Location effects of social partner on experimental foraging in the squirrel monkey

The effect of social context on experimental foraging in squirrel monkeys (Saimiri sciureus) was investigated. The 12 subjects comprised six pairs in which strong social preference and attraction had been demonstrated during observations of a stable group. Individuals were first trained to discriminate spatially separated rich and poor foraging bins containing 75% and 25% of the food items, respectively, with their partners restrained equidistant from the two bins. The monkeys invested an average of 75.5% of their foraging time in the rich bin. Each individual was then tested with its partner restrained in different locations relative to the bins to determine the effect of partner proximity on foraging patterns. Foraging efficiency at the start of a session was enhanced when the partner was restrained adjacent to the rich bin compared to restraint away from this bin. Over an entire foraging session, however, all conditions providing partner accessibility were similar in yielding enhanced foraging efficiency compared to partner absence. Little time was spent in close physical proximity to the partner under any condition. It is suggested that accessibility of the social partner, rather than close physical proximity, has an important influence on the foraging squirrel monkey. © 1995 Wiley-Liss, Inc.     

The social nature of primate cognition

The hypothesis that the enlarged brain size of the primates was selected for by social, rather than purely ecological, factors has been strongly influential in studies of primate cognition and behaviour over the past two decades. However, the Machiavellian intelligence hypothesis, also known as the social brain hypothesis, tends to emphasize certain traits and behaviours, like exploitation and deception, at the expense of others, such as tolerance and behavioural coordination, and therefore presents only one view of how social life may shape cognition. This review outlines work from other relevant disciplines, including evolutionary economics, cognitive science and neurophysiology, to illustrate how these can be used to build a more general theoretical framework, incorporating notions of embodied and distributed cognition, in which to situate questions concerning the evolution of primate social cognition.     

The advantages of social foraging in downy woodpeckers

I investigated the advantages gained by downy woodpeckers (Picoides pubescens) which join mixed-species winter flocks. Woodpeckers foraging alone showed high levels of vigilance as measured by head-cocking rates, and low feeding rates. Woodpeckers foraging with one or two flock members showed intermediate rates of head-cocking and feeding, while woodpeckers foraging with flocks of three or more birds showed low head-cocking rates and high feeding rates. Although local enhancement and copying may contribute to the woodpeckers' increased foraging efficiency in a flock, these do not appear to be the main factors. As downy woodpeckers spend less time on vigilance, they devote more time to foraging, thereby increasing their foraging efficiency     

The social selection alternative to sexual selection

Social selection offers an alternative to sexual selection by reversing its logic. Social selection starts with offspring production and works back to mating, and starts with behavioural dynamics and works up to gene pool dynamics. In social selection, courtship can potentially be deduced as a negotiation, leading to an optimal allocation of tasks during offspring rearing. Ornaments facilitate this negotiation and also comprise 'admission tickets' to cliques. Mating pairs may form 'teams' based on the reciprocal sharing of pleasure. The parent-offspring relation can be managed by the parent considered as the owner of a 'family firm' whose product is offspring. The cooperation in reproductive social behaviour evolves as a mutual direct benefit through individual selection rather than as some form of altruism requiring kin or multi-level selection.     

The use of social information about predation risk by foraging house sparrows: a feeder experiment

Journal of Ethology - There is increasing evidence of social information transfer about predation risk in foraging animal groups. However, little is known about whether individuals also acquire...     

The role of social cognition in decision making

Successful decision making in a social setting depends on our ability to understand the intentions, emotions and beliefs of others. The mirror system allows us to understand other people's motor actions and action intentions. 'Empathy' allows us to understand and share emotions and sensations with others. 'Theory of mind' allows us to understand more abstract concepts such as beliefs or wishes in others. In all these cases, evidence has accumulated that we use the specific neural networks engaged in processing mental states in ourselves to understand the same mental states in others. However, the magnitude of the brain activity in these shared networks is modulated by contextual appraisal of the situation or the other person. An important feature of decision making in a social setting concerns the interaction of reason and emotion. We consider four domains where such interactions occur: our sense of fairness, altruistic punishment, trust and framing effects. In these cases, social motivations and emotions compete with each other, while higher-level control processes modulate the interactions of these low-level biases.     

The effect of social dominance on foraging by the Three-toed Woodpecker Picoides tridactylus

During the winter, female Three-toed Woodpeckers Picoides tridactylus , when unaccompanied by the male, foraged at a lower height above the ground and on tree trunks of greater diameter than when foraging together with a male. Among males, however, no such differences were found between those birds foraging in the absence of, or in company with, a female. The niche breadth of the males was less than that of the females, indicating a higher degree of specialization by the males. The niche overlap between the sexes was less when the birds foraged together in pairs, especially as regards foraging height and foraging site diameter. The intersexual segregation of foraging niche recorded for the Three-toed Woodpecker is therefore probably not determined genetically, but is due to social dominance by males which obliges the females to occupy the less preferred niche. Both sexes spent less time being vigilant when foraging together, than when alone.     

Monkeys pay per view: adaptive valuation of social images by rhesus macaques

Individuals value information that improves decision making. When social interactions complicate the decision process, acquiring information about others should be particularly valuable. In primate societies, kinship, dominance, and reproductive status regulate social interactions and should therefore systematically influence the value of social information, but this has never been demonstrated. Here, we show that monkeys differentially value the opportunity to acquire visual information about particular classes of social images. Male rhesus macaques sacrificed fluid for the opportunity to view female perinea and the faces of high-status monkeys but required fluid overpayment to view the faces of low-status monkeys. Social value was highly consistent across subjects, independent of particular images displayed, and only partially predictive of how long subjects chose to view each image. These data demonstrate that visual orienting decisions reflect the specific social content of visual information and provide the first experimental evidence that monkeys spontaneously discriminate images of others based on social status.     

Group selection: The quest for social preferences

This paper surveys the literature on group selection. I describe the early contributions and the group selection controversy. I also describe the main approaches to group selection in the recent literature; fixation, assortative group formation, and reproductive externalities.     

Natural selection on unpalatable species imposed by state-dependent foraging behaviour

Müllerian mimicry is typically thought to arise as a consequence of defended prey species adopting a similar way of signalling their unprofitability, thereby reducing the costs of predator education. Here we consider subsequent selection on the morphology of prey species, in the potentially lengthy period of time when predators are generally aware of the noxious qualities of their prey (and so no further learning is involved). Using a pair of stochastic dynamic programming equations which describe both the toxin burdens of a predator and its energy level, we identified the optimal state-dependent rules that maximize a predator's long-term survivorship, and examined the implications of this behaviour for the evolution of prey morphologies. When palatable prey are in short supply then those prey species which contain relatively low doses of toxins become profitable to consume by hungry predators. Under these conditions, a weakly defended prey could gain selective advantage in the post educational period by resembling a prey species which contained a higher dose of the same or different toxins, although the precise nature of the ecological relationship between model and mimic could either be mutualistic or parasitic depending on how mimic density increases when favoured by selection. Our work formally demonstrates that one does not always need to invoke educational effects to explain why two or more unpalatable species have evolved a similar appearance, or to explain why mimetic similarity among distasteful species is maintained over time. When two species contain high levels of different toxins then they may gain mutual advantage by resembling one another, not only by educating the predator as to their common unprofitability (classical Müllerian mimicry), but also by increasing predator uncertainty as to the specific kind of toxin a prey item contains.     

The evolution of social cognition: goal familiarity shapes monkeys' action understanding

What is the evolutionary origin of the human ability to understand and predict the behavior of others? Recent studies suggest that human infants' early capacity for understanding others' goal-directed actions relies on nonmentalistic strategies [1-8]. However, there is no consensus about the nature of the mechanisms underpinning these strategies and their evolutionary history. Comparative studies can shed light on these controversial issues. We carried out three preferential looking-time experiments on macaques, modeled on previous work on human infants [1-5], to test whether macaques are sensitive to the functional efficacy of familiar goal-related hand motor acts performed by an experimenter in a given context and to examine to which extent this sensitivity also is present when observing non-goal-related or unusual goal-related motor acts. We demonstrate that macaque monkeys, similar to human infants, do indeed detect action efficacy by gazing longer at less efficient actions. However, they do so only when the observed behavior is directed to a perceptible and familiar goal. Our results show that the direct detection of the functional fitness of action, in relation to goals that have become familiar through previous experience, is the phylogenetic precursor of intentional understanding.     

The effect of energy reserves on social foraging: hungry sparrows scrounge more

Animals often use alternative strategies when they compete for resources, but it is unclear in most cases what factors determine the actual tactic followed by individuals. Although recent models suggest that the internal state of animals may be particularly important in tactic choice, the effects of state variables on the use of alternative behavioural forms have rarely been demonstrated. In this study, using experimental wind exposure to increase overnight energy expenditure, we show that flock-feeding house sparrows (Passer domesticus) with lowered energy reserves increase their use of scrounging (exploiting others' food findings) during their first feed of the day. This result is in accordance with the prediction of a state-dependent model of use of social foraging tactics. We also show that scrounging provides less variable feeding rates and patch finding times than the alternative tactic. These latter results support the theoretical assumption that scrounging is a risk-averse tactic, i.e. it reduces the risk of immediate starvation. As the level of energy reserves predicts the use of social foraging tactics, we propose that selection should favour individuals that monitor the internal state of flock mates and use this information to adjust their own tactic choice.     

Optimal foraging and ontogeny; food selection by Haplochromis piceatus

Summary We examined the influence of satiation level, prey density and light intensity on food uptake rate through the ontogeny of Haplochromis piceatus. Prey handling in the buccal cavity was found to be the main factor limiting prey uptake rate under light circumstances and at a sufficiently high prey density. Food uptake rate per unit body weight of different sizes of H. piceatus was equal when feeding on Chaoborus but decreased with increasing fish size when feeding on Daphnia magna. In choice experiments with Chaoborus and D. magna, prey selection by H. piceatus of all sizes was according to the predictions based on Charnov's 1976 model.     

Habitat selection as a hierarchy: the spatial scales of winter foraging by muskoxen

We studied the winter resource selection of muskoxen Ovibos moschatus in the High Arctic using a nested hierarchy of spatial scales 1) population range, 2) travel routes, 3) feeding sites (l e clusters of feeding craters), 4) feeding craters, and 5) diet (I e plant species) We found that, generally, patterns of selection remained consistent across all levels At successively smaller scales, muskoxen selected for higher graminoid abundance and particularly for thinner, softer snow cover, although we did not reject the hypothesis of random travel route selection Muskoxen uncovered forages from beneath the snow cover, by cratering, near the flonstic and nival extremes of availability Selection was consistently biased toward use of water sedge, Carex aquatilis As scale changed, however, muskoxen showed reversals of preference for some other forage species Diet was dominated by C aquatilis and cotton sedge, Eriophorum angustifolium , species characteristic of lowland meadows During spring melt, muskoxen moved to snow-free uplands to feed Dietary quality, as revealed by fecal nitrogen, increased at this time The consistency of the results across scales implied that these local levels of habitat selection occurred within one scaling domain     

Artificial pheromone for path selection by a foraging swarm of robots

Foraging robots involved in a search and retrieval task may create paths to navigate faster in their environment. In this context, a swarm of robots that has found several resources and created different paths may benefit strongly from path selection. Path selection enhances the foraging behavior by allowing the swarm to focus on the most profitable resource with the possibility for unused robots to stop participating in the path maintenance and to switch to another task. In order to achieve path selection, we implement virtual ants that lay artificial pheromone inside a network of robots. Virtual ants are local messages transmitted by robots; they travel along chains of robots and deposit artificial pheromone on the robots that are literally forming the chain and indicating the path. The concentration of artificial pheromone on the robots allows them to decide whether they are part of a selected path. We parameterize the mechanism with a mathematical model and provide an experimental validation using a swarm of 20 real robots. We show that our mechanism favors the selection of the closest resource is able to select a new path if a selected resource becomes unavailable and selects a newly detected and better resource when possible. As robots use very simple messages and behaviors, the system would be particularly well suited for swarms of microrobots with minimal abilities.     

Mechanisms underlying host plant selection by Holcocerus hippophaecolus adults

We determined the mechanisms underlying host selection by adults of the seabuckthorn carpenterworm, Holcocerus hippophaecolus Hua, Chou, Fang et Chen. Four sea buckthorn (Hippophae rhamnoides L.) subspecies (varieties) with different degrees of resistance to H. hippophaecolus were chosen for artificial insect infection in cages. The results showed that olfactory and visual cues are very important for the selection of host plants by H. hippophaecolus, but that olfactory stimuli play a more vital role in this process. The relative abundance of branches and leaves had no effect on the likelihood that adults landed on plants from four subspecies (varieties), but did influence landing rates within the same subspecies (varieties). When considering only the most resistant sea buckthorn subspecies (varieties), the presence of luxuriant branches and leaves led to lower landing rates. These results provide a theoretical basis for the understanding of H. hippophaecolus damage to sea buckthorn and the means to implement effective measures of control.     

Optimal foraging and community structure: The allometry of herbivore food selection and competition

I address the selection of plants with different characteristics by herbivores of different body sizes by incorporating allometric relationships for herbivore foraging into optimal foraging models developed for herbivores. Herbivores may use two criteria in maximizing their nutritional intake when confronted with a range of food resources: a minimum digestibility and a minimum cropping rate. Minimum digestibility should depend on plant chemical characteristics and minimum cropping rate should depend on the density of plant items and their size (mass). If herbivores do select for these plant characteristics, then herbivores of different body sizes should select different ranges of these characteristics due to allometric relationships in digestive physiology, cropping ability and nutritional demands. This selectivity follows a regular pattern such that a herbivore of each body size can exclusively utilize some plants, while it must share other plants with herbivores of other body sizes. I empirically test this hypothesis of herbivore diet selectivity and the pattern of resource use that it produces in the field and experimentally. The findings have important implications for competition among herbivores and their population and community ecology. Furthermore, the results may have general applicability to other types of foragers, with general implications for how biodiversity is influenced.