Systematic assessment of food item preference and reinforcer effectiveness: Enhancements in training laboratory-housed rhesus macaques

Should Zoo Food Be Chopped for Ruffed Lemurs? It's Not so Black and White

Whole food diets in zoos have the potential to reduce microbial contamination and keeper preparation time, whilst also reducing food nutrient breakdown. Given these benefits, it is important to determine whether there is any value in chopping up food. Lemurs (Family Lemuridae) are common in zoos, with over 7500 individuals housed globally. Given their regular occurrence in collections, plus the high incidence of frugivory, lemurs are an excellent taxon to investigate food presentation effects on behavior. A study was undertaken at Beale Wildlife Park on a group of four black-and-white ruffed lemurs (Varecia variegata) to investigate food presentation and preference. Animal behavior was recorded using instantaneous focal sampling at 60 s intervals to record state behaviors and continuous focal sampling to record event behaviors in 1-h sessions. Food preference was done by recording the first three food items consumed by individual lemurs. Overall, food manipulation was significantly increased during whole food presentation allowing the lemurs to display species-specific behaviors. Feeding and foraging were highest during very chopped food condition and inactivity was lowest in very chopped food presentation. When looking at aggressive interactions, there was an increase in stealing and locomotion with food during whole food presentation, whereas biting and startle were lower. Proving high-value food items chopped and low-value food items whole could reduce aggression while reduce aggression seen over high-value food items. For food preference, sweet potato was consistently in the top three food items for all lemurs, with beetroot being the second most-picked food item. This suggests that these individuals have a strong preference for food items high in carbohydrates. Keeper preparation time was significantly reduced during whole food preparation. Further research assessing a wider range of zoo-housed species would be beneficial to assess the effects of food presentation on behavior.

Potential Food Inclination of Crab-Eating Macaques in Laboratory Environments: Enhancing Positive Reinforcement Training and Health Optimization

Positive reinforcement and training for health optimization are pivotal for successful studies with monkeys. Potential food inclination is important for studies on crab-eating macaques in laboratory environments, but evaluations remain scarce. We explored crab-eating macaques' potential food inclination to establish a reward system for future behavioral assessments. Twelve male and three female monkeys underwent a food inclination assessment in which they were offered four food categories-fruits, vegetables, proteins, and nuts. The monkeys exhibited a higher inclination for plant-based foods, particularly fruits and vegetables, over animal-based proteins like chicken and tuna (p < 0.0001), with a notable inclination for nuts (eaten/provided = 100%). Additionally, the consistency of potential food inclination after repeated offerings was investigated, revealing a time-dependent increase in inclination for protein items. Food consumption ratios correlated positively with caloric intake (r = 0.59, p = 0.02), implying that individuals with a regular high caloric intake and increased body weight are more likely to accept food during positive reinforcement training. Our findings suggest fruits, vegetables, protein-rich foods, and nuts can help with health optimization. However, animal-based protein-rich foods initially had a low preference, which may increase over time. Our study can provide guidelines for positive reinforcement training and health optimization.

Efficacy of Edible and Leisure Reinforcers with Domestic Dogs

Preference assessments are often used to identify stimuli that function as potential reinforcers for training or intervention purposes. Specifically, various preference assessment formats have been used to identify preferred stimuli for humans, cockroaches, cotton-top tamarins, tortoises, and wolves, to name a few. However, to date, no study has evaluated the differential efficacy between food and leisure stimuli within domestic dogs. The current study aimed to compare the reinforcing value and efficacy between food and leisure stimuli for domestic dogs by comparing rates of behavior when receiving access to either their top-preferred food or leisure items. Overall results suggest (1) domestic dogs prefer food over leisure items, and (2) food is more likely to function as a reinforcer than leisure items for domestic dog's behavior. These results suggest that dog owners and trainers should consider using food reinforcers over leisure items as reinforcers when attempting to train dogs.

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.

Selective Prefrontal-Amygdala Circuit Interactions Underlie Social and Nonsocial Valuation in Rhesus Macaques

Lesion studies in macaques suggest dissociable functions of the orbitofrontal cortex (OFC) and medial frontal cortex (MFC), with OFC being essential for goal-directed decision-making and MFC supporting social cognition. Bilateral amygdala damage results in impairments in both of these domains. There are extensive reciprocal connections between these prefrontal areas and the amygdala; however, it is not known whether the dissociable roles of OFC and MFC depend on functional interactions with the amygdala. To test this possibility, we compared the performance of male rhesus macaques (Macaca mulatta) with crossed surgical disconnection of the amygdala and either MFC (MFC × AMY, n = 4) or OFC (OFC × AMY, n = 4) to a group of unoperated controls (CON, n = 5). All monkeys were assessed for their performance on two tasks to measure the following: (1) food-retrieval latencies while viewing videos of social and nonsocial stimuli in a test of social interest and (2) object choices based on current food value using reinforcer devaluation in a test of goal-directed decision-making. Compared with the CON group, the MFC × AMY group, but not the OFC × AMY group, showed significantly reduced food-retrieval latencies while viewing videos of conspecifics, indicating reduced social valuation and/or interest. By contrast, on the devaluation task, group OFC × AMY, but not group MFC × AMY, displayed deficits on object choices following changes in food value. These data indicate that the MFC and OFC must functionally interact with the amygdala to support normative social and nonsocial valuation, respectively.SIGNIFICANCE STATEMENT Ascribing value to conspecifics (social) versus objects (nonsocial) may be supported by distinct but overlapping brain networks. Here, we test whether two nonoverlapping regions of the prefrontal cortex, the medial frontal cortex and the orbitofrontal cortex, must causally interact with the amygdala to sustain social valuation and goal-directed decision-making, respectively. We found that these prefrontal-amygdala circuits are functionally dissociable, lending support for the idea that medial frontal and orbital frontal cortex make independent contributions to cognitive appraisals of the environment. These data provide a neural framework for distinct value assignment processes and may enhance our understanding of the cognitive deficits observed following brain injury or in the development of mental health disorders.

Nonhuman primate abnormal behavior: Etiology, assessment, and treatment

Across captive settings, nonhuman primates may develop an array of abnormal behaviors including stereotypic and self-injurious behavior. Abnormal behavior can indicate a state of poor welfare, since it is often associated with a suboptimal environment. However, this may not always be the case as some behaviors can develop independently of any psychological distress, be triggered in environments known to promote welfare, and be part of an animal's coping mechanism. Furthermore, not all animals develop abnormal behavior, which has led researchers to assess risk factors that differentiate individuals in the display of these behaviors. Intrinsic risk factors that have been identified include the animal's species and genetics, age, sex, temperament, and clinical condition, while environmental risk factors include variables such as the animal's rearing, housing condition, husbandry procedures, and research experiences. To identify specific triggers and at-risk animals, the expression of abnormal behavior in captive nonhuman primates should be routinely addressed in a consistent manner by appropriately trained staff. Which behaviors to assess, what assessment methods to use, which primates to monitor, and the aims of data collection should all be identified before proceeding to an intervention and/or treatment. This article provides guidance for this process, by presenting an overview of known triggers and risk factors that should be considered, steps to design a comprehensive evaluation plan, and strategies that might be used for prevention or treatment. It also outlines the tools and processes for assessing and evaluating behavior in an appendix. This process will lead to a better understanding of abnormal behavior in captive primate colonies and ultimately to improved welfare.

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.

Functional Analysis and Successful Treatment of a Captive Rhesus Macaque's Disruptive Behavior

Functional analysis (FA) is a method developed and used by behavior analysts in human clinical settings to identify possible environmental variables that reinforce undesired behavior. FA is increasingly being applied to better understand the behavior of nonhuman animals. When training monkeys in a room with others, disruptive behavior displayed by neighboring monkeys can impede training progress. In the present study, a FA identified possible reinforcers of disruptive behavior (loud shaking of a toy) exhibited frequently (24% duration pre-treatment) by a rhesus macaque (Macaca mulatta) during in-room training sessions. The functional analysis identified that contingent delivery of foods was maintaining the disruptive behavior, with a mean percent duration of 57% in this condition. The implementation of a function-based treatment consisting of continuous access to a preferred food during in-room training sessions successfully decreased disruptive behavior by over 90% as measured during 15 subsequent sessions. This study advances the current literature applying functional analysis to nonhuman primates as a means of determining the reinforcers maintaining aberrant or undesirable behavior and applying effective treatments based on understanding this function.

Animal Training, Environmental Enrichment, and Animal Welfare: A History of Behavior Analysis in Zoos

The modern zoo has been associated with two major behavioral welfare advances: (a) the use of training to increase voluntary husbandry care, and (b) the implementation of environmental enrichment to promote naturalistic behaviors. Both practices have their roots in behavior analysis, or the operant conditioning-centered, reward-based approach to behavioral psychology. Operant conditioning served as the foundation for the development of reinforcement-based training methods commonly used in zoos to make veterinary and husbandry procedures easier and safer for animals and their caregivers. Likewise, operant conditioning, with its focus on arranging environmental antecedents and consequences to change behavior, also provided a framework for successful environmental enrichment practices. In this paper, we outline the key individuals and events that shaped two of the cornerstones of the modern zoo: (1) the emergence of reward-based husbandry training practices, and (2) the engineering of environmental enrichment. In addition, we (3) suggest ways in which behavior analysis can continue to advance zoo welfare by (i) expanding the efficacy of environmental enrichment, (ii) using within-subject methodology, and (iii) improving animal-visitor interactions. Our goal is to provide a historical and contextual reference for future efforts to improve the well-being of zoo animals.

Investigating food preference in zoo-housed meerkats

Understanding food preference among animals in human care can support improvements to welfare through training and day-to-day care (e.g., diet management). Little has been published about food preference in zoo-housed meerkats. Assessing meerkat food preference would be useful, not only for the welfare of that species, but also for developing approaches to assessing food preference in other group-housed, social species. The specific aim of this study was to quantify food preference within the meerkat mob at Wellington Zoo. We developed a simple, cost-effective method for characterizing the food preference hierarchy in meerkats by presenting pairs of foods to the mob as a group. We observed stable preference with the hierarchy for pups closely resembling that for adults. This study demonstrated that it is possible to assess food preference and identify a food preference hierarchy for a group of animals from a social species where it was neither practical nor appropriate to assess individuals' preferences separately.

What's in a Click? The Efficacy of Conditioned Reinforcement in Applied Animal Training: A Systematic Review and Meta-Analysis

Simple Summary

Conditioned reinforcement, for example, clicker training, has become increasingly popular in recent decades. Hence, questions about the effectiveness of the conditioned reinforcer have become prominent in the animal training arena. This article summarizes the scientific literature on conditioned reinforcement in applied animal training settings (e.g., homes). It was found that dogs and horses were the most frequently studied animals. Clickers and food were the most often used training stimuli. Effect size analysis found a medium effect of clicker training. The literature reviewed here shows that conditioned reinforcement is an effective approach to change animal behavior; however, sizable information potentially related to its effectiveness was not clearly reported in the studies (e.g., food preferences). Although this review fills in a gap in the literature, it also points to the need for more research to further the understanding of conditioned reinforcement phenomena.

Abstract

A conditioned reinforcer is a stimulus that acquired its effectiveness to increase and maintain a target behavior on the basis of the individual’s history—e.g., pairings with other reinforcers. This systematic review synthesized findings on conditioned reinforcement in the applied animal training field. Thirty-four studies were included in the review and six studies were eligible for a meta-analysis on the effectiveness of behavioral interventions that implemented conditioned reinforcement (e.g., clicks, spoken word, or whistles paired with food). The majority of studies investigated conditioned reinforcement with dogs (47%, n = 16) and horses (30%, n = 10) implementing click–food pairings. All other species (cats, cattle, fish, goats, and monkeys) were equally distributed across types of conditioned (e.g., clicker or spoken word) and unconditioned reinforcers (e.g., food, water, or tactile). A meta-analysis on the effectiveness of conditioned reinforcement in behavioral interventions found a medium summary effect size (Tau-U 0.77; CI_95% = [0.53, 0.89]), when comparing baseline, where no training was done, and treatment levels. Moderators of conditioned reinforcement effectiveness were species (e.g., horses) and research design (e.g., multiple-baseline designs). The small number of intervention-focused studies available limits the present findings and highlights the need for more systematic research into the effectiveness of conditioned reinforcement across species.

Preference assessments as a tool to evaluate environmental enrichment

Environmental enrichment is an important tool utilized to improve animal welfare in zoological institutions through opportunity for mental and physical stimulation. Many past studies have focused on the impact enrichment has on animal behavior; however, none have conducted preference assessments on enrichment items to examine the relationship between animals' preferences and interaction with enrichment over a 24-hr period. Ten-minute free operant, paired-choice preference assessments were implemented in Study 1 to determine the enrichment preferences of African lions (N = 3). Following Study 1, Study 2 was conducted, which examined the behavior of African lions with enrichment items over the course of 30, 24-hr trials to evaluate the relationship between preferences established in Study 1 and long-term interaction with the enrichment. Generalized estimating equations revealed a statistically significant relationship between the percentage of time the enrichment was approached first and the average duration of interaction in Study 1 to the total duration of interaction and the percent of hours interacted with the item in Study 2. Additionally, the first 2 min of the preference data resulted in comparable statistically significant findings, demonstrating shorter preference assessments can produce similar results. The results support our prediction that preference assessments can be used to estimate the amount of interaction with enrichment over the course of time, with preferred items being interacted with more frequently and in longer duration. Information gained from this study suggests preference assessments can be a time and cost-effective tool to evaluate enrichment preference and predicted efficacy.

Training rhesus macaques to take daily oral antiretroviral therapy for preclinical evaluation of HIV prevention and treatment strategies

Background

Macaque models of simian or simian/human immunodeficiency virus (SIV or SHIV) infection are critical for the evaluation of antiretroviral (ARV)-based HIV treatment and prevention strategies. However, modelling human oral ARV administration is logistically challenging and fraught by limited adherence. Here, we developed a protocol for administering daily oral doses of ARVs to macaques with a high rate of compliance.

Methods

Parameters of positive reinforcement training (PRT), behavioral responses and optimal drug delivery foods were defined in 7 male rhesus macaques (Macaca mulatta). Animals were trained to sit in a specified cage location prior to receiving ARVs, emtricitabine (FTC) and tenofovir alafenamide (TAF), in a blended food mixture, which was followed immediately with a juice chaser. Consistency of daily oral adherence was evaluated in 4 trained macaques receiving clinically equivalent doses of FTC and TAF (20 and 1.5 mg/kg, respectively) in a short-term (1 month) and an extended (6 month) trial. Adherence was monitored using medication diaries and by quantifying intracellular FTC-triphosphate (FTC-TP) and tenofovir-diphosphate (TFV-DP) concentrations in peripheral mononuclear blood cells (PBMCs).

Results

Trained macaques quickly and consistently took daily oral ARVs for 1 month with an average 99.8% observed adherence. Intracellular concentrations of TFV-DP (median = 845.8 fmol/million cells [range, 620.8–1031.3]) and FTC-TP (median = 367.0 fmol/million cells [range, 289.5–413.5) in PBMCs were consistent with high adherence. Extended treatment with select subjects yielded similar observations for three months (99.5% adherence, 352/356 complete doses taken), although a sudden drop in adherence was observed after splenic biopsy surgery.

Conclusions

We demonstrate that trained macaques reliably adhere to a daily oral ARV regimen, although unexpected adherence issues are possible. Our approach, using clinical doses of oral FTC and TAF daily, further refines macaque models of HIV treatment and prevention by mimicking the human route and timing of ARV administration.

Effective chair training methods for neuroscience research involving rhesus macaques (Macaca mulatta)

BACKGROUND

Neuroscience research using macaques remains fundamental in our endeavours to understand how the human brain functions. Applying the refinement principle of the 3Rs is essential to optimise the monkeys' welfare and still produces high quality science.

NEW METHOD

Here we document refinements in our training methods for acclimation to transport devices (i.e. primate chair or transport box) while working with 46 male rhesus macaques. Our training methods always used positive reinforcement training (PRT). However, PRT was sometimes combined with negative reinforcement training (NRT), but not pole and collar techniques, to successfully transfer each monkey from its home enclosure to its transport device.

RESULTS AND COMPARISON WITH EXISTING METHODS

Training monkeys in pairs or groups, and starting their PRT training upon arrival within the unit reduced the days required to acclimate them. While the use of PRT is essential to establish a positive relationship with monkeys, NRT techniques are sometimes necessary, and are most effective when withdrawn immediately once the monkey makes the desired response, to reduce the days of acclimation. Once acclimatised to their chair, monkeys succeeded within 10 days to present their head voluntarily for neck-plating using PRT. Space reducers inside the chairs also facilitated head presentations for some monkeys.

CONCLUSIONS

Acclimating (shaping) the monkeys to transport devices can be a stressful experience for monkeys and trainers. The adaptations to our training substantially reduced the days spent on this stage. We view this reduction in days as an effective implementation of the 3Rs (refinement) in monkey neuroscience research.