Abstract: Social monitoring has been hypothesized to be an important component of primate social behavior. If the gaze direction of one animal can redirect the gaze of another, visual scanning of conspecifics can provide a more efficient means of locating food or predators than directly scanning the entire nonsocial environment. Social monitoring also allows distance regulation between members of a group, reducing the likelihood of agonistic encounters. Although assessment of gaze direction in freely moving primates is problematic, we were successful in assessing amounts of visual scanning among adult females of a captive, socially housed group of patas monkeys (Erythrocebus patas) using a focal sampling technique with on-the-dot recording (5-s sampling intervals). In study 1, relative amounts of scanning were assessed as subjects gazed at any other member of the group. Percentages of agreement between observers ranged from 80% to 92%, with corresponding &#115 values ranging from 0.74 to 0.92. In study 2, relative amounts of visual scanning were assessed so that specific targets of gaze were identified. The resultant data supported a long-standing prediction about the role of social monitoring in primate group dynamics. Lower-ranking animals gazed toward higher-ranking animals more often than vice versa. Although the specific cues eliciting social monitoring remain to be determined, visual attention in this social primate group appeared to be systematically related to hierarchical ranks, assessed by displacements. Minimally, these results suggest that patas monkeys structure their visual attention based on previous encounters with other members of their social group. While simple discrimination learning could account for these results, the demonstration of a systematic relationship between visual attention and primate social dynamics is relevant to current discussions of a primate's understanding of conspecific gaze direction.

Abstract: Learning about food palatability from watching what conspecifics eat might be one of the advantages of group living. A previous study investigated whether group members' presence or eating activity account for social facilitation of eating of foods never previously tasted. Capuchins encountered novel colored foods when (1) alone (Alone condition) or (2) with group members visible in the nearby cage (Group-present condition) or (3) with group members present and eating a familiar food that had not been colored (Group+food condition). Social facilitation of eating occurred when group members were eating, despite the difference in color between the familiar food eaten by them and the novel food presented to the experimental subject. To clarify what subjects learnt from group members when social facilitation occurred, we further analyze here the data from the previous study. The number of visual exposures to the colored novel food (as a group member) correlated with increased consumption of that novel food when encountered later (as experimental subject). In contrast, the number of times that an individual fed on the familiar food (as a group member) did not decrease its consumption of novel food (as experimental subject). Therefore, capuchins (1) habituated to the colors of the novel foods, and (2) did not take into account that seeing group members eating a food does not provide information about the palatability of a differently colored food. Since social facilitation of eating occurs when foods do not match in color, at least in capuchins, social facilitation of eating should not be considered as a way of learning about a safe diet, but rather as a way of overcoming neophobia.

Abstract: Abstract  Many wild primates occupy large home ranges and travel long distances each day. Navigating these ranges to find sufficient food presents a substantial cognitive challenge, but we are still far from understanding either how primates represent spatial information mentally or how they use this information to navigate under natural conditions. In the course of a long-term socioecological study, we investigated and compared the travel paths of sympatric spider monkeys (Ateles belzebuth) and woolly monkeys (Lagothrix poeppigii) in Amazonian Ecuador. During several field seasons spanning an 8-year period, we followed focal individuals or groups of both species continuously for periods of multiple days and mapped their travel paths in detail. We found that both primates typically traveled through their home ranges following repeatedly used paths, or “routes”. Many of these routes were common to both species and were stable across study years. Several important routes appeared to be associated with distinct topographic features (e.g., ridgetops), which may constitute easily recognized landmarks useful for spatial navigation. The majority of all location records for both species fell along or near identified routes, as did most of the trees used for fruit feeding. Our results provide strong support for the idea that both woolly and spider monkey use route-based mental maps similar to those proposed by Poucet (Psychol Rev 100:163-182, 1993). We suggest that rather than remembering the specific locations of thousands of individual feeding trees and their phenological schedules, spider and woolly monkeys could nonetheless forage efficiently by committing to memory a series of route segments that, when followed, bring them into contact with many potential feeding sources for monitoring or visitation. Furthermore, because swallowed and defecated seeds are deposited in greater frequency along routes, the repeated use of particular travel paths over generations could profoundly influence the structure and composition of tropical forests, raising the intriguing possibility that these and other primate frugivores are active participants in constructing their own ecological niches. Building upon the insights of Byrne (Q J Exp Psychol 31:147-154, 1979, Normality and pathology in cognitive functions. Academic, London, pp 239-264, 1982) and Milton (The foraging strategy of howler monkeys: a study in primate economics. Columbia University Press, New York, 1980, On the move: how and why animals travel in groups. University of Chicago Press, Chicago, pp 375-417, 2000), our results highlight the likely general importance of route-based travel in the memory and foraging strategies of nonhuman primates.

Abstract: Western scrub-jays (Aphelocoma californica) often visually assess and handle several whole (unshelled) peanuts before selecting one to transport and cache; this behavior is a search for a preferred heavy nut. I repeatedly video-taped individually identifiable jays as they landed on a feeding platform and chose from presentations of peanuts that varied in the number of items or in the distribution of sizes. I examined how differences among these presentations and a bird's social status affected the amount of assessment and the economic consequences of choice. I also examined the specific patterns of handling peanuts, called sampling, to quantify the degree to which sampling sequences were typified by repeated comparisons among sampled peanuts (retrospective sampling), or sequential assessment and rejection of peanuts (prospective sampling). Peanut assessment was more extensive and prospective when there were many options from which to choose than when there were few. Peanut assessment was more extensive and retrospective when options were similar in size than when they varied. Scrub-jays were more likely to make repeated comparisons immediately before selecting a peanut than elsewhere in a sampling sequence. Subordinate scrub-jays, who were at the greatest risk of pre-emption by competitors, assessed peanuts less extensively and were more prospective in their sampling than dominants. Unless peanuts were very similar in size, jays were more accurate at selecting a high-quality peanut and achieved a higher rate of food storage than if they had not assessed. These results show that scrub-jays can adaptively modify how they search to improve their rate of food storage, and also suggest some of the specific search tactics used by jays when assessing peanuts.

Abstract: Three experiments explored the baboon's discrimination of visual displays that comprised 2 to 24 black-and-white computer icons; the displayed icons were either the same as ( same) or different from one another ( different). The baboons' discrimination of same from different displays was a positive function of the number of icons. When the number of icons was decreased to 2 or 4, the baboons responded indiscriminately to the same and different displays, exhibiting strong position preferences. These results are both similar to and different from those of pigeons that were trained and tested under comparable conditions.