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Effects of Selected BehavioralEnrichment Devices onBehavior of Western LowlandGorillas (Gorilla gorilla gorilla)Matthew B. Rooney & Jonathan SleemanPublished online: 04 Jun 2010.

To cite this article: Matthew B. Rooney & Jonathan Sleeman (1998) Effects ofSelected Behavioral Enrichment Devices on Behavior of Western Lowland Gorillas(Gorilla gorilla gorilla), Journal of Applied Animal Welfare Science, 1:4, 339-351, DOI:10.1207/s15327604jaws0104_2

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JOURNAL OF APPLIED ANIMAL WELFARE SCIENCE, I(4), 339-351 Copyright O 1998, Lawrence Erlbaum Associates, Inc.

Effects of Selected Behavioral Enrichment Devices on Behavior of

Western Lowland Gorillas (Gorilla gorilla gorilla)

Matthew B. Rooney and Jonathan Sleeman Colorado State University College of Veterinary Medicine

and Biomedical Sciences

Environmental complexity plays an integral role in the activity and psychological well-being of primates. The experiment described in this article evaluates the effects of nonintrusive, inexpensive, and easily managed behavioral enrichment devices on the behavior of a group of captive Western lowland gorillas. Devices used included cardboard boxes containing food items, paper bags containing food items, burlap rags, and willow and maple browse. The enrichment devices increased foraging, social play, and solitary play behaviors. Sedentary behaviors decreased. Rags, bags, browse, and boxes did not statistically decrease the incidence of regurgitationlreingestation or coprophagy. Depending on the type of enrichment item used, the effects on agonism and manipulation of enrichment item were variable. To make informed management decisions about the psychological well-being of captive animals, it is important to objectively quantify and examine the influences on their behavior.

It is widely accepted that an impoverished captive environment results in different behaviors from those observed in the wild. Certain behavioral enrichments may decrease the incidence of abnormal captive-specific behaviors and promote wild- specific ones (Brent, Lee, & Eichberg, 1989; Bryant, Rupniak, & Iverson, 1988; Clarke, Juno, & Maple, 1982; Erwin & Deni, 1979; Maple, 1979; Maple & Finlay, 1989; Wilson, 1982). It is imperative to provide for the highest quality psychologi-

Requests for reprints should be sent to Matthew B. Rooney, Department of Clinical Sciences, Colorado State University College of Veterinary Medicine and Biomedical Sciences, Veterinary Teaching Hospital, 300 West Drake Road, Fort Collins, CO 80526.

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340 ROONEY AND SLEEMAN

cal enrichment for captive primates. To determine the quality of an enrichment, quantitative analysis should be undertaken.

The purpose of this research was to evaluate manipulable and feeding enrich- ments and to quantify their influences on abnormal and species-specific behaviors. Enrichment devices must be related to the natural behavior of the species (Line, 1987; Wilson, 1982). Having a variety of objects rotated would seem to minimize the effects of boredom as described by Paquette and Prescott (1988), promote different behaviors, accommodate for individual preferences, and provide variabil- ity within the environment.

The four enrichment devices chosen (see Table 1) were easy to maintain and incorporate into the keepers' routines. Estimated preparation time for each device was 10 min per day with an additional 5 min required to remove the devices and clean the exhibit.

Although prior to the study there was a structural, manipulable, and feeding enrichment repertoire, a number of gorillas continued to engage in coprophagy, regurgitationlreingestation (FUR), and aggressive behaviors. Gold (1993) described the structural enrichment of ropes, multilevel platforms, and steel climbing trees. For the past 10 years, various manipulable and feeding enrichments have been attempted. However, there is no known recorded history or formal study of enrichments used.

The enrichment items were analyzed across age groupings of subadults (younger than 10 years) and adults (older than 10 years) in order to evaluate the effects of enrichment on different age groups. Furthermore, enrichments were analyzed

TABLE 1 The Six Behavioral Enrichment Conditions Evaluated in This Study

STRAW (control) Approximately 8 in. of straw, bedding uniformly covered the floor of the enclosure. Three bales of straw and one bale of timothy hay (Phleum pratense) were used.

BOXES Cardboard boxes of varying sizes (without staples) containing food items were offered. There were twice as many bags as individuals to prevent hoarding and aggression. Straw bedding as per instructions in contro! was also provided (see control).

BAGS Brown paper bags containing food items and powdered milk were offered. Sizes ranged from grocegr bags to lunch bags. There were twice as many bags as individuals tc prevent hoarding and aggression. Straw bedding as per instructions was also provided (see control).

RAGS Burlap rags cut intc approximately 1 square meter sizes were offered. Straw bedding as per instructions was also provided (see control).

BROWSE Willow and maple cut by the zoo staff into lengths ranging from 0.25 to 1 meter were provided. No straw bedding was provided. The browse was less than I-week-old and was refrigerated and kept in water for storage.

BROWSE/STRAM1 Willow and mapie were cut and provided as in the BROWSE. Straw bedding was provided as well (see control).

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analyzed across mornings and afternoons so that the duration of enrichment effects within a day could be evaluated. The aim of the study was to increase feeding, play, and social behaviors, while decreasing sedentary, abnormal, and agonistic behaviors (see Table 2). Ultimately, the results could then be used to make informed management decisions regarding environmental enrichment for captive gorillas.

METHOD

Chicago's Lincoln Park Zoological Gardens housed together four male and five female Western lowland gorillas in the Great Ape House. Estimated ages of the gorillas were 4,7, 10, 11, 14,23,26,31, and 36 years. One was human-reared and eight were mother-reared. One was mother-reared in the wild until 1 year old and then human-reared. During the course of the study, all apes were cared for under the normal routine of the zookeepers, The gorillas were fed a light meal of fruits and vegetables at 9:30 a.m. and their main meal at 3:00 p.m. There was a milk feeding at noon for management purposes.

The animals were housed in a room 60 m2 x 12 m high. Furniture present within the enclosure included two steel trees extending from floor to ceiling, extensive ropes, perches, and platforms as described in Gold (1993). An off-exhibit holding facility was always accessible to the group.

TABLE 2 Ethogram of Gorilla Behaviors

Behavior Definition

Abnormal Regqitatiodreingestation or coprophagy. Agonism Bite, hit, chase, rush, slap ground. throw object, or sway. Canylhold food Animal is handling food item or carrying it while iocomoting. Carryhold object Self-explanatory. Not playing with object. Feeding Animal is foraging, processing, or ingesting food or water. Locomote Animal is moving in location without handling anything and without

social interaction. Manipulate object Tactile exploration of object. Masturbate Manipulating genitals by self or ~ b b i n g of same with inanimate object. Proximity Within one arm length of another. Sedentary Lie, sit, or stand for 10 sec or more. No other behavior. Self-directed Grooming, licking, scratching, or visually inspecting self. Sex Inspection of genitals or mounting. Social contact In physical contact without agonism. Social play Within one arm ieugth or in contact with another in a playful manner. Solitary play Animal is moving body in a playful manner without interacting with

others. Also includes playing with object.

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Procedure

The group of gorillas was observed under six experimental conditions (see Table 1): (a) baseline conditions with straw bedding uniformly covering the floor approxi- mately 8 cm deep for 5 days (STRAW), (b) bags containing food items and straw bedding (BAGS), (c) boxes containing food items and straw bedding (BOXES), (d) browse and straw bedding (BROWSEISTRAW), (e) browse without straw bedding (BROWSE), and (f) rags and straw bedding (RAGS). The furniture, climbing trees, and ropes were permanent and present in all conditions. The enrichment was provided daily prior to the animals' release into the exhibit at approximately 10:OO a.m., and evaluation continued for 4 hr.

Data Collection

Data were collected 5 days a week for a total of 6 weeks, and enrichments were still provided on weekends. Each individual was observed at random times between 10:00 a.m. and 2:00 p.m. A 1:O sampling method was used with 15-sec intervals for 5-min durations per individual (Altman, 1974; Leger, 1977). Using the ethogram in Table 2, a data collection sheet was used to note the occurrence of behaviors during each 15-sec interval.

With 15-sec intervals, there were 20 recordings per behavior within the 5-min duration that were summed and entered as one entry for each behavior (univariate F test was considered significant if p < .05).

RESULTS

A total of 56.9 hr of data collection occurred with 683 (5-min) intervals. The data were compared with all individuals' data compiled together, yielding any general behavioral changes in the group (see Figure 1). Forage, agonism, manipulation of object, sedentary, and self-directed behaviors had statistically significant (p c .05) differences in mean behavioral scores between the five conditions when compared to the straw baseline (see Figure 2). Data were analyzed by dividing the gorillas into subadults (younger than 10 years of age) and adults (older than 10 years of age). The analysis between age groupings and experimental conditions revealed that solitary play behavior had statistical significance (p > .05).

The data were analyzed from 10:OO a.m. until noon, from noon until 2:00 p.m., and between experimental conditions. Four behaviors were statistically significant (p < .05): foraging, solitary play, social play, and sedentary (see Figures 3-6). Of the other behaviors analyzed, agonism indicated a trend (p = .060).

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BEHAVIORAL ENRICHMENT DEVICES 343

FIGURE 1 Scores for statistically significant behaviors ( p < .05) when individuals' data was compiled together and analyzed across different enrichment conditions. Standard error is repre- sented by error bars. The score for behaviors are out of 20 points.

DISCUSSION

The data demonstrate that these enrichment devices promote wild-specific behaviors and decrease undesirable sedentary, agonistic, and self-directed be- haviors. Unfortunately, R/R and coprophagy behaviors were not affected by the enrichments.

Having a range of enrichment devices is healthier, less boring (Chamove, 1988), and provides for individual preferences. Although each individual's use of an enrichment item was not analyzed independently, it was observed that individuals interacted more with certain enrichment items. BROWSE, BROWSEISTRAW, BAGS, and BOXES promoted foraging (see Figures 1 and 3). The RAGS and BOXES allowed for nest building, manipulation (mainly shredding and tearing), and playing (especially play displays by the juveniles).

Sedentary behavior reflects boredom. With the exception of RAGS in the morning, sedentary behavior was decreased with the use of all enrichment devices

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Bags & Straw Boxes & Straw Browse Browse & Straw Rags & Straw Straw

FIGURE 2 When analyzed across enrich~ncnt conditions, solitary play behavior was the only significant behavior ( p < .05) between subadults (younger than 10 years of agc) and adults (older than I0 years of age). Standard error is represented by error bars. The score for behaviors are out of 20 points.

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Bags & Straw Boxes & Straw Browse Browse & Straw Rags & Straw Straw

FIGURE 3 When analyzed across enrichment conditions, foraging behavior was significant 0, < .05) between morning and afternoon scores. Standard error is represented by error bars. The score for behaviors are out of 20 points.

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Bags & Straw Boxes & Straw Browse Browse & Straw Rags & Straw Straw

FIGURE 4 When analyzed acrosb enrichment conditions, sedentary behavior was signific'mt 0, .: .05) between morning and afternoon scores. Standard crror is represented by error bars. Tl~e score for behaviors are out of 20 points.

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Bags & Straw Boxes & Straw Browse Browse & Straw Rags & Straw Straw

FIGURE 5 When analyzed across enrichment conditions, solilary play behavior was significant @ < .05) between morning and afternoon scores. Standard error is represented by error bars. The score for behaviors are out of 20 points.

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UPM Score

Bags & Straw Boxes & St.raw Browse Browse & Straw Rays & Straw Straw

FIGURE 6 When analyzed across enrichment conditions, social play behavior was significant (11 c "05) bctween ~rloming and afternoon scores. Standard error is rcprcscntcd by crror bars. The score for behaviors are out of 20 points.

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BEHAVIORAL ENRICHMENT DEVICES 349

when compared to STRAW (see Figures 1 and 4). These results indicate that, overall, the enrichments were effective in decreasing boredom.

In free ranging gorillas (Gorilla gorilla berengei), foraging occupied from 30% (Fossey, 1983) to 45% (Harcourt & Stewart, 1984) of the day. BAGS, BOXES, BROWSE, and RAGS increased the afternoon foraging from the STRAW baseline (see Figure 3), indicating a greater amount of foraging throughout the day. All enrichment items except RAGS were eaten and increased foraging time. With the willow and maple browse, the leaves were eaten and then the bark was stripped and eaten. These enrichments increased the gorillas' food-processing time and, as a result, their foraging time.

Brown, Calgano, Gold, and Thompson (1995) reported that coprophagy and R/R had highly significant differences between straw-bedded and unbedded conditions. Between the six environmental conditions in this study, there was not a statistically significant change in abnormal behavior. Straw bedding seems to have a greater effect on decreasing abnormal behavior. The data of this study suggests that enrichment devices, in addition to straw bedding, provide for certain behaviors that straw bedding cannot. A combination of straw bedding, manipulable, and feeding enrichment devices seems to promote species-typical behaviors as well as decrease sedentary and abnormal behaviors.

Writing about chimpanzees, Bloomsmith, Alford, and Maple (1988) found that a short feeding duration and lack of variety in the diet resulted in the "development and expression of numerous pathologic behaviors, particularly those in which a major component is orality, such as coprophagy, [and] repeated regurgitation" (p. 156). The presence of foraging material decreases aggression and abnormal behav- ior and increases feeding time and activity (Chamove, Anderson, & Morgan-Jones, 1982; Gould & Bres, 1986; Tripp, 1985; Woods, 1990). Gould and Bres's (1986) research indicated that browse increased feeding time from 11% to 27% of the day, but it did not completely eliminate R/R or coprophagy. This study did not show a statistically significant alteration in abnormal behaviors, but the enhancement of species-typical behaviors seems to warrant their use. No enrichment device has been reported to eliminate these abnormal behaviors. Either the enrichment devices studied to date are inadequate or the behaviors are deeply rooted. Hopefully, further studies will elucidate the pathogenesis of these behaviors so that they can be eliminated from captive gorillas.

Play behavior was common with the young gorillas. Young adults and juveniles often used cardboard boxes for play displays. There was some concern that cardboard and rags would be used by adults in display behavior, potentially increasing aggression. However, this was never observed.

It is important to implement a behavioral enrichment program that incorporates foraging and other species-specific behaviors. This is best done with a multidimen- sional enrichment program using manipulable objects and foraging items. The results of this research indicate that these enrichments, along with straw bedding,

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350 ROONEY AND SLEEMAN

promote species-typical behaviors and decrease sedentary behavior. It is generally accepted that floor coverings, such as straw bedding, provide the most influence on abnormal behaviors. The enrichment devices evaluated in this study further promote mental health by providing a greater variability of species-typical behav- iors and decrease boredom. These enrichment devices are easily incorporated into the keepers' routines, adding minimal time and work commitments.

ACKNOWLEDGMENTS

We thank Lincoln Park Zoo, the gorilla keepers, and especially Matt Geis, for making this study possible.

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