Abnormal behavior in captive chimpanzees Exclusion of abnormal behavior by modification of the environment.

Abnormal behavior in captive chimpanzees

Exclusion of abnormal behavior by modification of the

environment.

ABSTRACT - To understand human behavior in the light of evolution knowledge can be obtained from observing chimpanzee behavior and social structure. Chimpanzees have complex social structures with coalitions, a hierarchy and an alpha-male who stands on top of the

hierarchy. This social structure is important to promote the psychical well-being of chimpanzees. Captivity, however, is known to have a negative effect on chimpanzee well-being and leads to abnormal behavior. Here, a 19 year old alpha-male who performs abnormal behavior every morning is observed. The behavior is classified as extreme display behavior which sometimes ends in aggression. It is investigated if

modifications/enrichments that are known to decrease aggression and increase well-being in chimpanzees will affect him in a positive way. It is concluded that delaying the moment between seeing and receiving the food as well as prolonging the feeding time causes the alpha-male to stop performing the display behavior.

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Biology- Bachelor Thesis 2012

Student: Eva Frenaij Supervisor: Steph Menken

Date: 06-07-12 2d supervisor: Nicolette Snijders

Table of Contents

Discussion/Conclusion………

…..17

Introduction

To understand human behavior and our social structure in the light of

evolution, important information can be obtained from chimpanzee research who are, together with bonobos, our closest relatives. The social structure we see in the wild is a complex one where display behavior, aggression, loud vocalization and the forming of coalitions are all components which are present and needed to maintain the hierarchy (De Waal, 1982). The hierarchy in a population ensures that expensive risky behavior will be kept to a

minimum (Wroblewski et. Al, 2009). The whole population can be seen as a series of relationships between individuals and due to the hierarchy each individual can predict the outcome of a conflict. Only when the relationships are ambiguous, agonistic interactions occur (Newton-Fisher, 2004).

The highest ranked male, the alpha-male, gains benefits including a greater access to food (Foster et. al. 2009) and to sexual partners, so a greater reproductive success (Coe & Levin, 1980; Foster et. al. 2009; Wroblewski et. al. 2009). To achieve the status of alpha-male different strategies can be followed. Males with a small body size may engage more in grooming to ensure coalitionary support while males with greater body size use more aggression (Foster et. al. 2009). In the establishment and maintenance of the alpha position of a male chimpanzee, display behavior plays an important role. Display behavior can be divided in direct and non-direct displays. Direct displays communicate an aggressive intent, especially if the alpha-male does not use pant-hoot vocalization, i.e., vocalization from a subordinate to a dominant male which is used to measure dominance (Wroblewski et. al., 2009). Non-direct displays are most likely a response to environmental stimuli (e.g. small cages) or group tension (Coe & Levin, 1980). Dominant males show more direct displays and subordinate males show more non-direct displays to their group members.

The transition from one alpha-male to the next takes several months and “a shift in the pattern of displays signaled the ensuing status struggle” can be seen (Coe & Levin, 1980, p 171). Display behavior has been suggested to play an important role in the establishment and maintenance of chimpanzee alpha-males and is known to increase in the period before an alpha-male transition (Coe & Levin, 1980). The social structure we see in the wild is

suggested to play an important role in promoting physical well-being of chimpanzees (Ross et. Al., 2009). Chimpanzees, however, are endangered species and can nowadays be found in captivity (e.g. zoos). Captivity

influences the social structure, the well-being and leads to abnormal behavior compared to chimpanzees living in the wild (Birkitt & Newton-Fisher, 2011). This abnormal behavior can vary from body shaking to extreme social and self-aggressive behavior (Birkitt & Newton-Fisher, 2011). Abnormal behavior can be a consequence of poverty in psychological well-being of the

chimpanzee. It was only in 1985 when the Animal Welfare act was amended and the psychological well-being of animals was also taken into account (Videan et. Al, 2005). Due to this act, zoos nowadays try to make the

enclosure as natural as possible, where housing in the natural social groups (Birkitt & Newton-Fisher, 2011) and introducing environmental enrichments (Hosey, 2004) are most successful in promoting physical well-being of captive chimpanzees. The introduced enrichments have to be novel and complex but most importantly controllable to really have a positive effect on the well-being of chimpanzees (Videan et. al, 2005). Control over the environment and the presentation of events (e.g. de delivery of food) is known to have

behavioral benefits (Bloomsmith & Lambeth, 1995). In an experiment done by Videan et. al. (2005) chimpanzees had to choose between different objects. Here, chimpanzees used controllable object, i.e., objects that they could transform or destroy (e.g. plastic bottles or cardboard box), significantly more often than any other object present (Videan et. Al, 2005).

The degree of control is always less in captivity because the animals are being managed and thereby dependent on the routine of the zoo. This affects the behavior, even as the type of feeding is known to affect primates

behavior (Hosey, 2005). The famous primatologist Frans de Waal (1992) found that when chimpanzees see and observe their food, they first celebrate this observation. When this is followed too soon by actually receiving the food the celebration period in disturbed, this leads to more aggressive behavior during the meal (De Waal, 1992). Chimpanzees that live in captivity normally receive food following a predictable time schedule. But Bloomsmit & Lambeth (1995) found that feeding chimpanzees at an unpredictable schedule instead of an predictable schedule promotes their well-being. In general it appears

that control leads to behavioral benefits, but when there is no element of control, predictability can be more stressful than unpredictability (Bloomsmith & Lambeth, 1995). Another enrichment that is known to promote the

chimpanzees well-being is prolonging the feeding time. This can be done by using a foraging task were food is mixed with a forage substrate (e.g.

woodchips) and chimpanzees have to search for their food. This has shown to reduce social as well as self-directed aggression by almost 50 percent in stump-tailed macaques and decrease aggressive displaying in chimpanzees (Honess, 2006) The way food is delivered influences the well being of

primates but the type of food does not affect primates behavior (Howell et. Al, 1993). Another difference between the wild and captivity are the visitors; according to Hosey (2000) zoo visitors are a source of stress for primates. Especially large, noisy crowds that can interact with primates have a negative effect on primates behavior (Fernandez et. Al. 2009).

The case studied here, is the 19 year old alpha-male Tumbili housed in the Artis Magistra zoo in Amsterdam. Every morning after the inside feeding, when the chimpanzees are locked inside, Tumbili performs agonistic display behavior for approximately 10 minutes. This abnormal behavior can be best classified as trying to make as much noise as possible by using everything that is around him. He hits and stamps on the walls, shake the fences, and swings all movable objects present. During these 10 minutes he seems to be in trance; the other chimpanzees try, but do not succeed in making contact with him. At the end of such a period, his behavior sometimes escalates to such an extent that he attacks one of his fellow chimpanzees. There does not seem to be a direct cause for the display behavior but some behavior is characteristic to occur prior to the actual display behavior. These

characteristic behaviors are: walking around slowly, shaking his body and sitting and holding the fence. These are all events that can be used as an indication for the start of the behavior. According to the caregivers, he has shown this behavior from the moment he became the alpha male, 7 years ago. The displays show an aggressive intent and he does not use pant-hoot vocalization, what would mean that it is a direct display. But, on the other hand, the behavior is not directed at one particular group member, when he attacks another chimpanzee it is not always the same one. This means that

his behavior could also be classified as non-direct display behavior and could be a response to the environment or to group tension.

Research question

Not only is performing of the display behavior harmful for himself, also the other chimpanzees suffer from the stress he causes. That is why the main focus of this research is to find the cause of his abnormal behavior and to change or enrich the environment in such a way that Tumbili will stop performing the display behavior.

In this study, first the display behavior is quantified in terms of duration and in how many cases Tumibil attacks someone at the end of the display

behavior. Subsequently, it is investigated what the cause (or causes) can be of his extreme display behavior. Finally, changes in the environment that are known to reduce aggression and abnormal behavior will be made. These changes could lead to a decrease in duration or aggression or could

completely exclude the display behavior. The changes made are: (1) Delaying the moment between seeing the food for the first time and receiving it and closing the slide in the afternoon for 30 seconds to make it more

unpredictable. (2) Prolonging the feeding time by using a simple foraging task, and (3) introduce destructible objects (cardboard boxes) because this could neutralize the feeling of control loss that is caused by closing the slide.

Hypothesis

Tumbili is the only chimpanzee in the population who performs this behavior, so it probably has to do with his personality. Personality is classified as a behavioral trade that does not change over time or place (Koski, 2011). Personality is formed by nature and nurture and can give information about the performance of specific behavior.

The renowned ethologist Niko Tinbergen pointed out that there are four complementary explanations for animal behavior, four ways of answering the ‘why?’ question in biology: function (adaptation), causation (mechanism), development (ontogeny) and evolution (phylogeny) (Barnard, 2004). A

possible explanation for the occurrence of Tumbili’s extreme display behavior can be given from the development point of view. Tumbili became the alpha-male when he was only 12 years old. At this age, a chimpanzee is still an adolescent (the adolescent period ranges from 5 to 14 years). This period is characterized by an increase in risk taking and aggression, and

“determinations about social housing and compatibility are often influenced by this turbulent period” (Ross et. Al 2009, p. 624). The adolescent period could be seen as a phase that a chimpanzee has to go through to become a mature chimpanzee and in which future behavior in determined. Interruption of this period could lead to psychological disruption and thereby to the

abnormal behavior he is performing. He became the alpha-male at such an early age because the previous alpha-male (his father) died and he happened to be the oldest and only suitable man so he automatically became the alpha-male. As stated before normally a transition between two alpha-males takes several months (Coe & Levin, 1980). Tumbili, however, never underwent such a transition and thus never learned how to behave as a proper alpha-male. The explanation of the behavior given with regard to the animal development gives insight in the internal processes responsible for the performing of the behavior. When the why question is answered in light of mechanism, the underlying mechanisms and organizations that cause the achievement of this behavior are investigated (Barnard, 2004). From this view the question

becomes what the trigger is that causes Tumbili’s display behavior every morning. By answering this question it becomes possible to solve the problem by looking at the environment instead of the internal processes. Because

non-direct display behavior is mostly a response to the environment (Coe & Levin, 1980), the cause of his behavior could be found in the environment. Tumbili only performs the extreme display behavior in the morning, but not during the afternoon indoor feeding. The only difference between the morning and afternoon feeding is that in the morning, the chimpanzees are locked inside so that the caregivers can clean the outside exhibit. By closing the slide it is no longer possible to go outside, and therefore their living space is reduced. Reducing space is known to lead to an increase in aggression and abnormal behavior (Honess & Marin, 2006). Closure of the slide in the

morning can feel as a loss of control for Tumbili because he cannot go outside anymore (Videan et. al, 2005). That is why it is hypothesized that the closing of the slide every morning is the trigger for Tumbili’s behavior.

Because the caregivers need to clean the outside exhibit, it is not feasible to always leave the slide open. Other environmental changes are made from which it is known that they decrease aggression in chimpanzees. By introducing these changes, the environment becomes more naturalistic, which promotes the well-being of all the chimpanzees in the population.

Methods

(0) First, the display behavior is quantified in the existing settings and influences of closing the slide are investigated. To reject the alternative hypothesis that the performance of his behavior is influenced by the time of day for one week the slide will be closed in the afternoon instead of in the morning. For three weeks the following changes will all be made, which will all last for one week. (1) Delaying the moment between seeing the food for the first time and receiving it to make sure the celebration period is not disturbed (De Waal, 1992). To make the situation more unpredictable the slide is closed in the afternoon during this modification for 30 seconds to promote psychical well-being of the chimpanzees by making it more

unpredictable (Bloomsmith & Lambeth, 1995). (2) Prolonging the feeding time by using a simple foraging task which is known to reduce in aggression in all primate species (Honess, 2006). (3) Introducing destructible objects

(cardboard boxes) because this could neutralize the feeling of control loss that is caused by closing the slide (Videan et al. 2005).

Subjects and housing

All the observations were done with the chimpanzee population that is

housed in Artis Magistra Zoo in Amsterdam, during a time period of 2 months. The population contains 6 females and 3 males, ranging in age from 8 to 42. The chimpanzees have access to an in- and outside exhibit, with a surface of approximately 200 m2 and 300m2, respectively. Between the two places is a gangway which is possible to close so the chimpanzee cages can be cleaned. The focus of this research lies on the 19 year old alpha-male Tumbili who was the only one observed.

Feeding procedures

Routinely, the chimpanzees are fed four times a day, there are two inside feedings periods at 08.30 and 15.00 hours and two outside feeding periods at 09.00 and 14.00 hours. The feeding last for approximately 20 minutes (from the moment the chimpanzees receive the food until the last one finish). In this research only the inside feedings are observed. In the morning, the night

cabins are closed around 08.15 hours and food (apple, carrot, chicory, endive and fruits in different combinations) are put in the cabins. Around 08.20 hours all the chimpanzees are locked inside by closing the slide in the gangway and the night cabins are opened. The chimpanzees are locked inside for

approximately 30 minutes while the caregivers clean the outside exhibit. Around 09.00 hours the lock is opened and the chimpanzees go outside for their second feeding and are now locked outside until 15.00 hours.

At first (0), the influences of closing the slide in the setting that is used by the caregivers on performing the display behavior is measured. These findings are used as the norm, form here it is possible to see if the changes influence his performing of the behavior. This is followed by changing the inside

feeding, for a week the chimpanzees will be locked inside in the afternoon (15.00 hour) instead of in the morning (08.20 hour).

During the research the following changes were made on the feeding

procedure: (1) Closing the night cabins at 08.15 hours and food put in at the same time, at 08.30 hours the cabins were opened and the slide was closed. During the inside feeding at 15.00 hours the slide would be closed for

approximately 30 seconds. (2) Instead of the normal food the chimpanzees now received nuts/seeds and sunflowers mixed with wood snips at 08.20 hours to prolong handling and thus feeding time. In this method, Tumbili started performing the behavior before the night cabins were opened, so no effect of the foraging task could be observed. That is why in (3) the same procedure as in (2) was followed except that here the night cabins were opened before the closing of the slide.

Data collection procedures

Observational data were collected during the two inside feeding episodes. In the morning, the exact time of feeding and closing of the slide, the start time, the duration of the display behavior and the aggression level were measured. Performance of the display behavior was noted as yes or no, he could either perform it or not. During this period, every minute Tumbili’s most important interactions during that time interval with other chimpanzees (e.g.

copulation, aggression, grooming) were noted, as well as other remarkable events. When the slide was closed and more than one chimpanzee was not

inside, this day was excluded from the data.

Data analysis

Each day Performing the display behavior and aggression was noted as ‘yes’ or ‘no as well as the duration of the behavior when he performed it. The closing of the slide and the performance of aggression were also noted as ‘yes’ or ‘no’ and the important events during this period were also reported..

By quantifying the behavior this way it was possible to analyze the data with the chi-square test of homogeneity.

Results

(0) Influence of closing the slide.

During 11 days in total, the inside feeding was observed, two days were excluded from the data because on those days more than one of the chimpanzees did not come inside. In total he showed the behavior 7 times and in all cases of showing the slide was closed. He never performed the behavior when the slide was opened (figure 1).

Figure 1: Influence of closing the slide

Closing the slide causes Tumbili to perform the display behavior (Χ2 =13.4, df=1, p =0.000253). Tumbili’s display behavior took between 6 and 11 minutes (mean=9.14, sd=1.68) and in 57% of the cases aggression was measured, but this aggression did not seem to be directed at one particular chimpanzee.

Here, a distinction is made between an open and a closed slide, but because the slide is always closed in the morning and always open in the afternoon it is also possible that his behavior has to do with the time of the day. To

exclude this possibility, the closing of the slide was switched, so now it was closed in the afternoon. This resulted, as expected, in display behavior in the afternoon instead of in the morning. Not only did he perform the display behavior, it also seemed as if it was more intense than in the morning, it lasted for 14 minutes the first day, originally his behavior took between the 6 and the 11 minutes, 14 minutes is significantly longer than this setting, although he did not attack anyone. This increase probably has to do with the animal-visitor interaction, visitors are known to be a source of stress for

primates. Because the increase in intensity it was decided for ethical reasons not to switch it again.

(1) Delaying the time between seeing and receiving the food.

Here, the morning feeding schedule was changed for 7 days, one day more than one chimpanzee did not come inside before the slide was closed so this day was excluded. Instead of receiving the food immediately after seeing it, now there was a period of time ranging from 16 to 65 minutes between seeing the food and actually being able to eat it (mean=28.5, sd=19.4). The slide was closed every morning at the same time the night cabins opened and the food was received. From the 6 days measured he only performed the display behavior the first day. This was compared with the condition were no changes were made (0) (figure 2).

Figure 2: Influence of delaying the time between seeing and receiving the food

A positive effect of delaying the time between seeing and receiving was found on performing the display behavior (Χ2=5.4, df=1, p=0.020116).The display behavior lasted for 10 minutes and no aggression was observed. What was observed when the chimpanzees were waiting inside while the food was in the cabins was that all the females would lay down and groom each other while the three males were playing with each other. During the feeding, when the gate was closed, it was noticed that Tumbili got a lot of attention from the other chimpanzees. It happened that Tumbili started walking around slowly, started shaking or put his hand on the fence, events that all very often preceded the display behavior. But now, when such an event occurred,

one of the chimpanzees would come to him or follow him and cuddle, groom, kiss or have sex with him. This seemed to lower the tension in Tumbili and prevented him for performing the display behavior.

In the afternoon the slide was closed for 32 to 62 seconds (mean=45.0, sd=11.7). What was observed is that for 3 days Tumbili would just sit or eat, here the closing of the slide did not seem to influence him. For the other 3 days he immediately started shaking an enrichment when the slide was closed and would stop immediately when the slide opened. This finding indicates that the slide really influence his performance of the display behavior.

(2) Prolonging the feeding time by using a forage task.

During 7 days, the food received in the morning was changed; instead of receiving apples or carrots they received raisins/nuts and sunflowers mixed with wooden chips. One day, more than one chimpanzee did not come inside and this day was excluded. During this modification he performed the display behavior for 5 of the 6 days, so no positive effect was found (Χ2=0.1, df=1, p= 0,792147) (figure 3).

The display behavior took between 9 and 13 minutes (mean=10.4, sd=1.74) and in 50 % of the days aggression was measured. Introducing the forage task did not influence Tumbili’s behavior. For 5 of the 6 days he performed the behavior before the night cabins were opened and the food was presented. The food could not influence the display behavior that is why in (3) the night cabins were opened before closing the slide instead of introducing

destructible objects.

(3) Forage task where the night cabins were opened before closing the slide.

Here, for 7 days, the forage task was again introduced but now the opening of the night cabins was before closing the slide and locking the chimpanzees inside. The last 3 days only 6 chimpanzees went inside so these days were invalid and 4 days were left (figure 4).

Figure 4: Influence of prolonging the feeding time by using a forage tast : opening the night cabins before closing the slide.

Tumbili performed the display behavior only for 1 day, so a positive effect was found but due to the few valid days it is not possible to conclude this with certainty(Χ2=3.3, df=1, p=0,071031).

Discussion/Conclusion

The first conclusion that can be drawn is that closing the slide causes Tumbili to perform his behavior in the morning. Explanations why locking the

chimpanzees causes his behavior could be that reduction of space is known to promote aggression (Honess & Marin, 2006) and that it could feel as a loss of control (Videan et. Al, 2005). Because Tumbili is the only one of the nine chimpanzees who performs this behavior, it is possibly a result from the fact that he became the alpha-male too young and too sudden. It was found that delaying the moment between seeing and receiving the food had a positive influence and ensures that Tumbili stops performing the display behavior. According to the literature the chimpanzees should be celebrating and by that dance, kiss and hug, from the moment they saw the food (De Waal, 1992). Celebration was not recorded, instead all the females were lying in the inside cage and were grooming each other, while the 3 males were playing with each other. Grooming is known as the most important affinitive behavior among all primates (Foster et. Al, 2009). The grooming could create a

stronger bond between the females. When the night cabins were opened and the slide was closed it seemed as if everyone was paying attention to Tumbili. For example, it happened that he started shaking or walking around slowly and then immediately one of the other chimpanzees would come up to him and hug, hold or groom him. The attention of the other chimpanzees

prevented Tumbili from performing the display behavior until the slide was opened again.

A discussion point here is that two theories were tested at once. Not only was the time between seeing and receiving the food delayed, the circumstances were also made unpredictable because of closing the slide in the afternoon and making the time of feeding unpredictable. For future research it would be interesting to investigate the two theories separately to see which change is responsible for the stop of the behavior.

The other modification; prolonging the feeding time by using a forage task also seems to make the display behavior disappear. This was according to the literature, where introducing a forage task seems to reduce aggression and promote physical well-being is all primate species (Honess & Marin, 2006).

Days where more than one chimpanzee did not go inside were not taken into account because it was hypothesized that this could influence his

performance of the display behavior. Days where only one chimpanzee was outside and days where some aspects were different than normal (e.g. some days there was a lot of rain, there was someone cleaning the glass around the chimpanzees or someone was irrigating the plants) were also taken into account. All these events even could influence the performance of Tumbili’s behavior in either a positive or a negative way. It was decided that these days were used in the data because otherwise no data was left. To give a holistic view, more time is needed to generate more accurate data.

In this research it is tried to make Tumbili stop performing the display behavior by introducing modifications in the environment. Other

modifications could also influence Tumbili’s behavior in a positive way, future research could be done by introducing destructible objects. The introduction of destructible objects could give him a feeling of control and could neutralize the feeling of control loss caused by closing the slide. This introduction was initially one of the three planned modifications but due to the outcome by (2) this was not realized. Measuring the influence of the destructible objects could give more information and is therefore recommended. Other research could be done by making the occurring events more unpredictable,

unpredictability promotes chimpanzees well-being (Bloomsmith & Lambeth, 1995). This was also an initial plan but making the occurrence of events more unpredictable was not feasible for the caregivers. The caregivers had a tight schedule which ensured that only changes that did not consume time could be made. In the ideal situation all modifications should be possible to perform but in this research there were many limitations. Still, this research proves that simple changes that make the zoo environment more naturalistic can lead to better chimpanzee well-being.

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