Food-anticipatory Activity as a Cue for Local Enhancement in Golden Shiners (Pisces: Cyprinidae,Notemigonus crysoleucas)

The goal of this study was to test whether food-anticipatory activity, which is more subtle than feeding activity, can be used as a cue for local enhancement by fish. Golden shiners, Notemigonus crysoleucas, were offered a choice between spending time near a shoal of conspecifics normally fed at that time of day or a shoal normally fed at another time. Despite the fact that no food was delivered during the tests, the shoal that was normally fed at that time had more fish moving and more fish close to the surface, where food usually appeared, than the other shoal. This is evidence of food-anticipatory activity. The choosing shiners, after being deprived of food for 24-48 h, preferred to stay near the anticipating shoal rather than near the other one. When satiated, the shiners chose both shoals at random, indicating that hunger promotes the use of food-anticipatory cues in shoal choice and local enhancement. The results also support the idea that food-anticipatory activity can attract competitors for food and may therefore be costly. Food-anticipatory activity might also attract predators, but the fact that satiated shiners did not actively avoid anticipating shoals indicates that the potential cost of predator attraction would be either low or mitigated by other factors.     

How does hunger affect convergence on prey patches in a social forager?

Internal state, in this case hunger, is known to influence both the organisation of animal groups and the social foraging interactions that occur within them. In this study, we investigated the effects of hunger upon the time taken to locate and converge upon hidden simulated prey patches in a socially foraging fish, the threespine stickleback (Gasterosteus aculeatus). We predicted that groups of food‐deprived fish would find and recruit to prey patches faster than recently fed groups, reasoning that they might search more rapidly and be more attentive to inadvertent social information produced by other foragers. Instead we saw no difference between the two groups in the time taken to find the patches and found that in fact, once prey patches had been discovered, it was the recently fed fish that converged on them most rapidly. This finding is likely due to the fact that recently fed fish tend to organise themselves into fewer but larger subgroups, which arrived at the food patch together. Hunger has a significant impact upon the social organisation of the fish shoals, and it appears that this has a stronger effect upon the rate at which they converged upon the food patches than does internal state itself.     

Information transfer and the facilitation and inhibition of feeding in a schooling fish

Synopsis Recent studies show that fish forage actively when perceived risk is low, but decrease foraging and increase vigilance when perceived risk is high. Isolated juvenile chum salmon,Oncorhynchus keta, were visually exposed to groups of conspecifics engaged in different activities to examine their ability to gain information about foraging opportunity and risk by interpreting conspecific behavior. Isolates ate most when exposed to feeding groups, less when exposed to nonfeedig groups, and least when exposed to alarmed groups. Isolates exposed to alarmed conspecifics also spent more time motionless than did fish exposed to either feeding or nonfeeding conspecifics. These findings indicate that schooling fish gain information by interpreting conspecific behavior, and are consistent with research showing that animals balance the conflicting demands of foraging and vigilance.     

Variation in social information use: the influences of information reliability and mass on decision making in a group‐living fish Gambusia affinis

The effect of the reliability of available social information was assessed by examining whether the age of social information changes its effects on a foraging decision in a group‐living fish Gambusia affinis. Individuals switched their patch preference when faced with social information that conflicted with personal information in general; the age of the social information, however, did not significantly influence preference for feeding patch. The mass of decision makers was positively correlated with their use of available social information, with heavier individuals exhibiting a greater difference in patch preference than lighter individuals, suggesting that large and small G. affinis trade‐off the benefits of information acquisition and the costs of competition from conspecifics differently.     

Bumblebees (Bombus terrestris) use social information as an indicator of safety in dangerous environments

Avoiding predation is one of the most important challenges that an animal faces. Several anti-predation behaviours can be employed, yet simply using the presence of conspecifics can be a good signal of safety in an environment with potential predation hazards. Here, we show, for the first time, that past experience of predation causes bumblebees (Bombus terrestris) to aggregate with conspecifics, facilitating the identification of safe foraging patches. Bees were trained to differentiate between flowers that harboured predators and flowers that were predator free. When test subjects were subsequently presented solely with the previously predator-infested flower species, there was a significant preference to only land on flowers occupied by other feeding conspecifics. Yet, when safe flowers were made available to subjects previously entrained to discriminate safe from predator-occupied flowers, subjects ignored other bees and the social information potentially provided by them, demonstrating that attraction towards conspecifics is confined to dangerous situations. Our findings demonstrate a previously unknown social interaction in pollinators which may have important implications for plant–pollinator interactions.     

Space use and social association in a gregarious ungulate: Testing the conspecific attraction and resource dispersion hypotheses

Animals use a variety of proximate cues to assess habitat quality when resources vary spatiotemporally. Two nonmutually exclusive strategies to assess habitat quality involve either direct assessment of landscape features or observation of social cues from conspecifics as a form of information transfer about forage resources. The conspecific attraction hypothesis proposes that individual space use is dependent on the distribution of conspecifics rather than the location of resource patches, whereas the resource dispersion hypothesis proposes that individual space use and social association are driven by the abundance and distribution of resources. We tested the conspecific attraction and the resource dispersion hypotheses as two nonmutually exclusive hypotheses explaining social association and of adult female caribou (Rangifer tarandus). We used location data from GPS collars to estimate interannual site fidelity and networks representing home range overlap and social associations among individual caribou. We found that home range overlap and social associations were correlated with resource distribution in summer and conspecific attraction in winter. In summer, when resources were distributed relatively homogeneously, interannual site fidelity was high and home range overlap and social associations were low. Conversely, in winter when resources were distributed relatively heterogeneously, interannual site fidelity was low and home range overlap and social associations were high. As access to resources changes across seasons, caribou appear to alter social behavior and space use. In summer, caribou may use cues associated with the distribution of forage, and in winter caribou may use cues from conspecifics to access forage. Our results have broad implications for our understanding of caribou socioecology, suggesting that caribou use season‐specific strategies to locate forage. Caribou populations continue to decline globally, and our finding that conspecific attraction is likely related to access to forage suggests that further fragmentation of caribou habitat could limit social association among caribou, particularly in winter when access to resources may be limited.     

Potential disadvantages of using socially acquired information

The acquisition and use of socially acquired information is commonly assumed to be profitable. We challenge this assumption by exploring hypothetical scenarios where the use of such information either provides no benefit or can actually be costly. First, we show that the level of incompatibility between the acquisition of personal and socially acquired information will directly affect the extent to which the use of socially acquired information can be profitable. When these two sources of information cannot be acquired simultaneously, there may be no benefit to socially acquired information. Second, we assume that a solitary individual's behavioural decisions will be based on cues revealed by its own interactions with the environment. However, in many cases, for social animals the only socially acquired information available to individuals is the behavioural actions of others that expose their decisions, rather than the cues on which these decisions were based. We argue that in such a situation the use of socially acquired information can lead to informational cascades that sometimes result in sub-optimal behaviour. From this theory of informational cascades, we predict that when erroneous cascades are costly, individuals should pay attention only to socially generated cues and not behavioural decisions. We suggest three scenarios that might be examples of informational cascades in nature.     

Social learning strategies and predation risk: minnows copy only when using private information would be costly

Animals can acquire information from the environment privately, by sampling it directly, or socially, through learning from others. Generally, private information is more accurate, but expensive to acquire, while social information is cheaper but less reliable. Accordingly, the 'costly information hypothesis' predicts that individuals will use private information when the costs associated with doing so are low, but that they should increasingly use social information as the costs of using private information rise. While consistent with considerable data, this theory has yet to be directly tested in a satisfactory manner. We tested this hypothesis by giving minnows (Phoxinus phoxinus) a choice between socially demonstrated and non-demonstrated prey patches under conditions of low, indirect and high simulated predation risk. Subjects had no experience (experiment 1) or prior private information that conflicted with the social information provided by the demonstrators (experiment 2). In both experiments, subjects spent more time in the demonstrated patch than in the non-demonstrated patch, and in experiment 1 made fewer switches between patches, when risk was high compared with when it was low. These findings are consistent with the predictions of the costly information hypothesis, and imply that minnows adopt a 'copy-when-asocial-learning-is-costly' learning strategy.     

Social Dependence of Infant Slow Lorises to Learn Diet

Nocturnal lorises and pottos (Lorisinae) are among the least gregarious of primates. Mothers start to leave their infants alone during the night as early as the day of birth. However, captive studies also indicate that weaning young lorisines closely follow their mothers nearly all the time and obtain their first solid food via scrounging. Accordingly, it has been suggested that young lorisines depend on their mothers to obtain dietary information and to achieve dietary independence by watching their mothers feeding or interacting directly with their mothers over food. We tested for a social dependence on dietary learning by infants in a social network of wild slow lorises (Nycticebus coucang). The social network included one male infant, his mother, and two subadult females. The infant only took to mouth food items that were also part of the females' diet and showed concordance in the frequency of use of food patches with the females. These results contradict dietary learning by trial and error. They indicate that dietary learning by infants depends on information obtained from older conspecifics. However, the infant was never involved in direct interactions with conspecifics over food and fed mostly alone. He was not within a distance where he could see the females feeding more often than expected from the configuration and utilization of home ranges. The infant never looked at conspecifics feeding in his vicinity, which suggests that visual observation or direct interaction over food may not be the mechanisms by which information about food resources is passed from older individuals to young, but that other ways of obtaining such information are used.     

Social learning in nest-building birds: a role for familiarity

It is becoming apparent that birds learn from their own experiences of nest building. What is not clear is whether birds can learn from watching conspecifics build. As social learning allows an animal to gain information without engaging in costly trial-and-error learning, first-time builders should exploit the successful habits of experienced builders. We presented first-time nest-building male zebra finches with either a familiar or an unfamiliar conspecific male building with material of a colour the observer did not like. When given the opportunity to build, males that had watched a familiar male build switched their material preference to that used by the familiar male. Males that observed unfamiliar birds did not. Thus, first-time nest builders use social information and copy the nest material choices when demonstrators are familiar but not when they are strangers. The relationships between individuals therefore influence how nest-building expertise is socially transmitted in zebra finches.     

Public information for solitary foragers: timber rattlesnakes use conspecific chemical cues to select ambush sites

Many animals use public information (PI) gathered from conspecificsto assess the quality of potential foraging locations. To date,research on this phenomenon has focused almost exclusively onsocial foragers that live in groups and monitor nearby individuals.PI is potentially available to solitary foragers as well, inthe form of cues (such as chemical cues) that persist in theenvironment after conspecifics are no longer present. In thisstudy, I examined the response of a solitary sit-and-wait predator,the timber rattlesnake (Crotalus horridus), to chemical cuesfrom conspecifics that had recently fed as opposed to thosethat had been deprived of food. Experiments with a T-maze indicatedthat timber rattlesnakes always follow conspecific chemicaltrails out of the maze, regardless of whether or not the individualleaving the trail had recently fed. However, an enclosure choicetest found that individuals are more likely to select ambushsites in areas with chemical cues from conspecifics that hadrecently fed. These results indicate that snakes may use conspecificchemical cues not only to find mates, shelter sites, and hibernaculabut also profitable food patches. Additionally, this study highlightsthe possibility that other solitary foragers may use PI to guidetheir foraging behavior.     

European starlings recognize the location of robotic conspecific attention

Looking where others are allocating attention can facilitate social interactions by providing information about objects or locations of interest. We asked whether European starlings follow the orientation behaviour of conspecifics owing to their highly gregarious behaviour. Starlings reoriented their attention to follow that of a robot around a barrier more often than when the robot''s attention was directed elsewhere. This is the first empirical evidence of reorienting in response to conspecific attention in a songbird. Starlings may use this behaviour to obtain fine-tuned spatial information from conspecifics (e.g. direction of predator approach, spatial location of food patches), enhancing group cohesion.     

Inhibition of optimal behavior by social transmission in the guppy depends on shoaling

Previous research has suggested social learning of foragingbehavior can inhibit learning of the optimal behavior pattern.Based on their transmission chain design, we used small groupsof guppies (Poecilia reticulata) to determine the degree towhich the optimal behavior pattern was inhibited by sociallylearned information. A founder group was trained to take a long, energetically costly route to a food source. The members ofthis group were gradually replaced with naive conspecifics.Replicating the findings of the earlier researchers, it wasclear that the behavior of the founders strongly influencedthe behavior of the naive fish, probably through a process oflocal enhancement. When tested as a group, the naive fish chosethe long route to the food source significantly more oftenthan chance. Each naive fish was also tested in isolation.When tested alone, there was a significant tendency to choosethe short route despite following the long route when testedas a group. These results suggest social learning does notinhibit learning of optimal behavior patterns but that a trade-offoccurs when tested in the group condition. It is possible thatthe advantages for an individual fish of swimming with theshoal, and thus following the socially learned route, may haveoutweighed the potential energetic costs of taking this longerroute.     

Social requests and social affordances: how they affect the kinematics of motor sequences during interactions between conspecifics

The present study aimed at determining whether and what factors affect the control of motor sequences related to interactions between conspecifics. Experiment 1 demonstrated that during interactions between conspecifics guided by the social intention of feeding, a social affordance was activated, which modified the kinematics of sequences constituted by reaching-grasping and placing. This was relative to the same sequence directed to an inanimate target. Experiments 2 and 4 suggested that the related-to-feeding social request emitted by the receiver (i.e. the request gesture of mouth opening) is prerequisite in order to activate a social affordance. Specifically, the two experiments showed that the social request to be fed activated a social affordance even when the sequences directed towards a conspecific were not finalized to feed. Experiment 3 showed that moving inside the peripersonal space of a conspecific, who did not produce any social request, marginally affected the sequence. Finally, experiments 5 and 6 indicated that the gaze of a conspecific is necessary to make a social request effective at activating a social affordance. Summing up, the results of the present study suggest that the control of motor sequences can be changed by the interaction between giver and receiver: the interaction is characterized by a social affordance that the giver activates on the basis of social requests produced by the receiver. The gaze of the receiver is a prerequisite to make a social request effective.     

Site fidelity and homing in tropical coral reef cardinalfish: are they using olfactory cues?

A number of tropical coral reef fish hold station and display restricted home ranges. If artificially displaced, they will return to their home site. We questioned if marine fish are using the same mechanisms for home site detection as many freshwater fish, that is, by olfactory sensing of chemical signals deposited on the substrate by conspecific fish. Behavioral experiments were conducted on Lizard Island Research Station, Queensland, Australia, in 2001 and 2002. Five-lined cardinalfish (Cheilodipterus quinquelineatus) were tested in groups with split-branded cardinalfish (Apogon compressus) as a reference species and individually against Apogon leptacanthus as well as conspecifics of another reef site. The group tests showed that both species preferred artificial reef sites that had previously been occupied by conspecifics. Individual C. quinquelineatus preferred scent of conspecifics from their own reef site to that from another site. They also preferred the scent released by artificial reefs previously occupied by conspecifics of their reef site to that of similar reefs previously occupied by conspecifics of another reef site. No discrimination between species from the same reef site was obtained in experiments with individual fish. Our data suggest that cardinalfish are keeping station and are homing by use of conspecific olfactory signals.     

Social enhancement of foraging on an ephemeral food source in juvenile walleye pollock,Theragra chalcogramma

Synopsis The foraging effectiveness of walleye pollock juveniles, Theragra chalcogramma, was determined experimentally to test the hypothesis that social cues may facilitate the ability of individuals to exploit ephemeral food patches. Fish were tested when isolated, paired with one other fish, and in a group of six fish. Test fish exploited more food patches while in a group of six than when they were isolated. Patch exploitation by paired fish was intermediate to but not statistically different than isolate or grouped treatments. The number of pellets eaten by test fish in a group and a pair was more than 3.5 times that of when they were isolated, although the overall relationship between the amount of food eaten and group size was not statistically significant. Results support the hypothesis that juvenile walleye pollock exploit ephemeral food patches more effectively in the presence of conspecifics. In planktivores such as walleye pollock, social cues may enhance foraging on transient food sources either by facilitating detection of food patches (local enhancement) or by stimulating foraging activity when a food patch is located (social facilitation).     

Neural correlates of social target value in macaque parietal cortex

Animals as diverse as arthropods [1], fish [2], reptiles [3], birds [4], and mammals, including primates [5], depend on visually acquired information about conspecifics for survival and reproduction. For example, mate localization often relies on vision [6], and visual cues frequently advertise sexual receptivity or phenotypic quality [5]. Moreover, recognizing previously encountered competitors or individuals with preestablished territories [7] or dominance status [1, 5] can eliminate the need for confrontation and the associated energetic expense and risk for injury. Furthermore, primates, including humans, tend to look toward conspecifics and objects of their attention [8, 9], and male monkeys will forego juice rewards to view images of high-ranking males and female genitalia [10]. Despite these observations, we know little about how the brain evaluates social information or uses this appraisal to guide behavior. Here, we show that neurons in the primate lateral intraparietal area (LIP), a cortical area previously linked to attention and saccade planning [11, 12], signal the value of social information when this assessment influences orienting decisions. In contrast, social expectations had no impact on LIP neuron activity when monkeys were not required to make a choice. These results demonstrate for the first time that parietal cortex carries abstract, modality-independent target value signals that inform the choice of where to look.     

Shoal and prey patch choice by co-occurring fishes and prawns: inter-taxa use of socially transmitted cues

Animals can use socially transmitted information to learn about the distribution and quality of resources without incurring the costs associated with having to search for and sample them first hand. Recently, it has been shown that the use of chemical social information specific to patterns of diet and habitat use is an important mechanism underpinning recognition and social organization in shoaling fishes. In this study we revealed that the use of resource-specific chemical information is not limited to conspecifics, or even members of the same taxon. In a series of laboratory experiments, we showed that threespine sticklebacks (Gasterosteus aculeatus) could recognize similar patterns of habitat use in common prawns (Leander serratus), preferentially orientating towards groups of prawns exposed to the same habitats as themselves, and even selecting foraging patches located close to them. Prawns were seen to use habitat-specific cues generated by conspecifics, but not by sticklebacks, suggesting that the benefits of forming these heterospecific social association patterns may be unequal for prawns and fishes. Our findings suggest that some species might use co-occurring, unrelated species as information centres in order to orient and locate resources within their surroundings.     

Foraging Rules for Group Feeders: Area Copying Depends upon Food Density in Shoaling Goldfish

The decision rules governing forage area copying behaviour were investigated in shoaling fish. Shoaling goldfish were offered two equal food patches, one of which was adjacent to an equal-sized shoal feeding behind a transparent barrier. When food was low, goldfish foraged according to an area copying rule, but under high and zero food area copying disappeared. Only under high food density did equal numbers of fish feed at both sites as predicted by foraging theory. Under zero food the fish were less certain about where to forage. Precise visual cues from feeding fish were required: non-feeders did not attract area copiers. Furthermore, area copying was task-dependent since it reappeared strongly if fish were not able to forage on patches like their fellows. Control experiments eliminated an increase in group size for anti-predator advantage as an explanation. Two sequential decisions: to stay or move, and to join or leave may explain the results, which are not accommodated by simple optimality models. These decisions may be based on a comparison of current food intake with the anticipation of a higher reward by foraging socially.     

Immaculate tits: head plumage pattern as an indicator of quality in birds

Great tits, Parus major, display their white cheek patches to one another during intraspecific encounters. We measured the size of these patches and the regularity of their borders (immaculateness) as part of an investigation into their function as signals. Patch size was not significantly related to any of our measures of fitness, but male great tits with more immaculate cheek patches had significantly greater access to a safer feeding site in winter and produced heavier chicks in small woods. Females with more immaculate patches bred significantly earlier in 2 of the 3 years of the study in both large and small woods. We decreased the immaculateness of both sexes with dye and found that competition with other tits significantly increased their exposure to danger when feeding. Factors resulting in reduced immaculateness included ectoparasites, fighting with conspecifics, faster feather wear in young birds and the timing of the autumn moult. Selection for immaculateness by conspecifics may be one mechanism responsible for the evolution of regular head and body patterns in several species of birds and in other animals.