Foraging Site Research Articles

Foraging distance distributions reveal how honeybee waggle dance recruitment varies with landscape

Honeybee (Apis mellifera) colonies use a unique collective foraging system, the waggle dance, to communicate and process the location of resources. Here, we present a means to quantify the effect of recruitment on colony forager allocation across the landscape by simply observing the waggle dance on the dancefloor. We show first, through a theoretical model, that recruitment leaves a characteristic imprint on the distance distribution of foraging sites that a colony visits, which varies according to the proportion of trips driven by individual search. Next, we fit this model to the real-world empirical distance distribution of forage sites visited by 20 honeybee colonies in urban and rural landscapes across South East England, obtained via dance decoding. We show that there is considerable variation in the use of dancing information in colony foraging, particularly in agri-rural landscapes. In our dataset, reliance on dancing increases as arable land gives way to built-up areas, suggesting that dancing may have the greatest impact on colony foraging in the complex and heterogeneous landscapes of forage-rich urban areas. Our model provides a tool to assess the relevance of this extraordinary behaviour across modern anthropogenic landscape types.

Trade-Offs Between Forage Availability, Accessibility, and Predation Risk on Winter Foraging Strategies of Wood Bison (Bison bison athabascae).

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.

Wood Mice Utilize Understory Vegetation of Leafless Dead Dwarf Bamboo Culms as a Habitat and Foraging Site

Wood Mice Utilize Understory Vegetation of Leafless Dead Dwarf Bamboo Culms as a Habitat and Foraging Site

Individual foraging site fidelity persists within and across stopover seasons in a migratory shorebird, Numenius phaeopus (Whimbrel)

Abstract Site fidelity—returning repeatedly to the same site—can help many migratory species reduce uncertainty in their environment, especially when migratory stopover periods leave little time to explore and evaluate new habitat. Avian taxa, though, have shown wide variation in their levels of site fidelity during migration, and few studies have been able to examine individual-level fidelity at fine spatiotemporal scales. We used a high-resolution GPS tracking dataset of Numenius phaeopus (Whimbrel), a long-distance migratory shorebird, to assess levels of fidelity to specific foraging and roosting sites during migration, both within and between stopover seasons. We found that individuals are almost exclusively faithful to one shared roost site at night, but disperse to individual foraging territories during the day that overlap with each other by <20%. Individuals remain faithful to these distinct territories over time, on average shifting the center of their daily home ranges by <1.5 km within a single season, and overlapping with their previous season’s home range by 70% when they return during subsequent stopovers. Our findings reveal for the first time that a shorebird species exhibits fine-scale, individual foraging site fidelity during and between migratory stopovers—an important insight to inform effective conservation and management action.

Transcriptomic responses to location learning by honeybee dancers are partly mirrored in the brains of dance-followers.

The waggle dances of honeybees are a strikingly complex form of animal communication that underlie the collective foraging behaviour of colonies. The mechanisms by which bees assess the locations of forage sites that they have visited for representation on the dancefloor are now well-understood, but few studies have considered the remarkable backward translation of such information into flight vectors by dance-followers. Here, we explore whether the gene expression patterns that are induced through individual learning about foraging locations are mirrored when bees learn about those same locations from their nest-mates. We first confirmed that the mushroom bodies of honeybee dancers show a specific transcriptomic response to learning about distance, and then showed that approximately 5% of those genes were also differentially expressed by bees that follow dances for the same foraging sites, but had never visited them. A subset of these genes were also differentially expressed when we manipulated distance perception through an optic flow paradigm, and responses to learning about target direction were also in part mirrored in the brains of dance followers. Our findings show a molecular footprint of the transfer of learnt information from one animal to another through this extraordinary communication system, highlighting the dynamic role of the genome in mediating even very short-term behavioural changes.

Home ranges, directionality and the influence of moon phases on the movement ecology of Indian flying fox males in southern India.

Flying foxes of the genus Pteropus are amongst the largest fruit bats and potential long-range pollinators and seed dispersers in the paleotropics. Pteropus giganteus (currently P. medius) is the only flying fox that is distributed throughout the Indian mainland, including in urban and rural areas. Using GPS telemetry, we mapped the home ranges and examined flight patterns in P. giganteus males across moon phases in a semi-urban landscape in southern India. Home range differed between the tracked males (n=4), likely due to differences in their experience in the landscape. We found that nightly time spent outside the roost, distance commuted and the number of sites visited by tracked individuals did not differ significantly between moon phases. In 61% of total tracked nights across bats, the first foraging site was within 45˚ of the emergence direction. At the colony-level, scan-based observations showed emergence flights were mostly in the northeast (27%), west (22%) and southwest (19%) directions that could potentially be related to the distribution of foraging resources. The movement ecology of fruit bats in relation to the pollination and seed dispersal services they provide requires to be investigated in future studies. This article has an associated First Person interview with the first author of the paper.

Resource Selection and Herbaceous Biomass at Foraging Sites of Translocated Bighorn Sheep

Bighorn sheep (Ovis canadensis) historically inhabited the Black Hills region of South Dakota, but the species was extirpated from the area in the early 1900s. We translocated 26 bighorn sheep from Alberta, Canada to the northern Black Hills. We predicted that translocated bighorn sheep would exhibit similar resource use and selection as populations native to comparable habitats, specifically steep slopes with low overstory cover and high visibility. We used resource selection functions to estimate habitat selection by bighorn sheep and Robel pole and hand-clipped biomass to investigate the correlation between forage estimate methods. Bighorn sheep selected habitat types at varying levels, but were most strongly associated with barren and grassland landscapes while negatively associated with forest landscapes. Bighorn sheep had a positive association with slope and selected for fire-disturbed landscapes and elevation seasonally. Visual obstruction readings and herbaceous biomass at foraging sites (n = 78) were positively associated (r2 = 0.62). Herbaceous biomass ranged from 302.07 to 2,487.43 kg·ha−1. Foraging sites were typically located in areas with little overstory tree canopy cover (mean = 8.41%, standard error [SE] = 1.85), shorter distances to escape terrain (mean = 24.00 m, SE = 3.21), and low amounts of woody debris (mean = 0.25 kg·ha−1, SE = 0.07). The study area (Deadwood region of South Dakota) provided sufficient landscape attributes and herbaceous biomass to support the newly established bighorn sheep herd. Post-translocation assessments of resource use are crucial for evaluating conservation actions and potential success of future large mammal translocations.

Combined role of immediate early genes Egr-1, Hr-38 and Kakusei in the foraging behavior and learning in honeybees

The foraging behavior of honeybees is one of the most systematically composed behaviors among social insects which are admirable to watch. The main purpose of honeybee foraging is to collect food for their colony and since ancient days honeybee products have been used for various medicinal purposes (Singh and Takhellambam, 2021) (1). During foraging, honeybees gather information and transmit to their colony members regarding the location, distance, and profitability of forage sites with the help of unique movements called waggle dance. The capacities of honeybees’ time memory enable the foragers to return to a good food source in anticipation of the time of day. This highly intellectual, dynamic, and well-coordinated behavior of honeybees makes them to be one of the best choices of behavioral model to study various aspects of dynamic behaviors. As a result, vast knowledge in honeybee behavior has been accumulated and several recent studies immerge towards finding the underpinning regulatory biology of honeybee foraging behaviors. Immediate early genes (IE) genes are well documented neural markers and their promising roles in honeybee foraging have been demonstrated. Two of our recent studies showed three IE genes Egr-1, Hr-38 and Kakusei involvement during the daily foraging of honeybees. This finding has provided an avenue to further explore and identify the regulatory genes/proteins and neurons that underlie a specific behavior such as learning, memory, communication, and interaction etc. In this study we further analyze our previous published data to examine interaction of the three genes during the daily foraging of honeybees.

Individual foraging site fidelity increases from incubation to nestling rearing in a colonial bird

Foraging specialization, whereby animals exploit only a minor fraction of the population's foraging home range or trophic niche, may arise as a response to increasing levels of intraspecific competition. This phenomenon may be particularly frequent in colonial species, when individuals breed in large aggregations and are constrained to exploit shared foraging areas surrounding the colony site where competition for access to food resources may be high. Foraging specialization may be driven by individual foraging site fidelity, occurring whenever individuals consistently target specific foraging sites, which may differ from those used by other colony members. We assessed the extent of foraging specialization in a colonial breeding raptor, the lesser kestrel, Falco naumanni , by estimating the repeatability of foraging movement patterns of 45 GPS-tracked individuals during both incubation and nestling rearing. We found that the consistency of individual movement patterns was generally higher during nestling rearing than during incubation. Nestling-rearing individuals, but not incubating ones, travelled along relatively consistent routes when targeting foraging grounds and tended to target the same foraging areas throughout the tracking period. In colonial birds, and likely in altricial species more generally, an increased individual foraging site fidelity during nestling rearing versus incubation may result from increased energy demands due to frequent nestling provisioning in addition to self-provisioning. By consistently exploiting previously visited foraging sites that are likely to be rewarding, nestling-rearing birds might indeed increase their foraging efficiency, shortening food-searching time and maximizing their foraging effort. In addition, the use of distinct foraging areas may reduce intraspecific competition for food, thus buffering an important cost of coloniality. • Nestling-rearing lesser kestrels showed high individual foraging site fidelity. • Incubating birds were less consistent in foraging movement and commuting routes. • Site fidelity likely resulted in optimized foraging effort and food-searching time. • Site fidelity may increase foraging efficiency in a high energy-demanding phase. • Using distinct foraging sites could also reduce intraspecific competition.

Habitat selection and foraging site fidelity in Caspian Terns (Hydroprogne caspia) breeding in the Baltic Sea

Habitat preferences and foraging strategies affect population-level space use and are therefore crucial to understanding population change and implementing spatial conservation and management actions. We investigated the breeding season habitat preference and foraging site fidelity of the under-studied and threatened, Baltic Sea population of Caspian Terns (Hydroprogne caspia). Using GPS devices, we tracked 20 adult individuals at two breeding colonies, in Sweden and Finland, from late incubation through chick-rearing. Analyzing foraging movements during this period, we describe trip characteristics for each colony, daily metrics of effort, habitat use, and foraging site fidelity. We found that daily time spent away from the colony increased throughout the season, with colony-level differences in terms of distance travelled per day. In general, terns selected shallow waters between 0–5 meters in depth with certain individuals using inland lakes for foraging. We show, for the first time, that individual Caspian Terns are faithful to foraging sites throughout the breeding season, and that individuals are highly repeatable in their strategies regarding foraging site fidelity. These results fill important knowledge gaps for this at-risk population, and extend our general knowledge of the breeding season foraging ecology of this widespread species.

Performance of Urochloa and Megathyrsus Forage Grasses in Smallholder Farms in Western Kenya

Livestock productivity has remained low in sub-Saharan African countries compared to other places on the globe. The feeding component is the major limitation, in both quantity and quality. Among other inputs, feeding takes 55–70% of the costs involved. Livestock play a major role especially in smallholder mixed farms through provision of household nutrition and income through milk and meat. Equally, fertilization of cropland benefits from livestock manure, and livestock often act as insurance and savings by providing liquidity for unforeseen and urgent financial needs. Increasing livestock productivity would enhance the fore-mentioned benefits contributing to well-being and livelihoods. Toward this endeavor and with smallholder dairy farmers' participation, we undertook an evaluation of 10 selected forages from Urochloa Syn. Brachiaria and Megathyrsus syn. Panicum genus and compared them with Napier grass, i.e., Cenchrus purpureus Syn. Pennisetum purpureum commonly grown by farmers. For detailed and robust evaluation, we established the species in eight trial sites spread in four administrative counties in Western Kenya (Bungoma, Busia, Kakamega, and Siaya). In each site, the forages were established in plots in a randomized complete block design, replicated three times. Each site was linked to a group of farmers interested in dairy. For 2 years, dry matter production, plant height, and leaf-to-stem ratio was determined across all sites. Further, we guided farmers to generate participatory forage evaluation criteria, which they later administered across their respective forage demonstration sites individually on plot-by-plot basis to generate preference rating compared to what they normally grow—Napier grass. The results showed significant differences across the forage types within and between the sites. Cumulative dry matter yields ranged 13.7–49.9 t/ha over 10 harvestings across forage types and the counties, while values for crude protein were 1.85–6.23 t/ha and 110,222–375,988 MJ/ha for metabolizable energy. Farmer preferences emerged that highlighted forages with likely better chances of adoption with weighed scores ranging 5.5–7.6 against a scale of 1–9, across the counties. The observations provide additional and well-performing forage options for the farmers and possibly in similar production systems and ecologies. Awareness creation targeting livestock and dairy producers would be key, reaching, and informing them on alternative forage options, with potential to increase livestock productivity.

How shearwaters prey. New insights in foraging behaviour and marine foraging associations using bird-borne video cameras

Conventional bio-logging techniques used for ethological studies of seabirds have their limitations when studying detailed behaviours at sea. This study uses animal-borne video cameras to reveal fine-scale behaviours, associations with conspecifics and other species and interactions with fishery vessels during foraging of a Mediterranean seabird. The study was conducted on Scopoli's shearwaters (Calonectris diomedea) breeding in Linosa island (35°51′33″ N; 12°51′34″ E) during summer 2020. Foraging events were video recorded from a seabirds' view with lightweight cameras attached to the birds' back. Foraging always occurred in association with other shearwaters. Competitive events between shearwaters were observed, and their frequency was positively correlated to the number of birds in the foraging aggregation. Associations with tunas and sea turtles have been frequent observations at natural foraging sites. During foraging events, video recordings allowed observations of fine-scale behaviours, which would have remained unnoticed with conventional tracking devices. Foraging events could be categorised by prey type into “natural prey” and “fishery discards”. Analysis of the video footage suggests behavioural differences between the two prey type categories. Those differences suggest that the foraging effort between natural prey and fishery discards consumption can vary, which adds new arguments to the discussion about energy trade-offs and choice of foraging strategy. These observations highlight the importance of combining tracking technologies to obtain a complete picture of the at-sea behaviours of seabirds, which is essential for understanding the impact of foraging strategies and seabird-fishery interactions.Graphical abstract

A non-invasive, DNA-based method for beaver species identification in Finland

For the ability to control an invasive species and to protect an ecologically similar native species it is essential to map the exact distributions of both species. This is difficult if the species are so morphologically similar that their identification in the field is almost impossible. In Finland, the invasive North American beaver Castor canadensis is spreading towards the range of the native Eurasian beaver Castor fiber and at present, these species are partly sympatric. Effective management of these morphologically similar species requires an efficient method for species identification, ideally one that is non-invasive. Non-invasive genetic methods are used in a wide variety of wildlife species, for example in the research of large carnivores. Feces are a good source of DNA for terrestrial animals, but for the semi-aquatic animals like beavers, feces are not the best option. However, environmental DNA (eDNA) has been successfully used to detect species non-invasively in aquatic and terrestrial environments. We developed a non-invasive, eDNA-based method to map the distribution of the beaver species in Finland and to investigate within-species genetic diversity. The eDNA was obtained from the feed remains (wood chips) from beaver forage sites. With the help of Citizen science, wood chip samples were collected from different parts of Finland. We used our eDNA method to identify the ranges of both beaver species. Additionally, the presence of Eurasian beavers in south-east Finland was proven for the first time. Our non-invasive eDNA method is an effective way to accurately identify the ranges of both beaver species and will allow for the control of the invasive North American beaver and conservation of the native Eurasian beaver in Finland.

Pans as possible pedological hotspots in an arid African savanna

Vegetation dynamics in savannas are largely determined by water availability as well as soil nutrient dynamics. Species composition differs significantly from nutrient-rich soils to nutrient-poor soils, where the former is dominated by fine-leafed palatable woody species and the latter by broad-leafed and less palatable ones. Whilst this typically occurs at a landscape or catena scale, it is also interestingly observed at a localised and micro scale in areas such as wetlands and termite mounds. Wetlands are important edaphic contrasts in savannas and are paradoxically prevalent in the semi-arid to arid regions. In Southern Africa endorheic (inward draining) wetlands, known as pans, are particularly ubiquitous in arid regions but are not well studied compared to other wetland types. These wetlands were the focus of this study, which took place in the semi-arid savanna of the Limpopo plains, South Africa. The key research aims of this study were to determine how the pans differed from the surrounding terrestrial savanna landscape with respect to soil texture and chemistry, woody plant density and vegetation species composition. Top and sub soil samples were analysed to a depth of 30 and 60 cm and vegetation transects were carried out across three identified ‘hydro-ecological’ zones, i.e. the pan centre, the wooded wetland zone around the pan and representative terrestrial savanna habitat. In addition, drone aerial imagery was utilised to accurately determine woody species density and visually understand habitat changes. As hypothesised, the physiochemical properties of the soils differed along the study gradient from terrestrial to wetland, where in general the soil fertility, clay content and water holding capacity increased. The high clay content of the pans facilitates the surface pooling of rainwater and the possible maintenance of wetland conditions in these depressions which were found to be localised soil nutrient hotspots. The wooded wetland and terrestrial areas differed from each other in woody species composition where the terrestrial areas were largely dominated by broad leafed tree and shrub species and the wooded wetland areas had few to no broad-leafed species present but rather a dominance of fine-leafed Senegalia/Vachelia species. In addition, the Senegalia/Vachelia dominated habitat had a higher tree density than the surrounding bushveld, forming closed canopy patches in some areas. This change in vegetation and soil dynamics are important in savanna ecology as these habitats function quite differently from each other with respect to nutrient cycling, herbivore behaviour and biodiversity. It was concluded that these pans are nutrient-rich hotspots, likely playing an important ecological role in the savanna landscape. Furthermore, as they are likely to be key water sources and preferential forage sites, they could be the first to show signs of degradation and be useful indicators for land managers. These pans should be highlighted as sensitive habitats with regional conservation significance, which are deserving of adequate protection from surrounding threats such as mining.

Nitrogen fertilizer needs of first‐year small grain forages following alfalfa

AbstractSmall grain forages are commonly grown following alfalfa (Medicago sativa L.) in Utah and the Intermountain West, especially during drought years as small grains require less irrigation than corn (Zea mays L.). Several studies have shown that corn following alfalfa rarely needs nitrogen (N) fertilizer, yet few have evaluated N needs of small grains grown for forage. Objectives of this research were to determine whether N fertilizer is needed to economically optimize the yield and quality of first‐year small grain forages following alfalfa, and whether spring soil nitrate tests can predict N responsiveness. Fertilizer trials (four replications of six N rates) were conducted on 11 first‐year small grain forage sites in Utah during 2018 and 2019. Results indicated that N fertilizer was not needed to economically increase small grain forage yield at most (91%) site‐years. The one responsive site‐year followed an old and thinning alfalfa stand (9‐yr old) and required only 67 kg N ha−1. In contrast, forage quality improved with average N fertilizer applications ranging from 101 to 142 kg N ha−1 at all but one site‐year. Soil nitrate concentration was able to separate yield and forage quality response to N in 73 and 53% of the cases, respectively, suggesting it may be a viable prediction test for yield and some aspects of quality response in this rotation. Results indicate that growers often do not need to apply fertilizer N to first‐year small grain forages unless compensation for forage quality improvement outweighs fertilizer costs.

Intercolony variation in foraging flight characteristics of black-headed gulls Chroicocephalus ridibundus during the incubation period.

Using GPS loggers, we examined the influence of colony, sex, and bird identity on foraging flight characteristics of black‐headed gulls Chroicocephalus ridibundus during the incubation period. We studied tracks of 36 individuals breeding in one urban and two rural colonies in Poland. Birds from both rural colonies performed the furthest flights (mean max distance 8–12 km, up to 27 km) foraging mainly in agricultural areas. Gulls from the urban colony performed shorter flights (mean 5 km, up to 17 km) visiting mainly urbanized areas and water bodies. We found that females performed longer flights and their flight parameters were less repeatable compared to males. Males from both rural colonies visited water bodies more frequently than females. In all colonies, males (but not females) used habitats unproportionally to their availability in the vicinity. Relatively low interindividual and relatively high intraindividual overlap in home ranges indicated considerable foraging site fidelity. Individuals specialized in the use of a particular type of habitat performed shorter foraging flights compared to individuals using diverse habitats during their foraging flights. Our results indicate diverse foraging strategies of black‐headed gulls, including generalists that explore various habitats and specialists characterized by high foraging site and habitat fidelity.

Social vocalizations of big-footed myotis (Myotis macrodactylus) during foraging.

Acoustic signals play a crucial role in transmitting information and maintaining social stability in gregarious animals, especially in echolocating bats, which rely primarily on biological sonar for navigating in the dark. In the context of foraging without relying on tactile, visual or olfactory cues, acoustic signals convey information not only on food but also on ownership and defense of resources. However, studies on such information remain fragmentary. In the present study, we aim to document the social vocal repertoire of Myotis macrodactylus at natural foraging sites. Multiple acoustic analyses and spectrographic classification revealed a rich foraging vocal repertoire comprising 6 simple syllables and 2 composites. Discriminant function analyses associated with a subset-validation procedure provided an optimal method to spectrographically classify all recorded sounds into different syllable types. Multidimensional scaling of median values of multiple parameters further confirmed notable differences among these syllables in a 3-D space. In addition, Euclidean distance analysis showed that there were some spectral similarities between specific social vocal syllables and feeding buzzes, which implied a potential jamming role. Altogether, the data indicate that bats at foraging sites under natural conditions used variant social vocalizations with different functions in addition to echolocation calls, providing supporting evidence for further work on the function and vocal mechanisms of acoustic communication in mammals.

Seasonal and interspecific landscape use of sympatric greater prairie‐chickens and plains sharp‐tailed grouse

ABSTRACTNative grasslands throughout the Great Plains, USA, have undergone varying levels of fragmentation. The prairie ecosystems of Nebraska, USA, provide habitat for culturally and economically important galliforms, including greater prairie‐chicken (GRPC; Tympanuchus cupido pinnatus) and plains sharp‐tailed grouse (STGR; Tympanuchus phasianellus jamesi). The Sandhills region in north‐central Nebraska remains largely intact as grasslands, but cropland development at the margins has provided potential for alternative winter forage sites. Our objectives were to describe intraspecific seasonal shifts and interspecific differences in landscape use of these 2 species of prairie grouse in the Sandhills. We captured and radiomarked 87 birds (68 STGR, 19 GRPC) during 2015–2016 and used aerial telemetry to collect location data on birds. We used presence‐only location data and ecological and anthropogenic variables (e.g., land‐cover types, topography, vegetation productivity, and roads) in a maximum entropy (using MaxEnt software) approach to construct and compare seasonal species distribution models. During the breeding season, GRPC distribution probabilities were greater in areas more distant from center‐pivot irrigation locations, proximate to wet meadows, and at moderate distances from crop fields, whereas during the nonbreeding season, distributions were positively influenced by conifer and mixed‐grass (generally areas on peripheries of wetlands or meadows) land‐cover types. For STGR during both seasons, distribution probabilities were greatest in areas more distant from wet meadows, whereas during the nonbreeding season the probabilities were also greater in areas more distant from sandy ecological sites. Using an ecological‐niche‐similarity approach to examine interspecific use of the landscape, we found evidence that landscape use on our study area differed between species during the breeding season, but not during the nonbreeding season. Our results provide support for coordinated, landscape‐level management of galliforms, which can now be extended to seasonal priorities during management decisions on publicly and privately managed lands. © 2019 The Wildlife Society.

Killer whales redistribute white shark foraging pressure on seals

Predatory behavior and top-down effects in marine ecosystems are well-described, however, intraguild interactions among co-occurring marine top predators remain less understood, but can have far reaching ecological implications. Killer whales and white sharks are prominent upper trophic level predators with highly-overlapping niches, yet their ecological interactions and subsequent effects have remained obscure. Using long-term electronic tagging and survey data we reveal rare and cryptic interactions between these predators at a shared foraging site, Southeast Farallon Island (SEFI). In multiple instances, brief visits from killer whales displaced white sharks from SEFI, disrupting shark feeding behavior for extended periods at this aggregation site. As a result, annual predations of pinnipeds by white sharks at SEFI were negatively correlated with close encounters with killer whales. Tagged white sharks relocated to other aggregation sites, creating detectable increases in white shark density at Ano Nuevo Island. This work highlights the importance of risk effects and intraguild relationships among top ocean predators and the value of long-term data sets revealing these consequential, albeit infrequent, ecological interactions.

Recent prey capture experience and dynamic habitat quality mediate short-term foraging site fidelity in a seabird.

Foraging site fidelity allows animals to increase their efficiency by returning to profitable feeding areas. However, the mechanisms underpinning why animals 'stay' or 'switch' sites have rarely been investigated. Here, we explore how habitat quality and prior prey capture experience influence short-term site fidelity by the little penguin (Eudyptula minor). Using 88 consecutive foraging trips by 20 brooding penguins, we found that site fidelity was higher after foraging trips where environmental conditions were favourable, and after trips where prey capture success was high. When penguins exhibited lower site fidelity, the number of prey captures relative to the previous trip increased, suggesting that switches in foraging location were an adaptive strategy in response to low prey capture rates. Penguins foraged closer to where other penguins foraged on the same day than they did to the location of their own previous foraging site, and caught more prey when they foraged close together. This suggests that penguins aggregated flexibly when prey was abundant and accessible. Our results illustrate how foraging predators can integrate information about prior experience with contemporary information such as social cues. This gives insight into how animals combine information adaptively to exploit changing prey distribution in a dynamic environment.