For management and/or research purposes, chimpanzee mothers and their offspring are often physically separated from one another at an earlier age than they would be in the wild. Studies of the behavioural and physiological effects of mother-infant separation on infant behaviour have been conducted in both human and nonhuman primates. However, few studies have been conducted to examine the response of the mother to separation from her infant, particularly in great apes. The current study opportunistically examined the response of twelve chimpanzee mothers to separation from 15 of their offspring ranging from 1.8 to 5.4 years of age. Behavioural data (proximity of the mother to other group members, and fifteen behaviours representing six categories [agonistic, prosocial, vocalisations, abnormal, locomotor, inactive]) were collected for three weeks prior to and three to five weeks following the permanent removal of the offspring from their mothers. A repeated measures MANOVA conducted on all subjects revealed no significant change in behaviour following separation. There was a significant increase in inactivity following separation of the offspring (F2.21 = 5.47, P < 0.05) in a subgroup of mothers (n = 8) that was studied more intensively on the first day of separation. Maternal age, infant age, presence of other offspring, and past experience with mother-offspring separation had no effect on response to separation. These results contradict those of mother-infant separation studies in monkeys and indicate that most behavioural indicators of well-being are stable in chimpanzee mothers that remain in their familiar environment and social group following offspring separation.

This study measured the amount of time 17 chimpanzee infants devoted to stereotyped body rocking in a variety of nursery settings. Nine females and eight males ranging in age from three weeks to four years were included in the study. Some infants were placed in a peer group at a very early age and were given minimal human contact, while others were provided with more frequent human interaction and were placed in peer groups at varying ages. During the course of the study, infants were housed with varying numbers of chimpanzee companions and some were also provided with a canine companion. Four hundred and thirty-three hours of data were collected. Infants showed a decline in rocking over age and rocked less in the presence of a canine companion. Infant gender, the amount of human contact received at an early age, the age placed with at least one peer companion, and the current number of chimpanzee companions did not affect the time devoted to body rocking. These findings demonstrate that animal managers should look beyond conspecific stimulation for improving the social environment and overall welfare of chimpanzees. These results are further discussed in a framework of identifying possible strategies for minimizing rocking and promoting future behavioural competence in nursery-reared infants.

Captive primates rarely have to spend as much time searching for, obtaining and processing food as do their wild counterparts. Enrichment techniques designed to encourage captive primates to spend more species-appropriate amounts of time in foraging behaviours have been successful. The present study measured the behavioural effects of four feeding enhancements: two devices (mats and puzzles) and two foods (produce and frozen juice), on four cohorts (n = 63) of single-caged, yearling rhesus macaques (Macaca mulatta). Devices required considerable manipulation to retrieve rewards, whereas enrichment foods required additional processing. Analyses compared periods when one of the enhancements was available to interim periods when no enhancements were available. Planned comparisons revealed that subjects spent more time feeding, and less time inactive, self-grooming, exploring and behaving socially when feeding enrichment was available. Significantly more time was spent feeding when enrichment foods were provided, but more time was spent playing and using enrichment when devices were in the cage. More time was spent self-grooming and exploring with the acrylic puzzle than with the artificial turf mat. Subjects spent significantly more time feeding when produce was available than when frozen juice was available. Feeding enhancements resulted in more species-typical patterns of activity for single-caged, yearling rhesus. Since feeding devices were used in species-typical activities in addition to feeding, devices may be more valuable than foods. Feeding enrichment programmes which combine stimulating devices with foods that are novel and require processing can positively affect the behaviour of captive primates.

Chimpanzees are sometimes housed in conditions of restricted social contact during use in biomedical research, a practice that may adversely affect their behaviour. This study measured the impact of such conditions on levels of stereotyped body rocking in six young, nursery-reared chimpanzees. Subject age at the beginning of the biomedical research protocol ranged from 1.1 to 3.8 years. Over a six-month period the subjects were moved to a different facility. During this time they were used in a biomedical research study which involved some periods of single housing. They were then returned to their original facility. The percentage of time subjects devoted to stereotyped rocking was measured for 36 weeks before and 36 weeks after participation in the biomedical protocol. Data on body rocking were also analysed for a post-test control group of animals (n = 9) who had a similar history of handrearing, but who did not leave the facility to participate in a biomedical research study. The behavioural analyses included 263 hours of focal animal observational data and revealed that the experimental subjects devoted equivalent amounts of time to rocking before and after participation in the biomedical research protocol. The experimental subjects and the control subjects showed similar levels of rocking. These findings indicate that participation in this particular short-term biomedical research protocol did not affect the expression of stereotyped rocking in chimpanzees.

In the wild, chimpanzees spend most of their time foraging, so any device that stimulates this behaviour in captivity could potentially be effective enrichment. A simple grass foraging device constructed of a polyvinyl chloride (PVC) pipe cut in half lengthwise and planted with rye grass seed was designed to allow captive chimpanzees living in non-grassy enclosures to exhibit foraging similar to that of their wild counterparts. The grass containers were attached to the outside of six different enclosures. Observational data were collected on 14 adult chimpanzees (eight females, six males) within groups of either two or four members. A total of 54 hours of behavioural observations were conducted and comparisons were made across three conditions: baseline; grass container; grass container with extra foraging material (one half cup of sunflower seeds). Subjects used the grass container for 4.0 per cent of their time, but for 19.8 per cent of their time when the grass container with extra foraging material There was no statistical evidence of habituation to the device. Overall, the grass container only increased time spent foraging when it contained additional food items. Since behavioral benefits associated with this device are few, its potential application is limited.

Enrichment of the environments of captive primates is currently of interest as both a basic and an applied research question, particularly when social and inanimate enhancements are used simultaneously. We measured the behavioural effects of two intensities of inanimate enrichment on 12 unimale-multifemale groups and 12 all-male groups from three cohorts of three to four-year-old rhesus macaques (Macaca mulatta). Half of the groups received a simple, inexpensive enrichment programme while the other groups received a more complex and costly combination of physical andfeeding enhancements. Observations were conducted on 93 subadults of both sexes during their initial year of group housing. Intensity of enrichment did not differentially affect the amount of time subjects spent in any of the activities analysed. Subjects that received the more complex programme spent only 8.3 per cent of their time using the extra enhancements. Therefore, there was little demonstrated benefit of the more costly enrichment programme. The three cohorts differed in the amount of time that they spent inactive, behaving agonistically, playing and located near a group mate. A planned comparison of one cohort that had been single-housed without visual access to social groups, to the two cohorts that had visual access to social groups during single caging, revealed differences in play and socially-located behaviour, which may have been due to differences in extra-cage conditions two years prior to the present study. When primates are housed socially with conspecifics as ‘social enhancements ‘, the relatively simple inanimate enrichment programme we used was as effective as the more costly programme. When enrichment resources are limited, inanimate enrichment efforts should be focused on monkeys that are not socially enriched.

This study compared the effectiveness of kraft wrapping paper and rubber toys as enrichment for 22 chimpanzees group-housed in conventional indoor/outdoor runs. Objects were tested separately during 67 hours of data collection using a group scan sampling technique. Paper was used a mean 27 per cent of the available time, while the Kong Toys™ were used a mean 10 per cent of the available time. The degree of object manipulation and object contact was higher with the paper, but the level of social play and solitary play with the object was not differentially affected by the two objects. The objects had differing effects on the subjects’ levels of grooming, but affiliation, agonism, inactivity and sexual behaviour did not vary according to the object being used. A gender-by-age interaction was found, with immature males exhibiting the highest levels of solitary play with objects. Object use steadily declined over the first hour of exposure, showing evidence of habituation. Object use when the Kong Toy™ was present declined over the course of the study, but use of the paper remained consistent. Texture, destructibility, portability, complexity and adaptability may be important in determining the object's value as effective enrichment. The destructible wrapping paper was a more worthwhile enrichment object than the indestructible Kong Toy™ for the captive chimpanzees in this study.

It has been suggested that housing of laboratory primates in two-tiered racks adversely affects the psychological well-being of those primates housed on the lower row. Excessive darkness and its consequences are among the factors suggested to account for the supposed diminished well-being of lower-row inhabitants. Additionally, two-tiered housing has been suggested to introduce unacceptable variation into experimental designs, potentially necessitating additional subjects and/or invalidating results. Only recently have data been published to address these issues, but all studies have involved small numbers of subjects. In the present study, we compared the behaviour of 45 yearling rhesus macaques (Macaca mulatta) housed in upper-row cages with the behaviour of 48 yearling rhesus macaques housed in lower-row cages during a year of single housing. There were no significant differences across cage locations for time spent performing behaviours indicative of diminished psychological well-being (abnormal behaviour, inactivity, vocalisation, self-directed grooming) or for species-typical activities (feeding, playing). The difference in time spent exploring between macaques housed on the lower row and those housed on the upper row approached significance, with lower-row-housed animals spending more time exploring. Although lower-row cages are significantly darker than upper-row cages at our facility, the data from the present study demonstrate that the diminished lighting and other supposed disadvantages experienced by lower-row-housed monkeys have few behavioural consequences. Thus, there are now additional empirical data that suggest that lower-row-housed monkeys are not suffering in a “monkey cave”, and that the findings of research projects using two-tiered housing systems are unlikely to be compromised.

Positive reinforcement training is one component of behavioural management employed to improve psychological well-being. There has been regulatory promotion to compensate for restricted social housing in part by providing human interaction to singly caged primates, implying an efficacy standard for evaluating human interaction. The effect of positive reinforcement training on the behaviour of 61 singly housed laboratory rhesus macaques (Macaca mulatta) was evaluated at two large primate facilities. Training involved body part presentation and basic control behaviours. Baseline data were compared to two treatment phases presented in varying order across individuals, six minutes per week of positive reinforcement training and six minutes per week of unstructured human interaction. While a MANOVA involving behavioural categories and study conditions across study subjects was significant, univariate ANOVAs found no effect of phase within any behavioural category. Categorising subjects according to rearing, housing facility, or baseline levels of abnormal behaviour did not reveal changes in behaviour with positive reinforcement training or human interaction. This study failed to detect, to any degree, the types of behavioural changes documented in the scientific literature to result from pairing singly housed monkeys. Implementing short durations of positive reinforcement training across large numbers of singly housed animals may not be the most effective manner for incorporating positive reinforcement training in the behavioural management of laboratory macaques. Rather, directing efforts toward individuals with specific behavioural, management, clinical, research or therapeutic needs may represent a more fruitful approach to improving psychological well-being with this technique.