Patterns of individual diet choice and efficiency of foraging in wedge-capped capuchin monkeys (Cebus olivaceus).

Capuchin monkeys (Cebus olivaceus) exhibit extensive intragroup variability in foraging and diet. To consider how age, sex, and individual identity contribute to this variability, the authors examined foraging and diet in 18 wedge-capped capuchin monkeys in 1 social group in the wild. Age–sex classes did not differ in the time spent ingesting food, the reliance on plant foods, the foraging actions used or substrates exploited, or in the efficiency of exploiting animal foods. They did differ, however, in the time spent finding food, time devoted to animal foods and to vigorous foraging, and the efficiency of foraging. The sexes differed more than age groups. Individual differences within age–sex class were less extensive than expected and were more evident in juveniles than adults. Within-group variability in foraging reflected catholic selection and equivalent treatment of substrates by all individuals, rather than individual specializations. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Use of olfactory cues in foraging by owl monkeys (Aotus nancymai) and capuchin monkeys (Cebus apella).

The authors tested free-ranging New World monkeys (nocturnal owl monkeys [Aotus nancymai] and diurnal capuchin monkeys [Cebus apella]) to determine the extent to which they use olfactory cues to locate food hidden in containers at 2 of 6 feeding sites within a 1?-ha forested enclosure. These 2 sites were selected randomly for each trial and then were baited with banana and banana peel residue. The 4 other sites were unbaited and unscented. In trials in which the food was not visible to the monkeys, Aotus monkeys located the baited sites at a level greater than expected by chance, whereas Cebus monkeys did not. Use of olfactory information by Aotus monkeys in foraging may be an adaptation for nocturnal foraging because olfactory cues are more salient than visual cues at low light levels. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Postural effects on manual reaching laterality in squirrel monkeys (Saimiri sciureus) and cotton-top tamarins (Saguinus oedipus).

Squirrel monkeys (Saimiri sciureus) and cotton-top tamarins (Saguinus oedipus) made unimanual food reaches from either a horizontal, quadrupedal posture or a vertical, clinging posture. No population-level handedness occurred in either species. However, in both species, directional lateral preferences weakly expressed for reaching from the stable quadrupedal posture were intensified in the vertical cling posture. This phenomenon, which is designated as soft handedness, may have been an evolutionary precursor to population-level handedness. Right or left turning by the squirrel monkeys before reaching closely predicted use of the right or left hand. However, the magnitude of the association decreased in the more highly lateralized vertical cling condition. This result suggests that as lateral hand preference increases, hand use may become increasingly independent of constraints from prior behavioral and environmental influences. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Packrats (Neotoma albigula and N. micropus) compared in an operant analogue of foraging behaviors.

Used a barpress chamber as a simplified laboratory analog to illustrate a method of establishing behavioral economics and its potential for the study of foraging patterns in 2 closely related species of packrats. There were 16 adult Ss in each species. During the 1st 40 days of captivity, drinking water was freely available; on the 41st day of captivity, Ss faced a test requiring associative learning to obtain water by barpressing. Results show that N. albigula Ss, who were trapped from a relatively moist habitat, were not prepared to survive without water; they earned moderate amounts to drink whether terms of access were easy or difficult. N. micropus Ss, who were trapped from relatively barren and rocky terrain, gorged themselves when terms were easy and were frugal in expending energy when access was made difficult, a foraging pattern consistent with the conservatism of animals that maximize fitness in desert environments. Findings confirm the potential of traditional analog research in providing incisive comparative data in a simplified laboratory apparatus for the analysis of foraging patterns. (22 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Foraging experience affects gerbils' (Meriones unguiculatus) radial arm maze performance.

Tested D. S. Olton's (1978) hypothesis that the gerbil's ability to easily learn the radial maze task is due to a natural "win-shift" foraging strategy, a tendency to avoid recently visited food sites. 25 Mongolian gerbils at weaning were put in 1 of 2 environments—one in which the source of food and water was always located in the same place and the other in which the source changed location from day to day—until they were 60 days of age. They then were tested in a 17-arm radial maze. Ss reared in the environment with variable locations of food and water learned the maze task more quickly than Ss reared in the other environment. Results are consistent with Olton's hypothesis. (10 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Conditional copying fidelity in capuchin monkeys (Cebus apella).

In the last two decades, it became largely accepted that monkeys show little, if any, copying fidelity. However, some recent studies have begun to challenge this notion. To explore reasons for such contrary findings, we designed a foraging apparatus so that in each of two experiments with capuchin monkeys (Cebus apella), a model would demonstrate one of two alternative methods to obtain food. The apparatus had a V-shaped track on which a panel could be slid up left or right from the center to reveal food. In Experiment 1, food was located in a cup directly behind the center panel. In Experiment 2, sliding the panel left or right revealed food either in left or right ends of the V-track. Since this sliding movement led directly to one food location exclusive of the other, we predicted capuchins would show greater copying fidelity in this second Experiment. Instead, subjects were significantly more faithful to the model’s method in Experiment 1, which provided strong evidence of capuchins copying what they had observed. We suggest that the contrasting results of Experiment 1 may have occurred because capuchins prioritize exploratory behavior when alternative foraging locations are accessible. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Foraging and spatial memory in pigeons (Columba livia).

In two experiments pigeons were studied as they foraged through a simulated patchy environment. Patches consisted of four circular groupings of feeders placed at different locations within a laboratory room. The properties of these patches varied between experiments. In Experiment 1 all feeders in all patches were baited, but the number of food pellets per feeder varied between patches. In Experiment 2 density of food was varied between patches, with 25%, 50%, 75%, or 100% of the feeders randomly baited. A number of variables that indicated pigeons' patch preferences and their behavior within patches were measured. Pigeons showed strong initial preferences for patches containing larger numbers of pellets per feeder in Experiment 1 but did not show differential preferences for patches varying in food density in Experiment 2. Within patches pigeons visited more feeders in richer patches than in poorer patches, both on initial patch entry and on repeat visits. Although pigeons showed evidence of reference and working spatial memory for patches, both experiments failed to provide evidence for the use of working spatial memory for the positions of visited and unvisited feeders within patches. The implications of these findings for spatial memory and foraging theory are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Informative breath: Olfactory cues sought during social foraging among old world monkeys (Mandrillus sphinx, M. Leucophaeus, and Papio anubis).

Sociality provides a unique opportunity for animals to acquire information and learn from others. Especially during foraging, where trial-and-error food selection might be fatal, conspecifics could act as valuable sources of information. During a six-year study across captive, semifree ranging, and wild Old World monkeys, I investigated whether individuals garnered olfactory-based information from their group mates that could guide their feeding decisions. Each of three study species [mandrills (Mandrillus sphinx), drills (M. leucophaeus), and olive baboons (Papio anubis)] performed a prominent muzzle-muzzle behavior, potentially enabling individuals to smell others' mouths and determine via olfaction what foods their conspecifics had chosen. This muzzle-muzzle behavior (1) was preferentially directed by na?ve, younger individuals toward more experienced, older individuals, (2) occurred specifically while recipients were chewing and hence emitting the most potent chemical cues, (3) was typically followed by the actor consuming the very same food type the recipient had been eating, (4) was elicited most often in response to experiments involving novel foods, and (5) occurred less frequently as initially novel foods became more familiar. In contrast to this evidence for information acquisition, there was little support for previous proposals suggesting that muzzle-muzzle functions as a social display. Instead, the omnivorous diets and intensely social lifestyles of mandrills, drills, and baboons, may have each favored a convergent form of information acquisition: seeking out the breath of knowledgeable conspecifics to help decide what foods are safe to eat. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Reverse-reward learning in squirrel monkeys (Saimiri sciureus): Retesting after 5 years, and assessment on qualitative transfer.

Seven squirrel monkeys (Saimiri sciureus) previously trained on reverse-reward tasks were presented with the original “1-versus-4” task after a 5-year interval without reverse-reward experience (Experiment 1). None of them reliably selected the smaller food array; however, at around chance level, their performance was superior to when they were first exposed to the task almost 6 years previously, suggesting some long-term memory retention. One naive monkey consistently selected the larger array, as expected. In Experiment 2, trials consisting of 1 versus 1 piece of two qualitatively different types of food were interspersed among familiar 1-versus-4 trials. None of five monkeys tested reliably selected the less-preferred food to get the more preferred food as the reward, and one monkey scored below chance. However, when one piece of low-preference food was paired with four pieces of high-preference food (Experiment 3), all four monkeys tested avoided reaching for the latter and thereby obtained it as the reward; two monkeys obtained perfect scores on these trials. These two monkeys were trained on a specific qualitative reverse-reward pairing and then again tested on new pairings (Experiment 4), but transfer was incomplete. Compound trials that pit quantity against quality in novel ways appear taxing for squirrel monkeys, despite competence in reverse-reward on both dimensions separately. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Delay of gratification in capuchin monkeys (cebus apella) and squirrel monkeys (saimiri sciureus).

In two separate series of experiments four capuchin monkeys (Cebus apella) and four squirrel monkeys (Saimiri sciureus) were given demonstration trials in which a human transferred six pieces of food, one by one, from out of each monkey's reach to within reach. On test trials the monkey could reach for the transferred food at any time, an action that ended the trial. Therefore, it was in the monkey's interest to allow food items to accumulate before reaching for food. No capuchin monkey showed delay of gratification in the first phase of testing. An attempt to facilitate performance by presenting a single free food item immediately before the transfer failed (Phase 2). In Phase 3, when the transferred food items increased progressively in size, two capuchins maintained delays, and frequently waited for all 6 items to accumulate. One squirrel monkey started to delay gratification in Phase 1, and another did so in Phase 3. A return to single-sized food items did not impair the monkeys' ability to delay. Short (1 s) interitem delays were generally easier to maintain than longer delays (3 or 5 s). In both species the delaying individuals bridged the delays idiosyncratically. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Comparative studies of squirrel monkeys (Saimiri sciureus) and titi monkeys (Callicebus moloch): Performance on choice tasks in near space.

In 2 experiments, 12 adult squirrel monkeys and 10 adult titi monkeys were studied in tasks involving reaching for food in near space (arm's reach). Although performance by Ss of the 2 species differed in several ways consistent with previous studies, the species did not differ in the tendency to adopt a habitual position or limb during reaching. The findings contrast with previous work on spatial preferences in these species in tasks involving movement of the whole body. Together with the results of previous studies on movement patterns in these 2 species, the present findings are placed in a comparative psychological framework of the proximate sources of use of space in nature. (29 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Object permanence in orangutans (Pongo pygmaeus) and squirrel monkeys (Saimiri sciureus).

The authors tested orangutans (Pongo pygmaeus) and squirrel monkeys (Saimiri sciureus) on object permanence tasks. In Experiment 1, orangutans solved all visible displacements and most invisible displacements except those involving movements into 2 boxes successively. In Experiment 2, performance of orangutans on double invisible displacements and control displacements (assessing simple strategies) was compared. Orangutans did not use the simple strategy of selecting the box visited last by the experimenter. Instead, poorer performance on double invisible displacements may have been related to increased memory requirements. In Experiment 3, squirrel monkeys were tested using the procedure of Experiment 1. Squirrel monkeys solved visible but did not comprehend invisible displacements. Results suggest that orangutans but not squirrel monkeys possess Stage 6 object permanence capabilities. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Attention to combined attention in New World monkeys (Cebus apella, Saimiri sciureus).

Co-orientation by capuchin (Cebus apella) and squirrel (Saimiri sciureus) monkeys in response to familiar humans abruptly switching the direction of their visual attention was recorded. Co-orientation occurred more frequently overall in capuchins than squirrel monkeys. Capuchins showed a tendency to habituate within trials involving consecutive attention switches performed by 2 different people, whereas squirrel monkeys co-oriented more when the 2nd attention switch was by a 2nd actor. These results suggest variable attention-processing abilities in New World monkeys, including differences in summation of attention by others. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Training squirrel monkeys (Saimiri sciureus) to deceive: Acquisition and analysis of behavior toward cooperative and competitive trainers.

Three squirrel monkeys (Saimiri sciureus) learned to reach toward a container that covered food if a cooperative trainer rewarded such reaches by giving the food. A competitive trainer kept any food found, but wrong selections by this trainer were also rewarded. The monkeys initially reached toward the baited container indiscriminately, but gradually and with the aid of color-cued containers, all 3 reliably reached "honestly" and "deceptively" in the presence of the cooperative and competitive trainers, respectively. The monkeys did not appear to take the trainers' knowledge about the location of the food into account, and deception did not occur if food was placed under the normally unbaited container. With additional containers present, monkeys misled the competitive trainer into selecting the unbaited container farthest from the baited one. Although not indicative of mental attribution, the monkeys' behavior suggests awareness of the acquired communicative function of the reaching response. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Deterioration of planning ability with age in Japanese monkeys (Macaca fuscata).

To investigate the ability of aged monkeys to plan and the effect of aging on this ability, performance in a food retrieval task was assessed in aged and younger Japanese monkeys (Macaca fuscata). In this task, the monkeys had to retrieve food items by selecting from a set of 9 holes, each of which contained 1 food item. Results showed that task performance declined significantly with age. All monkeys showed, to a greater or lesser extent, some consistent patterns in their sequence of selecting holes for retrieving the food item. An analysis of these selection patterns indicated that the younger monkeys showed more consistent sequences in selection than the aged monkeys. Furthermore, success in the task performance correlated strongly with higher consistency in the sequence of selecting holes. The authors simulated performance for this task by monkeys without any strategies or plans. The results suggest that the empirical data were far more systematic than the simulated data. Thus, the authors conclude that Japanese monkeys have the ability to plan and that this ability to plan deteriorates with age. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

When, what, and whom to watch? Quantifying attention in ravens (Corvus corax) and jackdaws (Corvus monedula).

Complex social life requires monitoring of conspecifics. The amount and focus of attention toward others has been suggested to depend on the social relationships between individuals. Yet there are surprisingly few experiments that have tested these assumptions. This study compared attention patterns toward conspecifics in two corvid species, ravens (Corvus corax) and jackdaws (Corvus monedula). Birds were confronted with affiliated and non-affiliated conspecifics engaged in foraging and object manipulation. Visual access to the model bird was provided through two observation holes, which allowed measurement of exactly how often and for how long observers watched the other. Overall, ravens were more attentive to conspecifics than were jackdaws. Moreover, only ravens showed higher interest toward food-related than object-related behaviors of the model and toward close affiliates than non-affiliates by increasing the duration rather than the frequency of looks. These results are in accordance with predictions derived from the species' foraging biology and suggest that the facultative social, but highly manipulative, ravens use and value information from others differently than do the obligate social jackdaws. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Social transmission of food preferences in Japanese monkeys (Macaca fuscata) after mere exposure or aversion training.

In Experiment 1, 3 mother–child pairs of Japanese monkeys (Macaca fuscata) were given simultaneous choice tests between raisins and popcorn. The mothers and offspring showed different choice patterns. Cofeeding opportunities were then alternated with individual choice tests. In Experiment 2, 2 other pairs were added. Each animal was again offered simultaneous choice tests between marshmallows and almonds. Food aversion conditioning was used to create different choice patterns for mothers and offspring. After cofeeding and choice tests, the differences in choice patterns disappeared in both experiments. The changes after contact with the other's eating pattern during cofeeding was as follows: foods consumed by either came to be eaten by both; foods consumed by both continued to be eaten by both; and foods consumed by neither continued to be ignored. The results provide evidence for social transmission of food preferences in this species. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A study of long-term odor memory in squirrel monkeys (Saimiri sciureus).

Five squirrel monkeys (Saimiri sciureus) were trained to discriminate between pairs of odors, and their ability to recognize these as positive or negative was tested at intervals of up to 7 mo. Retention was excellent up to 15 wks and remained significantly above chance even after 30 wks. Good performance at the shorter intervals was not due to rapid relearning, although at the longer intervals considerable savings were demonstrated by the animals' ability to reach criterion more rapidly than with novel odors. Thus, squirrel monkeys possess a robust memory for odors and show flat forgetting curves consistent with reports for human Ss. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Enrichment and individual differences affect welfare indicators in squirrel monkeys (Saimiri sciureus).

Enrichment aims to improve captive animals' welfare by enhancing their environments. Two of the struggles associated with measuring welfare are identifying when animals' needs are being met or surpassed and identifying how individual differences play a role in these outcomes. Using a group of related Guyanese squirrel monkeys, we studied changes in five welfare indicators under different environmental conditions. Manipulating food presentation, walkways, and toys, we created five enrichment levels ranging from just above USDA standards to considerably more complex than the animals' normal housing. At the end of each level, a novelty test was performed in which an unfamiliar woman entered the enclosure and offered food. Changes in behavior as a function of enrichment condition were analyzed using a repeated-measures MANOVA. Compared to baseline, less enrichment consistently increased negative welfare indicators (abnormal behavior, aggression, and negative responses to the novelty test), while more enrichment sometimes decreased these indicators. Positive welfare indicators were less consistently related to enrichment, but positive response to the novelty test did increase somewhat in the most enriched condition. Across conditions, rank correlations revealed that individuals had highly consistent individual differences in positive responses to novelty and somewhat consistent individual differences in rates of aggression. The goal of the enrichment and the species, sex, and individual animals to be enriched should be considered when selecting a welfare indicator, and facilities measuring animal welfare should study changes in the behavior of specific individuals to control for individual differences. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Anticipation of future events in squirrel monkeys (Saimiri sciureus) and rats (Rattus norvegicus): Tests of the Bischof-Kohler hypothesis.

The Bischof-Kohler hypothesis holds that nonhuman animals cannot anticipate a future event and take appropriate action when that event involves satisfaction of a need not currently experienced. Tests of the Bischof-Kohler hypothesis were performed with squirrel monkeys (Saimiri sciureus) and rats (Rattus norvegicus). In experimental trials with both species, a nonthirsty animal had its water bottle removed and then chose between a smaller and larger quantity of food. Consumption of the food induced thirst. Choice of the smaller quantity led to the return of the water bottle sooner than choice of the larger quantity. Monkeys reversed their baseline preference for the larger quantity of food when the experimental contingencies were introduced, but rats continued to prefer the larger amount. Although the rat findings support the Bischof-Kohler hypothesis, the monkey findings challenge it. (PsycINFO Database Record (c) 2010 APA, all rights reserved)