Food variety-seeking in tufted capuchin monkeys (Cebus apella)

Applied behavior analysis and the zoo: Forthman and Ogden (1992) thirty years later

The field of applied behavior analysis has been directly involved in both research and applications of behavioral principles to improve the lives of captive zoo animals. Thirty years ago, Forthman and Ogden (1992) wrote one of the first papers documenting some of these efforts. Since that time, considerable work has been done using behavioral principles and procedures to guide zoo welfare efforts. The current paper reexamines and updates Forthman and Ogden's original points, with attention to the 5 categories they detailed: (a) promotion of species-typical behavior, (b) reintroduction and repatriation of endangered species, (c) animal handling, (d) pest control, and (e) animal performances. In addition, we outline 3 current and future directions for behavior analytic endeavors: (a) experimental analyses of behavior and the zoo, (b) applied behavior analysis and the zoo, and (c) single-case designs and the zoo. The goal is to provide a framework that can guide future behavioral research in zoos, as well as create applications based on these empirical evaluations.

A Food for All Seasons: Stability of Food Preferences in Gorillas across Testing Methods and Seasons

Decisions about which foods to use during training and enrichment for captive animals may be based on invalid assumptions about individuals’ preferences. It is important to assess the stability of food preferences given that one-time preferences are often used to inform which items are offered over a longer period of time. Presenting preference assessments using images of food items allows control over factors such as size, scent, and inadvertent cueing but requires validation. We presented three male gorillas with choices between randomly selected pairs of actual food items from their morning meal using PVC feeders. We also presented the gorillas with two-alternative forced-choice tests between images of these foods on a touchscreen computer. Ranked preferences were correlated across method and seasons. Furthermore, gorillas selected images of preferred over less preferred foods in a validation task on the touchscreen. However, selections of some food items changed within sessions, suggesting that preference may be relative to other contextual factors. Researchers should assess how choices affect subsequent preferences to understand whether animals demonstrate absolute preferences for particular food items, or prefer variety.

Observer effects in a remote population of large-headed capuchins, Sapajus macrocephalus

Human observers often are present when researchers record animal behavior, which can create observer effects. These effects are rarely explicitly investigated, often due to the assumption that the study animal is habituated to or unaffected by a human’s presence. We investigated the effect of human pressure gradients on a remote population of large-headed capuchins, Sapajus macrocephalus, looking specifically at the effects of number of observers, distance to observers, and distance to the research base. We conducted this study over 4 months in the Pacaya-Samiria Nature Reserve, Peru, and collected 199 two-minute focal samples of capuchin behavior. We found that capuchin monkeys fed less when human observers were closer to the focal individual, when more observers were present, and when capuchins were closer to the research base. We found no other consistent differences in capuchin monkey behavior across the measured human pressure gradients, although capuchins directed a high proportion of their vigilance toward humans (29% in adults and 47% in infants). Our results support the hypothesis that human pressure gradients influence animal behavior. Given the proportion of human directed vigilance, we recommend that all studies that use human observers to record animal behavior consider human-directed vigilance, record the number of observers, as well as the observer-focal animal distance, to check for these effects.

Conditional valuation for combinations of goods in primates

Valuing goods and selecting the one with the highest value forms the basis of adaptive behaviour across species. While it is obvious that the valuation of a given type of goods depends on ownership and availability of that type of goods, the effects of other goods on valuation of the original good are sometimes underappreciated. Yet, goods interact with each other, indicating that the valuation of a given good is conditional on the other goods it is combined with, both in the wild and the laboratory. Here, we introduce conditional valuation in the context of valuing multiple goods and briefly review how human and animal experimentalists can leverage economic tools for the study of interactions among goods. We then review evidence for conditional valuation for combined foods in both human and non-human primates. In the laboratory, non-human primates show increased valuation of certain combinations of foods but decreased valuation of other types of combinations. Thus, similarly to humans, monkeys appear to value combinations of goods in a conditional fashion. Additionally, both humans and monkeys appear to employ similar neural substrates for the valuation of single goods, such as the orbitofrontal cortex. Together, investigations of our evolutionary precursors may provide insights on how we value interacting goods. This article is part of the theme issue 'Existence and prevalence of economic behaviours among non-human primates'.

Quantity-quality trade-off in the acquisition of token preference by capuchin monkeys (Sapajus spp.)

Money represents a cornerstone of human modern economies and how money emerged as a medium of exchange is a crucial question for social sciences. Although non-human primates have not developed monetary systems, they can estimate, combine and exchange tokens. Here, we evaluated quantity-quality trade-offs in token choices in tufted capuchin monkeys as a first step in the investigation of the generalizability of tokens as reinforcers, which is a potentially relevant factor underlying the emergence of money in humans. We measured capuchins' exchange preferences when they were repeatedly provided with 10 units of three token types yielding food combinations varying in quantity and quality. Overall, capuchins maximized their quantitative payoff, preferring tokens associated with a higher food amount, rather than showing violations of rationality. However, some individuals did not maximize their qualitative payoff, possibly because of conditional valuation effects or owing to the choice overload phenomenon, according to which too many options reduce the accuracy of choice. Our study supports the importance of comparative research to finely analyse the multiple components shaping the economic behaviours of other species, possibly to achieve a more comprehensive, evolutionary- and ecologically based understanding of human economic behaviour. This article is part of the theme issue 'Existence and prevalence of economic behaviours among non-human primates'.

The role of novelty and fat and sugar concentration in food selection by captive tufted capuchins (Sapajus apella)

Capuchins, like other primates, use feedback from sensory cues and digestion to make decisions about which foods to consume and which to avoid. However, little is known about how capuchins make consumption decisions when simultaneously presented with novel and familiar foods, or how food familiarity and macronutrient concentration together influence food choice, topics with potential implications for developmental and health research. In this study, we evaluated the role of familiarity, as well as fat and sugar concentration, in the food selections of captive tufted capuchins (Sapajus apella). In the first experiment, over 10 sessions, subjects were assigned to either a group that chose between one familiar and one novel food item both high in fat or sugar (high condition), or to a group that chose between one familiar and one novel food item both low in fat or sugar (low condition). In the second experiment, subjects were divided into three groups, familiarized with food over five feeding sessions, and then offered the familiarized food and a novel food that varied in fat or sugar for 10 sessions. When offered foods high in fat, capuchins showed no clear signs of neophobia, forming an initial preference for the novel food, rejecting foods less frequently, and selecting foods faster than when offered foods low in fat. These trends were generally not observed in response to foods with sugar. When presented with options that varied in macronutrient concentration, subjects showed an initial interest in the novel food irrespective of whether it was high in fat or sugar, yet formed a final preference for the higher-concentration item. Findings suggest that the concentration of fat or sugar in novel foods may be an important mediator of exploratory behavior and that capuchins rely on immediate feedback from taste and other sensory cues to make consumption decisions.

Do tufted capuchin monkeys play the odds? Flexible risk preferences in Sapajus spp

As humans, several non-human animal species avoid risk, defined as "variability in rate of gain". However, non-human primate studies revealed a more complicated picture, with different species ranging from risk aversion to risk proneness. Within an ecological rationality framework, a species' feeding ecology should influence its risk preferences, as it has been shown in bonobos and chimpanzees. Although the feeding ecology hypothesis is promising, it has not been yet verified in species other than apes. Here, we aimed to assess whether this hypothesis holds true in tufted capuchin monkeys (Sapajus spp.). Ten capuchins were presented with choices between a "safe" option and a "risky" option in three conditions differing for the probability of receiving the larger reward when selecting the risky option. Similarly to chimpanzees, capuchins were risk prone. However, capuchins' behaviour was not the result of a bias towards the choice of the risky option, since-when facing options with different probabilities of obtaining the larger outcome-they were able to flexibly modify their preferences. Capuchins' decision-making under risk mirrors their risk-prone behaviour in the wild, where they often rely on unpredictable and/or hazardous food sources, thus satisfying the feeding ecology hypothesis.

How to spend a token? Trade-offs between food variety and food preference in tufted capuchin monkeys (Cebus apella)

Humans and non-human animals often choose among different alternatives by seeking variety. Here we assessed whether variety-seeking, i.e. the tendency to look for diversity in services and goods, occurs in capuchin monkeys--South-American primates which--as humans--are omnivorous and susceptible to food monotony. Capuchins chose between a Variety-token, that allowed to select one among 10 different foods (one more-preferred and nine less-preferred) and a Monotony-token, that--upon exchange with the experimenter--either allowed to select one among 10 units of the same more-preferred food or gave access to one unit of the more-preferred food. To examine how food preference affects variety-seeking, in the B-condition we presented nine moderately preferred foods, whereas in the C-condition we presented nine low-preferred foods. Overall, capuchins preferred the Variety-token over the Monotony-token and often selected one of the less-preferred foods. These results suggest that variety-seeking is rooted in our evolutionary history, and that it satisfies the need of experiencing stimulation from the environment; at the ultimate level, variety-seeking may allow the organism to exploit novel foods and obtain a correct nutritional intake. Finally, variety-seeking could have contributed to the transition from barter to money in many human cultures.