Sniffing Out a Path to Enrichment

By Anna Miller; Explorer;
Little Rock Zoo, Little Rock, AR 72205

William K. Baker Jr., Curator
Little Rock Zoo, Little Rock, AR 72205

ABSTRACT:

Environmental enrichment studies improve both the lives of captive animals and the education of the public. An experiment was conducted to test the reactions of a pair of warthogs (Phacochoerus aethiopicus) to the urinary samples of several species. It was hypothesized that the urinary samples would increase the overall activity level, predator samples would cause a negative reaction, and non-predator samples would produce a more positive reaction. Activity levels appeared to increase only with the non-predator species. With leopard and lion samples, the effect was a decrease in overall activity.

Introduction

In recent years, environmental enrichment has become a more complex and important facet of the zoological industry. Because of a rising concern for the well-being of captive creatures, enrichment has become a key factor in the care of any specimen that a zoo may have, be it large or small. Enrichment provides the animals with stimulation of the mind and body, letting them have an important break from the tedium of their usual activities. Not only does it allow for a greater activity level, but enrichment can also help the creature hone skills that it uses in the wild but often lacks an outlet for in the typical zoo setting.

The experience of patrons is directly linked to the experience of the animals: bored animals equal bored humans. This relationship was validated in a study, published in The Shape of Enrichment, which states that "research indicates that enriched zoo environments are valued by zoo-goers, and that enrichment can help zoos further their public relations and education goals" (Shapiro" 1997). A natural environment with an active animal is appealing to the public and keeps them coming back. This of course is not only profitable for the zoo, but it is also a valuable educational experience for the patrons. Thus, the benefits spread to everyone when the animals' environments are enriched.

The remaining question is how to enrich the captive environment. The most feasible and cost- effective way is by using what a zoo has already. One of these existing resources is that of scent. In the wild, one of the main methods of communication is through marking areas with scent and thereby claiming them. Several studies have been conducted in this area. One, published in The Shape of Enrichment, was conducted with African lions (Panthera leo) at the Houston Zoological Gardens (Baker, 1997). Eight prey species and two adversary species were identified, and fecal samples from these species were placed in the lion habitat, each approximately five meters from the other. Then, the lions were released into the area and were videotaped as they discovered and reacted to the samples (Baker, 1997). There was "increased activity and social interaction" throughout the experiment, as well as 48 hours of "investigative behavior" and "social activity at diminished levels," even after the samples had been removed (Baker, 1997). Studies have also been performed to test the reaction of hedgehogs (Erinaceus europaeus) to badger (Meles meles) feces in their usual foraging area (Ward, 1997). When tested in pens, the hedgehogs avoided the area "tainted" with badger feces for up to four days, but foraged freely in areas containing non-predator feces (Ward, 1997). However, free-ranging hedgehogs "showed a reduction in foraging effort in response to badger odor over periods of five to 30 min, but no evidence of site avoidance over a 24-h period" (Ward, 1997). Both of these studies show that using scent as a stimulus in enrichment programs could be an effective and low-cost way of inducing natural behavior in captive creatures.

Despite extensive research into the information available on environmental enrichment, not a single source was found that mentioned warthogs (Phacochoerus aethiopicus). True, they are not the most attractive of animals, with their protective warts and nearly hairless hides, but they are nevertheless important to the savanna ecosystem (Estes, 1991 ). The warthog exhibits great intelligence in its anti-predatory behavior, which consists of fleeing to a nearby "underground refuge" and at the last moment turning about so that should the predator attempt to follow the warthog into the hole, it will be faced with two sets of dangerous tusks (Estes, 1991 ). Some of the main predators of the warthogs include, in order from most predation to least: African lion (Panthera leo), African leopard (Panthera pardus), cheetah (Acinonyx jubatus), wild dog (Lvcaon pictus), and hyena (Crocuta crocuta) (Cumming, 1975). Warthogs' primary food sources are grasses of most sorts, as well as woody undergrowth (Cumming, 1915).

In this experiment, the effects of urinary samples of various species on the behavior of warthogs were tested. One hypothesis in this study was that the addition of these scents would cause a higher level of activity in the 1.1 warthog pair. The second hypothesis was that they would have a negative response to the predator urinary samples (i.e. vocalization, avoidance of area marked, etc.). Third, while the non-predator samples would cause an increase in activity, it would not necessarily be a negative response.

Procedure

The test subjects were a 1.1 warthog pair located in the Hoofed Mammal Area of the Little Rock Zoo. They remained in their usual living quarters and environment for the duration of the experiment. For stimuli, two urine samples from each of the following was used: lion, giraffe, leopard, and the 0.1.3 warthogs that were housed in a separate enclosure. The urinary samples were collected on the day of the observation by soaking each up with wood wool (chosen for its availability, compatibility, and organic nature) and stored in resealable bags for transport. The sample was then placed in an enrichment device { a PVC pipe with eight holes drilled in an alternating zigzag pattern on each axis and threaded caps on each end) and into the warthog environment.

PVC Pipe used as holder for various scents in warthog enrichment study at Little Rock Zoo. PVC pipe measures 24" long by 3" in diameter (61cm x 7.6cm).

The 1.1 warthogs were videotaped for 60 minutes and then the sample was removed. A minimum of three days passed between each placement to allow the previous odor to be completely dissipated before a new stimulus was added. Each species' samples were placed in the warthog environment twice during the experiment.

Experiment Timeline of Events

When the videotapes were observed, the behaviors of the 1.1 warthogs were recorded (see Appendix C). These observations were taken at 15-second intervals. Inter-rater reliability was used to check for reliability of the codes and to prevent experimental bias. The percentage of agreement across the behaviors was 85%. The percentage of agreement for the "interaction with enrichment device" behavior, however, was 100%.

Results

One extraneous factor that might have affected results was the diminishing sunlight and warmth as the seasons changed. However, as Appendices A and B show, this did not alter activity level. When the pair was active, their activity differed widely. To reflect this, they are presented separately.

Figure 1: The numbers shown here represent the number of times each activity was observed. This was favored over percentages in order to show all behaviors, no matter how rarely they occurred.

Figure 2: The numbers shown here represent the number of times each activity was observed. This was favored over percentages in order to show all behaviors, no matter how rarely they occurred.

The first hypothesis was that the introduction of the enrichment devices would cause an increase in activity levels. The second was that the pair would react negatively to the predator samples. Lastly, the reaction to the non-predator samples would be a heightened activity level not including a negative response. Figures 3, 4 and 5 deal with these hypotheses.

Figure 3: "Active" represents the percentage of total time spent in some activity other than inside/out of sight or lying down. " Active/ or near device" represents the percentage of active behavior spent interactin2 with or within 1- feet of the enrichment device.

Figure 4: See caption for Figure 3.

Figure 5: Figures 3 and 4 combined and averaged

The subject pair were most active in the presence of the giraffe samples, second most active in the presence of the warthog samples, and least in the presence of the leopard and lion samples. However, the highest levels of interaction with and proximity to the enrichment device itself were demonstrated during the lion samples, followed by giraffe and then leopard. They interacted with and were near the enrichment device least when the warthog sample was present.

When the total activity level is divided into specific activities, the activity that is subject to the most change is sniffing and rooting, as shown below in Figures 6 and 7.

Figure 6: Each of the male's activities (excluding the most infrequent) is displayed across each set of observations.

Figure 7: See caption for Figure 6.

Discussion

The warthog pair's reaction to the scent samples was complex. Activity levels appeared to increase only with the non-predator species. The activity that held most sway over total activity level was that of sniffing and rooting, a strongly exploratory action. The effect of lion and leopard samples was a decrease in overall activity instead of the hypothesized increase in negative behavior or distress such as vocalization or retreat into the night house. However, given that the goal of enrichment is to increase activity levels, anything that is associated with a decrease in activity could be described as a negative reaction. In addition, the presentation of an empty device as a control was associated with the lowest activity level of all. The introduction of the enrichment device may have had the opposite effect when the device stopped being associated with a scent. The pair may have become habituated to the device and withdrew when it was no longer a source of new stimulation. This could have serious implications for how enrichment devices such as this one are used.

The effect of the predator scent was more pronounced with the lion sample than with the leopard. This may be explained by the social habits of lions and leopards. While lions travel in prides, leopards are solitary creatures. Theoretically, a single leopard presents less of a threat than a pride of lions, and so the lion sample likely held more clout than the leopard sample. Also, as previously stated, leopard ranks second in the overall level of predation of warthogs and lion the first (Cumming 1975). However, as this 1.1 pair of warthogs has been raised in captivity, and thus has had no previous known experience with these predators, this hypothesis poses an interesting question concerning the concept of inherited instinct.

The male showed an increase in activity when presented with either of the non-predator samples. His enthusiasm and the female's relative disinterest in the 0.1.3 warthog samples could be explained by their familiarity: the female knew the mother's scent and was only concerned with that of the young, while the male recognized his mate's scent. However, both he and the female had extraordinarily high activity levers with the giraffe samples. A reason for this result might be linked to the role of giraffes on the savanna. Based on information presented in ~: "Cheetahs in a Hot Spot" (aired on AETN on January 20, 2002), it seems that the giraffe acts as a sentry for smaller creatures because of its extraordinary height. Thus, when a giraffe is present, one may hypothesize that the nearest predator is out of visual range. As said previously, this poses an interesting question and would be a good point for further research.

If further research were done, the gender of each animal that supplied the sample would be recorded and, if the animal were female, whether or not she was in estrus when the samples were collected. A wider range of species would be used as stimuli, including more non-predator samples. The observations would be done at a point in the year where the seasonal changes are gentler than those of late autumn and early winter. The sample and control/baseline observations would be staggered in order to prevent habituation. Also, an enrichment device would be filled with some sort of treat in order to compare the reactions to the promise of food to that of predation.

Conclusion

This study demonstrates that scent samples can function as an effective form of enrichment for warthogs. However, care must be taken with the choice of sample species. Some species may lead to an increase in activity while others can lead to a decrease in activity, Keepers should also be aware that various samples effect males and females in different ways. The more pronounced reactions of the warthogs to the giraffe and lion samples are an interesting point for further research.

Acknowledgements

Thanks to Mr. W.K. Baker, Jr,) and Mr. Robert Sinteff, both of the Little Rock Zoo, for their extensive help throughout this study, and to James Miller for the cover image.

Appendix A

Appendix B

Appendix C

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Bibliography