Destructible toys as enrichment for captive chimpanzees

The use of destructible objects or toys as enrichment for nonhuman primates has had promising results in terms of increased use and positive behavioral effect. The purpose of this project was to determine the use and durability of a number of inexpensive, destructible toys provided one at a time or several at once. Nine singly caged chimpanzees were provided with 8 different toys made of plastic, vinyl, or cloth, and the frequency of use of the toys was determined during 15 min trials 2 times per day. A toy was removed when it was destroyed or when it was not contacted during 4 trials. The chimpanzees contacted the toys an average of 11 times per trial, and the use of the individual toys was significantly higher when provided 1 at a time rather than all at once. Use of the toys was fairly stable over time, and the toys remained in the cages an average of 3.2 days. The durability of the toys was related to the type of toy (e.g., more flexible cloth and vinyl toys lasted longer than rigid plastic toys). The destructible toys were used significantly more often than other permanent cage toys or televisions. Toy use was not related to age, level of abnormal behavior, or use of existing permanent toys or television. The implications of the results were related to the management of an environmental enrichment program and indicated that the provision of flexible, inexpensive toys 1 at a time can be an effective method of enrichment for captive chimpanzees.     

Controllability in environmental enrichment for captive chimpanzees (Pan troglodytes)

This study considers the use of nonsocial environmental enrichment by captive chimpanzees at the Primate Foundation of Arizona. The goal was to determine whether a relationship existed between controllability of enrichment items by captive chimpanzees and frequency of use. The study measured controllability, the ability of nonhuman animals to alter aspects of their environment by the potential destructibility of the enrichment item. This study examined additional factors that may affect enrichment use: individual age, sex, rearing history, social group composition, and availability of outdoor access. The chimpanzees in the study used destructible items—the enrichment category with the highest level of controllability—more than indestructible items across all age, sex, and rearing classes. Thus, controllability seems to be an important factor in chimpanzee enrichment. Younger individuals and groups with outdoor access used enrichment more than did older individuals and groups with indoor-only access. Individual sex, rearing history, and social group composition had minimal effects on enrichment use. These results support the importance of control to captive chimpanzees and further enable captive management to customize enrichment programs to the needs of particular animals.     

Effects of inedible, manipulable objects on captive bears

Bears in captivity often show abnormal behaviors such as stereotypies and periods of excessive inactivity. Most of the research aimed at reducing abnormal behaviors in bears has focused on feeding enrichment. However, the effects of feeding enrichment only seem to last as long as it takes a bear to consume the food. This study investigated the effects of inedible, manipulable objects on bears. Two polar bears (Ursus maritimus) received plastic floats. A sloth bear (Melursus ursinus) and a spectacled bear (Treniarctos ornatus) received plastic balls. During a 7-week period, polar bears nearly doubled their activity in the presence of toy floats, and the spectacled bear halved its pacing in the presence of toys. The sloth bear did not respond to the objects. These findings indicate that access to manipulable nonfood objects such as plastic toys can result in prolonged engagement in appetitive behaviors by polar bears.     

Environmental enrichment of brown capuchins (Cebus apella): Behavioral and plasma and fecal cortisol measures of effectiveness

No consensus exists about the quantity and variety of environmental enrichment needed to achieve an acceptable level of psychological well‐being among singly housed primates. Behavioral and plasma and fecal cortisol measures were used to evaluate the effectiveness of four levels of toy and foraging enrichment provided to eight wild‐caught, singly housed adult male brown capuchins (Cebus apella). The 16‐week‐long study comprised six conditions and began with a 4‐week‐long preexperimental and ended with a 4‐week‐long postexperimental period during which the subjects were maintained at baseline enrichment levels. During the intervening 8 weeks, the subjects were randomly assigned to a sequence of four 2‐week‐long experimental conditions: control (baseline conditions), toy (the addition of two plastic toys to each cage), box (access to a foraging box with food treats hidden within crushed alfalfa), and box & toy (the addition of two plastic toys and access to a foraging box). Behavioral responses to changes in enrichment were rapid and extensive. Within‐subject repeated‐measure ANOVAs with planned post hoc contrasts identified highly significant reductions in abnormal and undesirable behaviors (and increases in normal behaviors) as the level of enrichment increased from control to toy to box to box & toy. No significant behavioral differences were found between the control and pre‐ and postexperimental conditions. Plasma and fecal cortisol measures revealed a different response to changing enrichment levels. Repeated‐measure ANOVA models found significant changes in both these measures across the six conditions. The planned post hoc analyses, however, while finding dramatic increases in cortisol titers in both the pre‐ and postexperimental conditions relative to the control condition, did not distinguish cortisol responses among the four enrichment levels. Linear regressions among weekly group means in behavioral and cortisol measures (n = 16) found that plasma cortisol was significantly predicted by the proportions of both normal and abnormal behaviors; as the proportion of normal behaviors increased, the plasma cortisol measures decreased. Plasma cortisol weekly group means were also significantly and positively predicted by fecal cortisol weekly group means, but no behavioral measure significantly predicted fecal cortisol weekly group means. In sum, these findings argue strongly that access to a variety of toy and foraging enrichment positively affects behavioral and physiological responses to stress and enhances psychological well‐being in singly housed brown capuchins. Am. J. Primatol. 48:49–68, 1999. © 1999 Wiley‐Liss, Inc.     

Sex differences in rhesus monkey toy preferences parallel those of children

Sex differences in toy preferences in children are marked, with boys expressing stronger and more rigid toy preferences than girls, whose preferences are more flexible. Socialization processes, parents, or peers encouraging play with gender-specific toys are thought to be the primary force shaping sex differences in toy preference. A contrast in view is that toy preferences reflect biologically-determined preferences for specific activities facilitated by specific toys. Sex differences in juvenile activities, such as rough-and-tumble play, peer preferences, and infant interest, share similarities in humans and monkeys. Thus if activity preferences shape toy preferences, male and female monkeys may show toy preferences similar to those seen in boys and girls. We compared the interactions of 34 rhesus monkeys, living within a 135 monkey troop, with human wheeled toys and plush toys. Male monkeys, like boys, showed consistent and strong preferences for wheeled toys, while female monkeys, like girls, showed greater variability in preferences. Thus, the magnitude of preference for wheeled over plush toys differed significantly between males and females. The similarities to human findings demonstrate that such preferences can develop without explicit gendered socialization. We offer the hypothesis that toy preferences reflect hormonally influenced behavioral and cognitive biases which are sculpted by social processes into the sex differences seen in monkeys and humans.     

Infants' exploration of scented toys: effects of prior experiences

To evaluate breastfed infants' responses to scented objects, we videotaped the facial and bodily reactions of sixty-three infants as they explored, in succession, three toys that were identical in appearance but different in their characteristic odor. Two of the toys were scented with odorants previously shown to be transmitted to human milk, one with ethanol and the other with vanilla, whereas the third toy was unscented. Each videotape was subjected to frame-by-frame analysis to measure a variety of behaviors that are considered either to be exploratory in nature in that they lead to perceptual information about the object or to reflect the infants' hedonic reaction. Analyses of these behaviors revealed that the infants looked more and vocalized less in the presence of the vanilla-scented toy and spent less time manipulating the ethanol-scented toy when compared with the unscented toy. Moreover, differential exposure to the odors of ethanol and vanilla, as indicated by differential consumption of alcohol by a parent or use of vanilla-scented product by the mother, was related to differential responses to these odors. These findings suggest that human infants are able to detect and retain information about the chemical features of their environment.      

Primate puzzleboard: A simple environmental enrichment device for captive chimpanzees

An environmental enrichment device was designed and evaluated for captive chimpanzees. The puzzleboard consisted of a 61-cm, square piece of clear plastic with holes of various sizes drilled into the center. The puzzleboard was bolted to the roof of a chimpanzee enclosure. Flavored primate treats were arranged on top of the board, and the chimpanzee used a finger to manipulate the food across the board to be retrieved through the larger holes. The behavior and puzzle use of 29 chimpanzees housed in eight groups were evaluated while the device was empty and while filled with food. For each group, four 1-hr scan samples were recorded for each condition. Data showed that an average of 40 min elapsed from the time the puzzleboard was filled to the last recorded contact by a subject. Mean individual use ranged from 4.8 to 23.8 min/hr. Female chimpanzees used the puzzle significantly more often than did males. Aggressive, affiliative, inactive, and self-directed behaviors were significantly reduced when the puzzle was filled. In addition, the puzzleboard was inexpensive, sturdy, and easily constructed, mounted, and operated.     

Influence of different types of environmental enrichment on the behaviour of finishing pigs in two different housing systems: 3. Hanging toy versus rootable toy of the same material

This study aimed to assess the effects of (1) environmental enrichment with either straw bedding or a plastic toy and (2) the way in which the plastic toy was presented on the behaviour of finishing pigs in two different housing systems. One thousand and twenty four (Large White × Landrace) × Large White pigs were housed contemporarily in either a straw-based (ST) or fully slatted (FS) building from 35 kg to slaughter at 104 kg. In each building, half of the pens received additional environmental enrichment in the form of a hanging plastic toy. The remaining pens in the ST house were enriched only by the straw bedding. In the FS house, the remaining pens were provided with a rootable toy of the same plastic material presented on the floor of the pen. There was no significant effect of housing system on the level of manipulation of the hanging toy. Within the FS system, the level of manipulation of the hanging toy tended to be higher than that of the plastic toy presented on the floor (P = 0.052). Neither form of additional environmental enrichment provided a comparable level of occupation to that of straw bedding. In the absence of straw, more investigatory behaviours were directed towards both pen-mates (P < 0.001) and pen components (P < 0.001). Further study is required to identify functional forms of environmental enrichment in slatted systems to occupy pigs and prevent them from performing adverse behaviours.     

Cage Toys Reduce Abnormal Behavior in Individually Housed Pigtail Macaques

As part of a behavioral intervention program that identifies and treats individual nonhuman primates exhibiting abnormal behavior, five individually housed pigtail macaques (Macaca nemestrina) were provided with multiple cage toys in an effort to reduce high levels of abnormal behavior. Ten 30-min observations of each subject were conducted during the baseline condition and again after novel toys were presented, both loose inside the cage and attached to the outside of the cage. The new toys were used during 27% of the observation time. Kong Toys were used most consistently by the macaques during the 5-week observation period. Significant decreases in abnormal behavior and cage-directed behavior, as well as significantly increased enrichment use, were evident after the toys were added. Several of the toys were destroyed quickly, and individual differences were evident in the levels of enrichment use and abnormal behavior. Providing multiple manipulable toys as enrichment for pigtail macaques was effective in reducing abnormal behavior and was an important part of an environmental enrichment program for monkeys who could not be housed socially.     

Cage toys reduce abnormal behavior in individually housed pigtail macaques

As part of a behavioral intervention program that identifies and treats individual nonhuman primates exhibiting abnormal behavior, five individually housed pigtail macaques (Macaca nemestrina) were provided with multiple cage toys in an effort to reduce high levels of abnormal behavior. Ten 30-min observations of each subject were conducted during the baseline condition and again after novel toys were presented, both loose inside the cage and attached to the outside of the cage. The new toys were used during 27% of the observation time. Kong Toys were used most consistently by the macaques during the 5-week observation period. Significant decreases in abnormal behavior and cage-directed behavior, as well as significantly increased enrichment use, were evident after the toys were added. Several of the toys were destroyed quickly, and individual differences were evident in the levels of enrichment use and abnormal behavior. Providing multiple manipulable toys as enrichment for pigtail macaques was effective in reducing abnormal behavior and was an important part of an environmental enrichment program for monkeys who could not be housed socially.     

Rigid plastic balls as enrichment devices for captive chimpanzees

The use of rigid, plastic balls as enrichment devices for 16 captive chimpanzees was studied at The University of Texas M.D. Anderson Cancer Center chimpanzee colony. After the subjects were presented with balls, 10 hours of data were collected for each subject using a scan-sampling technique. The mean percentage of ball-use time for all subjects during the study was 7.1%. There was no sex difference in ball use. Age and housing effects were obtained, with younger animals and those housed in more barren environments exhibiting higher levels of ball use. It is concluded that the balls were worthwhile additions to the chimpanzee environments with use stabilizing at a mean of 2.5% of the subjects' time.     

An investigation into the effectiveness of compressed straw blocks in reducing abnormal behaviour in growing pigs

The provision of manipulable material to pigs is a legal requirement to ensure their good welfare. Loose straw is edible, chewable, investigable and manipulable, and has been proven to be effective in reducing abnormal behaviour. However, it is incompatible with slatted systems and therefore not a viable option for many intensive units. Thus, there is a need to identify enrichment materials that are as effective as loose straw and compatible with slatted floors. This study investigated the viability of using compressed straw blocks on a commercial farm in terms of cost and effectiveness in reducing biting relative to plastic hanging toys. A total of 880 slaughter pigs were used, among which half (n = 440, 8 groups) were provided with commercial pig toys (TOY) and the other half (n = 440, 8 groups) were provided compressed straw blocks (STRAW BLOCK). Animals were separated according to sex to investigate whether there was a higher propensity to tail and ear bite depending on sex. Pigs were monitored from weaning to slaughter, with tails being examined post scalding and any condemnations recorded at the abattoir. Throughout their life, the tails and ears of all pigs were examined individually, and behavioural observations of each pig group were conducted fortnightly. Salivary cortisol was also obtained from a subsample of pigs from each group every fortnight to monitor stress levels. The highest straw usage was recorded in the second weaner stage (39 to 67 days after weaning). Enrichment type or sex had no effect on tail lesion scores or cold carcass weight recorded at the abattoir. There was also no effect of enrichment type or sex on body, tail, or ear lesion scores during either the weaner (0 to 39 days after weaning) or finisher stage (67 to145 days after weaning). Female pigs showed more biting behaviour than males, and female pigs that were provided STRAW BLOCK performed better than those provided TOY. In both the weaner and finisher accommodation, more instances of interaction were recorded with TOY pens as enrichment than with STRAW BLOCK, but the interaction duration was not recorded. There was no effect of sex on either stage. More instances of aggression were observed with the TOY than with STRAW BLOCK in the weaner stage (P < 0.05). Enrichment type or sex had no effect on cortisol levels. Thus, relative to plastic hanging toys, compressed straw blocks provided in this manner did not benefit pig welfare.     

Chimpanzees use self-distraction to cope with impulsivity

It is unknown whether animals, like humans, can employ behavioural strategies to cope with impulsivity. To examine this question, we tested whether chimpanzees (Pan troglodytes) would use self-distraction as a coping strategy in a situation in which they had to continually inhibit responses to accumulating candies in order to earn a greater amount of those rewards. We tested animals in three conditions in which they were sometimes given a set of toys and were sometimes allowed physical access to the accumulating candies. Chimpanzees allowed the rewards to accumulate longer before responding when they could divert their attention to the toys, and they manipulated the toys more when the candies were physically accessible. Thus, chimpanzees engaged in self-distraction with the toys when such behaviour was most beneficial as a coping mechanism.     

Environmental enrichment for nonhuman primates: theory and application

Investigators have an obligation to promote the psychological well-being of nonhuman primates used in research. Considerable emphasis has been placed on providing nonhuman primates with enriched environments as a means to achieve this objective. A framework is provided that consists of a set of hypotheses about well-being, and the extent to which exposure to various enrichment devices and procedures actually promotes well-being is evaluated. Two hypotheses are concerned with fostering species-typical behavior: use (versus nonuse) of the enrichment, and whether use of enrichment helps normalize other aspects of the behavioral repertoire. Two additional hypotheses are concerned with abnormal behavior: whether currently existing enrichment lowers levels of abnormal behavior, and whether it prevents the behavior. This framework is applied to various enrichment strategies ranging from toys and foraging devices to social interaction. Most devices are used by nonhuman primates and thus constitute an important way to enrich the captive environment. However, enrichment devices vary as to their effectiveness in normalizing the behavioral repertoire and eliminating abnormal behavior. Only social contact satisfies the goal of promoting a wide variety of species-typical activities while at the same time reducing or preventing the development of abnormal behavior.     

Assessing the effects of cognitive experiments on the welfare of captive chimpanzees (Pan troglodytes) by direct comparison of activity budget between wild and captive chimpanzees

We investigated the effects of cognitive experiments by direct comparison of activity budgets between wild and captive chimpanzees. One goal of captive management is to ensure that the activity budgets of captive animals are as similar as possible to those of their wild counterparts. However, such similarity has rarely been achieved. We compared the activity budget among three groups of chimpanzees: wild chimpanzees in Bossou (Guinea, n = 10), and captive chimpanzees who participated in cognitive experiments (experimental chimpanzees, n = 6) or did not participate in the experiments (nonexperimental chimpanzees, n = 6) at the Primate Research Institute (Japan). The experimental chimpanzees voluntarily participated in computer‐controlled cognitive tasks and small pieces of fruits were provided as rewards. The data from captivity were obtained on the experimental days (weekdays) and nonexperimental days (weekends). In both study sites, we followed each chimpanzee from about 7 a.m. until the time when chimpanzees started to rest in the evening. The behaviors were recorded every 1 min. The results showed that on weekdays, feeding time and resting time of the experimental chimpanzees were almost the same as those of wild chimpanzees. However, for the nonexperimental chimpanzees, feeding time was significantly shorter and resting time was longer than those of the wild chimpanzees. In contrast, no difference was found in feeding time or resting time of the two groups of captive chimpanzees on weekends. The results suggested that the cognitive experiments worked as an efficient method for food‐based enrichment. Am. J. Primatol. 73:1231–1238, 2011. © 2011 Wiley Periodicals, Inc.     

Sex differences in response to children's toys in nonhuman primates (Cercopithecus aethiops sabaeus)

Sex differences in children's toy preferences are thought by many to arise from gender socialization. However, evidence from patients with endocrine disorders suggests that biological factors during early development (e.g., levels of androgens) are influential. In this study, we found that vervet monkeys (Cercopithecus aethiops sabaeus) show sex differences in toy preferences similar to those documented previously in children. The percent of contact time with toys typically preferred by boys (a car and a ball) was greater in male vervets (n=33) than in female vervets (n=30) (P<.05), whereas the percent of contact time with toys typically preferred by girls (a doll and a pot) was greater in female vervets than in male vervets (P<.01). In contrast, contact time with toys preferred equally by boys and girls (a picture book and a stuffed dog) was comparable in male and female vervets. The results suggest that sexually differentiated object preferences arose early in human evolution, prior to the emergence of a distinct hominid lineage. This implies that sexually dimorphic preferences for features (e.g., color, shape, movement) may have evolved from differential selection pressures based on the different behavioral roles of males and females, and that evolved object feature preferences may contribute to present day sexually dimorphic toy preferences in children.     

Shade as a thermoregulatory resource for captive chimpanzees

In nature, the thermoregulatory strategies of species have evolved in response to the environmental conditions in which they live. Primates display extensive behavioural flexibility but few have examined the role of this behavioural flexibility with regard to thermoregulation. Chimpanzees, under free-living conditions, utilise natural vertical light/thermal gradients in rainforest canopies as a means of thermoregulation, moving along the gradient to maintain homoeostasis. In contrast, captive chimpanzees are often housed at latitudes outside their natural range under conditions that do not allow for this natural behavioural thermoregulation. We investigated the use of shade by captive chimpanzees as a behavioural thermoregulatory strategy at the Johannesburg Zoo, South Africa. We performed behavioural observations over the austral winter/spring period on a group of captive chimpanzees recording their behaviour in relation to shade use. Despite experiencing temperatures in Johannesburg below or just within their thermoneutral zone, chimpanzees consistently spent more time in shade than in direct sun. This pattern of shade use was most pronounced for the hotter midday period than for other times, was not dependent on the overall availability of shade within the enclosure and was not predicted by mean daily or hourly temperatures nor thermal maxima or minima. Instead, ultraviolet radiation and humidity levels appear to predict the observed patterns of shade utilisation and these findings suggest that chimpanzees in captivity adopt a sun-avoidance strategy, possibly as a result of the rapid heat gain associated with their dark skin and pelage. The findings suggest that chimpanzees are flexible when responding to the thermal challenges associated with housing outside of their natural environment.     

Assessing the effectiveness of environmental enrichment in bottlenose dolphins (Tursiops truncatus)

Environmental enrichment is often used to improve well-being and reduce stereotyped behaviors in animals under human care. However, the use of objects to enrich animal environments should not be considered to be effective until its success has been scientifically demonstrated. This study was conducted at Asterix Park in France in April 2009. The study investigated the use of 21 familiar objects with a group of six bottlenose dolphins (Tursiops truncatus). The dolphin trainers introduced four different objects into the dolphin pool every day on a rotating basis. Using a focal-object sampling method, we collected and analyzed data from twenty-one 15 min sessions. The results revealed a positive correlation between interest behaviors and interactive behaviors. Some dolphins had "favorite toys". However, only 50% of objects elicited manipulative behaviors. These findings demonstrate that dolphins do not treat all objects provided to them as "toys". Behavioral changes in the animals subsequent to the introduction of objects do not necessarily indicate an enrichment effect of the objects; rather, the motivation for the dolphins' behaviors toward the objects must be investigated. The animals' behavior must be considered in light of the social context and of the animals' individual behavioral profiles. The relevance of a constructivist approach to evaluating the effectiveness of enrichment programs is discussed.     

Long-term use of televisions,balls, and mirrors as enrichment for paired and singly caged chimpanzees

The evaluation of environmental enrichment techniques for nonhuman primates over long periods of time has had mixed results. Some studies report rapid habituation to new enrichment items, while others note continued use. We have investigated the use of three different enrichments that had been available to paired and singly caged chimpanzees for several years. Twenty subjects were observed during 200 hr of scan sampling while singly caged and while pair housed. Each subject had a variety of enrichments available and their use of a television, ball, and mirror were recorded. The chimpanzees had previous exposure to all of the items: televisions had been available for a mean of 22.75 months, balls had been available for 55.9 months, and mirrors had been available for 25.9 months. The results indicated that the chimpanzees continued to use the enrichments for small amounts of time (0.27%–1.53% of the observations) even after such prolonged exposure. Television and ball use were significantly higher than mirror use. Housing condition was not a significant factor in the analyses, contrary to expectations. We concluded that several simple enrichment items may be effective in offering variety and choices to the nonhuman primate and can be one element in a comprehensive environmental enhancement plan. © 1996 Wiley-Liss, Inc.