Foraging Patterns Research Articles

Past, Present, and Future of Forbs in Old-Growth Tropical and Subtropical Grasslands

Forbs are important contributors to species diversity and ecosystem functions in low-latitude grasslands, where they support diverse herbivore communities and millions of people. Native forb assemblages tolerate disturbances and physiological stressors (fire, herbivory, drought, and frost) that together have shaped their exceptional functional diversity. Yet, compared to trees and grasses, forbs have received much less attention in grassland studies until recently. Here, we review forb-centric literature to illustrate that land conversion and responsible management of fire and herbivory are crucial to maintaining forb diversity. Management practices promoting forb diversity offer (a) high-quality food items and medicinal resources that support rural livelihoods and animal diversity (from wild ungulates and livestock to fossorial rodents and insects), including their adaptive foraging patterns, and (b) carbon and nutrient inputs that regulate belowground processes. Improved understanding of the above- and belowground regeneration strategies of forbs is critical for restoration and conservation to secure their services in future old-growth tropical and subtropical grasslands.

Palynological characterization of a diverse desertic ecosystem: the Peruvian Lomas

The Pacific coastal Peruvian landscapes are dominated by desert and dry-forest biomes, which have undergone shifts in extent and floral composition in response to Plio–Pleistocene climatic fluctuations. Within this context, the coastal Lomas develop as seasonal vegetation patches, renowned for their high endemism, rich floral diversity, and essential ecosystem services. Despite growing within the desert biome, the Lomas exhibit characteristic elements and vegetation structure typical of a dry-forest biome, evidencing an active species migration between xeric biomes. However, assessing the historical evolution of this arid flora and, by extension, the coastal desert landscape, presents challenges. The scarcity of continental sedimentary records and a lack of extended and well-described palynological references impede these efforts. In response to this, our study offers a thorough morphological review of the Lomas palynoflora, encompassing over 194 genera from 76 families, representing approximately 80% of the known Lomas flora. Our review includes at least one species per reviewed genus, featuring 37 palynomorphs from endemic species (18.5% of the studied flora). This palynological characterization is intended to serve as accessible reference material for investigating the historical and long-term evolution of the coastal dry flora. Furthermore, these findings facilitate the analysis of honeys and bee floral foraging patterns, as well as the study of animal–plant or human–plant interactions from middens and archaeological remains.

Spatial and seasonal foraging patterns drive diet differences among north Pacific resident killer whale populations.

Highly social top marine predators, including many cetaceans, exhibit culturally learned ecological behaviours such as diet preference and foraging strategy that can affect their resilience to competition or anthropogenic impacts. When these species are also endangered, conservation efforts require management strategies based on a comprehensive understanding of the variability in these behaviours. In the northeast Pacific Ocean, three partially sympatric populations of resident killer whales occupy coastal ecosystems from California to Alaska. One population (southern resident killer whales) is endangered, while another (southern Alaska resident killer whales) has exhibited positive abundance trends for the last several decades. Using 185 faecal samples collected from both populations between 2011 and 2021, we compare variability in diet preference to provide insight into differences in foraging patterns that may be linked with the relative success and decline of these populations. We find broad similarities in the diet of the two populations, with differences arising from spatiotemporal and social variability in resource use patterns, especially in the timing of shifts between target prey species. The results described here highlight the importance of comprehensive longitudinal monitoring of foraging ecology to inform management strategies for endangered, highly social top marine predators.

Unveiling the mysteries of Asian herbivores resource partitioning in tropical wet-grassland ecosystem

Ecological niche partitioning is fundamental for the coexistence of sympatric species. However, the relationship between herbivore body size and forage availability on resource segregation and selection remains debatable. This study quantifies the niche differentiation and selectivity of forage species consumed by six Asian large herbivores (SLH), including mega-herbivores like Greater one-horned rhino (Rhinoceros unicornis), Asian elephant (Elephas maximus) and Asiatic wild buffalo (Bubalus arnee), and meso-herbivores like swamp deer (Rucervus duvaucelii), hog deer (Axis porcinus) and sambar (Rusa unicolor) in tropical wet-grasslands of the Brahmaputra floodplains. We hypothesized that body size influences dietary niche breadth and interspecific dietary similarities or dissimilarities, while forage availability influences forage selectivity among Asian herbivores. We used micro-histological technique, harvest method and Jacobs Index to quantify SLH foraging patterns, forage availability and preference, respectively. Results of the study revealed high niche breadth for elephant (0.56>Bs≤0.74) among mega-herbivores and for sambar (0.49>Bs≤0.64) among meso-herbivores. SLH showed a significant positive correlation between body size and niche breadth in wet season. High dietary overlap was recorded between buffalo and hog deer (0.79–0.86) and swamp deer and hog deer (0.75–0.86) among SLH, rhino and buffalo (0.80–0.83) among mega-herbivores, and swamp deer and hog deer (0.75–0.86) among meso-herbivores. High dietary dissimilarity was recorded between elephant and swamp deer (36–37 %), elephant and buffalo (27–33 %), and swamp deer and sambar (27–29 %). Compared to dry season (1354.54 ±641.30 g m˗2), significantly higher biomass was recorded in wet season (3026.93 ±1632.65 g m˗2; p<0.05). From dry to wet season, rhino, buffalo and hog deer shift their preferred forage from dicot to monocot. Dicot was the most preferred forage of elephant among mega-herbivores, and monocot of swamp deer and sambar among meso-herbivores. Mega- and meso-herbivores avoid invasives Merremia umbellata and Mimosa spp., while meso-herbivores avoid Mikania micrantha. Body size explains niche partitioning only for rhino, elephant and swamp deer. Forage availability contributed to niche breadth and forage preference. In conclusion, forage segregation, despite being challenging to interpret at taxonomic level, influences niche partitioning among mega- and meso-herbivores.

Using motion-detection cameras to monitor foraging behaviour of individual butterflies.

The activity of many animals follows recurrent patterns and foraging is one of the most important processes in their daily activity. Determining movement in the search for resources and understanding temporal and spatial patterns in foraging has therefore long been central in behavioural ecology. However, identifying and monitoring animal movements is often challenging. In this study we assess the use of camera traps to track a very specific and small-scale interactions focused on the foraging behaviour of Heliconiini butterflies. Data on floral visitation was recorded using marked individuals of three pollen-feeding species of Heliconius (H. erato, H. melpomene and H. sara), and two closely related, non-pollen feeding species (Dryas iulia and Dryadula phaetusa) in a large outdoor insectary. We demonstrate that camera traps efficiently capture individual flower visitation over multiple times and locations and use our experiments to describe some features of their spatial and temporal foraging patterns. Heliconiini butterflies showed higher activity in the morning with strong temporal niche overlap. Differences in foraging activity between males and females was observed with females foraging earlier than males, mirroring published field studies. Some flowers were more explored than others, which may be explained by butterflies foraging simultaneously affecting each other's flower choices. Feeding was grouped in short periods of intense visits to the same flower, which we refer to as feeding bouts. Heliconius also consistently visits the same flower, while non-Heliconius visited a greater number of flowers per day and their feeding bouts were shorter compared with Heliconius. This is consistent with Heliconius having more stable long-term spatial memory and foraging preferences than outgroup genera. More broadly, our study demonstrates that camera traps can provide a powerful tool to gather information about foraging behaviour in small insects such as butterflies. © 2024 The Authors. Ecology and Evolution published by John Wiley & Sons Ltd.

Spatiotemporal organization of ant foraging from a complex systems perspective

We use complex systems science to explore the emergent behavioral patterns that typify eusocial species, using collective ant foraging as a paradigmatic example. Our particular aim is to provide a methodology to quantify how the collective orchestration of foraging provides functional advantages to ant colonies. For this, we combine (i) a purpose-built experimental arena replicating ant foraging across realistic spatial and temporal scales, and (ii) a set of analytical tools, grounded in information theory and spin-glass approaches, to explore the resulting data. This combined approach yields computational replicas of the colonies; these are high-dimensional models that store the experimental foraging patterns through a training process, and are then able to generate statistically similar patterns, in an analogous way to machine learning tools. These in silico models are then used to explore the colony performance under different resource availability scenarios. Our findings highlight how replicas of the colonies trained under constant and predictable experimental food conditions exhibit heightened foraging efficiencies, manifested in reduced times for food discovery and gathering, and accelerated transmission of information under similar conditions. However, these same replicas demonstrate a lack of resilience when faced with new foraging conditions. Conversely, replicas of colonies trained under fluctuating and uncertain food conditions reveal lower efficiencies at specific environments but increased resilience to shifts in food location.

Foraging behavior and the nest architecture of a high-Andean stingless bee (Hymenoptera: Apidae: Meliponini) revealed by X-ray computerized tomography

Stingless bees (Hymenoptera: Apidae: Meliponini) are key pollinators of both cultivated and wild plants in tropical and subtropical areas of the world. While most species are found in lowland to mid-elevations, a few have adapted to high elevations, and their biology remains poorly understood. We assess the foraging pattern of Parapartamona zonata (Smith) in the central Andes of Colombia (2583 m.a.s.l.) and apply computer tomography to visualize and characterize its internal nest architecture. Bees foraged for pollen and nesting materials (resin and/or mud) from sunrise (5:40 h) to sunset (17:45), even at ambient temperatures as low as 11 °C. Foraging varied significantly throughout the day and temperature and sky condition explained 47% of its variance. Differences in the nest architecture, when compared with previous records, suggest that nesting behavior might be variable. These results are discussed in the context of behavioral adaptations in this unique environmental niche.

Association of maternal genetics with the gut microbiome and eucalypt diet selection in captive koalas.

Koalas, an Australian arboreal marsupial, depend on eucalypt tree leaves for their diet. They selectively consume only a few of the hundreds of available eucalypt species. Since the koala gut microbiome is essential for the digestion and detoxification of eucalypts, their individual differences in the gut microbiome may lead to variations in their eucalypt selection and eucalypt metabolic capacity. However, research focusing on the relationship between the gut microbiome and differences in food preferences is very limited. We aimed to determine whether individual and regional differences exist in the gut microbiome of koalas as well as the mechanism by which these differences influence eucalypt selection. Foraging data were collected from six koalas and a total of 62 feces were collected from 15 koalas of two zoos in Japan. The mitochondrial phylogenetic analysis was conducted to estimate the mitochondrial maternal origin of each koala. In addition, the 16S-based gut microbiome of 15 koalas was analyzed to determine the composition and diversity of each koala's gut microbiome. We used these data to investigate the relationship among mitochondrial maternal origin, gut microbiome and eucalypt diet selection. This research revealed that diversity and composition of the gut microbiome and that eucalypt diet selection of koalas differs among regions. We also revealed that the gut microbiome alpha diversity was correlated with foraging diversity in koalas. These individual and regional differences would result from vertical (maternal) transmission of the gut microbiome and represent an intraspecific variation in koala foraging strategies. Further, we demonstrated that certain gut bacteria were strongly correlated with both mitochondrial maternal origin and eucalypt foraging patterns. Bacteria found to be associated with mitochondrial maternal origin included bacteria involved in fiber digestion and degradation of secondary metabolites, such as the families Rikenellaceae and Synergistaceae. These bacteria may cause differences in metabolic capacity between individual and regional koalas and influence their eucalypt selection. We showed that the characteristics (composition and diversity) of the gut microbiome and eucalypt diet selection of koalas differ by individuals and regional origins as we expected. In addition, some gut bacteria that could influence eucalypt foraging of koalas showed the relationships with both mitochondrial maternal origin and eucalypt foraging pattern. These differences in the gut microbiome between regional origins may make a difference in eucalypt selection. Given the importance of the gut microbiome to koalas foraging on eucalypts and their strong symbiotic relationship, future studies should focus on the symbiotic relationship and coevolution between koalas and the gut microbiome to understand individual and regional differences in eucalypt diet selection by koalas.

Predictable oceanographic processes drive the formation of a distribution hotspot for Indo-Pacific humpback dolphins at a manmade harbor

Marine mammals often aggregate and forage in specific ‘hotspot’ areas, which are associated with the predictability of prey sources driven by certain oceanographic processes. However, our understanding of the interactions between marine predators and the oceanographic processes remains incomplete, particularly in near-coastal and estuarine regions. This study investigated how predictable oceanographic processes influence the distribution patterns of Indo-Pacific humpback dolphins (Sousa chinensis) foraging in a known hotspot within the Pearl River Estuary, characterized by the complex topography of its manmade harbor and the interplay between strong tidal flows and river plumes. To address the fine-scale spatial distribution pattern of dolphin foraging, we conducted fixed passive acoustic monitoring of foraging ‘buzzes’ both inside and outside the harbor. Additionally, boat-based transect surveys were conducted to explore the relationship between dolphin foraging and associated water properties and current fields driven by oceanographic processes. Temporal trend analyses of buzzes revealed a pronounced tidal-related pattern in dolphin foraging activity, with increased detections during ebbing tides outside the harbor. Transect surveys indicated areas with elevated chlorophyll and turbidity levels attracted more dolphins during flood tides, whereas regions with high surface salinity gradients were preferred by dolphins during ebb tides. Oceanographic analysis recognized these bio-physical links as indicators of oceanographic features, including chlorophyll-rich river plumes, converging fronts, and shear-induced turbulence. These features enhance prey abundance and availability for humpback dolphins. This study highlights that oceanographic processes are crucial for determining the fine-scale spatiotemporal distribution of foraging in coastal dolphins, and offers insights into the effective prediction of dolphin aggregation.

Feral ecologies of the human deep past: multispecies archaeology and palaeo‐synanthropy

AbstractThis article articulates recent advances in palaeo‐ecology with the goals and ambitions of multispecies archaeology. It centres the synanthropic nexus as a key context for the study of early human‐animal relationships and argues that its evolution yields important yet currently overlooked dynamics shaping the structure of the archaeological record. I first show how the dominant heuristic of wild versus domesticated nonhuman animals obfuscates the inherent variability and creativity of past animal agency. I then illustrate how such agency is caught up with human behaviour and ecosystem impacts from relatively early on in human history, navigating historically shifting configurations of autonomy and control. Drawing on deep‐historical examples of synanthropic niches co‐assembled by human foragers and nonhuman animals, I argue that such interspecies configurations require careful attention to concepts of liminality and ferality and challenge species‐level approaches. I finally highlight potential human behavioural, material, and cosmological consequences of the synanthropic nexus, including integrative foraging patterns and notions of the giving animal, which play an important role in many Indigenous and ethnographic forager societies and illustrate the value of attending to this nexus as a focus of comparative multispecies research.

Agricultural habitat use and selection by a sedentary bird over its annual life cycle in a crop-depredation context

BackgroundModern agriculture has undoubtedly led to increasing wildlife-human conflicts, notably concerning bird damage in productive and attractive crops during some parts of the annual cycle. This issue requires utmost attention for sedentary birds that may impact agricultural crops at any stage of their annual life cycle. Reducing bird-human conflicts requires a better understanding of the relationship between bird foraging activity and the characteristics of agricultural areas, notably with respect to changes in food-resource availability and crop sensitivity across the year.MethodsWe explored how GPS-tagged adult male western jackdaws– sedentary corvids– utilize agricultural areas throughout their annual cycle, in a context of crop depredation. More precisely, we described their daily occurrence distribution and the extent of habitat use and selection consistency with respect to landscape composition across time.ResultsJackdaws moved in the close agricultural surroundings of their urban nesting place over the year (< 2.5 km from the nest, on average). Daily occurrence distributions were restricted (< 2.2 km2), relatively centered on the nesting locality (distance between the daily occurrence centroid and the nest < 0.9 km), and rather spatially stable during each annual life-cycle period (overlap range: 63.4–76.1%). Their foraging patterns highlighted that they fed mainly in grasslands all year round, and foraged complementarily and opportunistically in maize (during sowing– coinciding with the first stages of the birds’ breeding period) and cereal crops (during harvesting– their post-fledging period).ConclusionsOur findings demonstrate the very limited space use by breeding male jackdaws which foraged preferentially in grasslands. We call for future investigations in other agricultural contexts and also considering non-breeders for extrapolation purposes.

Temporal and Spatial Foraging Activity of Indian Honey Bee (Apis cerana indica F.) at Different Migratory Sites

Migratory beekeeping increases honey production and reduces the feeding costs of stationary beekeeping during longer dearth periods. This study discerns the influence of environmental conditions on the foraging behavior of the Indian honey bee, Apis cerana indica F., at different migratory sites in Southern India. The total number of foraging bees, pollen foraging efficiency, and nectar foraging efficiency were estimated. Furthermore, the influence of environmental factors, including temperature, relative humidity, rainfall, and solar radiation, was recorded to identify its impact on the foraging behavior of honey bees. Among the climatic factors, maximum temperature (&gt;30 °C) was the most crucial, negatively affecting bee activity with correlation coefficients of -0.83, -0.34, and -0.33 for outgoing bees, nectar, and pollen collectors, respectively. The relative humidity showed a positive impact on the frequency of worker bees moving out of the hive (r = 0.79), those coming in with nectar (r = 0.27), and pollen (r = 0.29). Rainfall hampered foraging activity, while solar radiation was found to have no significant effect on bee activity. Diurnal variations showed peak activity of bee foragers between 6.00 and 10.00 am. The visits by honey bees were significantly higher at low temperatures, solar radiation, precipitation, and high relative humidity. They made about 90% of their flower visits in the early morning, although plenty of bee flora was available throughout the day. Also, the environmental conditions at different sites strongly influenced the foraging behavior. However, the honey bees still focused their activities on favorable conditions depending on their biology and fixed their daily foraging patterns, improving beekeeping and honey production throughout the year.

Modelling bee movements to improve pollination

Modelling bee movements to improve pollination The ERC Consolidator Grant “Pollination ecology: how do bees move across the landscape and fashion plant reproduction (Bee-Move)” aims to link the study of bee spatial foraging patterns in the field with pollen dispersal and plant reproduction success. It will identify key mechanisms of pollination on which we could act for ecological, economic or public health issues.

Species-Specific Responses of Insectivorous Bats to Weather Conditions in Central Chile.

Insectivorous bats play a crucial role in agroecosystems by providing invaluable pest control services. With the escalating impacts of climate change, a comprehensive understanding of the environmental factors influencing bat activity becomes imperative for their conservation in agricultural landscapes. This study investigates the influence of weather conditions, specifically air temperature and relative humidity, on the timing activity and the relative abundance of five insectivorous bat species in central Chile. Data from automatic bat detectors and climatological stations are utilized for analysis. Our results unveil species-specific behaviors, with Tadarida brasiliensis exhibiting early emergence and extended activity periods compared to other bat species. Histiotus montanus and Lasiurus villosissimus display delayed onsets on more humid evenings, whereas Lasiurus varius and T. brasiliensis initiate activity earlier on colder nights compared to warmer ones. Relative humidity emerges as a key factor influencing relative abundance for all species, with more minutes with bat passes detected on drier nights. These findings suggest that global warming may influence observed bat behaviors, potentially altering foraging patterns and activity levels of these bat species. Moreover, as climate change continues, understanding the long-term impact on bat populations and their adaptive strategies is crucial for effective conservation measures. Further studies exploring these dynamics can provide valuable insights for shaping conservation efforts in the face of evolving environmental challenges.

How free-ranging Indian Flying Fox (Pteropus medius) forage in urban areas? A study from Kolkata, India

Abstract Foraging behaviour plays a significant role in the fitness of animals and is influenced by habitat quality. Habitat change due to rapid urbanization often results in altered behaviour and resource use patterns in animals thriving in such changed habitats. Bats play a crucial role as tree pollinators, seed dispersers and forest regenerators. Particularly in urban areas they are among the few pollinators that help regenerating the urban green spaces. Therefore, it is crucial to understand their foraging patterns in these human-dominated landscapes. Loss and degradation of roost and foraging resources threatens the survival of many bat species, including Indian Flying Foxes (IFF). Still, very few studies have been carried out on their feeding behaviour and ecology. Hence, we carried out this study to (i) identify the foraging sites of IFF, (ii) find out the urban land cover features influencing their foraging site selection and (iii) to identify the foraging trees used by them in urban areas. IFFs were observed to forage on 16 species of trees belonging to 10 families in four different sites in urban areas, of which Ficus species are most important. Amongst various urban land covers, the area of tree cover in the foraging sites were found to significantly influence the number of foraging IFFs. Our findings strongly advocate for the protection of the trees preferred by IFFs along with overall urban tree canopy covers, as these are essential resources for the survival of bats, as well as many other species in urban areas.

Abundant resources compensate for the uneven distribution of ungulates in desert grassland.

Strategically managing livestock grazing in arid regions optimizes land use and reduces the damage caused by overgrazing. Controlled grazing preserves the grassland ecosystem and fosters sustainability despite resource limitations. However, uneven resource distribution can lead to diverse grazing patterns and land degradation, particularly in undulating terrains. In this study, we developed a herbivore foraging algorithm based on a resource selection function model to analyze foraging distribution patterns, predict the probability of foraging, and identify the determinants of foraging probability in cattle. The study area was a complex desert landscape encompassing dunes and interdunes. Data on cattle movements and resource distribution were collected and analyzed to model and predict foraging behavior. Our findings revealed that cattle prefer areas with abundant vegetation in proximity to water sources and avoid higher elevations. However, abundant resource availability mitigated these impacts and enhanced the role of water points, particularly during late grazing periods. The analysis showed that available resources primarily determine foraging distribution patterns and lessen the effects of landforms and water distance on patch foraging. The results suggest that thoughtful water source placement and the subdivision of pastures into areas with varied terrain are crucial for sustainable grazing management. By strategically managing these factors, land degradation can be minimized, and the ecological balance of grassland ecosystems can be maintained. Further research is needed to refine the model and explore its applicability in other arid regions.

Biotic and abiotic factors affecting Atlantic ghost crab (Ocypode quadrata) spatiotemporal activity at an important shorebird nesting site in Virginia.

Atlantic ghost crabs (Ocypode quadrata) are predators of beach-nesting shorebird nests and chicks on the United States' Atlantic and Gulf coasts. Ghost crabs may also disturb birds, altering foraging, habitat use, or nest and brood attendance patterns. Shorebird conservation strategies often involve predator and disturbance management to improve reproductive success, but efforts rarely target ghost crabs. Despite the threat to shorebird reproductive success, ghost crabs are a poorly understood part of the beach ecosystem and additional knowledge about ghost crab habitat selection is needed to inform shorebird conservation. We monitored ghost crab activity, defined as burrow abundance, throughout the shorebird breeding season on Metompkin Island, Virginia, an important breeding site for piping plovers (Charadrius melodus) and American oystercatchers (Haematopus palliatus). We counted burrows at shorebird nests and random locations throughout the breeding season and investigated whether ghost crab activity was greater at nest sites relative to random locations without shorebird nests. While we observed burrows at all nest sites (n = 63 nests), we found that burrow counts were lower at piping plover nests with shell cover, relative to random locations with no shell cover. Ghost crabs may avoid piping plover nest sites due to anti-predator behaviors from incubating adults or differences in microhabitat characteristics selected by piping plovers. We also investigated the effects of habitat type, date, and air temperature on the abundance of ghost crab burrows. We found that while crab burrows were present across the barrier island landscape, there were more burrows in sandy, undisturbed habitats behind the dunes, relative to wave-disturbed beach. Additionally, ghost crab activity increased later in the shorebird breeding season. Understanding when and where ghost crabs are most likely to be active in the landscape can aid decision-making to benefit imperiled shorebird populations.

Space use by African savannah elephants in an arid protected area dominated by a mosaic of different vegetation

AbstractThe African savannah elephant (Loxodonta Africana) migrate in response to limiting environmental factors in arid areas. Using global positioning systems (GPS) telemetry data, we determined: (i) the dominant vegetation types used by African savannah elephants and (ii) the differences in the area occupied by dominant vegetation types in Gonarezhou National Park (GNP) in Zimbabwe. Significant spatiotemporal differences (p &lt; 0.05) detected in vegetation types utilised by the African savannah elephant, and in the area covered by vegetation types induced a determinate foraging pattern. Global positioning system telemetry is a smart conservation tool for surveillance of movement patterns of African savannah elephants in protected areas.

Surf & Turf: The role of intensification and surplus production in the development of social complexity in coastal vs terrestrial habitats

Social complexity in coastal and terrestrial environments both emerge as forms of subsistence intensification on previous foraging patterns but take different trajectories because of differences in the spatial and temporal structure and density of harvestable biomass between the two ecozones. Norms and values surrounding standards of living motivate households to intensify production above what is needed for mere survival (i.e., surplus), which in turn has the effect of providing a buffer against unpredictable shortfalls and longer-term population-resource imbalances caused by population growth. Economies of scale introduced by increasing labor group size and differentiation as well as technology fund the production and consumption of surplus and drive the emergence of social complexity among foragers and cultivators alike.

Stream hydrology and a pulse subsidy shape patterns of fish foraging.

Pulsed subsidy events create ephemeral fluxes of hyper-abundant resources that can shape annual patterns of consumption and growth for recipient consumers. However, environmental conditions strongly affect local resource availability for much of the year, and can heavily impact consumer foraging and growth patterns prior to pulsed subsidy events. Thus, a consumer's capacity to exploit pulse subsidy resources may be influenced by antecedent environmental conditions, but this has rarely been shown in nature and is unknown in aquatic ecosystems. Here, we sought to understand the importance of hydrologic variation and a salmon pulse subsidy on the foraging and growth patterns of two stream salmonids in a coastal southeast Alaska drainage. To do this, we sampled fish stomach contents at a high temporal frequency (daily-weekly measurements) and analyzed fish consumption rates in relation to streamflow and pulse subsidy resource availability. We then explored the influence of interannual hydrologic variation on access to pulse subsidy resources (i.e. whether fish exceeded an egg consumption gape limit) in a bioenergetic simulation. Prior to Pink Salmon spawning, Dolly Varden and Coho Salmon displayed distinct and nonlinear flow-foraging relationships, where forage for both species consisted primarily of macroinvertebrates. During this time period, consumption maxima coincided with baseflow and the highest observed flow conditions, and consumption minima were observed at severe low-water and intermediate flow values. After salmon spawning began, forage was not significantly related to flow and consisted primarily of salmon eggs. Further, consumption rates increased overall, and foraging patterns did not appear to be affected by flow in either species. Bioenergetic simulations revealed that patterns of interannual hydrologic variation may shift Coho Salmon growth trajectories among years. Together, our results suggest that access to marine pulse subsidy resources may depend on whether antecedent hydrologic conditions are suitable for juvenile salmonids to grow large enough to consume salmon eggs by the onset of spawning.