test how such movements vary with environmental conditions, we investigated foraging patterns of the deposit-feeding sand-bubbler crab, Scopimera intermedia Balss, 1934 at multiple spatial and temporal scales on soft sediment shores in Hong Kong. On a broad, annual, scale the crabs produced foraging tracks of different length and foraged over different areas around their burrows between hot and cool seasons. Although foraging movements of the crabs were slower and more restricted during the cool season, probably due to low environmental temperatures, foraging areas during the hot season were larger but limited by increasing conspecific interactions. Over a smaller scale at which the crabs make movement decisions, parameters such as turning angle and speed were variable, even within individual foraging excursions. Such variations appeared to be responses to small-scale variations in sediment food patches, which resulted in the crabs employing multiple movement modes. This context-dependent foraging strategy enables the crabs to feed for a longer time in food-rich patches compared with a fixed strategy and is, therefore, critical for species living in environments such as intertidal sediments, where food distribution is heterogeneous and foraging time is constrained by the tide.

Structure and functioning of wild and agricultural grazing ecosystems: A comparative review

For more than 10 million years, large, herd forming ruminants have thrived as parts of sustainable grazing ecosystems. Conversely, since their domestication 8,000–11,000 years ago, cattle, sheep, and goats have often exhibited dysfunctional relationships with the ecosystems they inhabit. A considerable literature, developed over decades, documents the negative impacts of animal agriculture and associated activities (e.g., feed production) on grassland ecosystems. Coincident with the accumulating data documenting the impacts of “conventional” animal agriculture, has been a growing interest in restoring functionality to agricultural grazing ecosystems. These “regenerative” protocols often seek to mimic the structure and functions of wild grazing ecosystems. The objectives of this paper were two-fold: First to review the literature describing the structure and some key functional attributes of wild and agricultural grazing ecosystems; and second, to examine these attributes in conventionally and regeneratively managed grazing ecosystems and, assuming the wild condition to be the standard for sustainable grazer-environment relationships, to ascertain whether similar relationships exist in conventionally or regeneratively managed agricultural grazing ecosystems. Not unexpectedly our review revealed the complexity of both wild and agricultural grazing ecosystems and the interconnectedness of biological, chemical, and physical factors and processes within these systems. Grazers may increase or decrease system functionality, depending upon environmental conditions (e.g., moisture levels). Our review revealed that biodiversity, nitrogen cycling, and carbon storage in regenerative grazing systems more closely resemble wild grazing ecosystems than do conventional grazing systems. We also found multiple points of disagreement in the literature, particularly with respect to aboveground primary production (ANPP). Finally, we acknowledge that, while much has been accomplished in understanding grazing ecosystems, much remains to be done. In particular, some of the variability in the results of studies, especially of meta-analyses, might be reduced if datasets included greater detail on grazing protocols, and a common definition of the term, “grazing intensity.”

Effects of fences and fence gaps on the movement behavior of three southern African antelope species

Globally, migratory ungulates are affected by fences. While field observational studies reveal the amount of animal–fence interactions across taxa, GPS tracking-based studies uncover fence effects on movement patterns and habitat selection. However, studies on the direct effects of fences and fence gaps on movement behavior, especially based on high-frequency tracking data, are scarce. We used GPS tracking on three common African antelopes (Tragelaphus strepsiceros, Antidorcas marsupialis, and T. oryx) with movement strategies ranging from range residency to nomadism in a semi-arid, Namibian savanna traversed by wildlife-proof fences that elephants have regularly breached. We classified major forms of ungulate–fence interaction types on a seasonal and a daily scale. Furthermore, we recorded the distances and times spent at fences regarding the total individual space use. Based on this, we analyzed the direct effects of fences and fence gaps on the animals’ movement behavior for the previously defined types of animal–fence interactions. Antelope-fence interactions peaked during the early hours of the day and during seasonal transitions when the limiting resource changed between water and forage. Major types of ungulate–fence interactions were quick, trace-like, or marked by halts. We found that the amount of time spent at fences was highest for nomadic eland. Migratory springbok adjusted their space use concerning fence gap positions. If the small home ranges of sedentary kudu included a fence, they frequently interacted with this fence. For springbok and eland, distance traveled along a fence declined with increasing utilization of a fence gap. All species reduced their speed in the proximity of a fence but often increased their speed when encountering the fence. Crossing a fence led to increased speeds for all species. We demonstrate that fence effects mainly occur during crucial foraging times (seasonal scale) and during times of directed movements (daily scale). Importantly, we provide evidence that fences directly alter antelope movement behaviors with negative implications for energy budgets and that persistent fence gaps can reduce the intensity of such alterations. Our findings help to guide future animal–fence studies and provide insights for wildlife fencing and fence gap planning.

Patch quality and habitat fragmentation shape the foraging patterns of a specialist folivore

Research on use of foraging patches has focused on why herbivores visit or quit patches, yet little is known about visits to patches over time. Food quality, as reflected by higher nutritional quality and lower plant defenses, and physical patch characteristics, which offer protection from predators and weather, affect patch use and hence should influence their revisitation. Due to the potentially high costs of moving between patches, fragmented habitats are predicted to complicate foraging decisions of many animals. We aimed to determine how food quality, shelter availability and habitat fragmentation influence tree reuse by a specialist folivore, the koala, in a fragmented agricultural landscape. We GPS-tracked 23 koalas in northern New South Wales, Australia and collated number of revisits, average residence time, and average time-to-return to each tree. We measured tree characteristics including food quality (foliar nitrogen and toxic formylated phloroglucinol compounds, FPCs concentrations), tree size, and tree connectedness. We also modeled the costs of locomotion between trees. Koalas re-visited isolated trees with high leaf nitrogen disproportionately often. They spent longer time in trees with high leaf nitrogen, and in large trees used for shelter. They took longer to return to trees with low leaf nitrogen. Tree connectivity reduced travel costs between patches, being either individual or groups of trees. FPC levels had no detectable effect on patch revisitation. We conclude that food quality and shelter drive koala tree re-visits. Scattered, isolated trees with nutrient-rich leaves are valuable resource patches for koalas despite movement costs to reach them.

Integrating herbivore assemblages and woody plant cover in an African savanna to reveal how herbivores respond to ecosystem management

African savannas are experiencing anthropogenically-induced stressors that are accelerating the increase of woody vegetation cover. To combat this, land managers frequently implement large-scale clearing of trees, which can have a cascading influence on mammalian herbivores. Studies rarely focus on how differences in woody cover influence the herbivore assemblage, making it difficult to assess how aggressive measures, or the lack of management, to counteract increasing woody cover affect the local composition and biodiversity of herbivores. We address this knowledge gap by applying a model-based clustering approach to field observations from MalaMala Game Reserve, South Africa to identify multiple herbivore-vegetation 'configurations,' defined as unique sets of herbivore assemblages (i.e., groups of herbivores) associated with differing woody plant covers. Our approach delineated how tree-clearing influences the distribution and abundance of the herbivore community in relation to surrounding savanna areas, which represent a natural mosaic of varying woody cover. Regardless of season, both intensively managed areas cleared of trees and unmanaged areas with high tree cover contained configurations that had depauperate assemblages of herbivores (low species richness, low abundance). By contrast, habitats with intermediate cover of woody vegetation had much higher richness and abundance. These results have substantial implications for managing African savannas in a rapidly changing climate.

Cumulative effects of widespread landscape change alter predator-prey dynamics

Predator search efficiency can be enhanced by anthropogenic landscape change, leading to increased predator–prey encounters and subsequent prey population declines. Logging increases early successional vegetation, providing ungulate forage. This increased forage, however, is accompanied by linear feature networks that increase predator hunting efficiency by facilitating predator movement and increasing prey vulnerability. We used integrated step selection analyses to weigh support for multiple hypotheses representing the combined impact of logging features (cutblocks and linear features) on wolf (Canis lupus) movement and habitat selection in interior British Columbia. Further, we examine the relationship between logging and wolf kill-sites of moose (Alces alces) identified using spatiotemporal wolf location cluster analysis. Wolves selected for linear features, which increased their movement rates. New (0–8 years since harvest) cutblocks were selected by wolves. Moose kill-sites had a higher probability of occurring in areas with higher proportions of new and regenerating (9–24 years since harvest) cutblocks. The combined selection and movement responses by wolves to logging features, coupled with increased moose mortality sites associated with cutblocks, indicate that landscape change increases risk for moose. Cumulative effects of landscape change contribute to moose population declines, stressing the importance of cohesive management and restoration of anthropogenic features.

Assessing the effect of complex ground types on ground-dwelling arthropod movements with video monitoring: Dealing with concealed movements under a layer of plant residues

Understanding the effect of ground types on foraging movements of ground-dwelling arthropods is a key step to managing their spatial distribution as required for successful conservation biological control. Indeed, fine movements at the centimeter scale can strongly influence the foraging ability of pest predators. However, because radio frequency identification or harmonic tracking techniques are not yet suitable for small species and video tracking focuses on uniform and light backgrounds, foraging movements have rarely been studied in relation to ground types. We present a method to track a ground-dwelling arthropod (the earwig Euborellia caraibea) at night, walking on two contrasted ground types: bare soil and soil partly covered with a stratum of banana plant residues allowing individuals to hide periodically. The tracking of individuals within these ground types was achieved by infrared light, tagging individuals, video treatments, and semi-automatic cleaning of trajectories. We tested different procedures to obtain segments with identical durations to quantify speeds and sinuosities. These procedures were characterized by the junction time gap between trajectory fragments, the rediscretization time of trajectories, and whether or not to use interpolation to fill in missing points in the trajectories. Earwigs exhibited significantly slower and more sinuous movements on soil with banana plant residues than on bare soil. Long time gaps for trajectory junction, extended rediscretization times, and interpolation were complementary means to integrate concealed movements in the trajectories. The highest slowdown in plant residues was detected when the procedure could account for longer periods under the residues. These results suggest that earwigs spent a significant amount of time concealed by the residues. Additionally, the residues strongly decreased the earwigs' movement. Since the technical solutions presented in this study are inexpensive, easy to set up, and replicate, they represent valuable contributions to the emerging field of video monitoring.

Machine learned daily life history classification using low frequency tracking data and automated modelling pipelines: application to North American waterfowl

BACKGROUND

Identifying animal behaviors, life history states, and movement patterns is a prerequisite for many animal behavior analyses and effective management of wildlife and habitats. Most approaches classify short-term movement patterns with high frequency location or accelerometry data. However, patterns reflecting life history across longer time scales can have greater relevance to species biology or management needs, especially when available in near real-time. Given limitations in collecting and using such data to accurately classify complex behaviors in the long-term, we used hourly GPS data from 5 waterfowl species to produce daily activity classifications with machine-learned models using "automated modelling pipelines".

METHODS

Automated pipelines are computer-generated code that complete many tasks including feature engineering, multi-framework model development, training, validation, and hyperparameter tuning to produce daily classifications from eight activity patterns reflecting waterfowl life history or movement states. We developed several input features for modeling grouped into three broad categories, hereafter "feature sets": GPS locations, habitat information, and movement history. Each feature set used different data sources or data collected across different time intervals to develop the "features" (independent variables) used in models.

RESULTS

Automated modelling pipelines rapidly developed easily reproducible data preprocessing and analysis steps, identification and optimization of the best performing model and provided outputs for interpreting feature importance. Unequal expression of life history states caused unbalanced classes, so we evaluated feature set importance using a weighted F1-score to balance model recall and precision among individual classes. Although the best model using the least restrictive feature set (only 24 hourly relocations in a day) produced effective classifications (weighted F1 = 0.887), models using all feature sets performed substantially better (weighted F1 = 0.95), particularly for rarer but demographically more impactful life history states (i.e., nesting).

CONCLUSIONS

Automated pipelines generated models producing highly accurate classifications of complex daily activity patterns using relatively low frequency GPS and incorporating more classes than previous GPS studies. Near real-time classification is possible which is ideal for time-sensitive needs such as identifying reproduction. Including habitat and longer sequences of spatial information produced more accurate classifications but incurred slight delays in processing.

Grouping behaviour and activity patterns of impala (Aepyceros melampus) in a nutrient –rich and a nutrient-poor savanna in Tanzania

African savannas are broadly categorised into nutrient-rich and nutrient-poor according to soil nutrient availability and precipitation. Soil nutrients limit plant growth in the nutrient-rich savannas, leading to little plant biomass of high nutrient concentrations. In the nutrient-poor savannas soil nutrients are depleted before plant growth ceases, resulting in large production of nutrient-poor plant biomass. Impala (Aepyceros melampus), are medium-sized antelopes occurring in both savannas, but they face feeding challenges in the nutrient-poor savannas because of high energy requirements. Activity patterns of impala are well studied, but few studies compared savannas with differing soil nutrients and animal communities. I used the scanning methods to study impala activities in a nutrient-rich savanna, the Serengeti National Park, and a nutrient-poor savanna, the Mikumi National Park in Tanzania, during the wet and dry seasons. Impala are gregarious and mixed feeders, utilising grasses during the wet season, switching to browsing during the dry season, making them good candidates for comparing savannas and seasons. The impala formed bigger groups in Mikumi during the wet season splitting during the dry season. Grazing time was higher in the wet season than in the dry season in Serengeti, but did not differ between the seasons in Mikumi. Browsing time was longer in Mikumi than Serengeti during the dry season, and longer in Serengeti than Mikumi during the wet season. Resting time was longer in Serengeti than Mikumi during the wet season, while walking time was longer in Mikumi than Serengeti during the dry season. Family groups spent longer time resting than bachelor groups in both sites. The study shows obvious differences in grouping and activity patterns of impala between the sites and the seasons. Further studies are recommended to explore the influence of savanna and season on grouping behaviour and activity patterns of herbivores.

Towns and trails drive carnivore movement behaviour, resource selection, and connectivity

BACKGROUND

Global increases in human activity threaten connectivity of animal habitat and populations. Protection and restoration of wildlife habitat and movement corridors require robust models to forecast the effects of human activity on movement behaviour, resource selection, and connectivity. Recent research suggests that animal resource selection and responses to human activity depend on their behavioural movement state, with increased tolerance for human activity in fast states of movement. Yet, few studies have incorporated state-dependent movement behaviour into analyses of Merriam connectivity, that is individual-based metrics of connectivity that incorporate landscape structure and movement behaviour.

METHODS

We assessed the cumulative effects of anthropogenic development on multiple movement processes including movement behaviour, resource selection, and Merriam connectivity. We simulated movement paths using hidden Markov movement models and step selection functions to estimate habitat use and connectivity for three landscape scenarios: reference conditions with no anthropogenic development, current conditions, and future conditions with a simulated expansion of towns and recreational trails. Our analysis used 20 years of grizzly bear (Ursus arctos) and gray wolf (Canis lupus) movement data collected in and around Banff National Park, Canada.

RESULTS

Carnivores increased their speed of travel near towns and areas of high trail and road density, presumably to avoid encounters with people. They exhibited stronger avoidance of anthropogenic development when foraging and resting compared to travelling and during the day compared to night. Wolves exhibited stronger avoidance of anthropogenic development than grizzly bears. Current development reduced the amount of high-quality habitat between two mountain towns by more than 35%. Habitat degradation constrained movement routes around towns and was most pronounced for foraging and resting behaviour. Current anthropogenic development reduced connectivity from reference conditions an average of 85%. Habitat quality and connectivity further declined under a future development scenario.

CONCLUSIONS

Our results highlight the cumulative effects of anthropogenic development on carnivore movement behaviour, habitat use, and connectivity. Our strong behaviour-specific responses to human activity suggest that conservation initiatives should consider how proposed developments and restoration actions would affect where animals travel and how they use the landscape.

Global long-term stability of individual dietary specialization in herbivorous mammals

Dietary variation within species has important ecological and evolutionary implications. While theoreticians have debated the consequences of trait variance (including dietary specialization), empirical studies have yet to examine intraspecific dietary variability across the globe and through time. Here, we use new and published serial sampled δ¹³C_enamel values of herbivorous mammals from the Miocene to the present (318 individuals summarized, 4134 samples) to examine how dietary strategy (i.e. browser, mixed-feeder, grazer) affects individual isotopic variation. We find that almost all herbivores, regardless of dietary strategy, are composed of individual specialists. For example, Cormohipparion emsliei (Equidae) from the Pliocene of Florida (approx. 5 Ma) exhibits a δ¹³C_enamel range of 13.4‰, but all individuals sampled have δ¹³C_enamel ranges of less than or equal to 2‰ (mean = 1.1‰). Most notably, this pattern holds globally and through time, with almost all herbivorous mammal individuals exhibiting narrow δ¹³C_enamel ranges (less than or equal to 3‰), demonstrating that individuals are specialized and less representative of their overall species' dietary breadth. Individual specialization probably reduces intraspecific competition, increases carrying capacities, and may have stabilizing effects on species and communities over time. Individual specialization among species with both narrow and broad dietary niches is common over space and time-a phenomenon not previously well recognized or documented empirically.

Clair C, Kutz SJ, Hebblewhite M, Merrill EH. What makes elk tick: winter tick (Dermacentor albipictus) grooming behavior in wild elk (Cervus canadensis)

Ungulates groom to remove ectoparasites but grooming may interfere with foraging, vigilance, and rumination, and it is possible that these effects differ among migratory tactics due to differences in parasite infestations. We compared the effects of grooming for winter ticks (Dermacentor albipictus) on winter foraging behavior by migrating and resident elk (Cervus canadensis) in the partially migratory population at the Ya Ha Tinda, adjacent to Banff National Park, Canada. We used hair loss on the dorsal shoulder area (“withers”) measured from photographic images as an index of tick infestation of individual elk. We conducted 594 focal observations on 48 radio-collared and 18 uncollared individuals that were uniquely identifiable from ear-tags (N = 66) in 2019 to assess whether grooming for ticks in winter reduced time spent foraging, ruminating, or being vigilant. Because rubbing or hair loss from radio-collars may influence tick infestations and behavior, we controlled for whether elk were collared or uncollared in our analyses. Neck hair loss was 3−5% greater in collared elk than uncollared elk, but neither withers hair loss nor time spent grooming differed. Grooming occurred during 42% of the observations but grooming comprised only ~1% of observation time. Nevertheless, 40% of all grooming was observed during resting, and grooming interrupted vigilance behavior ~8 times more than foraging. We found no differences among elk following different migratory tactics in time spent grooming or in other behaviors, but one of the two groups of migrant elk had higher withers hair loss. Our results suggest winter ticks may have slight effects on elk relative to other ungulates, particularly moose (Alces alces), in North America.

Conceptual and methodological advances in habitat-selection modeling: guidelines for ecology and evolution

Habitat selection is a fundamental animal behavior that shapes a wide range of ecological processes, including animal movement, nutrient transfer, trophic dynamics and population distribution. Although habitat selection has been a focus of ecological studies for decades, technological, conceptual and methodological advances over the last 20 yr have led to a surge in studies addressing this process. Despite the substantial literature focused on quantifying the habitat-selection patterns of animals, there is a marked lack of guidance on best analytical practices. The conceptual foundations of the most commonly applied modeling frameworks can be confusing even to those well versed in their application. Furthermore, there has yet to be a synthesis of the advances made over the last 20 yr. Therefore, there is a need for both synthesis of the current state of knowledge on habitat selection, and guidance for those seeking to study this process. Here, we provide an approachable overview and synthesis of the literature on habitat-selection analyses (HSAs) conducted using selection functions, which are by far the most applied modeling framework for understanding the habitat-selection process. This review is purposefully non-technical and focused on understanding without heavy mathematical and statistical notation, which can confuse many practitioners. We offer an overview and history of HSAs, describing the tortuous conceptual path to our current understanding. Through this overview, we also aim to address the areas of greatest confusion in the literature. We synthesize the literature outlining the most exciting conceptual advances in the field of habitat-selection modeling, discussing the substantial ecological and evolutionary inference that can be made using contemporary techniques. We aim for this paper to provide clarity for those navigating the complex literature on HSAs while acting as a reference and best practices guide for practitioners.

Five hundred million years to mobility: directed locomotion and its ecological function in a turtle barnacle

Movement is a fundamental characteristic of life, yet some invertebrate taxa, such as barnacles, permanently affix to a substratum as adults. Adult barnacles became 'sessile' over 500 Ma; however, we confirm that the epizoic sea turtle barnacle, Chelonibia testudinaria, has evolved the capacity for self-directed locomotion as adults. We also assess how these movements are affected by water currents and the distance between conspecifics. Finally, we microscopically examine the barnacle cement. Chelonibia testudinaria moved distances up to 78.6 mm yr-1 on loggerhead and green sea turtle hosts. Movements on live hosts and on acrylic panels occasionally involved abrupt course alterations of up to 90°. Our findings showed that barnacles tended to move directly against water flow and independent of nearby conspecifics. This suggests that these movements are not passively driven by external forces and instead are behaviourally directed. In addition, it indicates that these movements function primarily to facilitate feeding, not reproduction. While the mechanism enabling movement remained elusive, we observed that trails of cement bore signs of multi-layered, episodic secretion. We speculate that proximal causes of movement involve one or a combination of rapid shell growth, cement secretion coordinated with basal membrane lifting, and directed contraction of basal perimeter muscles.

UAV reveals substantial but heterogeneous effects of herbivores on Arctic vegetation

Understanding how herbivores shape plant biomass and distribution is a core challenge in ecology. Yet, the lack of suitable remote sensing technology limits our knowledge of temporal and spatial impacts of mammal herbivores in the Earth system. The regular interannual density fluctuations of voles and lemmings are exceptional with their large reduction of plant biomass in Arctic landscapes during peak years (12-24%) as previously shown at large spatial scales using satellites. This provides evidence that herbivores are important drivers of observed global changes in vegetation productivity. Here, we use a novel approach with repeated unmanned aerial vehicle (UAV) flights, to map vegetation impact by rodents, indicating that many important aspects of vegetation dynamics otherwise hidden by the coarse resolution of satellite images, including plant-herbivore interactions, can be revealed using UAVs. We quantify areas impacted by rodents at four complex Arctic landscapes with very high spatial resolution UAV imagery to get a new perspective on how herbivores shape Arctic ecosystems. The area impacted by voles and lemmings is indeed substantial, larger at higher altitude tundra environments, varies between habitats depending on local snow cover and plant community composition, and is heterogeneous even within habitats at submeter scales. Coupling this with spectral reflectance of vegetation (NDVI), we can show that the impact on central ecosystem properties like GPP and biomass is stronger than currently accounted for in Arctic ecosystems. As an emerging technology, UAVs will allow us to better disentangle important information on how herbivores maintain spatial heterogeneity, function and diversity in natural ecosystems.

Annual movement strategy predicts within-season space use by moose

Abstract

The heterogeneity of resource availability shapes animal movements at different spatio-temporal scales. Given that movements at various scales are assumed to be linked, the space use of temperate ungulates within seasonal ranges (winter, summer) should be related to their movement patterns at the annual scale. In this study, we aimed to evaluate the level of stationarity of moose (Alces alces) within their seasonal ranges and to link annual movement patterns to within-season space use. We analysed the ranging behaviour of 32 moose fitted with GPS collars from two study areas in Eastern Poland, where at the annual scale a fraction of individuals migrate between summer and winter ranges (partial migration). Our results revealed that moose stationarity within seasonal home ranges expressed remarkable variation. The probability of moose stationarity within seasonal ranges was significantly higher (by 23%), and the mean home range size tended to be lower (9.7 km2) among individuals that seasonally migrated than among non-migratory moose (14.3 km2). In addition, we found that (i) in summer, moose were significantly more stationary (by 19%) and exhibited a smaller mean home range size than in winter (9.0 and 15.9 km2, respectively) and (ii) the mean seasonal home range size of males (19.6 km2) was remarkably greater than that of females (9.6 km2). Given the significant link between annual and seasonal scales of animal movements, any environmental change (e.g. climate warming) affecting an animal’s annual movement strategy could alter within-season animal space use and presumably individual fitness.

Significance statement

To maximize their fitness, animals adjust their movements to deal with variations in resource distribution in the landscape. The scale of spatio-temporal variation causes different types of migratory behaviours, ranging from year-round stationarity to migration, when individuals establish spatially separated seasonal ranges. Studies on ungulates suggest that the stability and the size of seasonal home ranges can be linked to annual movement behaviour. Using the locations of GPS-tracked moose, we demonstrate in this study that migratory individuals were more prone to establishing stable seasonal home ranges (especially in summer) than moose that occupied the same area throughout the year. Moreover, stable seasonal home ranges were remarkably smaller in summer than in winter, which may suggest a season-specific spatial distribution and a renewability of moose forage. Our results show a clear link between different temporal scales of animal movements.

Some Memories Never Fade: Inferring Multi-Scale Memory Effects on Habitat Selection of a Migratory Ungulate Using Step-Selection Functions

Understanding how animals use information about their environment to make movement decisions underpins our ability to explain drivers of and predict animal movement. Memory is the cognitive process that allows species to store information about experienced landscapes, however, remains an understudied topic in movement ecology. By studying how species select for familiar locations, visited recently and in the past, we can gain insight to how they store and use local information in multiple memory types. In this study, we analyzed the movements of a migratory mule deer (Odocoileus hemionus) population in the Piceance Basin of Colorado, United States to investigate the influence of spatial experience over different time scales on seasonal range habitat selection. We inferred the influence of short and long-term memory from the contribution to habitat selection of previous space use within the same season and during the prior year, respectively. We fit step-selection functions to GPS collar data from 32 female deer and tested the predictive ability of covariates representing current environmental conditions and both metrics of previous space use on habitat selection, inferring the latter as the influence of memory within and between seasons (summer vs. winter). Across individuals, models incorporating covariates representing both recent and past experience and environmental covariates performed best. In the top model, locations that had been previously visited within the same season and locations from previous seasons were more strongly selected relative to environmental covariates, which we interpret as evidence for the strong influence of both short- and long-term memory in driving seasonal range habitat selection. Further, the influence of previous space uses was stronger in the summer relative to winter, which is when deer in this population demonstrated strongest philopatry to their range. Our results suggest that mule deer update their seasonal range cognitive map in real time and retain long-term information about seasonal ranges, which supports the existing theory that memory is a mechanism leading to emergent space-use patterns such as site fidelity. Lastly, these findings provide novel insight into how species store and use information over different time scales.