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Open Access Publications from the University of California


The International Journal of Comparative Psychology is sponsored by the International Society for Comparative Psychology. It is a peer-reviewed open-access digital journal that publishes studies on the evolution and development of behavior in all animal species. It accepts research articles and reviews, letters and audiovisual submissions.

Volume 26, Issue 1, 2013


The Importance of Behavioral Research in Zoological Institutions: An Introduction to the Special Issue

Behavioral research within zoological institutions (zoos and aquariums) has a long history that has helped to increase basic scientific knowledge and to facilitate the ability of institutions to make informed animal management decisions. Kleiman (1992) stated that "behavior research in zoos has enormous potential to contribute positively to the science of animal management, long-term breeding programs, conservation biology, and the advancement of scientific theory" (p. 309). As evidenced by the papers in this issue, behavioral research in zoos continues to be important. The purpose of this special issue is to highlight some of the behavioral research being conducted within zoos and aquariums and to demonstrate the importance of such work to zoological institutions and the greater scientific community. With a better understanding of the importance of behavioral research, we hope to inspire more zoological facilities to become involved either through funding/conducting research or by actively promoting the use of their animal collections for behavioral research to both the zoological and academic communities.  Historically, most of the behavioral research in zoos and aquariums was intended to increase basic scientific knowledge. More recently, there has been a shift in focus to applied topics in order to help solve animal management issues (Hutchins & Thompson, 2008; Kleiman, 1992; Stoinski, Lukas, & Maple, 1998). Such issues range from reproduction and behavioral development of species that are difficult to breed to determining the effects of environmental or management factors on the welfare of individual or groups of animals. The abstracts submitted for consideration for this special issue reflect this trend towards applied research in zoos and aquariums. Applied research represented approximately 76% (n = 50) of the abstracts that were submitted for the special issue. While not necessarily representative of behavioral research as a whole throughout zoological institutions around the world, the numbers nonetheless suggest that applied research comprises the majority of the behavioral research focus within zoos and aquariums.

Sexual Conditioning in the Dyeing Poison Dart Frog (Dendrobates tinctorius)

Amphibian populations worldwide are currently in decline. One approach to preventing extinction of some of the affected species is to create assurance colonies. These sustainable populations might some day be used to reestablish wild populations. One issue with creating assurance colonies is successful breeding; often difficulties arise when attempting to breed exotic animals in zoological institutions. Sexual conditioning, a form of Pavlovian conditioning, has been shown to improve breeding behavior. In this study the efficacy of sexual conditioning to improve breeding behavior in the dyeing dart frog (Dendrobates tinctorius) was tested. Pairs of frogs were exposed to one of three conditions. In two conditions pairs were trained with a stimulus (a flashing green light) that was either predictive of (experimental) or independent of (active control) exposure to a member of the opposite sex. The third condition was a no-treatment control. After training all three conditions were given five days to interact. Members of the experimental condition showed shorter latencies to a variety of breeding behaviors and produced more eggs than those in the control conditions. The sexual conditioning procedure was successful in increasing breeding behavior in this population of frogs.

Utilizing First Occurrence, Nursing Behavior, and Growth Data toEnhance Animal Management: An Example with African Elephants (Loxodonta africana)

One of the many goals of zoological institutions is to actively breed endangered species to enhance conservation efforts. Unfortunately, many of these species are not reproducing at high enough levels to sustain populations within zoos. Low reproductive success and high infant mortality are two areas of concern for some of these species. Collecting behavioral data on developmental milestones following successful births can create a database of information to aide animal management to help make more informed decisions during subsequent births. The current study provides valuable information for African elephant calf developmental norms and demonstrates how data on first occurrences, nursing behavior and growth patterns can aide animal management. Data were collected on eleven African elephants (Loxodonta africana) at the San Diego Zoo Safari Park in Escondido, CA of which ten have survived. Results show that on average African elephant calves were standing within 40 minutes, attempted to nurse within an hour and a half, and successfully nursed within six hrs. There were no significant differences in nursing rates, growth patterns, or first occurrence behaviors between males and females during the first 75 days of life and elephants gained on average 0.59 kg/day over that same period of time. Results also show a significant change in nursing behavior on day 22 for the elephant calf that died. This information is intended to serve as a resource for elephant managers with newborn African elephants and to serve as a model to develop similar type databases for other species in need within zoological institutions.

The Neighbor Effect in Bachelor and Breeding Groups of Western Lowland Gorillas (Gorilla gorilla gorilla)

Behavioral monitoring is an essential tool for understanding how animal management decisions, including exhibit design choices, impact animal behavior and welfare. The purpose of this study was to use behavioral monitoring techniques to determine the interaction between 2 groups (bachelor and breeding groups) of western lowland gorillas that are housed in separate habitats that partially face one another. We performed simultaneous, 30-minute group observations on the breeding and bachelor groups and recorded all occurrences of agonistic and affiliative behavior, vocalizations, and visual monitoring of the adjacent group. At 5-minute intervals, we also recorded which gorillas in the observed group were potentially visible to the neighboring group. Our results indicated that there was considerable variation in the percentage of time each gorilla spent monitoring the neighboring group. We were also able to demonstrate that the visibility of individuals in the breeding group of gorillas was related to behavior of the gorillas in the bachelor group. Although non-contact aggression increased with the visual presence of the adult male of the breeding group, more severe aggression that could cause injury was not influenced by his presence. Results also showed an association between visual presence of a particular female in the breeding group and a decrease in contact aggression in the bachelor group. Since many zoological exhibits allow visual access to other animals, it is important to determine the impact that neighbors may have on each other. Our study investigating interactions between neighboring gorilla groups is an example of how behavioral monitoring can be used to assess the impact of a wide range of management decisions on animal behavior and welfare.

The Effects of Housing on Zoo Elephant Behavior: A Quantitative Case Study of Diurnal and Seasonal Variation

One of the greatest challenges for zoo managers is ensuring the best possible welfare for zoo elephants. Few studies have focused on behavioral health of elephants over a 24-hour period and across seasons, making evaluations of behavioral variation challenging. This study examined the behavior of two zoo-housed African elephants (Loxodonta africana) over a two-year period to determine the roles of 1) indoor/outdoor housing, 2) time of day, and 3) seasonal variation on activity. Daytime behavioral differences were contrasted with nighttime activity, and across seasons. Significant differences were noted when the elephants were indoors vs. outdoors, between day and night, and between summer and winter, suggesting that evaluations of zoo elephant activity should occur throughout circadian cycles and account for seasonal variability

Approaches to Understanding and Managing Pacing in Sloth Bears in a Zoological Setting

A significant challenge for animal care staff in zoos is the prevention or reduction of stereotypic behaviors in the animals they manage. Zoo professionals work to create opportunities for animals to demonstrate species-typical behaviors and to teach visitors about the natural behaviors of the animals on exhibit. Therefore the expression of stereotypic behavior presents a multi-disciplinary problem. Behavioral researchers have repeatedly examined stereotypic behavior in zoological settings to determine successful approaches to address this challenge. Three investigations of pacing in two adult male sloth bears (Melursus ursinus) at Smithsonian's National Zoological Park are presented here. In addition, a case report detailing observations of the rapid onset of an intense stereotypy in a young male sloth bear is included. The first study investigates the effects of five different enrichment strategies on pacing behavior in an adult male with a long history of pacing. The second is a two-year study examining seasonal changes and the effects of social companionship on pacing when the same adult male was housed with a breeding female, a non-breeding (contracepted) female, or a young male. In the third study, we present preliminary data on the effects of the selective serotonin re-uptake inhibitor, fluoxetine, as an adjunct pharmacological treatment for pacing. And finally, our case report details the development an intense stereotypy in a young male sloth bear just after he is weaned and separated from his mother. The findings reveal that the causes, degree, and effective management of even a single observed behavior such as pacing within even a single species can vary greatly by individual and circumstance, highlighting the need for individualized assessment and management plans.

Correlations of Swimming Patterns with Spinal Deformities in the Sand Tiger Shark, Carcharias taurus

Spinal deformities among captive sand tiger sharks, Carcharias taurus, are unfortunately common, and abnormal swimming behavior due to constrained aquarium space has been hypothesized to contribute to the development of this condition. Public aquaria across the United States were surveyed for number, condition (healthy vs. affected), and total length of resident C. taurus specimens and for dimensions of their aquaria. They were also asked to record 10 minute video segments of individual C. taurus swimming in lateral view. Total length of sharks, regardless of condition, averaged 225 ± 5 (mean ± SE) cm. Aquarium shapes varied widely, but aquaria held median volumes of 1.03 X 106 L, and were a median of 4.6 m in depth and 20.7 m in greatest horizontal distance. The greatest horizontal distance of aquaria was negatively correlated with disease prevalence of resident populations in a logarithmic fashion (r = 0.72). Behaviorally, sharks were assessed for total time and percentage of time spent swimming in a specific direction (clockwise, counter-clockwise, or linear), in a glide, and tail-beat duration. Regardless of condition, C. taurus spent a median of 98.9% of time swimming and 0.62% of time gliding. Healthy sharks spent a median of 0.67% gliding versus a median of 0% for afflicted sharks (p= 0.036), suggesting an increased swim-to-glide ratio among the latter group. All sharks swam asymmetrically in either a clockwise or counter-clockwise direction for a median of 99.7% of observed time. Affected specimens had tail beat durations of 3.37 ± 0.23 s vs. 2.72 ± 0.10 s for healthy sharks (p = 0.005). The increase in swim-to-glide ratios and inordinate time spent swimming asymmetrically for all affected sharks support the hypothesis that swimming patterns induced by captive exhibits may contribute to spinal deformities in C. taurus due to more stress placed on the spine. Large, complex aquarium designs are recommended in the planning of new exhibits to discourage stereotypical swimming behavior and also to provide sufficient length for sharks to complete natural swimming repertoires. Comprehensive behavioral enrichment activities that encourage complex movement are also recommended as well as considerations such as even weight distribution of the animal during capture, sourcing of appropriately aged sharks, and nutritional supplementation.

Behavioral Monitoring of Big Cats Involved in ‘Behind-the-Scenes’ Zoo

While interactive tours have been argued to hold great conservation potential for zoo visitors, the influence on the participating animal’s behavior is often ignored. To investigate this, we observed the behavior of one Sumatran tiger (Panthera tigris sumatrae) and three African lions (Panthera leo leo) involved in a protected contact tour, as well as that of three cheetahs (Acinonyx jubatus) involved in a hands-on tour, at Zoos South Australia. Instantaneous scan sampling (30-s intervals) was used to record animal behavior before, during, and after behind-the-scenes tours, as well as for equivalent times on non-tour days, over a three-month period. Estimated proximity (close, < 2 m; moderate, 2-5 m; and distant, > 5 m) to humans was also recorded as an indirect measure of interaction. The animals in the protected contact tour displayed decreased inactivity and increased feeding and pacing during the tours, compared to before and after. We suggest that the increased pacing is more associated with the animals being fed during the tours, rather than the tours being a stressful experience. Those in the hands-on tour showed variation in proportions of multiple behavior categories and primarily these were shifts in species-typical behaviors. In contrast to those in the protected contact tour, they showed decreased pacing during the tour sessions. No aggressive or otherwise antagonistic behaviors directed at humans were observed by animals in either tour, with these animals typically spending more than half of their tour times in distant proximity to keepers and visitors. Combined, these findings indicate that large felid behavior may be altered by participation in interactive tours, but that these changes are not necessarily indicative of compromised wellbeing. Additional research is needed to determine the impact that these experiences are having on the welfare of the animals. This study reinforces the potential for behavioral monitoring to be used as a method for assessing the influence of visitors on zoo animals.

Cognitive Research in Asian Small-Clawed Otters

Little research has been conducted on cognitive abilities in Asian small-clawed otters (Aonyx cinereus) despite behavioral and social characteristics which suggest that this species would perform well on cognitive tasks and are likely to provide relevant data for comparison to other taxa. Asian small-clawed otters are relatively long-lived and have complex social systems that t involve cooperative breeding, paternal care and reproductive suppression. These life-history characteristics have been associated with highly intelligent behavior, yet little is known about the cognitive abilities of this species. The current study explored spatial memory in Asian small-clawed otters using a modification of the radial arm maze. Performance on all measures improved significantly across sessions. These results provide evidence that Asian small-clawed otters have spatial memory for food locations and illustrate the potential for cognitive testing with this species.