Social influences on foraging in vertebrates: causal mechanisms and adaptive functions

Spatial memory obviates following behaviour in an information centre of wild fruit bats

According to the information centre hypothesis (ICH), colonial species use social information in roosts to locate ephemeral resources. Validating the ICH necessitates showing that uninformed individuals follow informed ones to the new resource. However, following behaviour may not be essential when individuals have a good memory of the resources' locations. For instance, Egyptian fruit bats forage on spatially predictable trees, but some bear fruit at unpredictable times. These circumstances suggest an alternative ICH pathway in which bats learn when fruits emerge from social cues in the roost but then use spatial memory to locate them without following conspecifics. Here, using an unique field manipulation and high-frequency tracking data, we test for this alternative pathway: we introduced bats smeared with the fruit odour of the unpredictably fruiting Ficus sycomorus trees to the roost, when they bore no fruits, and then tracked the movement of conspecifics exposed to the manipulated social cue. As predicted, bats visited the F. sycomorus trees with significantly higher probabilities than during routine foraging trips (of >200 bats). Our results show how the integration of spatial memory and social cues leads to efficient resource tracking and highlight the value of using large movement datasets and field experiments in behavioural ecology. This article is part of the theme issue 'The spatial-social interface: a theoretical and empirical integration'.

Social interactions and information use by foraging seabirds

What do seabirds perceive about the world? How do they do so? And how do they use the information available to them to make foraging decisions? Social cues provide seabirds with information about the location of prey. This can, of course, be passive and not involve higher-order cognitive processes (e.g. simple conspecific or heterospecific attraction). However, seabirds display many behaviours that promote learning and the transmission of information between individuals: the vast majority of seabirds are colonial living, have an extended juvenile phase that affords them time to learn, routinely form intra- and interspecific associations, and can flexibly deploy a combination of foraging tactics. It is worth evaluating their foraging interactions in light of this. This review describes how seabirds use social information both at the colony and at sea to forage, and discusses the variation that exists both across species and amongst individuals. It is clear that social interactions are a critical and beneficial component of seabird foraging, with most of the variation concerning the way and extent to which social information is used, rather than whether it is used. While it may seem counterintuitive that large groups of potential competitors congregating at a patch can result in foraging gains, such aggregations can alter species dynamics in ways that promote coexistence. This review explores how competitive interference at a patch can be mitigated by behavioural modifications and niche segregation. Utilising others for foraging success (e.g. via social cues and facilitation at a patch) is likely to make population declines particularly damaging to seabirds if the quantity or quality of their social foraging interactions is reduced. Environmental changes have the potential to disrupt their social networks and thus, how these species obtain food and transfer information.

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

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

A social foraging trade-off in echolocating bats reveals that they benefit from some conspecifics but are impaired when many are around

Social foraging is very common in the animal kingdom. Numerous studies have documented collective foraging in various species and many reported the attraction of various species to foraging conspecifics. It is nonetheless difficult to quantify the benefits and costs of collective foraging, especially in the wild. We examined the benefits and costs of social foraging using on-board microphones mounted on freely foraging Molossus nigricans bats. This allowed us to quantify the bats' attacks on prey and to assess their success as a function of conspecific density. We found that the bats spent most of their time foraging at low conspecific densities, during which their attacks were most successful in terms of prey items captured per time unit. Notably, their capture rate dropped when conspecific density became either too high or too low. Our findings thus demonstrate a clear social foraging trade-off in which the presence of a few conspecifics probably improves foraging success, whereas the presence of too many impairs it.

The combination operation of grouping and ensemble coding for structured biological motion crowds in working memory

Massive studies have explored biological motion (BM) crowds processing for their remarkable social significance, primarily focused on uniformly distributed ones. However, real-world BM crowds often exhibit hierarchical structures rather than uniform arrangements. How such structured BM crowds are processed remains a subject of inquiry. This study investigates the representation of structured BM crowds in working memory (WM), recognizing the pivotal role WM plays in our social interactions involving BM. We propose the group-based ensemble hypothesis and test it through a member identification task. Participants were required to discern whether a presented BM belonged to a prior memory display of eight BM, each with distinct walking directions. Drawing on prominent Gestalt principles as organizational cues, we constructed structured groups within BM crowds by applying proximity and similarity cues in Experiments 1 and 2, respectively. In Experiment 3, we deliberately weakened the visibility of stimuli structures by increasing the similarity between subsets, probing the robustness of results. Consistently, our findings indicate that BM aligned with the mean direction of the subsets was more likely to be recognized as part of the memory stimuli. This suggests that WM inherently organizes structured BM crowds into separate ensembles based on organizational cues. In essence, our results illuminate the simultaneous operation of grouping and ensemble encoding mechanisms for BM crowds within WM.

Slow-exploring captive red knots were quicker to find food in a social setting than fast explorers

Individuals foraging in groups face increased competition but can benefit from social information on foraging opportunities that can ultimately increase survival. Personality traits can be associated with food-finding strategies, such as shyer individuals scrounging on the food discoveries of others. How personality and foraging strategy interact in a social foraging context with different group compositions received less attention. Here, we conducted experiments to investigate the relationship between exploratory personality, group size (1-4 birds) and foraging success (i.e. speed of finding a food patch) in wild-caught red knots. We found that faster explorers, when foraging alone, discover food patches quicker than slower explorers. In groups, however, slower-exploring birds became quicker at finding food than fast explorers. This shows that slower-exploring individuals benefit from group foraging. They seem to be more perceptive to social cues, and in contrast to faster explorers, they become quicker at finding food when they are in a group than when foraging alone. We discuss how individuals with different personalities and foraging strategies can coexist in a social foraging context with different costs and benefits associated with their strategies.

Social niche shapes social behavior and cortisol concentrations during adolescence in female guinea pigs

Individualized social niches arise in social groups, resulting in divergent social behavior profiles among group members. During sensitive life phases, the individualized social niche can profoundly impact the development of social behavior and associated phenotypes such as hormone (e.g. cortisol) concentrations. Focusing on adolescence, we investigated the relationship between the individualized social niche, social behavior, and cortisol concentrations (baseline and responsiveness) in female guinea pigs. Females were pair-housed in early adolescence (initial social pair formation), and a social niche transition was induced after six weeks by replacing the partner with either a larger or smaller female. Regarding social behavior, dominance status was associated with aggression in both the initial social pairs and after the social niche transition, and the results suggest that aggression was rapidly and completely reshaped after the social niche transition. Meanwhile, submissive behavior was rapidly reshaped after the social niche transition, but this was incomplete. The dominance status attained in the initial social pair affected the extent of submissive behavior after the social niche transition, and this effect was still detected three weeks after the social niche transition. Regarding cortisol concentrations, higher baseline cortisol concentrations were measured in dominant females in the initial social pairs. After the social niche transition, cortisol responsiveness significantly increased for the females paired with a larger, older female relative to those paired with a smaller, younger female. These findings demonstrate that the social niche during adolescence plays a significant role in shaping behavior and hormone concentrations in females.

Social demonstration of colour preference improves the learning of associated demonstrated actions

We studied how different types of social demonstration improve house sparrows' (Passer domesticus) success in solving a foraging task that requires both operant learning (opening covers) and discrimination learning (preferring covers of the rewarding colour). We provided learners with either paired demonstration (of both cover opening and colour preference), action-only demonstration (of opening white covers only), or no demonstration (a companion bird eating without covers). We found that sparrows failed to learn the two tasks with no demonstration, and learned them best with a paired demonstration. Interestingly, the action of cover opening was learned faster with paired rather than action-only demonstration despite being equally demonstrated in both. We also found that only with paired demonstration, the speed of operant (action) learning was related to the demonstrator's level of activity. Colour preference (i.e. discrimination learning) was eventually acquired by all sparrows that learned to open covers, even without social demonstration of colour preference. Thus, adding a demonstration of colour preference was actually more important for operant learning, possibly as a result of increasing the similarity between the demonstrated and the learned tasks, thereby increasing the learner's attention to the actions of the demonstrator. Giving more attention to individuals in similar settings may be an adaptive strategy directing social learners to focus on ecologically relevant behaviours and on tasks that are likely to be learned successfully.

Environmental harshness does not affect the propensity for social learning in great tits, Parus major

According to the harsh environment hypothesis, natural selection should favour cognitive mechanisms to overcome environmental challenges. Tests of this hypothesis to date have largely focused on asocial learning and memory, thus failing to account for the spread of information via social means. Tests in specialized food-hoarding birds have shown strong support for the effects of environmental harshness on both asocial and social learning. Whether the hypothesis applies to non-specialist foraging species remains largely unexplored. We evaluated the relative importance of social learning across a known harshness gradient by testing generalist great tits, Parus major, from high (harsh)- and low (mild)-elevation populations in two social learning tasks. We showed that individuals use social learning to find food in both colour-associative and spatial foraging tasks and that individuals differed consistently in their use of social learning. However, we did not detect a difference in the use or speed of implementing socially observed information across the elevational gradient. Our results do not support predictions of the harsh environment hypothesis suggesting that context-dependent costs and benefits as well as plasticity in the use of social information may play an important role in the use of social learning across environments. Finally, this study adds to the accumulating evidence that the harsh environment hypothesis appears to have more pronounced effects on specialists compared to generalist species.

Role of social structure in establishment of an invasive large mammal after translocation

BACKGROUND

Data on the movement behavior of translocated wild pigs is needed to develop appropriate response strategies for containing and eliminating new source populations following translocation events. We conducted experimental trials to compare the home range establishment and space-use metrics, including the number of days and distance traveled before becoming range residents, for wild pigs translocated with their social group and individually.

RESULTS

We found wild pigs translocated with their social group made less extensive movements away from the release location and established a stable home range ~5 days faster than those translocated individually. We also examined how habitat quality impacted the home range sizes of translocated wild pigs and found wild pigs maintained larger ranges in areas with higher proportion of low-quality habitat.

CONCLUSION

Collectively, our findings suggest translocations of invasive wild pigs have a greater probability of establishing a viable population near the release site when habitat quality is high and when released with members of their social unit compared to individuals moved independent of their social group or to low-quality habitat. However, all wild pigs translocated in our study made extensive movements from their release location, highlighting the potential for single translocation events of either individuals or groups to have far-reaching consequences within a much broader landscape beyond the location where they are released. These results highlight the challenges associated with containing populations in areas where illegal introduction of wild pigs occurs, and the need for rapid response once releases are identified. © 2023 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Inferred Attractiveness: A generalized mechanism for sexual selection that can maintain variation in traits and preferences over time

Sexual selection by mate choice is a powerful force that can lead to evolutionary change, and models of why females choose particular mates are central to understanding its effects. Predominant mate choice theories assume preferences are determined solely by genetic inheritance, an assumption still lacking widespread support. Moreover, preferences often vary among individuals or populations, fail to correspond with conspicuous male traits, or change with context, patterns not predicted by dominant models. Here, we propose a new model that explains this mate choice complexity with one general hypothesized mechanism, "Inferred Attractiveness." In this model, females acquire mating preferences by observing others' choices and use context-dependent information to infer which traits are attractive. They learn to prefer the feature of a chosen male that most distinguishes him from other available males. Over generations, this process produces repeated population-level switches in preference and maintains male trait variation. When viability selection is strong, Inferred Attractiveness produces population-wide adaptive preferences superficially resembling "good genes." However, it results in widespread preference variation or nonadaptive preferences under other predictable circumstances. By casting the female brain as the central selective agent, Inferred Attractiveness captures novel and dynamic aspects of sexual selection and reconciles inconsistencies between mate choice theory and observed behavior.

Social information facilitates learning about novel food sources in adult flower-visiting bats

Incorporating novel food sources into their diet is crucial for animals in changing environments. Although the utilization of novel food sources can be learned individually, learning socially from experienced conspecifics may facilitate this task and enable a transmission of foraging-related innovations across a population. In anthropogenically modified habitats, bats (Mammalia: Chiroptera) frequently adapt their feeding strategy to novel food sources, and corresponding social learning processes have been experimentally demonstrated in frugivorous and animalivorous species. However, comparable experiments are lacking for nectarivorous flower-visiting bats, even though their utilization of novel food sources in anthropogenically altered habitats is often observed and even discussed as the reason why bats are able to live in some areas. In the present study, we investigated whether adult flower-visiting bats may benefit from social information when learning about a novel food source. We conducted a demonstrator-observer dyad with wild Pallas' long-tongued bats (Glossophaga soricina; Phyllostomidae: Glossophaginae) and hypothesized that naïve individuals would learn to exploit a novel food source faster when accompanied by an experienced demonstrator bat. Our results support this hypothesis and demonstrate flower-visiting bats to be capable of using social information to expand their dietary repertoire.

Competition and generalization impede cultural formation in wild jackdaws

Animal cultures have now been demonstrated experimentally in diverse taxa from flies to great apes. However, experiments commonly use tasks with unrestricted access to equal pay-offs and innovations seeded by demonstrators who are trained to exhibit strong preferences. Such conditions may not reflect those typically found in nature. For example, the learned preferences of natural innovators may be weaker, while competition for depleting resources can favour switching between strategies and generalizing from past experience. Here we show that in experiments where wild jackdaws (Corvus monedula) can freely discover depleting supplies of novel foods, generalization has a powerful effect on learning, allowing individuals to exploit multiple new opportunities through both social and individual learning. Further, in contrast to studies with trained demonstrators, individuals that were first to innovate showed weak preferences. As a consequence, many individuals ate all available novel foods, displaying no strong preference and no group-level culture emerged. Individuals followed a 'learn from adults' strategy, but other demographic factors played a minimal role in shaping social transmission. These results demonstrate the importance of generalization in allowing animals to exploit new opportunities and highlight how natural competitive dynamics may impede the formation of culture.

Increased initial task difficulty drives social foragers to develop sub-optimal conformity instead of adaptive diversity

The extent to which animal societies exhibit social conformity as opposed to behavioural diversity is commonly attributed to adaptive learning strategies. Less attention is given to the possibility that the relative difficulty of learning a task socially as opposed to individually can be critical for social learning dynamics. Here we show that by raising initial task difficulty, house sparrows previously shown to exhibit adaptive social diversity become predominantly conformists. The task we used required opening feeding well covers (easier to learn socially) and to choose the covers with the rewarding cues (easy to learn individually). We replicated a previous study where sparrows exhibited adaptive diversity, but did not pre-train the naive sparrows to open covers, making the task initially more difficult. In sharp contrast to the previous study results, most sparrows continued to conform to the demonstrated cue even after experiencing greater success with the alternative rewarding cue for which competition was less intense. Thus, our study shows that a task's cognitive demands, such as the initial dependency on social demonstration, can change the entire learning dynamics, causing social animals to exhibit sub-optimal social conformity rather than adaptive diversity under otherwise identical conditions.

Stable isotopes and foraging behaviors support the role of antipredator benefits in driving the association between two marine fishes

Research from terrestrial communities shows that diminished predation risk is a principal driver of heterospecific grouping behavior, with foraging ecology predicting the roles that species play in groups, as more vulnerable foragers preferentially join more vigilant ones from whom they can benefit. Meanwhile, field studies examining the adaptive significance of heterospecific shoaling among marine fish have focused disproportionately on feeding advantages such as scrounging or prey-flushing. Juvenile bonefish (Albula vulpes) occur almost exclusively among mojarras (Eucinostomus spp.) and even elect to join them over conspecifics, suggesting they benefit from doing so. We evaluated the roles of risk-related and food-related factors in motivating this pattern of affiliation, estimating: (1) the relative levels of risk associated with each species' search and prey capture activities, via behavioral vulnerability traits discerned from in situ video of heterospecific shoals, and (2) resource use redundancy, using stable isotopes (δ¹³C, δ¹⁵N, and δ³⁴S) to quantify niche overlap. Across four distinct metrics, bonefish behaviors implied a markedly greater level of risk than those of mojarras, typified by higher activity levels and a reduced capacity for overt vigilance; consistent with expectations if their association conformed to patterns of joining observed in terrestrial habitats. Resource use overlap inferred from stable isotopes was low, indicating that the two species partitioned resources and making it unlikely that bonefish derived substantive food-related benefits. Collectively, these findings suggest that the attraction of juvenile bonefish to mojarras is motivated primarily by antipredator advantages, which may include the exploitation of risk-related social cues.

Do chimpanzee food calls bias listeners toward novel items?

Social learning is beneficial in almost every domain of a social animal's life, but it is particularly important in the context of predation and foraging. In both contexts, social animals tend to produce acoustically distinct vocalizations, alarms, and food calls, which have remained somewhat of an evolutionary conundrum as they appear to be costly for the signaller. Here, we investigated the hypothesis that food calls function to direct others toward novel food items, using a playback experiment on a group of chimpanzees. We showed chimpanzees novel (plausibly edible) items while simultaneously playing either conspecific food calls or acoustically similar greeting calls as a control. We found that individuals responded by staying longer near items previously associated with food calls even in the absence of these vocalizations, and peered more at these items compared with the control items, provided no conspecifics were nearby. We also found that once chimpanzees had access to both item types, they interacted more with the one previously associated with food calls than the control items. However, we found no evidence of social learning per se. Given these effects, we propose that food calls may gate and thus facilitate social learning by directing listeners' attention to new feeding opportunities, which if integrated with additional cues could ultimately lead to new food preferences within social groups.

How social information impacts action in rodents and humans: the role of the prefrontal cortex and its connections

Day-to-day choices often involve social information and can be influenced by prior social experience. When making a decision in a social context, a subject might need to: 1) recognize the other individual or individuals, 2) infer their intentions and emotions, and 3) weigh the values of all outcomes, social and non-social, prior to selecting an action. These elements of social information processing all rely, to some extent, on the medial prefrontal cortex (mPFC). Patients with neuropsychiatric disorders often have disruptions in prefrontal cortical function, likely contributing to deficits in social reasoning and decision making. To better understand these deficits, researchers have turned to rodents, which have revealed prefrontal cortical mechanisms for contending with the complex information processing demands inherent to making decisions in social contexts. Here, we first review literature regarding social decision making, and the information processing underlying it, in humans and patient populations. We then turn to research in rodents, discussing current procedures for studying social decision making, and underlying neural correlates.

Habitat quality influences trade-offs in animal movement along the exploration-exploitation continuum

To successfully establish itself in a novel environment, an animal must make an inherent trade-off between knowledge accumulation and exploitation of knowledge gained (i.e., the exploration-exploitation dilemma). To evaluate how habitat quality affects the spatio-temporal scale of switching between exploration and exploitation during home range establishment, we conducted experimental trials comparing resource selection and space-use of translocated animals to those of reference individuals using reciprocal translocations between habitat types of differing quality. We selected wild pigs (Sus scrofa) as a model species to investigate hypotheses related to the movement behavior of translocated individuals because they are globally distributed large mammals that are often translocated within their introduced range to facilitate recreational hunting. Individuals translocated to higher quality habitat (i.e. higher proportions of bottomland hardwood habitats) exhibited smaller exploratory movements and began exploiting resources more quickly than those introduced to lower quality areas, although those in lower-quality areas demonstrated an increased rate of selection for preferred habitat as they gained knowledge of the landscape. Our data demonstrate that habitat quality mediates the spatial and temporal scale at which animals respond behaviorally to novel environments, and how these processes may determine the success of population establishment.

Observational learning in rats: Interplay between demonstrator and observer behavior

BACKGROUND

Observational learning is a vital skill for survival. This form of learning has been seen in humans and certain non-human animals. However, the neural circuitry underlying this form of learning is still poorly understood.

NEW METHOD

To better understand the factors underlying successful observation in rats, we employed a task where an observer must base its behavior on that of a demonstrator rat to identify a reward location. A comparison was made of behavior during a social and non-social observation condition.

RESULTS

Observers oriented more, responded faster and omitted less responses in the social compared to the non-social condition. Observer performance was also linked to initial orientation, proximity, and the manner in which the demonstrator rat performed the task.

COMPARISON WITH EXISTING METHOD

Previous work on observational learning encompassed multiple exposures to a single solution over days or weeks. The current method provides data from multiple individual novel observational learning trials, leading to much faster and more robust social learning. This method provides a clearly defined interval in which observation must take place. Allowing for precise tracking of both the observer and demonstrator behavior during the learning period.

CONCLUSIONS

This study highlights observer and demonstrator interplay in successful observational learning and provides a novel method for analyzing social behavior in rodents.

Social factors influence solo and rat dyads exploration of an unfamiliar open field

Exploring new and unfamiliar environments is critical for survival, providing information on food, shelter, mates, and sources of danger. The open field paradigm is commonly used to study exploration and anxiety-like behaviors in the lab. Many social animals, like humans and rats, may explore their environments in social groups; however, relatively few studies have investigated the influence of conspecifics on open field activity. Here, we provide a comparison of individual (solo) or pairs of male rats (dyads) exploring and interacting across repeated exposures to an unfamiliar (Day 1) or more familiar (Day 2) open field. Both solo rats and dyads explored a larger area, traveled further, and spent less time near the maze walls on the second maze exposure. Solo rats explored a larger area and spent less time near the maze walls than dyads on both days because dyads spent more time socializing rather than exploring the environment. Furthermore, we compared familiar dyads that were co-housed for seven days versus stranger dyads that met for the first time in the open field. While familiar and stranger dyads did not differ in maze exploration, strangers spent more time interacting nose to nose than nose to anogenital. These results indicate that the degree of familiarity with the environment does not interact with the tendency of dyads to socialize rather than explore the environment.

Resilience of bumblebee foraging behavior despite colony size reduction

Foraging behavior is driven by diverse factors, notably life history traits. Foraging strategies are particularly complex among eusocial species such as bumblebees, because they depend primarily on the needs of the colony, rather than on individual's needs. Colony size, i.e. the number of workers in a colony vary a lot among eusocial insects. While a large colony can be adaptive, several drivers can strongly decrease colony size, like pesticides or high temperatures. In this study, we used the bumblebee Bombus terrestris to assess if workers adapted their foraging behavior to such rapid decreases in colony size. We conducted the foraging experiments with two plant species commonly used by bumblebees: Borago officinalis and Echium plantagineum. Several foraging parameters were measured: foraging time, number of foraging trips, number of workers foraging, handling time and visiting rate. Despite a drastic reduction in colony size, nearly all the foraging behavior parameters were unaffected by the colony size reduction. Colonies that were subject to a large decrease in workers instead displayed high resilience and behavioral plasticity by quickly increasing the proportion of foragers. Ultimately, further research should assess if this consistency in foraging behavior also allows bumblebee colonies to maintain both the efficiency of the resources collection and pollination.

Scavenging in the realm of senses: smell and vision drive recruitment at carcasses in Neotropical ecosystems

Social information, acquired through the observation of other individuals, is especially relevant among species belonging to the same guild. The unpredictable and ephemeral nature of carrion implies that social mechanisms may be selected among scavenger species to facilitate carcass location and consumption. Here, we apply a survival-modelling strategy to data obtained through the placement and monitoring of carcasses in the field to analyse possible information transmission cascades within a Neotropical scavenger community. Our study highlights how the use of different senses (smell and sight) within this guild facilitates carcass location through the transmission of social information between species with different carrion foraging efficiencies. Vultures with a highly developed sense of smell play a key role in this process, as they are the first to arrive at the carcasses and their presence seems to serve as a visual cue for other species to locate the resource. Our study supports the local enhancement hypothesis within scavengers, whereby individuals locate carcasses by following foraging heterospecifics, also suggesting the importance of the sense of smell in the maintenance of the community structure.

Insectivorous bats form mobile sensory networks to optimize prey localization: The case of the common noctule bat

Animals that depend on ephemeral, patchily distributed prey often use public information to locate resource patches. The use of public information can lead to the aggregation of foragers at prey patches, a mechanism known as local enhancement. However, when ephemeral resources are distributed over large areas, foragers may also need to increase search efficiency, and thus apply social strategies when sampling the landscape. While sensory networks of visually oriented animals have already been confirmed, we lack an understanding of how acoustic eavesdropping adds to the formation of sensory networks. Here we radio-tracked a total of 81 aerial-hawking bats at very high spatiotemporal resolution during five sessions over 3 y, recording up to 19 individuals simultaneously. Analyses of interactive flight behavior provide conclusive evidence that bats form temporary mobile sensory networks by adjusting their movements to neighboring conspecifics while probing the airspace for prey. Complementary agent-based simulations confirmed that the observed movement patterns can lead to the formation of mobile sensory networks, and that bats located prey faster when networking than when relying only on local enhancement or searching solitarily. However, the benefit of networking diminished with decreasing group size. The combination of empirical analyses and simulations elucidates how animal groups use acoustic information to efficiently locate unpredictable and ephemeral food patches. Our results highlight that declining local populations of social foragers may thus suffer from Allee effects that increase the risk of collapses under global change scenarios, like insect decline and habitat degradation.

Social information-mediated population dynamics in non-grouping prey

Abstract

Inadvertent social information (ISI) use, i.e., the exploitation of social cues including the presence and behaviour of others, has been predicted to mediate population-level processes even in the absence of cohesive grouping. However, we know little about how such effects may arise when the prey population lacks social structure beyond the spatiotemporal autocorrelation originating from the random movement of individuals. In this study, we built an individual-based model where predator avoidance behaviour could spread among randomly moving prey through the network of nearby observers. We qualitatively assessed how ISI use may affect prey population size when cue detection was associated with different probabilities and fitness costs, and characterised the structural properties of the emerging detection networks that would provide pathways for information spread in prey. We found that ISI use was among the most influential model parameters affecting prey abundance and increased equilibrium population sizes in most examined scenarios. Moreover, it could substantially contribute to population survival under high predation pressure, but this effect strongly depended on the level of predator detection ability. When prey exploited social cues in the presence of high predation risk, the observed detection networks consisted of a large number of connected components with small sizes and small ego networks; this resulted in efficient information spread among connected individuals in the detection networks. Our study provides hypothetical mechanisms about how temporary local densities may allow information diffusion about predation threats among conspecifics and facilitate population stability and persistence in non-grouping animals.

Significance statement

The exploitation of inadvertently produced social cues may not only modify individual behaviour but also fundamentally influence population dynamics and species interactions. Using an individual-based model, we investigated how the detection and spread of adaptive antipredator behaviour may cascade to changes in the demographic performance of randomly moving (i.e., non-grouping) prey. We found that social information use contributed to population stability and persistence by reducing predation-related per capita mortality and raising equilibrium population sizes when predator detection ability reached a sufficient level. We also showed that temporary detection networks had structural properties that allowed efficient information spread among prey under high predation pressure. Our work represents a general modelling approach that could be adapted to specific predator-prey systems and scrutinise how temporary local densities allow dynamic information diffusion about predation threats and facilitate population stability in non-grouping animals.

The importance of elders: Extending Hamilton's force of selection to include intergenerational transfers

In classical evolutionary models, the force of natural selection diminishes with age toward zero by last reproduction. However, intergenerational resource transfers and other late-life contributions in social species may select for postreproductive longevity. We present a formal framework for estimating indirect fitness contributions via production transfers in a skills-intensive foraging niche, reflecting kinship and cooperation among group members. Among contemporary human hunter-gatherers and horticulturalists, indirect fitness contributions from transfers exceed direct reproductive contributions from before menopause until ages when surpluses end, around the modal age of adult death (∼70 y). Under reasonable assumptions, these benefits are the equivalent to having up to several more offspring after age 50. Despite early independence, minimal production surplus, and a shorter lifespan, chimpanzees could theoretically make indirect contributions if they adopted reliable food-sharing practices. Our results for chimpanzees hypothetically adopting hunter-gatherer subsistence suggest that a skills-intensive foraging ecology with late independence and late peak production could select for human-like life histories via positive feedback between longevity and late-life transfers. In contrast, life history changes preceding subsistence shifts would not favor further life extension or subsistence shifts. Our results formalize the theory that longevity can be favored under socioecological conditions characterized by parental and alloparental care funded through transfers of mid- to late-life production surpluses. We also extend our analysis beyond food transfers to illustrate the potential for indirect fitness contributions from pedagogy, or information transfers. While we focus mostly on humans, our approach is adaptable to any context or species where transfers can affect fitness.

Social Cues of Safety Can Override Differences in Threat Level

Animals in groups integrate social with directly gathered information about the environment to guide decisions regarding reproduction, foraging, and defence against predatory threats. In the context of predation, usage of social information has acute fitness benefits, aiding the detection of predators, the mounting of concerted defensive responses, or allowing the inference of safety, permitting other beneficial behaviors, such as foraging for food. We previously showed that Drosophila melanogaster exposed to an inescapable visual threat use freezing by surrounding flies as a cue of danger and movement resumption as a cue of safety. Moreover, group responses were primarily guided by the safety cues, resulting in a net social buffering effect, i.e., a graded decrease in freezing behavior with increasing group sizes, similar to other animals. Whether and how different threat levels affect the use of social cues to guide defense responses remains elusive. Here, we investigated this issue by exposing flies individually and in groups to two threat imminences using looms of different speeds. We showed that freezing responses are stronger to the faster looms regardless of social condition. However, social buffering was stronger for groups exposed to the fast looms, such that the increase in freezing caused by the higher threat was less prominent in flies tested in groups than those tested individually. Through artificial control of movement, we created groups composed of moving and freezing flies and by varying group composition, we titrated the motion cues that surrounding flies produce, which were held constant across threat levels. We found that the same level of safety motion cues had a bigger weight on the flies’ decisions when these were exposed to the higher threat, thus overriding differences in perceived threat levels. These findings shed light on the “safety in numbers” effect, revealing the modulation of the saliency of social safety cues across threat intensities, a possible mechanism to regulate costly defensive responses.

Captive Asian short-clawed otters (Aonyx cinereus) learn to exploit unfamiliar natural prey

Foraging plays a vital role in animal life histories, and learning whether unfamiliar food items are palatable is a key part of this process. Animals that engage in extractive foraging must also learn how to overcome the protective measures of their prey. While otters (subfamily Lutrinae) are a taxon known for their extractive foraging behaviour, how they learn about prey palatability and acquire extractive foraging techniques remains poorly understood. Here we investigated (i) how captive Asian short-clawed otters (Aonyx cinereus) learned to interact with, and extract meat from, unfamiliar natural prey and (ii) how their exploitation of such prey compared to their ability to overcome artificial foraging tasks containing familiar food rewards. Network-based diffusion analysis showed that otters learned to interact with unfamiliar natural prey by observing their group mates. However, once interacting with the prey, they learned to extract the meat mainly asocially. In addition, otters took longer to overcome the protective measures of unfamiliar natural prey than those of extractive food puzzles. Asian short-clawed otter populations are declining in the wild. Increasing our understanding of how they learn to overcome novel foraging challenges could help develop pre-release training procedures as part of reintroduction programmes for otter conservation.

Social information use shapes the coevolution of sociality and virulence

Social contacts can facilitate the spread of both survival-related information and infectious diseases, but little is known about how these processes combine to shape host and parasite evolution. Here, we use a theoretical model that captures both infection and information transmission processes to investigate how host sociality (contact effort) and parasite virulence (disease-associated mortality rate) (co)evolve. We show that selection for sociality (and in turn, virulence) depends on both the intrinsic costs and benefits of social information and infection as well as their relative prevalence in the population. Specifically, greater sociality and lower virulence evolve when the risk of infection is either low or high and social information is neither very common nor too rare. Lower sociality and higher virulence evolve when the prevalence patterns are reversed. When infection and social information are both at moderate levels in the population, the direction of selection depends on the relative costs and benefits of being infected or informed. We also show that sociality varies inversely with virulence, and that parasites may be unable to prevent runaway selection for higher contact efforts. Together, these findings provide new insights for our understanding of group living and how apparently opposing ecological processes can influence the evolution of sociality and virulence in a range of ways.

Considering Organismal Physiology in Laboratory Studies of Rodent Behavior

Any experiment conducted in a rodent laboratory is done so against the backdrop of each animal's physiological state at the time of the experiment. This physiological state can be the product of multiple factors, both internal (e.g., animal sex, strain, hormone cycles, or circadian rhythms) and external (e.g., housing conditions, social status, and light/dark phases). Each of these factors has the potential to influence experimental outcomes, either independently or via interactions with others, and yet there is little consistency across laboratories in terms of the weight with which they are considered in experimental design. Such discrepancies-both in practice and in reporting-likely contribute to the perception of a reproducibility crisis in the field of behavioral neuroscience. In this review, we discuss how several of these sources of variability can impact outcomes within the realm of common learning and memory paradigms. Expected final online publication date for the Annual Review of Neuroscience, Volume 45 is July 2022. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

Social foraging can benefit artisanal fishers who interact with wild dolphins

Abstract

Social foraging decisions depend on individual payoffs. However, it is unclear how individual variation in phenotypic and behavioural traits can influence these payoffs, thereby the decisions to forage socially or individually. Here, we studied how individual traits influence foraging tactics of net-casting fishers who interact with wild dolphins. While net-casting is primarily an individual activity, in the traditional fishery with dolphins, fishers can choose between fishing in cooperative groups or solitarily. Our semi-structured interviews with fishers show their social network is mapped onto these foraging tactics. By quantifying the fishers’ catch, we found that fishers in cooperative groups catch more fish per capita than solitary fishers. By quantifying foraging and social traits of fishers, we found that the choice between foraging tactics—and whom to cooperate with—relates to differences in peer reputation and to similarities in number of friends, propensity to fish with relatives, and frequency of interaction with dolphins. These findings indicate different payoffs between foraging tactics and that by choosing the cooperative partner fishers likely access other benefits such as social prestige and embeddedness. These findings reveal the importance of not only material but also non-material benefits of social foraging tactics, which can have implications for the dynamics of this rare fishery. Faced with the current fluctuation in fishing resource availability, the payoffs of both tactics may change, affecting the fishers’ social and foraging decisions, potentially threatening the persistence of this century-old fishery involving humans and wildlife.

Significance statement

Social foraging theory proposes that decisions to forage in groups are primarily driven by cost–benefit trade-offs that individuals experience, but it remains unclear whether, and how much, individual foragers’ characteristics influence these trade-offs and consequently the choice to forage in social groups. We study the artisanal net-casting fishers who choose between cooperating with each other or fishing alone when engaging in a rare interaction with wild dolphins. Our findings suggest that cooperative fishers capture more fish than solitary fishers, and that by choosing cooperative partners based on similarities and differences in key social (peer reputation, kinship, friendships) and foraging (fishing frequency) traits; these fishers also experience higher social prestige and more social embeddedness. These results suggest that material gains from foraging—but also non-material benefits accrued from socializing with like-minded individuals—can influence the dynamics of human social foraging.

Fecal Microbiota Dynamics Reveal the Feasibility of Early Weaning of Yak Calves under Conventional Grazing System

Simple Summary

Yak (Bos grunniens) is the most economically and culturally important domestic bovine species adapted to the extreme ecological environment of the Qinghai–Tibetan Plateau (QTP), which provides milk, meat, transportation, fuel (yak dung), and wool for local nomads as well as major sources of income. Calves are an important part of the sustainable development of the yak industry on the QTP, and the quality of calf rearing directly determines the production performance of adult animals. Under the traditional grazing management, late weaning (>180 days) of yak calves seriously affects the improvement of their production performance. A comparative study of fecal microbiota dynamics of yak and cattle (Bos taurus) calves in different months after weaning will help to understand the changes in intestinal microbiota structure, and will aid in in improving growth rate and survivability of early weaned calves. Our research will contribute to the development of appropriate strategies to regulate the gut microbiome and thus improve the growth and health of the grazing ruminants on the QTP.

Abstract

Background: The gut microbiota plays an important role in the health and production of animals. However, little information is available on the dynamic variations and comparison of intestinal microbiota in post-weaning yak calves living on the QTP. Methods: We explored the fecal bacterial microbiota succession of yak calves at different months after early weaning (60 d) compared with cattle calves by 16S rRNA gene amplicon sequencing and functional composition prediction. Results: We found no significant difference in blood biochemical parameters related to glucose and lipid metabolism between yaks and calves in different months after weaning. The core fecal bacterial microbiota from both species of calves was dominated by Ruminococcaceae, Rikenellaceae, and Bacteroidaceae. The fecal microbial community has a great alteration within the time after weaning in both cattle and yak calves, but cattle showed a larger change. After five months, the microbiota achieves a stable and concentrated state. This is also similar to the functional profile. Conclusions: Based on the exploration of dynamic changes in the fecal microbiota at an early stage of life, our results illustrated that there were no negative effects of intestinal microbiota succession on yak calves when early weaning was employed.

Ability to share emotions of others as a foundation of social learning

The natural habitats of most species are far from static, forcing animals to adapt to continuously changing conditions. Perhaps the most efficient strategy addressing this challenge consists of obtaining and acting upon pertinent information from others through social learning. We discuss how animals transfer information via social channels and what are the benefits of such exchanges, playing out on different levels, from theperception of socially delivered information to emotional sharing, manifesting themselves across different taxa of increasing biological complexity. We also discuss how social learning is influenced by different factors including pertinence of information for survival, the complexity of the environment, sex, genetic relatedness, and most notably, the relationship between interacting partners. The results appear to form a consistent picture once we shift our focus from emotional contagion as a prerequisite for empathy onto the role of shared emotions in providing vital information about the environment. From this point of view, we can propose approaches that are the most promising for further investigation of complex social phenomena, including learning from others.

The Cognitive Ecology of Animal Movement: Evidence From Birds and Mammals

Cognition, defined as the processes concerned with the acquisition, retention and use of information, underlies animals’ abilities to navigate their local surroundings, embark on long-distance seasonal migrations, and socially learn information relevant to movement. Hence, in order to fully understand and predict animal movement, researchers must know the cognitive mechanisms that generate such movement. Work on a few model systems indicates that most animals possess excellent spatial learning and memory abilities, meaning that they can acquire and later recall information about distances and directions among relevant objects. Similarly, field work on several species has revealed some of the mechanisms that enable them to navigate over distances of up to several thousand kilometers. Key behaviors related to movement such as the choice of nest location, home range location and migration route are often affected by parents and other conspecifics. In some species, such social influence leads to the formation of aggregations, which in turn may lead to further social learning about food locations or other resources. Throughout the review, we note a variety of topics at the interface of cognition and movement that invite further investigation. These include the use of social information embedded in trails, the likely important roles of soundscapes and smellscapes, the mechanisms that large mammals rely on for long-distance migration, and the effects of expertise acquired over extended periods.

Effects of learning and adaptation on population viability

Cultural adaptation is one means by which conservationists may help populations adapt to threats. A learned behavior may protect an individual from a threat, and the behavior can be transmitted horizontally (within generations) and vertically (between generations), rapidly conferring population-level protection. Although possible in theory, it remains unclear whether such manipulations work in a conservation setting; what conditions are required for them to work; and how they might affect the evolutionary process. We examined models in which a population can adapt through both genetic and cultural mechanisms. Our work was motivated by the invasion of highly toxic cane toads (Rhinella marina) across northern Australia and the resultant declines of endangered northern quolls (Dasyurus hallucatus), which attack and are fatally poisoned by the toxic toads. We examined whether a novel management strategy in which wild quolls are trained to avoid toads can reduce extinction probability. We used a simulation model tailored to quoll life history. Within simulations, individuals were trained and a continuous evolving trait determined innate tendency to attack toads. We applied this model in a population viability setting. The strategy reduced extinction probability only when heritability of innate aversion was low (<20%) and when trained mothers trained >70% of their young to avoid toads. When these conditions were met, genetic adaptation was slower, but rapid cultural adaptation kept the population extant while genetic adaptation was completed. To gain insight into the evolutionary dynamics (in which we saw a transitory peak in cultural adaptation over time), we also developed a simple analytical model of evolutionary dynamics. This model showed that the strength of natural selection declined as the cultural transmission rate increased and that adaptation proceeded only when the rate of cultural transmission was below a critical value determined by the relative levels of protection conferred by genetic versus cultural mechanisms. Together, our models showed that cultural adaptation can play a powerful role in preventing extinction, but that rates of cultural transmission need to be high for this to occur.

Observer's adrenal corticosterone secretion involvement in vicarious fear conditioning

Vicarious learning represents a far-reaching value for the survival of social animals. Adrenal hormones are known to affect many forms of learning, yet the roles of adrenal hormones in vicarious learning remain unexplored. This study was undertaken to assess whether observation-stimulated corticosterone (CORT) secretion may affect the magnitude of a vicarious fear conditioning. Mouse observers were individually subjected to an observational compartment next to the training compartment wherein three their cage-mate demonstrators received (1) 5 days of 15 randomly-scheduled footshocks (0.5 mA, 2 s in duration over a 30 min session) (G1); (2) a 30-min presentation of vanilla odors (G2); or (3) footshock delivery and vanilla odors in combination (G3). Demonstrator mice receiving G3 training session and their respective observer mice were found to exhibit greater training-induced and slightly greater observation-stimulated CORT secretion, greater vanilla odors-induced fear responses (FR) and conditioned place aversion (CPA), as compared with the observers vicariously learning from demonstrators receiving G1 or G2 sessions. Observers held in their home cages during demonstrators' trainings and those receiving null demonstrator (No Demonstrator) failed to exhibit vanilla odors-induced FR. Moreover, observers undergoing adrenalectomy (ADX) and G3 sessions exhibited lower vanilla odors-induced FR and CPA as compared to sham surgical (Sham) observers observing G3 sessions. Furthermore, systemic metyrapone injections (50 and 100 mg/kg) prior to daily vicarious G3 training session resulted in decreases in vanilla odors-induced FR and CPA magnitudes in observers. Finally, CORT (1 mg/kg)-pretreated G2 observers failed to display odors-induced FR escalation. These results, taken together, suggest that observation-stimulated CORT secretion is necessary for reliable establishment of vicarious fear conditioning in observer mice.

Social transmission in the wild can reduce predation pressure on novel prey signals

Social transmission of information is taxonomically widespread and could have profound effects on the ecological and evolutionary dynamics of animal communities. Demonstrating this in the wild, however, has been challenging. Here we show by field experiment that social transmission among predators can shape how selection acts on prey defences. Using artificial prey and a novel approach in statistical analyses of social networks, we find that blue tit (Cyanistes caeruleus) and great tit (Parus major) predators learn about prey defences by watching others. This shifts population preferences rapidly to match changes in prey profitability, and reduces predation pressure from naïve predators. Our results may help resolve how costly prey defences are maintained despite influxes of naïve juvenile predators, and suggest that accounting for social transmission is essential if we are to understand coevolutionary processes.

The development and maintenance of sex differences in dietary breadth and complexity in Bornean orangutans

ABSTRACT

Orangutans show a pronounced sexual dimorphism, with flanged males (i.e., males with fully grown secondary sexual characteristics) reaching twice the size of adult females. Furthermore, adult orangutans show sex-specific dispersal and activity patterns. This study investigates sex differences in adult foraging behavior and sheds light on how these differences develop in immatures. We analyzed 11 years of feeding data on ten adult female, seven flanged male, and 14 immature Bornean orangutans (Pongo pygmaeus wurmbii) at Tuanan in Central Kalimantan, Indonesia. We found that the diets of the adult females were significantly broader and required more processing steps before ingestion than the diets of flanged males. We also found evidence for a similar difference in overall diet repertoire sizes. For the immatures, we found that whereas females reached 100% of their mothers' diet spectrum size by the age of weaning, males reached only around 80%. From the age of 4 years on (i.e., years before being weaned) females had significantly broader daily diets than males. We found no difference in daily or overall diet processing intensity of immature males and females but found preliminary evidence that immature males included fewer items of their mother's diet in their own diets that were processing-intensive. Overall, our results suggest that by eating a broader variety and more complex to process food items, female orangutans go to greater lengths to achieve a balanced diet than males do. These behavioral differences are not just apparent in adult foraging behavior but also reflected in immature development from an early age on.

SIGNIFICANCE STATEMENT

In many species, males and females have different nutritional needs and are thus expected to show sex-specific foraging behavior. Sex differences in several aspects of foraging behavior have been found in various species, but it remains largely unclear when and how those develop during ontogeny, which is especially relevant for long-lived altricial species that learn foraging skills over many years. In our study, we analyzed a cross-sectional and longitudinal data set containing more than 750,000 feeding events of adult and immature Bornean orangutans (Pongo pygmaeus wurmbii). We found that adult females had significantly broader and more complex diets than males. We also found that these differences started to develop during infancy, suggesting that immature orangutans prepare for their sex-specific foraging niches long before those become physiologically relevant while they are still in constant association with their mothers and before being frequently exposed to other role models.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s00265-021-03014-3.

Opposite valence social information provided by bio-robotic demonstrators shapes selection processes in the green bottle fly

Social learning represents a high-level complex process to acquire information about the environment, which is increasingly reported in invertebrates. The animal-robot interaction paradigm turned out to be an encouraging strategy to unveil social learning in vertebrates, but it has not been fully exploited in invertebrates. In this study, Lucilia sericata adults were induced to observe bio-robotic conspecific and predator demonstrators to reproduce different flower foraging choices. Can a fly manage two flows of social information with opposite valence? Herein, we attempt a reply. The selection process of L. sericata was affected by social information provided through different bio-robotic demonstrators, by avoiding coloured discs previously visited by a bio-robotic predator and preferring coloured discs previously visited by a bio-robotic conspecific. When both bio-robotic demonstrators visited the same disc, the latency duration increased and the flies significantly tended to avoid this disc. This indicates the complex risk-benefit evaluation process carried out by L. sericata during the acquisition of such social information. Overall, this article provides a unique perspective on the behavioural ecology of social learning in non-social insects; it also highlights the high potential of the animal-robot interaction approach for unveiling the full spectrum of invertebrates' abilities in using social information.