Foraging Behavior In Response Research Articles

Weathering the hunt: The role of barometric pressure in predator insects' foraging behaviour.

Abiotic factors strongly influence ecological interactions and the spatial distribution of organisms. Despite the essential role of barometric pressure, its influence on insect behaviour remains poorly understood, particularly in predators. The effect of barometric pressure variation can significantly impact biological control programs involving entomophagous insects, as they must efficiently allocate time and energy to search for prey in challenging environments. We investigated how predatory insects from different taxonomic groups (Coleoptera, Dermaptera and Neuroptera) adapt their foraging behaviour in response to variations in barometric pressure (low, medium and high). We also examined the response of different life stages to changes in pressure regimes during foraging activities. Our results showed that the searching time of Doru luteipes (Dermaptera: Forficulidae) was faster in a favourable high-pressure regime, whereas Chrysoperla externa (Neuroptera: Chrysopidae) and Eriopis connexa (Coleoptera: Coccinellidae) had similar searching times under varying pressure regimes. Although no differences in prey feeding time were observed among the studied species, the consumption rate was influenced by low barometric pressure leading to a decrease in the number of preyed eggs. Moreover, we provide novel insights into how hemimetabolous (D. luteipes) and holometabolous (E. connexa) species at different life stages respond to barometric pressure. Doru luteipes nymphs and adults had similar consumption rates across all pressure regimes tested, whereas E. connexa larvae consumed fewer eggs under low barometric pressure, but adults were unaffected. This highlights the importance of investigating how abiotic factors affect insects foraging efficiency and predator-prey interactions. Such studies are especially relevant in the current context of climate change, as even subtle changes in abiotic factors can have strong effects on insect behaviour. Barometric pressure is a key meteorological variable that serve as a warning signal for insects to seek shelter and avoid exposure to weather events that could potentially increase their mortality. Understanding the effects of barometric pressure on predatory insects' behaviour can help us develop more effective pest management strategies and promote the resilience of agroecosystems. We provide new insights into the complex relationship between barometric pressure and predator-prey interactions.

Lower nutritional state and foraging success in an Arctic seabird despite behaviorally flexible responses to environmental change

The degree to which individuals adjust foraging behavior in response to environmental variability can impact foraging success, leading to downstream impacts on fitness and population dynamics. We examined the foraging flexibility, average daily energy expenditure, and foraging success of an ice-associated Arctic seabird, the thick-billed murre (Uria lomvia) in response to broad-scale environmental conditions at two different-sized, low Arctic colonies located <300 km apart. First, we compared foraging behavior (measured via GPS units), average daily energy expenditure (estimated from GPS derived activity budgets), and foraging success (nutritional state measured via nutritional biomarkers pre- and post- GPS deployment) of murres at two colonies, which differ greatly in size: 30,000 pairs breed on Coats Island, Nunavut, and 400,000 pairs breed on Digges Island, Nunavut. Second, we tested whether colony size within the same marine ecosystem altered foraging behavior in response to broad-scale environmental variability. Third, we tested whether environmentally induced foraging flexibility influenced the foraging success of murres. Murres at the larger colony foraged farther and longer but made fewer trips, resulting in a lower nutritional state and lower foraging success compared to birds at the smaller colony. Foraging behavior and foraging success varied in response to environmental variation, with murres at both colonies making longer, more distant foraging trips in high ice regimes during incubation, suggesting flexibility in responding to environmental variability. However, only birds at the larger colony showed this same flexibility during chick rearing. Foraging success at both colonies was higher during high ice regimes, suggesting greater prey availability. Overall, murres from the larger colony exhibited lower foraging success, and their foraging behavior showed stronger responses to changes in broad-scale conditions such as sea ice regime. Taken together, this suggests that larger Arctic seabird colonies have higher behavioral and demographic sensitivity to environmental change.

Eat, Drink, Live: Foraging behavior of a nectarivore when relative humidity varies but nectar resources do not

To meet energetic and osmotic demands, animals make dynamic foraging decisions about food quality and quantity. In the wild, foraging animals may be forced to consume a less preferred or sub-optimal food source for long periods of time. Few choice feeding assays in laboratory settings approximate such contingencies. In this study the foraging behaviors of the hawkmoth Manduca sexta were measured when adult moths were placed within different relative humidity (RH) environments (20%, 40%, 60% and 80% RH) and provided with only one of the following experimental nectars: 0% (water), 12% or 24 % w/V sucrose solutions. Overall, ambient humidity influenced survivorship and foraging behaviors. Moth survivorship increased at higher ambient humidity regardless of experimental nectar. Moths that had access to experimental nectar imbibed large volumes of fluid regardless of what nectar was offered when placed at the lowest humidity (20% RH). However, when placed at the highest humidity (80% RH), moths imbibed higher volumes of fluid when given access to experimental nectar with sucrose in comparison with water. RH also influenced daily foraging behaviors: peak nectar consumption occurred earlier at lower RH levels. Consistent with previous studies in which moths could choose among nectar solutions, total energy intake was not affected by ambient RH under no-choice conditions. However, the proportion of time spent foraging and total energy consumption were significantly reduced across all RH levels in no-choice assays, when compared with previous studies of choice assays under the same conditions. Our results show that even when M. sexta moths are presented with limited options, they can alter their foraging behavior in response to environmental changes, enabling them to meet osmotic and/or energetic demands.

Lack of Self-Medication by Fungus Infected Lasius platythorax (Formicidae, Formicinae) Ants in a Multitrophic Experiment

In laboratory conditions, ants can combat a pathogen infection by means of the medicinal use of reactive oxygen species (ROS). However, it is still unknown where they obtain medicinal compounds in the wild and how they use them. Due to an upregulation of ROS in response to herbivory, aphid-infested plants have been suggested to be a potential source of ROS for ants in the wild. We investigated whether infection would cause Lasius platythorax ants to change their foraging on extrafloral nectar on aphid-infested plants. We found no clear evidence for the ants significantly changing their foraging behaviour in response to the pathogen, nor for the extrafloral nectar to contain ROS. The aphids in our experiment had a relatively high concentration of ROS and future research should determine whether predation on aphids could be a potential source of both protein and ROS needed to combat a disease.

Exploitative competition for floral resources reduces sugar intake but differently impacts the foraging behaviour of two non‐bee flower visitors

Identifying which behavioural strategies maximize individual fitness is a key objective in ecology. Organisms are known to adapt their foraging behaviour to their environment in response to abiotic and biotic constraints, such as the distribution of resources or the presence of competitors. For instance, bees are known to avoid recently visited flowers and thus focus their foraging on more rewarding patches. Whether other flower‐visiting insects adapt their foraging behaviour in response to exploitative competition for floral resources remains unknown. Here, we asked if a predatory hoverfly Episyrphus balteatus and a parasitoid Aphidius colemani 1) are physiologically impacted by flower resource limitation following exploitation of flowers by a competitor (either the bumblebee Bombus terrestris or E. balteatus); 2) have the ability to discriminate flowers that were previously exploited by a competitor; and 3) modify their foraging behaviour accordingly. Episyrphus balteatus and A. colemani individuals foraging on previously exploited flowers were found to be less concentrated in sugar compounds, especially in fructose and glucose, suggesting that previously exploited flowers contained less available sugars. Nevertheless, individuals did not avoid previously exploited patches in the choice experiment. On the contrary, E. balteatus females preferentially landed on inflorescences that had previously been exploited by conspecifics (but not by B. terrestris), while A. colemani did not show preferences between inflorescences. However, female hoverflies spent more time feeding on unexploited patches, suggesting that exploited patches were resource limited. To our knowledge, this study provides the first evidence of the use of social cues among E. balteatus individuals in food foraging strategies. It also shows that even insects with tiny nectar requirements, such as parasitoids, can suffer from heavy exploitative competition. Such results may have applied consequences for the understanding of natural enemy conservation, in particular in agroecosystems where competition with honeybees may be important.

Between the devil and the deep blue sea: herbivory induces foraging for and uptake of cadmium in a metal hyperaccumulating plant.

Plants have been shown to change their foraging behaviour in response to resource heterogeneity. However, an unexplored hypothesis is that foraging could be induced by environmental stressors, such as herbivory, which might increase the demand for particular resources, such as those required for herbivore defence. This study examined the way simulated herbivory affects both root foraging for and uptake of cadmium (Cd), in the metal-hyperaccumulating plant Arabidopsis halleri, which uses this heavy metal as herbivore defence. Simulated herbivory elicited enhanced relative allocation of roots to Cd-rich patches as well as enhanced Cd uptake, and these responses were exhibited particularly by plants from non-metalliferous origin, which have lower metal tolerance. By contrast, plants from a metalliferous origin, which are more tolerant to Cd, did not show any preference in root allocation, yet enhanced Cd sharing between ramets when exposed to herbivory. These results suggest that foraging for heavy metals, as well as their uptake and clonal-sharing, could be stimulated in A. halleri by herbivory impact. Our study provides first support for the idea that herbivory can induce not only defence responses in plants but also affect their foraging, resource uptake and clonal sharing responses.

Avian Predation in a Declining Outbreak Population of the Spruce Budworm, Choristoneura fumiferana (Lepidoptera: Tortricidae).

Simple SummaryCages preventing access to birds were used to measure the rate of predation by birds in a spruce budworm population during the decline of an outbreak. Three species of budworm-feeding warblers were involved in this predation on larvae and pupae. It was found that bird predation is a very important source of mortality in declining spruce budworm populations, and that bird foraging behavior changes as budworm prey become rare at the end of the outbreak.The impact of avian predation on a declining population of the spruce budworm, Choristoneura fumifereana (Clem.), was measured using single-tree exclosure cages in a mature stand of balsam fir, Abies balsamea (L.), and white spruce, Picea glauca (Moench.) Voss. Bird population censuses and observations of foraging and nest-feeding activity were also made to determine the response of budworm-linked warblers to decreasing food availability. Seasonal patterns of foraging. as well as foraging success in the declining prey population was compared to similar information from birds observed in another stand where the spruce budworm population was rising. Avian predation was an important source of mortality between the 4th instar and moth emergence in the declining outbreak population. Mortality by predation increased from negligible to over 98% as budworm density dropped from 100 to <1 larva/kg of host foliage, over 3 years. Calculations based on nest-feeding activity and basic metabolic demands support these observed rates. Seasonal and yearly differences in predation rates observed between the two host-tree species correspond to equivalent shifts in bird foraging behavior in response to dropping insect density. In particular, a preference for searching on white spruce disappeared, although budworm-linked birds remained more efficient at finding food on this plant. The ability to change foraging behavior as prey density dropped differed between bird species.

Observations on Long-Term Memory in Honey Bees

Honey bees (Apis mellifera) must adjust their foraging behavior in response to their continuously shifting food resources. Spatiotemporal uncertainty of food availability can arise from the diurnal...

From trips to bouts to dives: temporal patterns in the diving behaviour of chick-rearing Adélie penguins, East Antarctica

Breeding Adélie penguins forage at sea and return to land to provision their chicks, adjusting their foraging behaviour in response to environmental fluctuations over time. At Béchervaise Island, a nesting site in an East Antarctic population, Adélie penguin diving behaviour remains undocumented. This represents a key area of uncertainty in efforts to understand and predict foraging success at this colony. We compiled a multi-year telemetry dataset from time-depth recorders deployed from 1992 to 2004 on 64 birds at Béchervaise Island. We examined diving activity at multiple scales, ranging from foraging trips (n = 125) to dive bouts (n = 3461) to individual dives (n = 84521), and then characterised the stage- and sex-specific variation in diving behaviour of chick-rearing Adélie penguins using linear mixed effect models. Total foraging trip effort (trip duration, number of dives, vertical distance travelled and number of wiggles [a proxy for prey ingestion]) substantially increased as the chick-rearing period progressed (guard through crèche), consistent with increasing chick provisioning and self-maintenance requirements over time. Foraging activity was predominantly structured in periods of sustained diving bouts, indicating sustained foraging effort over the course of the foraging trip. Diving behaviour (dive-level depth, duration, bottom time and attempts of catch per unit effort) varied in relation to sex and chick-rearing stage. Dives were performed more frequently during high and low levels of solar light, which is likely linked to visual predation strategies or prey activity. Our findings advance our understanding of this population’s foraging behaviour, which is ultimately required to underpin the conservation and management of this breeding colony.

Architectural Response of Wheat Cultivars to Row Spacing Reveals Altered Perception of Plant Density.

Achieving novel improvements in crop management may require changing interrow distance in cultivated fields. Such changes would benefit from a better understanding of plant responses to the spatial heterogeneity in their environment. Our work investigates the architectural plasticity of wheat plants in response to increasing row spacing and evaluates the hypothesis of a foraging behavior in response to neighboring plants. A field experiment was conducted with five commercial winter wheat cultivars possessing unique architectures, grown under narrow (NI, 17.5 cm) or wide interrows (WI, 35 cm) at the same population density (170 seeds/m2). We characterized the development (leaf emergence, tillering), the morphology (dimension of organs, leaf area index), and the geometry (ground cover, leaf angle, organ spreading, and orientation). All cultivars showed a lower number of emerged tillers in WI compared to NI, which was later partly compensated by lower tiller mortality. Besides, the upper leaf blades were larger in WI. Finally the leaf area index at flowering showed little difference between WI and NI treatments. The rate of leaf emergence and the final leaf number were higher in WI compared to NI, except for one cultivar. Around the start of stem elongation, pseudo-stems were more erect in WI, while around the time of flowering, stems were more inclined and leaves were more planophile. Cultivars differed in their degrees of responses, with one appearing to prospect more specifically within the interrow space in WI treatment. Altogether, our results suggest that altering interrow distance leads to changes in the perceived extent of competition by plants, with responses first mimicking the effect of a higher plant density and later the effect of a lower plant density. Only one cultivar showed responses that suggested a perception of the heterogeneity of the environment. These findings improve our understanding of plant responses to spatial heterogeneity and provide novel information to simulate light capture in plant 3D models, depending on cultivar behavior.

Influence of shelf oceanographic variability on alternate foraging strategies in long-nosed fur seals

Central place foragers often change their foraging behaviour in response to changes in prey availability in the environment. Lactating long-nosed fur seals Arctocephalus forsteri (LNFS) at Cape Gantheaume in South Australia have been observed to display alternate foraging strategies, whereby they forage on the shelf in summer and switch to oceanic foraging in winter. We investigated the relationship between changes in shelf summertime upwelling and the timing and variability when females switch from predominantly shelf to oceanic foraging. Geolocation tags were deployed on females from summer to winter in 2016 and 2017, giving us longitudinal tracks over the transition period. The timing of switching from shelf to oceanic foraging was primarily driven by seasonal oceanographic changes on the shelf—specifically when the strength of the seasonal localised upwelling began to decline. The individual variability in the timing of the switch was driven by the strength of the coastal upwelling, with variability being greater in years when upwelling strength was weaker. By comparing our results to those of previous studies on the same colony, we found qualitative evidence that inter-annual environmental variability likely influences whether individuals display a single or multiple foraging strategies. This further highlights the flexibility in foraging strategies used by LNFS in response to environmental changes. The effect of inter-annual differences in foraging strategies on overall reproductive success warrants further investigation.

Vertical foraging shifts in Hawaiian forest birds in response to invasive rat removal.

Worldwide, native species increasingly contend with the interacting stressors of habitat fragmentation and invasive species, yet their combined effects have rarely been examined. Direct negative effects of invasive omnivores are well documented, but the indirect effects of resource competition or those caused by predator avoidance are unknown. Here we isolated and examined the independent and interactive effects of invasive omnivorous Black rats (Rattus rattus) and forest fragment size on the interactions between avian predators and their arthropod prey. Our study examines whether invasive omnivores and ecosystem fragment size impact: 1) the vertical distribution of arthropod species composition and abundance, and 2) the vertical profile of foraging behaviors of five native and two non-native bird species found in our study system. We predicted that the reduced edge effects and greater structural complexity and canopy height of larger fragments would limit the total and proportional habitat space frequented by rats and thus limit their impact on both arthropod biomass and birds’ foraging behavior. We experimentally removed invasive omnivorous Black rats across a 100-fold (0.1 to 12 ha) size gradient of forest fragments on Hawai‘i Island, and paired foraging observations of forest passerines with arthropod sampling in the 16 rat-removed and 18 control fragments. Rat removal was associated with shifts in the vertical distribution of arthropod biomass, irrespective of fragment size. Bird foraging behavior mirrored this shift, and the impact of rat removal was greater for birds that primarily eat fruit and insects compared with those that consume nectar. Evidence from this model study system indicates that invasive rats indirectly alter the feeding behavior of native birds, and consequently impact multiple trophic levels. This study suggests that native species can modify their foraging behavior in response to invasive species removal and presumably arrival through behavioral plasticity.

Feeding in fear: Indirect effects of predatory fish on macrophyte communities mediated by altered crayfish foraging behaviour

Abstract The threat of predation influences decisions made by prey animals and alters the way that prey interact with other species in their environment. Animals often alter their foraging behaviour in response to a predatory threat by increasing or decreasing food consumption or by changing their feeding preferences to focus on foods that limit their exposure to the threat. Changes in grazing pressure and diet selectivity can have significant impacts on the abundance and diversity of the prey's food resources. In this study, we examined the indirect effects of a predatory fish on macrophyte biomass, mediated by crayfish responses to predator odours. Largemouth bass (Micropterus salmoides, Centrarchidae) were housed in flow‐through stream mesocosms to produce odour cues that initiated a nonconsumptive effect on rusty crayfish (Faxonius rusticus, Cambaridae) held in an adjacent section of the stream. Crayfish were offered three species of macrophytes (Myriophyllum exalbescens, Haloragaceae; Elodea canadensis, Hydrocharitaceae; Chara spp., Characeae) and were allowed to graze for 48 hr. Consumption of each plant species was measured by weighing the plant samples before and after every trial. The plant samples were further analysed for total phenolic content using the Folin–Ciocalteu method. Foraging and shelter use behaviours were quantified by analysis of video recordings for time spent foraging in the mesocosm and time spent in the shelter zone of the mesocosm. Crayfish consumed greater quantities of macrophyte tissue when predator cues were present, and this result was unexpected and is contrary to most observations in the literature. When threatened, the crayfish also showed a preference for two of the macrophyte species, which did not exist in trials without bass odour. This could be due to differences in total phenolic content among the three plant species tested. The results provide evidence for a strong indirect effect of predatory fish on the macrophyte community mediated by changes in crayfish behaviour under threat. Crayfish act as keystone species in stream ecosystems; thus, changes in their foraging behaviour and dietary preferences caused by exposure to predator odour cues could have important effects on macrophyte communities in lotic systems.

Can starlings use a reliable cue of future food deprivation to adaptively modify foraging and fat reserves?

Regulation of mass in small birds is based on simultaneously minimizing starvation and predation risk, but the mechanisms birds use to assess starvation risk are still debated. While we know that birds anticipate periods of unpredictable food availability/energy expenditure (e.g. the winter and night) by increasing their fat reserves, we do not know whether this anticipation involves learning. This study investigated whether birds could learn to use a light cue that predicted a period of food unavailability, to adaptively regulate their foraging and/or body weight. Sixteen captive starlings, Sturnus vulgaris, were subjected to 42 days of an irregular schedule of food deprivation that involved depriving them of food for 5 h on 20 pseudorandomly chosen days. Birds were randomly allocated to two treatment groups for which a 30 min period of reduced ambient light either provided perfect information (Predictable) or no information (Unpredictable) about upcoming food deprivation. Both groups of birds increased their dawn body mass over the period of the experiment, consistent with a response to unpredictable food deprivation. However, no differences in either foraging behaviour or dawn body mass emerged between the groups, suggesting that the Predictable birds were unable to learn to use the light cue to initiate anticipatory foraging ahead of food deprivation. Furthermore, both groups immediately decreased their foraging behaviour in response to the onset of the light cue, suggesting that starlings do not have an evolved anticipatory foraging response to low light levels. Further work is needed to test alternative cues and designs before any general conclusions can be drawn regarding the flexibility of anticipatory foraging.

Brazilian free-tailed bats (Tadarida brasiliensis) adjust foraging behaviour in response to migratory moths

Insect migrations represent large movements of resources across a landscape, which are attractive to predators capable of detecting and catching them. Brazilian free-tailed bats (Tadarida brasiliensis (I. Geoffroy, 1824)) consume migratory noctuid moths, which concentrate in favourable winds resulting in aggregations of prey that attract bats hundreds of metres above ground. Although T. brasiliensis are known to feed on these aggregations of migratory moths, changes in their foraging behaviours have not been linked to moth migration events. We investigated possible shifts in the bats’ foraging behaviours when moths are migrating with respect to altitude and moth abundance. We recorded 1104 echolocation call passes of T. brasiliensis at ground level and at altitudes of ∼100 and ∼200 m above ground level. We found proportionally more bat activity at higher altitudes when migratory moth abundance was high. We also found that bats decreased call frequency and bandwidth and increased call duration at higher altitudes and behaved similarly with increasing moth abundance even at ground level. Our results support predictions that bats change foraging behaviour in response to seasonal availability of migratory moths and document alterations in echolocation call parameters that are consistent with optimizing prey detection.

Tracking Aedes aegypti (Diptera: Culicidae) Larval Behavior Across Development: Effects of Temperature and Nutrients on Individuals' Foraging Behavior.

Immature mosquitoes alter their foraging behavior in response to variation in nutrients, predators, and temperature, with consequences on the adult stage where pathogens are transmitted. These patterns of behavior have not been described with respect to both developmental stage and environmental variation, nor has behavior been examined within an individual across instars. We hypothesized that individual larvae have distinct behavioral syndromes, and predict that the rank of foraging activity in the third instar will be correlated with foraging activity in the fourth instar for an individual across all conditions. We also hypothesized that individuals that fail to achieve adulthood forage more intensely than those that will emerge due to the need for greater resources. To examine these hypotheses, we conducted an experiment in which we exposed 96 individual Aedes aegypti L. (Diptera: Culicidae) larvae to four combinations of temperature and nutrients. We recorded larvae in the third and fourth instar, and generated time budgets of active and passive foraging behaviors. We found correlations between individual behavior in the third and fourth instar when conditions were the most stressful (cool temperatures and low nutrients). Controlling for this intra-individual behavior, there was variation between instar behaviors, but this was dependent on both temperature and nutrients. We also found that larvae that failed to pupate within 28 d before emergence foraged more intensely than those that emerged. While we found no evidence that mosquitoes have distinct behavioral syndromes in Ae. aegypti, we did find support that nutrients and temperature affect behavior differently at different instars.

Parasite-altered feeding behavior in insects: integrating functional and mechanistic research frontiers.

Research on parasite-altered feeding behavior in insects is contributing to an emerging literature that considers possible adaptive consequences of altered feeding behavior for the host or the parasite. Several recent ecoimmunological studies show that insects can adaptively alter their foraging behavior in response to parasitism. Another body of recent work shows that infection by parasites can change the behavior of insect hosts to benefit the parasite; manipulations of host feeding behavior may be part of this phenomenon. Here, we address both the functional and the underlying physiological frontiers of parasite-altered feeding behavior in order to spur research that better integrates the two. Functional categories of parasite-altered behavior that are adaptive for the host include prophylaxis, therapy and compensation, while host manipulation is adaptive for the parasite. To better understand and distinguish prophylaxis, therapy and compensation, further study of physiological feedbacks affecting host sensory systems is especially needed. For host manipulation in particular, research on mechanisms by which parasites control host feedbacks will be important to integrate with functional approaches. We see this integration as critical to advancing the field of parasite-altered feeding behavior, which may be common in insects and consequential for human and environmental health.

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.

Optimal foraging or predator avoidance: why does the Amazon spider Hingstepeira folisecens (Araneae: Araneidae) adopt alternative foraging behaviors?

Strategies that increase foraging efficiency may also increase predation risk. We investigated how individuals of Hingstepeira folisecens Hingston, 1932, which build shelters at the orb hub, modulate their foraging behaviors in response to the trade-off between capturing prey and becoming exposed by leaving their shelters. We evaluated whether the position of the prey on the web alters the frequency at which spiders leave their shelters. Hingstepeira folisecens spiders were more likely to capture prey positioned below than above the entrance of the shelter. Moreover, when the prey was near the entrance of the shelter, the spider pulled the threads with the entangled prey without leaving the shelter. Conversely, when the prey was distant from the entrance of the shelter, an attack (leaving the shelter) was favored. We argue that the pulling behavior may be an adaptation to reduce exposure to predators.

Do Carolina chickadees (Poecile carolinensis) and tufted titmice (Baeolophus bicolor) attend to the head or body orientation of a perched avian predator?

Individuals of many prey species adjust their foraging behavior in response to the presence of a predator. Responding to predators takes time away from searching for and exploiting food resources. To balance between the need to avoid predation and the need to forage, individuals should attend to cues from predators that indicate risk. Two such cues might be the predator's head orientation (where it might be looking) and body orientation (where it might be moving). In the current study, flocks of Carolina chickadees, Poecile carolinensis, and tufted titmice, Baeolophus bicolor, were presented with perched hawk and owl models. Predator model head and body orientation were independently manipulated relative to a feeding station birds were using. Chickadees and titmice avoided the feeders more when the heads of the models were facing toward the feeders compared to facing away from the feeders. Calling behavior of birds was also affected by head orientation of the models. No effect of predator body orientation on chickadee and titmouse behavior was detected. The results indicate that when chickadees and titmice detect a perched avian predator, they assess risk primarily based upon its head orientation. (PsycINFO Database Record