Central Place Foragers Research Articles

Species-specific differences in the fine structure of learning walk elements in Cataglyphis ants.

Cataglyphis desert ants are famous navigators. Like all central place foragers, they are confronted with the challenge to return home, i.e. relocate an inconspicuous nest entrance in the ground, after their extensive foraging trips. When leaving the underground nest for the first time, desert ants perform a striking behavior, so-called learning walks that are well structured. However, it is still unclear how the ants initially acquire the information needed for sky- and landmark-based navigation, in particular how they calibrate their compass system at the beginning of their foraging careers. Using high-speed video analyses, we show that different Cataglyphis species include different types of characteristic turns in their learning walks. Pirouettes are full or partial rotations (tight turns about the vertical body axis) during which the ants frequently stop and gaze back in the direction of the nest entrance during the longest stopping phases. In contrast, voltes are small walked circles without directed stopping phases. Interestingly, only Cataglyphis ant species living in a cluttered, and therefore visually rich, environment (i.e. C. noda and C. aenescens in southern Greece) perform both voltes and pirouettes. They look back to the nest entrance during pirouettes, most probably to take snapshots of the surroundings. In contrast, C. fortis inhabiting featureless saltpans in Tunisia perform only voltes and do not stop during these turns to gaze back at the nest - even if a set of artificial landmarks surrounds the nest entrance.

A Breath of Fresh Air in Foraging Theory: The Importance of Wind for Food Size Selection in a Central-Place Forager.

Empirical data about food size carried by central-place foragers do not often fit with the optimum predicted by classical foraging theory. Traditionally, biotic constraints such as predation risk and competition have been proposed to explain this inconsistency, leaving aside the possible role of abiotic factors. Here we documented how wind affects the load size of a central-place forager (leaf-cutting ants) through a mathematical model including the whole foraging process. The model showed that as wind speed at ground level increased from 0 to 2 km/h, load size decreased from 91 to 30 mm2, a prediction that agreed with empirical data from windy zones, highlighting the relevance of considering abiotic factors to predict foraging behavior. Furthermore, wind reduced the range of load sizes that workers should select to maintain a similar rate of food intake and decreased the foraging rate by ∼70% when wind speed increased 1 km/h. These results suggest that wind could reduce the fitness of colonies and limit the geographic distribution of leaf-cutting ants. The developed model offers a complementary explanation for why load size in central-place foragers may not fit theoretical predictions and could serve as a basis to study the effects of other abiotic factors that influence foraging.

Combined use of tri-axial accelerometers and GPS reveals the flexible foraging strategy of a bird in relation to weather conditions.

Tri-axial accelerometry has proved to be a useful technique to study animal behavior with little direct observation, and also an effective way to measure energy expenditure, allowing a refreshing revisit to optimal foraging theory. This theory predicts that individuals should gain the most energy for the lowest cost in terms of time and energy when foraging, in order to maximize their fitness. However, during a foraging trip, central-place foragers could face different trade-offs during the commuting and searching parts of the trip, influencing behavioral decisions. Using the lesser kestrel (Falco naumanni) as an example we study the time and energy costs of different behaviors during the commuting and searching parts of a foraging trip. Lesser kestrels are small insectivorous falcons that behave as central-place foragers during the breeding season. They can commute by adopting either time-saving flapping flights or energy-saving soaring-gliding flights, and capture prey by using either time-saving active hovering flights or energy-saving perch-hunting. We tracked 6 lesser kestrels using GPS and tri-axial accelerometers during the breeding season. Our results indicate that males devoted more time and energy to flight behaviors than females in agreement with being the sex responsible for food provisioning to the nest. During the commuting flights, kestrels replaced flapping with soaring-gliding flights as solar radiation increased and thermal updrafts got stronger. In the searching part, they replaced perch-hunting with hovering as wind speed increased and they experienced a stronger lift. But also, they increased the use of hovering as air temperature increased, which has a positive influence on the activity level of the preferred prey (large grasshoppers). Kestrels maintained a constant energy expenditure per foraging trip, although flight and hunting strategies changed dramatically with weather conditions, suggesting a fixed energy budget per trip to which they adjusted their commuting and searching strategies in response to weather conditions.

Suite of simple metrics reveals common movement syndromes across vertebrate taxa

BackgroundBecause empirical studies of animal movement are most-often site- and species-specific, we lack understanding of the level of consistency in movement patterns across diverse taxa, as well as a framework for quantitatively classifying movement patterns. We aim to address this gap by determining the extent to which statistical signatures of animal movement patterns recur across ecological systems. We assessed a suite of movement metrics derived from GPS trajectories of thirteen marine and terrestrial vertebrate species spanning three taxonomic classes, orders of magnitude in body size, and modes of movement (swimming, flying, walking). Using these metrics, we performed a principal components analysis and cluster analysis to determine if individuals organized into statistically distinct clusters. Finally, to identify and interpret commonalities within clusters, we compared them to computer-simulated idealized movement syndromes representing suites of correlated movement traits observed across taxa (migration, nomadism, territoriality, and central place foraging).ResultsTwo principal components explained 70% of the variance among the movement metrics we evaluated across the thirteen species, and were used for the cluster analysis. The resulting analysis revealed four statistically distinct clusters. All simulated individuals of each idealized movement syndrome organized into separate clusters, suggesting that the four clusters are explained by common movement syndrome.ConclusionsOur results offer early indication of widespread recurrent patterns in movement ecology that have consistent statistical signatures, regardless of taxon, body size, mode of movement, or environment. We further show that a simple set of metrics can be used to classify broad-scale movement patterns in disparate vertebrate taxa. Our comparative approach provides a general framework for quantifying and classifying animal movements, and facilitates new inquiries into relationships between movement syndromes and other ecological processes.

Modeling food web effects of low sardine and anchovy abundance in the California Current

Populations of sardine, anchovy, and other forage species can fluctuate to low levels due to climate variability and fishing, leading to indirect effects on marine food webs. In the context of recent declines of sardine (Sardinops sagax) and anchovy (Engraulis mordax) in the California Current, we apply an end-to-end Atlantis ecosystem model that is spatially explicit, includes trophic interactions, and allows high and low recruitment regimes (production of juveniles). Our simulations suggest that depleted sardine populations, whether caused by fishing or natural cycles, may lead to declines in predator groups such as dolphins and large piscivorous flatfish (e.g. California halibut Paralichthys californicus). Birds exhibited more moderate declines, and California sea lions (Zalophus californianus) exhibited relatively weak declines. The Atlantis ecosystem model also predicted indirect positive effects of sardine depletion, primarily for prey species such as zooplankton. Overall our model predicted moderate declines in most predators during simulated severe declines in sardine and anchovy, illustrating the important buffering role provided by forage species other than sardine and anchovy. This ‘buffered response’ is weaker than what would be suggested by another ecosystem model (Ecosim), as predicted by diet information and a global synthesis of Ecosim models (the PREP equation). One limitation of the Atlantis model is that it did not include processes that might give rise to localized depletion of sardine at scales relevant to central place foragers, such as birds and pinnipeds. This analysis will contribute to a collaborative multi-model approach that evaluates the role of sardine in the California Current.

Experimental manipulation of brood size affects several levels of phenotypic variance in offspring and parent pied flycatchers

Parental provisioning of offspring should reflect selection on life history aspects of parenting and on foraging behavior. Life history and foraging theory generally make predictions about mean behavior, but some circumstances might favor changes in the variance of parent and offspring behaviors. We analyzed data on free-living pied flycatchers (Ficedula hypoleuca) experiencing a brood size manipulation. We used double hierarchical generalized linear models to investigate patterns in means and variances of provisioning, brood begging, and parental mass. As predicted by life history theory, parents with enlarged broods of intensely begging nestlings fed at higher rates and delivered more food per unit of time. They also delivered food at a more consistent rate. This contradicts the prediction from variance-sensitive foraging theory that parents facing higher brood demand should choose more variable foraging options. Indirect evidence suggests that reduced variance in trip time arose from shifts in parental time budgets. Exploratory analyses revealed patterns in residual variance of both nestling begging and parental mass changes, with enlarged broods begging less consistently and female body mass changes being more variable after longer foraging trips. We show that parent pied flycatchers simultaneously adjust means and variances in multiple aspects of their provisioning effort to changes in brood demand and that these responses might be linked with nestling begging and changes in parental body mass. Our study highlights both the importance of adopting sophisticated statistical approaches and the potential intersection of two bodies of theory that may affect strategic adjustments of individuals engaged in central place provisioning. Central place foragers, such as many parent birds provisioning offspring, are subject to selective forces from both life history and foraging ecology. Most effects of selection are expected on mean behaviors, but adaptive life histories or foraging decisions can also influence variances. We analyzed both means and variances in parent pied flycatchers experiencing either increases or decreases in brood size. Parents with enhanced broods had shorter foraging trips and offspring that begged more, matching predictions from life history theory. They also exhibited less variation in trip time, contrary to predictions from variance sensitive foraging theory. However, patterns in the residual variance in offspring begging and parental mass are less easily explained and raise new questions. Statistical models of means and variances illuminate the intersection between two bodies of theory and reveal new processes affecting provisioning behavior.

Hierarchical influences of prey distribution on patterns of prey capture by a marine predator

Summary Prey distribution acts at multiple spatial scales to influence foraging success by predators. The overall distribution of prey may shape foraging ranges, the distance between patches may influence the ability of predators to detect and move between profitable areas, and individual patch characteristics may affect prey capture efficiency. In this study, we assessed relationships between spatially explicit patterns of prey capture by a central place forager, the little penguin (using GPS tracking and accelerometry), and the distribution of aggregations of potential forage fish prey (using boat‐based active acoustics) in eastern Australia. We used complementary resource selection functions to estimate the distribution of both prey captures and aggregations across the study area, based on a suite of habitat characteristics. We found that 99% of prey captures by penguins occurred in the top 20 m of the water column. The estimated distribution of prey captures across the study area was similar to the distribution of aggregations above 20 m depth, indicating that penguins effectively matched the local distribution of their prey. The distances between consecutive prey captures followed a bimodal distribution, with means of 8·1 ± 2·2 and 57·4 ± 1·7 m. Based on the length of aggregations and the distances separating aggregations along survey transects, this implies that foraging behaviour occurs on multiple spatial scales corresponding to within‐patch and between‐patch movements respectively. Morphological characteristics of aggregations above 20 m depth were important for explaining variance in the number of prey caught by penguins in an area, with penguins catching more prey where aggregations were relatively dense, compact and shallow. These results reveal spatially explicit patterns of prey capture, and provide a framework for understanding how features of prey distribution influence prey intake by predators in patchy environments. A lay summary is available for this article.

Habitat use and spatial fidelity of male South American sea lions during the nonbreeding period.

Conditions experienced during the nonbreeding period have profound long‐term effects on individual fitness and survival. Therefore, knowledge of habitat use during the nonbreeding period can provide insights into processes that regulate populations. At the Falkland Islands, the habitat use of South American sea lions (Otaria flavescens) during the nonbreeding period is of particular interest because the population is yet to recover from a catastrophic decline between the mid‐1930s and 1965, and nonbreeding movements are poorly understood. Here, we assessed the habitat use of adult male (n = 13) and juvenile male (n = 6) South American sea lions at the Falkland Islands using satellite tags and stable isotope analysis of vibrissae. Male South American sea lions behaved like central place foragers. Foraging trips were restricted to the Patagonian Shelf and were typically short in distance and duration (127 ± 66 km and 4.1 ± 2.0 days, respectively). Individual male foraging trips were also typically characterized by a high degree of foraging site fidelity. However, the isotopic niche of adult males was smaller than juvenile males, which suggested that adult males were more consistent in their use of foraging habitats and prey over time. Our findings differ from male South American sea lions in Chile and Argentina, which undertake extended movements during the nonbreeding period. Hence, throughout their breeding range, male South American sea lions have diverse movement patterns during the nonbreeding period that intuitively reflects differences in the predictability or accessibility of preferred prey. Our findings challenge the long‐standing notion that South American sea lions undertake a winter migration away from the Falkland Islands. Therefore, impediments to South American sea lion population recovery likely originate locally and conservation measures at a national level are likely to be effective in addressing the decline and the failure of the population to recover.

Breeding success of a marine central place forager in the context of climate change: A modeling approach.

In response to climate warming, a southward shift in productive frontal systems serving as the main foraging sites for many top predator species is likely to occur in Subantarctic areas. Central place foragers, such as seabirds and pinnipeds, are thus likely to cope with an increase in the distance between foraging locations and their land-based breeding colonies. Understanding how central place foragers should modify their foraging behavior in response to changes in prey accessibility appears crucial. A spatially explicit individual-based simulation model (Marine Central Place Forager Simulator (MarCPFS)), including bio-energetic components, was built to evaluate effects of possible changes in prey resources accessibility on individual performances and breeding success. The study was calibrated on a particular example: the Antarctic fur seal (Arctocephalus gazella), which alternates between oceanic areas in which females feed and the land-based colony in which they suckle their young over a 120 days rearing period. Our model shows the importance of the distance covered to feed and prey aggregation which appeared to be key factors to which animals are highly sensitive. Memorization and learning abilities also appear to be essential breeding success traits. Females were found to be most successful for intermediate levels of prey aggregation and short distance to the resource, resulting in optimal female body length. Increased distance to resources due to climate warming should hinder pups’ growth and survival while female body length should increase.

A Markov model for planning and permitting offshore wind energy: A case study of radio-tracked terns in the Gulf of Maine, USA

Quantifying and managing the potential adverse wildlife impacts of offshore wind energy is critical for developing offshore wind energy in a sustainable and timely manner, but poses a significant challenge, particularly for small marine birds that are difficult to monitor. We developed a discrete-time Markov model of seabird movement around a colony site parameterized by automated radio telemetry data from common terns (Sterna hirundo) and Arctic terns (S. paradisaea), and derived impact functions that estimate the probability of collision fatality as a function of the distance and bearing of wind turbines from a colony. Our purpose was to develop and demonstrate a new, flexible tool that can be used for specific management and wind-energy planning applications when adequate data are available, rather than inform wind-energy development at this site. We demonstrate how the tool can be used 1) in marine spatial planning exercises to quantitatively identify setback distances under development scenarios given a risk threshold, 2) to examine the ecological and technical trade-offs of development alternatives to facilitate negotiation between objectives, and 3) in the U.S. National Environmental Policy Act (NEPA) process to estimate collision fatality under alternative scenarios. We discuss model limitations and data needs, and highlight opportunities for future model extension and development. We present a highly flexible tool for wind energy planning that can be easily extended to other central place foragers and data sources, and can be updated and improved as new monitoring data arises.

Flexibility in food resource allocation in parents and selectivity for offspring: variations in δ15N and δ13C values during breeding of the blue-footed booby

It is common for marine animals to be selective in the amount and quality of foods during reproduction due to the higher energetic demands. As central place foragers, seabirds are often selective with the prey species they deliver to their offspring. We evaluated trophic segregation between parents and their offspring in blue-footed booby (Sula nebouxii) by measuring stable isotope ratios (δ15N and δ13C) in blood samples during two breeding seasons and at different reproductive stages (incubation, early and late chick rearing). Additionally, we examined if δ15N values from chicks were correlated with their condition as reflected in blood alkaline phosphatase (ALP) levels. δ15N values increased and δ13C values decreased in adults as the breeding season progressed, indicating differences in foraging regions or the assimilated prey. δ15N values differed significantly between sexes; males had higher δ15N values than females during all reproductive stages sampled during the 2011 season, whereas in 2012 the difference between sexes was only observed during incubation. Offspring had higher δ15N values and lower δ13C values than adults, suggesting that, when feeding their chicks, parents feed them with prey from higher trophic levels and possibly from more oceanic environments. ALP levels, a proxy for bone growth and condition, measured in the offspring were positively correlated with δ15N values during the chick-rearing period. Although the diet of parents differed between reproductive stages, a multi-source Bayesian mixing model indicated that their primary prey were Pacific anchovy and halfbeaks, with a combined modal fractional contribution of 50–70% of the diet. The diet of the offspring was dominated by Pacific anchovy (≈36%), which was also the prey with the highest lipid content (C:N ratio 5.57), whereas the contributions of other fish species (or groups) were similar (17–24% each). Our findings suggest that parents actively feed their young with high-quality prey, which seems to increase some of the individual fitness components associated with better growth.

Ability to reorient is weakly correlated with central-place versus non-central-place foraging in acacia ants

Cognitive abilities evolve by natural selection to help an organism cope with problems encountered in the organism’s typical environment. In acacia ants, coevolution with the acacia tree led workers to forage exclusively on the host plant (“in-nest” foraging), instead of the central-place foraging typical for most social insects. To test whether foraging ecology altered the orientation skills of acacia ants, we developed a novel field disorientation assay to evaluate the ability of foraging workers to quickly reorient after being disoriented (rotated) in an experimental arena. We compared 10 behaviors among disoriented and sham-treated workers of three in-nest foraging species (Pseudomyrmex nigrocinctus, P. flavicornis, and P. spinicola) and two central-place foraging species that regularly forage off the host tree (P. gracilis, P. nigropilosus). We predicted that experimental disorientation of workers should affect in-nest foraging species (acacia ants) more than central-place foraging species. Behavioral differences between control and disoriented ants were not consistently associated with foraging ecology, although the species least able to recover after disorientation was an acacia ant (P. nigrocinctus), and the species performing best after disorientation was a central-place forager (P. gracilis). Only one of the 10 behaviors studied consistently differed in experimentally disoriented workers compared to controls in all three species of acacia ants, whereas none of the experimentally disoriented central-place foragers differed from control workers for this specific behavior. Future studies could evaluate additional ant species living in obligate associations with plants, to further compare the cognitive abilities of in-nest versus central-place foraging organisms. Foraging ecology influences the evolution of spatial orientation abilities. Acacia ants exclusively nest and forage on acacia trees; unlike most other ants that are central-place foragers, acacia ants therefore do not face the challenge of finding the way back home after collecting food. We compared the performance of three species of acacia ants to the performance of two species of central-place foragers on a disorientation assay in the field. We found that the ability to reorient was not consistently associated with foraging ecology, although the species least able to recover after disorientation was an acacia ant (P. nigrocinctus), and the species performing best after disorientation was a central-place forager (P. gracilis). Other behaviors related with the mutualism with the acacia tree—such as pruning nearby vegetation and falling off branches to attack potential herbivores—could also select for orientation abilities because workers reorient back to the host tree.

Taking a goal-centred dynamic snapshot as a possibility for local homing in initially naïve bumblebees.

It is essential for central place foragers, such as bumblebees, to return reliably to their nest. Bumblebees, leaving their inconspicuous nest hole for the first time need to gather and learn sufficient information about their surroundings to allow them to return to their nest at the end of their trip, instead of just flying away to forage. Therefore, we assume an intrinsic learning programme that manifests itself in the flight structure immediately after leaving the nest for the first time. In this study, we recorded and analysed the first outbound flight of individually marked naïve bumblebees in an indoor environment. We found characteristic loop-like features in the flight pattern that appear to be necessary for the bees to acquire environmental information and might be relevant for finding the nest hole after a foraging trip. Despite common features in their spatio-temporal organisation, first departure flights from the nest are characterised by a high level of variability in their loop-like flight structure across animals. Changes in turn direction of body orientation, for example, are distributed evenly across the entire area used for the flights without any systematic relationship to the nest location. By considering the common flight motifs and this variability, we came to the hypothesis that a kind of dynamic snapshot is taken during the early phase of departure flights centred at the nest location. The quality of this snapshot is hypothesised to be 'tested' during the later phases of the departure flights concerning its usefulness for local homing.

Effects of variation in the abundance and distribution of prey on the foraging success of central place foragers

Summary Seabirds and pinnipeds are vulnerable to reductions in prey availability, especially during the breeding season when spatial constraints limit their adaptive capacity. There are growing concerns about the effects of fisheries on prey availability in regions where large commercial fisheries target forage fish. For breeding seabirds and pinnipeds, prey availability depends on a combination of abundance, accessibility, patchiness and distance from the colony. An understanding of the aspects of prey availability that determine foraging success is essential for the design of effective management responses. We used a mechanistic individual‐based foraging model based on observed data for two seabird species, the Peruvian Booby Sula variegata and Guanay Cormorant Phalacrocorax bougainvilliorum, to simulate the foraging patterns of seabirds feeding on schooling fish. We ran the model over simulated prey fields representing eight possible combinations of high or low prey abundance, shallow or deep prey, and broadly distributed or spatially concentrated prey. The results highlight the importance of the accessibility of prey. Depth distribution was the primary factor determining modelled foraging success for both species, followed by abundance, and then spatial configuration. Synthesis and applications. The individual‐based foraging model provides a spatially explicit framework for assessing the effects of fisheries on the foraging success of seabirds and other central place foragers, and for evaluating the potential effectiveness of marine‐protected areas and other fisheries management strategies for safeguarding central place foragers in dynamic ecosystems. Our analysis indicates that broad‐scale fisheries management strategies that maintain forage fish above critical biomass levels are essential, but may need to be supplemented by targeted actions, such as time–area closures, when environmental conditions lead to low prey abundance or reduce prey accessibility for seabirds or pinnipeds of conservation concern. The individual‐based foraging model is adaptable and could be reconfigured for application to other species and systems.

Honeybees Learn Landscape Features during Exploratory Orientation Flights

Exploration is an elementary and fundamental form of learning about the structure of the world [1-3]. Little is known about what exactly is learned when an animal seeks to become familiar with the environment. Navigating animals explore the environment for safe return to an important place (e.g., a nest site) and to travel between places [4]. Flying central-place foragers like honeybees (Apis mellifera) extend their exploration into distances from which the features of the nest cannot be directly perceived [5-10]. Bees perform short-range and long-range orientations flights. Short-range flights are performed in the immediate surroundings of the hive and occur more frequently under unfavorable weather conditions, whereas long-range flights lead the bees into different sectors of the surrounding environment [11]. Applying harmonic radar technology for flight tracking, we address the question of whether bees learn landscape features during their first short-range or long-range orientation flight. The homing flights of single bees were compared after they were displaced to areas explored or not explored during the orientation flight. Bees learn the landscape features during the first orientation flight since they returned faster and along straighter flights from explored areas as compared to unexplored areas. We excluded a range of possible factors that might have guided bees back to the hive based on egocentric navigation strategies (path integration, beacon orientation, and pattern matching of the skyline). We conclude that bees localize themselves according to learned ground structures and their spatial relations to the hive.

Quality versus quantity: Foraging decisions in the honeybee (Apis mellifera scutellata) feeding on wildflower nectar and fruit juice.

Foraging animals must often decide among resources which vary in quality and quantity. Nectar is a resource that exists along a continuum of quality in terms of sugar concentration and is the primary energy source for bees. Alternative sugar sources exist, including fruit juice, which generally has lower energetic value than nectar. We observed many honeybees (Apis mellifera scutellata) foraging on juice from fallen guava (Psidium guajava) fruit near others foraging on nectar. To investigate whether fruit and nectar offered contrasting benefits of quality and quantity, we compared honeybee foraging performance on P. guajava fruit versus two wildflowers growing within 50 m, Richardia brasiliensis and Tridax procumbens. Bees gained weight significantly faster on fruit, 2.72 mg/min, than on either flower (0.17 and 0.12 mg/min, respectively). However, the crop sugar concentration of fruit foragers was significantly lower than for either flower (12.4% vs. 37.0% and 22.7%, respectively). Fruit foragers also spent the most time handling and the least time flying, suggesting that fruit juice was energetically inexpensive to collect. We interpret honeybee foraging decisions in the context of existing foraging models and consider how nest‐patch distance may be a key factor for central place foragers choosing between resources of contrasting quality and quantity. We also discuss how dilute solutions, such as fruit juice, can help maintain colony sugar–water balance. These results show the benefits of feeding on resources with contrasting quality and quantity and that even low‐quality resources have value.

BEESCOUT: A model of bee scouting behaviour and a software tool for characterizing nectar/pollen landscapes for BEEHAVE

Social bees are central place foragers collecting floral resources from the surrounding landscape, but little is known about the probability of a scouting bee finding a particular flower patch. We therefore developed a software tool, BEESCOUT, to theoretically examine how bees might explore a landscape and distribute their scouting activities over time and space. An image file can be imported, which is interpreted by the model as a “forage map” with certain colours representing certain crops or habitat types as specified by the user. BEESCOUT calculates the size and location of these potential food sources in that landscape relative to a bee colony. An individual-based model then determines the detection probabilities of the food patches by bees, based on parameter values gathered from the flight patterns of radar-tracked honeybees and bumblebees. Various “search modes” describe hypothetical search strategies for the long-range exploration of scouting bees. The resulting detection probabilities of forage patches can be used as input for the recently developed honeybee model BEEHAVE, to explore realistic scenarios of colony growth and death in response to different stressors. In example simulations, we find that detection probabilities for food sources close to the colony fit empirical data reasonably well. However, for food sources further away no empirical data are available to validate model output. The simulated detection probabilities depend largely on the bees’ search mode, and whether they exchange information about food source locations. Nevertheless, we show that landscape structure and connectivity of food sources can have a strong impact on the results. We believe that BEESCOUT is a valuable tool to better understand how landscape configurations and searching behaviour of bees affect detection probabilities of food sources. It can also guide the collection of relevant data and the design of experiments to close knowledge gaps, and provides a useful extension to the BEEHAVE honeybee model, enabling future users to explore how landscape structure and food availability affect the foraging decisions and patch visitation rates of the bees and, in consequence, to predict colony development and survival.

Pronounced inter-colony variation in the foraging ecology of Australasian gannets: influence of habitat differences

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 556:261-272 (2016) - DOI: https://doi.org/10.3354/meps11845 Pronounced inter-colony variation in the foraging ecology of Australasian gannets: influence of habitat differences Lauren P. Angel*, Maud Berlincourt, John P. Y. Arnould School of Life and Environmental Sciences (Burwood campus), Deakin University, Geelong, Victoria 3216, Australia *Corresponding author: lauren.angel@deakin.edu.au ABSTRACT: The predictability of prey due to oceanographic features can result in large aggregations of apex predators. Central place foragers, such as seabirds, are limited in their foraging duration and range during the breeding period, which can restrict their ability to reach such locations. Segregation by colony and sex can further restrict foraging range and may have direct implications for the foraging ecology of a species. In parts of its range, the Australasian gannet Morus serrator breeds in colonies of relatively close proximity and has recently been found to display sexual dimorphism. Two neighbouring breeding colonies in Bass Strait that experience divergent environmental conditions were investigated to determine whether these conditions or the sex of the individual are important variables influencing foraging behaviour in this species. GPS tracking and accelerometry were paired with stable isotope analysis to compare differences in foraging effort, habitat use and diet. Birds from Point Danger, a large colony located near a seasonally strong upwelling, travelled considerably further (77%) than birds from Pope’s Eye, a small colony in a nutrient-poor embayment. However, within colonies no sexual differences in foraging effort were found. While the colonies did not overlap in foraging areas, a degree of sexual segregation was apparent within both colonies (Point Danger 46.3% overlap and Pope’s Eye 73.7% overlap in home range). Furthermore, stable isotope analysis indicated birds from each colony fed at different trophic niches. This study reveals differences in habitat use and, consequently, dietary niches between and within neighbouring colonies. KEY WORDS: Foraging ecology · GPS tracking · Accelerometry · Stable isotopes · Sexual‑segregation · Morus serrator Full text in pdf format PreviousNextCite this article as: Angel LP, Berlincourt M, Arnould JPY (2016) Pronounced inter-colony variation in the foraging ecology of Australasian gannets: influence of habitat differences. Mar Ecol Prog Ser 556:261-272. https://doi.org/10.3354/meps11845 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 556. Online publication date: September 08, 2016 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2016 Inter-Research.

The price of associating with breeders in the cooperatively breeding chestnut-crowned babbler: foraging constraints, survival and sociality.

Understanding the costs of living with breeders might offer new insights into the factors that counter evolutionary transitions from selfish individuals to cooperative societies. While selection on early dispersal is well understood, it is less clear whether costs are also associated with remaining with family members during subsequent breeding, a prerequisite to the evolution of kin-based cooperation. We propose and test the hypothesis that living in groups containing breeders is costly and that such costs are exacerbated by increasing group size. For example, in group-living central-place foragers, group members might suffer from resource depletion when foraging in a restricted area during breeding and significant costs of repeatedly travelling between foraging patches and the site of offspring. Using the cooperatively breeding chestnut-crowned babbler (Pomatostomus ruficeps), for which grouping during breeding is obligatory, we show that reproduction is associated with substantially reduced foraging areas and evidence of resource depletion, particularly in larger groups. Such effects largely persisted from the onset of incubation through to offspring independence 4-5months later. All group members, irrespective of their breeder or helper status, lost significant body mass over this period, and, in males, mass loss was associated with reduced interannual survival. Although babblers are constrained from living outside of breeding groups due to high risks of predation and the poor success of breeding without helpers, we suggest that the effects we describe may generally select against group living during breeding attempts in species where constraints to independent breeding and costs of dispersal are less acute.

Evidence of trapline foraging in honeybees.

Central-place foragers exploiting floral resources often use multi-destination routes (traplines) to maximise their foraging efficiency. Recent studies on bumblebees have showed how solitary foragers can learn traplines, minimising travel costs between multiple replenishing feeding locations. Here we demonstrate a similar routing strategy in the honeybee (Apis mellifera), a major pollinator known to recruit nestmates to discovered food resources. Individual honeybees trained to collect sucrose solution from four artificial flowers arranged within 10 m of the hive location developed repeatable visitation sequences both in the laboratory and in the field. A 10-fold increase of between-flower distances considerably intensified this routing behaviour, with bees establishing more stable and more efficient routes at larger spatial scales. In these advanced social insects, trapline foraging may complement cooperative foraging for exploiting food resources near the hive (where dance recruitment is not used) or when resources are not large enough to sustain multiple foragers at once.