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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 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.

The variation in niche breadth can affect how species respond to environmental and resource changes. However, there is still no clear understanding of how seasonal variability in food resources impacts the variation of individual dietary diversity, thereby affecting the dynamics of a population’s dietary niche breadth. Optimal foraging theory (OFT) and the niche variation hypothesis (NVH) predict that when food resources are limited, the population niche breadth will widen or narrow due to increased within-individual dietary diversity and individual specialization or reduced within-individual dietary diversity, respectively. Here, we used DNA metabarcoding to examine the composition and seasonality of diets of the avivorous bat Ia io. Furthermore, we investigated how the dietary niches changed among seasons and how the population niche breadth changed when the availability of insect resources was reduced in autumn. We found that there was differentiation in dietary niches among seasons and a low degree of overlap, and the decrease of insect resource availability and the emergence of ecological opportunities of nocturnal migratory birds might drive dietary niche shifts toward birds in I. io. However, the population’s dietary niche breadth did not broaden by increasing the within-individual dietary diversity or individual specialization, but rather became narrower by reducing dietary diversity via predation on bird resources that served as an ecological opportunity when insect resources were scarce in autumn. Our findings were consistent with the predictions of OFT, because birds as prey for bats provided extremely different resources from those of insects in size and nutritional value. Our work highlights the importance of size and quality of prey resources along with other factors (i.e., physiological, behavioral, and life-history traits) in dietary niche variation.

Hunter decision-making influences prey selection and is key to understanding the impacts of hunting on biodiversity. Optimal foraging theory (OFT) is often used to describe the decision-making and prey selection of subsistence hunters. We examined the behavior and game meat use of hunters in an indigenous Amazonian community and used free listing and generalized linear mixed-effects models under the framework of OFT to assess the decision-making of individuals who hunt for economic gain and subsistence. We found that prey selection generally followed OFT, and was influenced by hunters’ skills, patch choice, and characteristics of the prey encountered. Hunters preferred paca (Cuniculus paca), collared peccary (Pecari tajacu), and brocket deer (Mazama americana), and only partially preferred tapir (Tapirus terrestris) and large-bodied primates likely due to economic influences such as access to markets and prices, contrary to OFT predictions.

Optimal foraging theory (OFT) predicts that animals employ foraging strategies that maximize a particular currency, such as net energetic efficiency, to meet their nutritional demands. Two nonexclusive patterns that arise from OFT are convergence on high‐quality resources and resource partitioning. Honey bees make collective decisions by integrating their individual foraging with social recruitment behaviors: returning foragers communicate the approximate vector to high‐quality resources using waggle dances. Because we can eavesdrop on their communications, waggle dance decoding is a valuable tool for exploring OFT predictions as it allows us to map how honey bees use landscapes. In this study, we analyzed 8049 dances from colocalized colonies across three landscapes to investigate whether neighboring colonies forage by not partitioning patches (i.e., converging their food collection on the same patches), by partitioning at the landscape level, or by partitioning at the local level. To differentiate between these three possible scenarios, we examined three metrics: (1) interdance distances between and within colonies; (2) k‐nearest neighbors; and (3) k‐means clustering. We observed no difference in the distances between dances performed by bees from the same colony compared to those from different colonies. Also, we found at each of the three field sites that dances from the same colony were not more likely to appear as close neighbors to each other. Finally, k‐means cluster analysis demonstrates that dance locations advertised by the same colony aggregated nonrandomly in the three sites, where dances from the same colony comprised a significant majority of dances within k‐means clusters and 62% of clusters consisted entirely of dances from a single colony. Together, these results support a foraging scenario where honey bees partition their foraging, but at the local level. This strategy may help limit intercolony foraging competition. In this article, we explore optimal foraging theory predictions for competing honey bee colonies by quantifying the relative spatial foraging patterns of 8049 waggle dances from colocalized colonies across three landscapes. Our results demonstrate that neighboring colonies distribute their foraging widely at the landscape scale, while partitioning resources at the local scale. These findings suggest that honey bees employ a foraging strategy that simultaneously exploits available resources and limits inter‐colony competition.

As a habitat for waterbirds, wetlands are key to their survival, reproduction and development. Waterbirds usually prefer breeding, wintering and resting in fixed locations. Siberian cranes (Grus leucogeranus), which are highly dependent on wetlands, have long fed on farmland at migratory stopover sites. To explore the reason for this phenomenon, the time budgets of Siberian crane populations stopping over on farmland or in wetland habitats were studied and compared in this study. The results showed that the farmlands visited by the Siberian cranes are rich in food resources and have experienced low levels of disturbance. The temporal distribution of feeding behavior on farmland (53.50%) was greater than that in wetland habitats (31.96%). The variations in warning, flying and walking behavior on farmland were less than those in wetlands. The feeding efficiency on farmland was significantly greater than that in wetlands. Therefore, Siberian cranes transiting the Songnen Plain leave wetland habitats and stop over on farmland, representing a behavior that occurs more than just occasionally. Instead, they change their foraging habitat choices based on the optimal foraging theory. As a transit feeding area for Siberian cranes, farmland poses a significant risk, and the restoration of wetland habitats and food resources is still needed. This study can provide theoretical support for the conservation of rare and endangered species (the Siberian crane) and the management of stopover sites.

Optimal foraging theory (OFT) and the energy maximization hypothesis (EMH) have long been essential when examining wildlife habitat selection. At high latitudes and altitudes, animals in winter face greater limitations in availability and accessibility of forage. Here we explore the foraging behavior of wood bison (Bison bison athabascae) during winter within the Ronald Lake bison herd in northeastern Alberta, Canada, and examine the trade‐offs they face due to limitations in forage abundance and availability (snow conditions), as well as the need to minimize predation risk. We used Global Positioning System (GPS) location data collected from 70 female wood bison to identify winter foraging sites and craters selected by bison to access forage beneath the snow. Within wetlands used by bison we selected 190 pairs of used (foraged) and random (available) sites to test eight a priori hypotheses explaining how bison traded‐off between forage availability, accessibility, and minimizing predation risk. We found with matched‐paired logistic regression that Carex atherodes was 1.21‐times more likely to be selected per unit increase in ground cover, compared to 1.17‐times per unit ground cover for C. aquatilis and C. utriculata. However, all Carex species showed an increase in selection when cover was > 50% cover within individual craters. While the importance of Carex was clear, forage site selection was still inversely related to snow depth. There is also a neutralizing combined effect of snow depth and Carex species ground cover which suggests that bison maximized their energy return by avoiding areas with deep snow (> 30 cm) that demanded intensive cratering, even when highly selected forage was accessible beneath. Avoidance of forage areas with deep snow demonstrates that wood bison employed a foraging strategy that considers both forage availability and environmental conditions, with snow depth being a limiting factor. We highlight the relationship between optimal foraging based on food availability and the trade‐offs within an energy restrictive winter season, furthering the understanding of how large herbivores forage strategically to maximize energy intake in northern environments. We studied the winter foraging ecology of wood bison in northeastern Alberta. Finding that wood bison select for sedge species, but, increased snow depths lead to decreased selection despite the presence of highly selected forage species beneath. This study highlights bison strategies to maximize energy in northern winters.

In social animals, areas where the home ranges of neighboring groups overlap are often underused. The Risk Hypothesis posits that the costs of intergroup conflict create a “landscape of fear,” discouraging the use of such shared areas. To test this hypothesis, we observed the behavior of white-faced capuchins (Cebus capucinus) in central vs. peripheral areas of their home ranges. If capuchins perceive areas of home range overlap as “risky,” we predicted they would change activity budgets, vocalization rates, and foraging behavior in these areas. A spatially explicit behavioral comparison based on nearly 100 h of focal follows revealed that capuchins socialize less in the periphery (vs. the center) of their home range. Time spent resting, foraging, and engaging in vigilance, as well as vocalization rates, varied in consistent ways across all four study groups, but these differences did not reach statistical significance. Fruit trees near range borders (vs. the center) contained more ripe fruit, and groups spent more time in these trees, with more individuals entering to feed and consuming more fruits. However, capuchins did not alter their foraging behavior in potentially risky peripheral areas in a manner consistent with predictions of optimal foraging theory: intake rates at patch departure were not significantly lower and groups depleted trees to a greater extent along the periphery vs. in the center of their range. These results suggest that while peripheral areas are perceived as risky and this “landscape of fear” contributes to behavioral changes, they also provide resources whose value may outweigh the cost of intergroup encounters.

We analyzed diel vertical migration (DVM) of overwintering Antarctic krill at South Georgia, a region that remains ice-free during the austral winter. We considered DVM in relation to krill body length, based on Japanese krill fishery data (1990–2012), and examined DVM in relation to food availability and predator (Antarctic fur seal) avoidance. We report that diel changes in median trawling depth (a proxy for krill vertical distribution) showed significant interannual variation; the overall trend was such that during both daytime and nighttime, the larger the average size of krill, the deeper their median depth. Consistent with the literature, this size-dependent DVM relates to food availability and size-dependent diet; that is, with increasing body length, krill tend to rely less on phytoplankton (which are available in surface layers) as a winter food source. Concerning predator avoidance, and based on analyses using an optimal foraging dive model for fur seals, DVM showed close agreement with size-dependent predation risk; that is, larger krill remained deeper, thereby reducing mortality from fur seals. Therefore, DVM of overwintering krill appears to reflect a compromise between adequate feeding conditions and minimizing predation risk. There was, however, an exception that krill occurred at a shallow depth in winter 2006 when phytoplankton abundance was particularly low and krill density was very high. This supports the hypothesis that physiological demands (i.e. hunger) may become a more important factor affecting DVM than predator avoidance under conditions of insufficient food availability.

Optimal foraging and individual specialization theories suggest that different properties of the interactions between prey and predators determine foraging strategies. However, none of these theories consider how the nutritional status of the predators and the risk of being attacked by other predators may affect prey foraging strategy. Shelter-building spiders, such as Metazygia laticeps (Araneidae), build webs as dynamic traps to capture prey and may optimize capture efficiency while adopting strategies to minimize their exposure to predators by building a shelter and staying inside it most of the time. Prey capture, however, involves leaving the shelter, which may contribute to an increased risk of predation. Individuals may be more likely to take risks when they are in poor nutritional status. In this study, we conducted field experiments to assess support for the hypotheses that M. laticeps spiders with poor nutritional status (i) expose themselves to greater risk of predation during foraging and (ii) invest more silk in different web structures to increase prey capture success. Nutritional state was unrelated to exposure to predation and did not restrict web investment in M. laticeps. However, spiders left the shelter more quickly at night than during the day, regardless of their nutritional state. We suggest that individual’s nutritional state does not determine foraging, and predation risk can affect general activity of spiders depending on foraging period.

Generalist parasites seem to enjoy the clear ecological advantage of a greater chance to find a host, and genetic trade‐offs are therefore often invoked to explain why specialists can coexist with or outcompete generalists. Here we develop an alternative perspective based on optimal foraging theory to explain why spatial clustering can favor specialists even without genetic trade‐offs. Using analytical and simulation models inspired by bacteriophage, we examine the optimal use of two hosts, one yielding greater reproductive success for the parasite than the other. We find that a phage may optimally ignore the worse host when the two hosts are clustered together in dense, ephemeral patches. We model conditions that enhance or reduce this selective benefit to a specialist parasite and show that it is eliminated entirely when the hosts occur only in separate patches. These results show that specialists can be favored even when trade‐offs are weak or absent and emphasize the importance of spatiotemporal heterogeneity in models of optimal niche breadth. Specialist parasites are common despite some clear advantages to a broader host range. Here we develop an optimal foraging model to explain why spatial clustering can favor specialists even without genetic trade‐offs. We find that a parasite may optimally ignore the worse host when the two hosts are jointly clustered in dense, ephemeral patches, even when trade‐offs are weak or absent.