differences in social hierarchies in wild vs captive chimp communities: cultural adaptation

Analysis of the differences in social hierarchy and dominance between wild and captive

chimpanzee communities as a result of cultural adaptation

Noelle Tankard

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Newbury Park High School

May 2007

(3,999 words)

Noelle Tankard Social hierarchy and dominance in chimpanzee communities

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Table of Contents

Abstract ..........................................................................................................................................................3

Introduction ....................................................................................................................................................4

Background ....................................................................................................................................................5

Chimpanzee social behaviors.....................................................................................................................5

Sexual differences ......................................................................................................................................6

Differences in wild and captive environments...........................................................................................7

Intelligence, learning, and culture..............................................................................................................8

Conventional wisdom: the alpha male ...........................................................................................................9

Case studies: Alphas in the wild ..................................................................................................................11

Gombe Stream..........................................................................................................................................11

Mahale Mountains....................................................................................................................................11

A different kind of leader.............................................................................................................................12

Captive Chimpanzee Populations ................................................................................................................13

Arnhem Zoo .............................................................................................................................................13

Los Angeles Zoo ......................................................................................................................................14

Other AZA Communities.........................................................................................................................16

Conclusion ...................................................................................................................................................17

Appendix 1: Chimpanzees mentioned .........................................................................................................19

Appendix 2: Notes on aggressive behavior..................................................................................................20

Works Cited .................................................................................................................................................21


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Abstract

This paper explores the differences in the hierarchal structures of captive and

wild chimpanzee communities by focusing on the role, function, and identity of the

alpha male. Issues including the comparatively higher rank of females, the ambiguity

of individual leadership, and the lack of ritualized dominance behaviors are analyzed

as effects of such characteristics of captive environments as resource abundance,

security, and variable group composition.

The background information provided in the first section of the paper serves as

a context in which to understand the social structure and behavior of chimpanzees,

describes the applicable sexual differences, the fundamental differences in the captive

and wild environments, and briefly references the cultural learning capacities of

chimpanzees. This information helps to set up the hypothesis of cultural adaptation as

an explanation for the observed differences in dominance between captive and wild

communities. Appendices following the paper provide supplementary information.

The conventional model of chimpanzee dominance is directly explained by

reference to the variety of literature on the subject and indirectly described by the case

studies of Jane Goodall at Gombe Stream and Toshisada Nishida at Mahale Mountains

National Park.

The alternative model of leadership as demonstrated in captive environments

and the evidence to support the interpretation of cultural adaptation is presented in the

following portion. Several specific cases are examined, including Frans de Waal’s

study at the Arnhem Zoo and the contemporary chimpanzee populations of the various

American zoos, including the Los Angeles Zoo.

The conclusion, which finds cultural adaptation responsible for the observed

differences, presents a brief commentary on gender roles and function as well as a

fundamental challenge to the traditional understanding of dominance relationships as

well as the application of behavioral models based on wild behavior to captive

environments.

(290 words)


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Introduction

I volunteer for the Research Department of the Los Angeles Zoo. Although my involvement began

accidentally – striking up a conversation with a volunteer while visiting the zoo, attending a UCLA course in

ethology that began the same night, and subsequently becoming the youngest-ever member of the team – my prior

interest in paleoanthropology led me to seize the opportunity to observe the chimpanzees, whom I spent nearly two

years getting to know and respect as individuals before the study ended in August 2006. Last summer, I traveled to

Mahale National Park in Tanzania. Although many visitors spend days searching for a sight of the chimps, they

came down to the Nkungwe Camp each of the five days I stayed there. The first day, on a hike into the jungle, a

young male chimp, Darwin1, dragging a large branch behind him, rushed me in an aggressive display. One after

another I continued to see classic textbook behaviors of which I had only previously read: the alpha male led a hunt

and ate the catch (the chimps at the LA Zoo have been known to play with the corpse of a rat in their enclosure, but

are vegetarian2); the young and subservient greeted their elders with bows and gruff pant-hoots, males groomed

each other with hand-clasps and mothers, with a child following behind, carried their infants on their backs. Alofu,

perhaps following Darwin’s example, came to the camp and introduced himself as alpha in an inspiring display

involving the thick wooden poles that supported Tent 7. I was impressed not only by his percussion skills but by the

clear hierarchy.

The final key to my understanding came in October 2006 at the ChimpanZoo Conference3, where the

pattern of vague hierarchal arrangements, apparent lenience in the designated alphas, and the surprisingly high rank

of females as presented by keepers and observers from other captive environments, in tandem with discussion of

the problematic differences in environments led me to realize the broader significance of the differences I had

noted.

1 All chimpanzees mentioned by name are listed in Appendix 1 for reference.

2 Chimpanzees are omnivorous but can live healthily on a vegetarian diet. Although they eat meat in the wild, most captive

groups are never given meat to eat and as a result never learn to it or think of flesh as edible; this in itself is a cultural

adaptation to captive life. (Sclimenti 2006) 3 ChimpanZoo is an international coalition of zoos, sanctuaries, and other captive settings founded and funded by the Jane

Goodall Institute. Conferences meet yearly and attendance is open to the public. The theme and title of 2006 was “War of the

Worlds: Chimpanzee protection vs. chimpanzee exploitation.”


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Background

Chimpanzee social behaviors

Evaluating primates social hierarchies is quite difficult as identification of dominance behaviors is a highly

subjective process requiring evaluation of intent rather than result. (Discriminating between an attack and an

accident requires analysis of the initiator’s intent.) Ethology prefers empirical description over functional analysis

in initial observation, but as comparative studies require categorization, cautious delineation of even apparently

simple definitions is imperative. Dominance is formed by intraspecial social behaviors, which can generally be

classified as aggressive or affiliative.

“Aggression” popularly means “self-assertive or go-getting

behavior,” but ethologically denotes “behavior directed towards causing

physical injury to another individual,” according to Fedigan. To those

familiar with chimps, a problem is immediately apparent: non-contact

aggression, “bluff displays” in which chimps show off their strength and

attempt to intimidate others, constitute the vast majority of intracommunal

chimpanzee conflict. Only 1% of conflicts – 0.4% of conflicts between

males – result in physical clash (de Waal 1980, 87). The significant event

in dominance interactions is often the threat of a fight rather than the fight

itself. When a physical fight does occur serious injury is rare (males

restrain conflict to an apparent “unwritten” set of rules) and the response

of the remainder of the group to the fight and is just as important as the

outcome of the fight. (De Waal 1980).4

4 Please see Appendix 2 for additional information regarding the functions and definitions of aggressive behaviors.

Figure 1: “Figan brandishes a stick upon

seeing his reflection in a mirror,”

(Goodall 1971).


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Affiliative behaviors play an important role in hierarchal

formation. Physical domination is neither the sole nor determining factor

in dominance; sheer physical prowess is balanced by negotiation,

connections, alliances – essentially, politics (de Waal 1982). Alliances

are key; maintenance of a power position requires support and alphas are

frequently deposed not by a single challenger but a coalition. Building

relationships is time-consuming; the sharing of food and even mere

physical proximity are often as significant as overt action. Affiliation is a

broad generalization that includes grooming, playing, stationary contact,

and any sort of cooperation.

For the purpose of this analysis, I will use aggression synonymously with agonism5, considering all

behavior directed towards causing physical or psychological injury6 to another individual. Other behaviors, such as

mating and abnormalities7, enter this analysis extraneously.

Sexual differences

Chimpanzees are sexually dimorphic: males are larger, stronger, and though male and female hierarchies

are sometimes identified in parallel8, males are stereotypically dominant to females. Females hold responsibility for

infant care. As data from the LA Zoo reiterates, females spend a much larger portion of their time in affiliative

behavior, whereas male affiliation tends to be restricted to times of tension. Rank is dependent not only on an

individual’s own abilities and relationships, but on the rank of their siblings, and children (or vice versa); a high-

ranked female often passes her rank to her eldest daughter. In the wild, foreign males are seen as threatening but

5 In an attempt to avoid confusion between intentional and reactional aggression, the alternative term many alternative term

“agonism” , which excludes defense, and hunting, and interspecial conflicts, is used by many primatologists and ethologists to

isolate behaviors specific to social and dominance maneuverings. 6 I.e.: loss of status, rank, or confidence potentially but not necessarily as a result of physical injury.

7 E.g.: the ingestion or exploration of excrement, attempt by an adult male to nurse, an adult throwing a tantrum. Behaviors

designated “abnormal” (sometimes “undesirable”) in captive situations because they are symptomatic of larger problems. 8 In many communities, male and female hierarchies are delineated separately. The highest-ranking female is not dominant to

all other females, but holds the collective “female power” and often leading the females in fights against males and guiding

their support and affiliation with particular males.

Figure 2: Yeroen and Nikkie screaming

together, demonstrating their alliance (de

Waal 1980).


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females are welcome to emigrate9; their predilection for social affiliation is

indubitably helpful. Interestingly, sexual differentiation is less exaggerated:

Among monkeys living in conditions of relative safety and abundance,

males and females tend to be alike in functions, behaviors, and status.

Among monkeys living in more difficult conditions, males tend to be

specialized for leading the band, a function that requires high status,

and females for rearing the young; males and females are brought up in

different ways. (Russell 1972, 47.)

Safety and abundance are defining characteristics of captive chimpanzee life.

Interestingly, studies note that wild males are more gregarious than mothers,

whose attention is presumably focused on child-care (Wrangham 2000),

demonstrating the effect of resource abundance on social behavior.

Differences in wild and captive environments

The lack of hunger is the most profound difference in the lives of captive and wild chimps. Food never

concerns captive chimpanzees; nutrition is the constant obsession of wild chimps, who spend over half their time

foraging. Captive settings limit foraging (despite the best efforts of keepers and enrichment staff) and with

increased leisure time as a benefit, captive chimps have a much more concentrated social life (de Waal, 1986). The

lack of space also severely moderates the general fission-fusion10

social model of chimp communities (Sclimenti

2006).

Maturation rates differ significantly between wild and captive populations. Where Goodall’s observations

at Mahale set puberty at age 8 or 9, Jean and Zoe at the LA Zoo became pubescent at age 6. Goodall concluded that

males became socially mature at age 15; Jerrard at the LA Zoo became alpha male at the precocious age of 9. The

LA Zoo is not the only zoo or sanctuary to observe early maturation.11

Additionally, the medical attention available

to captive chimps greatly extends their life span (Conlee 2005).

9 Immigration between communities is a rare occurrence for females, generally exercised in early maturity or near the first

estrus, when their fertility is an obvious asset to a new community. 10

A social structure in which individuals come together occasionally but generally forage alone, common in primate species

with large habitats, often characterized by multiple smaller groups which break from the total community (Conlee 2005). 11

The accelerating rate of chimpanzee maturation in captivity may be linked to the increasing rate of modern human

maturation, which studies suggest is a result of improving nutrition and the increasing amount of hormones in our diet.

Figure 3: Yeroen and Luit groom

each other (de Waal 1980).


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Moreover, the problems that face chimpanzees in captivity are entirely different than those that face wild

chimps. Among captive populations physical danger is drastically limited: without access to other communities,

there is no potential for an escalation of violence and no need for males to physically

protect females and infants from external attacks; captivity’s lack of space and

vegetarian diet eliminate the hunt. The greatest stressor to captive chimps is the

introduction and reintroduction of strange individuals. Instead, the voluntary fission-

fusion of wild groups, the inconsistent group composition and the assimilation of

new individuals in captive settings12

, creates an unpredictable and presumably

stressful environment.

Intelligence, learning, and culture

Chimpanzees are capable of learning; through both observation and direct

training they share knowledge and techniques to a degree widely considered culture.

Jane Goodall’s radical discovery of chimpanzee tool use (1960) changed the understanding of chimpanzee

intelligence. Tool use and construction is now well documented in both

wild and captive environments and chimps have been seen to transmit

techniques between generations (Goodall 1971).

Apes are the indubitable masters of imitation (de Waal 2001).

Learning is more than imitation, and it occurs with less than expected

frequency:

The first … experiment seeding an expert tool user into a naïve

community found surprisingly little evidence of imitation.

Doubters soon began to ask: ‘Do apes ape?’ A raft of more

focused experiments ensued and [studies have shown]

‘emulation’, in which learning is focused on the outcomes of

what the model achieved rather than precisely how it was

done. The emerging picture is that apes do ape, but that

12

Sanctuaries deal with this to a larger extent than zoos, but both take in chimpanzees “retiring” from entertainment and

laboratory careers who not only have shorter life-expectancies than zoo/sanctuary-bred chimps, but whose poor health often

requires them to be pulled out from the group on a regular basis for medical care (Schultz 2006).

Figure 4: Flo fishes for

termites with a grass tool

(Goodall 1971).

Figure 5: Jonas watches Gorilla

extract insects from rotten wood (de

Waal 1980).


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imitation is just one of a ‘portfolio’ of varied social learning

processes, and perhaps most interestingly of all, it is applied

selectively. (Whiten 2005, 54.)

Experiments with captive chimps continue to raise our estimate of chimp

intelligence. Chimpanzees are capable of learning words, arranging them

in new formations and even inventing words13

(Goodall 1990). Chimps

are also able to lie and trick each other (Goodall 1990). Cultural

differences between wild populations include tools use, diet and greeting

customs.

Conventional wisdom: the alpha male

The alpha male is often the largest and most impressive member of a chimpanzee community, but his

strength and size are not determining factors in acquisition of rank. Maintenance of a power position often causes

the male to appear larger than he would otherwise due to the constant state of piloerection14

and increased

endocrine production. (Sapolsky 1993)

The considerable role of coalitions in the

power struggle combined with the prevalence of

bluff displays make it evident that much of the

dominance struggle is psychological. Formalized

dominance, rather than real dominance, is what

delineates the alpha’s identity. “Greeting is a …

ritualized confirmation [of] dominance,” (de Waal,

79) which, unlike grooming behavior that occurs

reciprocally (Goodall 1971), the lower-ranking

13

Washoe, a female chimpanzee who was raised in a human family and taught ASL, knows more than 300 words and taught

her adopted son Loulis many words, through direct coaching, and uses them not only with humans but other chimps. The first

time that she was exposed to a group of chimps who did not speak sign language she ran furiously back to her human

caregivers complaining about being left with the “dirty animals”. (Goodall 1990) 14

The physiological state of all body hair being pulled erect.

Figure 6: Nikkie as alpha (de Waal

1980).

Figure 7: Nikkie bows to Yeroen, who ignores him, while Luit

watches (de Waal 1980).


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always greets the higher-ranking (de Waal 1982). Greeting generally involves a “series of low, panting grunts” (de

Waal, 79) and though it may occur after a conflict it is not limited to reconciliation situations (de Waal 81).

Submissive males crouch before the dominant individual, who may acknowledge the greeting in a variety of ways

including vaulting over the submissive male’s back. The female greeting, an anogenital presentation is identical to

the sexual invitation (de Waal, 78).

Theoretically, the alpha male reserves all mating rights. When a female chimpanzee comes into estrus her

genital area swells for roughly ten days, during which time she is assiduously courted. Dominant males are

intolerant of other males mating – though many high ranking males will allow a close friend or ally to mate as a

“reward”– so other males attempt to lure swollen females away from the group to mate in secret (Goodall 1990).

The alpha male typically leads a hunt and “gets” the catch. He eats the meat or doles it out as he sees fit

(generally to females he wishes to court). In addition to presenting “prizes”, his interactions with the rest of the

group generally involve peace-keeping or “policing”:

“ [the] policing function… significantly contributes to maintaining stable resource

networks in the face of chronic perturbations that arise through conflict. … Policing not only

controls conflict, we find it significantly influences the structure of networks that constitute

essential social resources in gregarious primate societies [which play] a critical role in infant

survivorship, emergence and spread of cooperative behavior, social learning, and cultural

traditions.” (Flack, 426 in Nature)

Policing is incredibly important to the community. Other individuals, particularly in captivity may act in policing

functions15

but the alpha male is able to do so most effectively as a result of his authority.

15

At both Arnhem and the LA Zoo, past alphas were seen to perform policing functions, at times even more frequently than the

current alpha.


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Case studies: Alphas in the wild

Gombe Stream

The most dramatic power transition witnessed by Jane Goodall at

Gombe occurred in 1963. Mike rose from lowest ranking male to alpha,

thanks in large part to his display incorporating empty kerosene cans from the

camp into his displays: he dragged as many as six along the ground as he

ran.16

Once the former alpha, Goliath, accepted Mike’s dominance, they

developed a strong relationship (Goodall 1971). Mike was notably ambitious

and Goodall believes that even without the aid of human objects, he would

have achieved dominance due to his intelligence and courage.

Humphrey calmly succeeded the aging Mike, but was quickly

displaced by Figan (1973), whose intelligence and confidence as a youth

caused Goodall to predict his rise. Figan’s strong relationship with his older brother Faben17

helped him.

Humphrey, who had appeared quite nervous in front of Figan for some time, submitted after a single incident of

direct conflict. Figan maintained stability within the group, assiduously policed, and held a position of absolute

power for the first two years of his reign though he allowed Faben a large number of privileges, including mating

rights and meat.

Mahale Mountains

October 1965, Toshisada Nishida and a group of Japanese primatologists began an ongoing study at

Mahale Mountains National Park. The first stage aimed to “search for the social unit” (Nishida 1979, 92) and they

followed both the K and M groups. Over 7 years, the dominance hierarchy “remained stable”. Nishida noted the

tendency of young males to gain rank by forming a close association with an older male, a strategy that Goodall

referred to as “hero-following” (Goodall, 1990) and had conjectured was the key to identification of the alpha male

16

Once Mike learned to hurl the cans it became dangerous and efforts were made to insure that no cans were left within his

access, he attempted to use any other human object he could get his hands on, causing Goodall and her colleagues much

difficulty. (Goodall 1971) 17

Faben’s arm was crippled by polio and although still quite strong, he lacked the power to mount a campaign for power in his

own right. (Goodall 1971)

Figure 8: Mike bows to Goliath,

alpha (Goodall 1971).


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was by the frequency with which younger males chose to follow him. Kasonta was identified as alpha of the K-

group. He assumed leadership in scouting and chasing and the only male able to defeat a male from the M-group on

his own. Kasonta was intelligent and cautious, but not particularly “brave”: the most shy of any of the males and

took the longest to become habituated to human observers. (Nishida 1979)

A different kind of leader

Although researchers, keepers, and

observers begin with the assumption that there is

an individual who can be labeled the alpha due to

their rank and privileges and search to identify

that individual, this may be erroneous. Many

captive groups, due to their smaller size or family

bonds, may simply not contain a lead individual.

Nonetheless, the nature of dominance and its role

to group dynamics and the psychological well-

being of a chimpanzee community validates the

investigation of dominance and alpha identity.

The definition of alpha male roles and functions are, like all current chimpanzee behavioral models, based

on the behavior of wild chimpanzees. Studies at Mahale and Gombe have been used as a basis of comparison for

captive chimpanzees. Deviation, often symptomatic of a grave problem, is understandably worrisome. The

psychological health of captive chimps has been problematic and there have been significant efforts over the last 30

years, improving conditions and environments. The recent trend towards naturalism is a positive endeavor, the fact

remains that despite efforts, there are still, and always will be significant differences in the lives of captive and wild

chimpanzees. These differences are crucial and central to the behavior and personality of chimpanzees; creatures

with a high degree of social learning and culturalization.

Figure 9: Mama intervenes in a squabble between the adult Nikkie

and juvenile Fons by greeting and calming Nikkie and comforting

Fons (de Waal 1980).


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Furthermore, differences in the hierarchal behaviors of wild and captive chimps appear to directly

correspond to the environmental variations, as the following examples will illustrate.

Captive Chimpanzee Populations

Arnhem Zoo

Frans de Waal’s comprehensive analysis of chimpanzee hierarchy and dominance in 1979 at the Arnhem

Zoo established the significance of dominance in captive populations. The Arnhem community is one of the largest

in captivity, containing 25 individuals at the time of de Waal’s study and a very high number of males, along with a

large exhibit space and progressive design which makes the Arnhem community the closest approximation of wild

chimps in a captive setting and significantly different from other captive colonies.

A female named Mama had held the dominant

position in the Arnhem colony. When three mature males

were introduced, it was only through human interference18

that the trio was able to gain dominance over the rest of

the females. Yeroen’s subsequent dominance became

apparent in behavior and physiology: he was frequently

greeted submissively19

, never greeted anyone else, was

intolerant of other males mating, and physically striking.

Luit’s challenge was first displayed by mating

openly in front of Yeroen, and over the next two months,

Yeroen’s power eroded. During the transition, injuries were noted twice on the two males. Luit worked to isolate

Yeroen, who had dramatically increased the amount of time he spent in the company of adult females when Luit

began his challenge by interrupting his grooming bouts; Luit’s time spent in affiliative behavior with females

18

Mama and her closest ally, Gorilla, were removed from the group. When they retuned they had no support, as the other

females. This step was taken, de Waal explains, in response to the extremely high frequency and severity of violence in the

group following the introduction of the males. Yeroen’s aggression was far more restrained than Mama’s, whose fierce attacks

on the other chimps often caused injuries. Additionally, the keepers felt that as males are dominant in the wild the males would

inevitably achieve dominance and wished to protect the group from continuous violence until this occurred (de Waal, 1982). 19

At one point he received 90% of the pant-greetings and at no point less than 75%.

Figure 10: Nikkie bows to Luit, alpha (de Waal 1982).


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increased as he worked to gain their support. Yeroen had begun to throw “tantrums” to force the females to comfort

him, which stopped once he lost all support. The females did not support Luit until four months after he succeeded,

but the point at which they stopped supporting Yeroen was key to the dominance struggle. More important to Luit

than the female’s allegiance was his alliance with Nikkie. Nikkie had been subordinate even to many of the females

before Luit’s rise and afterwards, second only to Luit.

De Waal considered the dominance transition resolved when Yeroen was seen to greet Luit. Luit’s behavior

changed radically: previously, he had occasionally intervened in fights between females and children; now, the

frequency increased and he became a “loser-supporter”20

87% of the time, up from 35%. Both Nikkie and Luit

began to seek Yeroen’s friendship. Luit successfully prevented an alliance between Yeroen and Nikkie (which

would have allowed Nikkie to contend with him for power) for roughly three years, until Nikkie seized power in an

aggressive and violent takeover. Nikkie was feared, but not respected: although he received the majority of

greetings he was not groomed most often and he never became a loser-supporter. Yeroen continued to police,

preventing Nikkie from doing so, and regained as much respect and support from the females as he had received

during his time as alpha.

Los Angeles Zoo

In 1995 the LA Zoo’s Research Department organized a temporary study to observe the transition of the

chimp group into a new exhibit area. Three years later, unexpected pregnancies21

surprised the zoo and the study

was continued to monitor the infants, whose birth coincided with a power transition between the alpha male, Judeo,

and his son Jerrard. One of the infants was a victim of the struggle: Jerrard accidentally killed Toshi22

, and the other

infants were removed to be hand-raised. The study continued in order to follow the eventual reintroduction of the

20

“Looser supporter” is a term used by de Waal to refer to “an individual who intervenes in a conflict on the side of the party

who otherwise would have lost” (de Waal 1980), as opposed to a “winner-supporter”. 21

As a result of a failed vasectomy. 22

A third infant was placed with them: Zoe had been born to a lab chimp who was unable to raise or recognize her, and was

sent the LA Zoo. Zoe, born in Florida to a lab chimp who didn’t recognize her offspring, was brought to be raised with Jean

and Judeo. When the three reached three years of age in 2002, they were placed with Toto and Bonnie, the eldest male and

female. Bonnie suffered from diabetes and arthritis and needed to be separate from the energy of the main group and Toto, a

year older, kept her company and became particularly attached to the three young chimps; he played with them, comforted

them, and protected them from others (including those higher ranking than him) during the introductions that occurred during

the next three years.


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juveniles23

, which was finally completed in 2005, but the study once more stalled by new developments: the eldest

male died of heart failure and an increasing level of violence upset the precarious social balance as it became

apparent that Jerrard’s status was being challenged. Further issues, including the death of two more chimps and the

maturation of two young females complicated matters.

Group composition24

frequently changes for medical checkups or to avoid conflict. There are two

matriarchal lines: Pandora, and her offspring who have benefited from her high rank, and Bonnie’s descendents.

Jerrard’s precocious rise to power was in large part due to Pandora’s influence. Ripley benefited both from Pandora

and Jerrard’s power. Ripley is more adventurous but less belligerent than Glenn, who is roughly the same age.

Ripley spends much of his time away from the group, frequently playing with the juveniles. Shaun and Glenn,

Bonnie’s grandsons, had no such advantage; their mother, Nan, was frequently separated from the main group

during the last few years leaving them without her help. Shaun is two years older than Jerrard, slightly larger, and

known for his gentle temperament, though he often intervenes to maintain peace. Glenn has become the tallest,

leanest, and most aggressive of the males. He bullies the juveniles and frequently displays at the public. Judeo and

Jake can be disqualified from the dominance hierarchy due to their ages, respectively too old and too young. Judeo,

former alpha, continued to show many signs of being alpha: he performed a large portion of the peace-keeping

duties within the group before his death, was respected, and was followed in “hero worship” by Jake. Additionally,

he was a close ally to Jerrard, with whom he had developed a close relationship after being supplanted.

23

A third infant was placed with them: Zoe had been born to a lab chimp who was unable to raise or recognize her, and was

sent the LA Zoo. Zoe, born in Florida to a lab chimp who didn’t recognize her offspring, was brought to be raised with Jean

and Judeo. When the three reached three years of age in 2002, they were placed with Toto and Bonnie, the eldest male and

female. Bonnie suffered from diabetes and arthritis and needed to be separate from the energy of the main group and Toto, a

year older, kept her company and became particularly attached to the three young chimps; he played with them, comforted

them, and protected them from others (including those higher ranking than him) during the introductions that occurred during

the next three years. 24

The exhibit structure enables the chimps to split into as many as eleven separate groups. The chimps are generally kept in

two groups; “main group” refers to the larger.


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Pandora is generally referred to as the highest-ranking female, which

may be an understatement. She holds a position of great authority within the

group, is the main peace-keeper, and has a particularly interactive

relationship with the keepers, being known to intervene on the keeper’s

behalf at their request.25

It may be that some of her power derived from being

the alpha’s mother, nonetheless she is a significant figure in the group and

has never lost or decreased her influence.

Other AZA Communities

Marbles was without prior experience in a chimpanzee community

when he was transferred to the Sedgewick County Zoo and became the

default alpha. In his 20-year reign he never displayed many of the typical

behaviors: he did not stop aggressive displays or mating by other males and, in fact, showed little interest in mating

himself. Younger males began challenging him in 2000; Bahati dominated the group in 2001. Keepers at

Sedgewick note that dominance interactions are nominal. Pant-greetings are not present and the transition between

Marbles and Bahati was without conflict. In fact, there was more conflict following the death of the ranking female

and matriarch, Holly, in 2005, leading observers at Sedgewick to wonder if Holly had always outranked the

apparent alpha male. Holly, who had never shown extreme deference to Marbles or any male and had always

openly seized objects from them, both intervened in peace-keeping efforts and led the females in fights against the

males. Holly was quite close to Marbles until 2001; Bahati was able to take over only after Holly offered him

support and after her death, Moshi and Mahati challenged Bahati’s authority. Observers at Sedgewick say that there

is currently no clear alpha male or dominant individual. Although another female, Audra, attempted to take over

Holly’s peace-keeping role, she lacked authority, was severely injured during an intervention and backed off.

(Bailey 2006)

25

I was told a story by another researcher of a screwdriver falling into the chimp exhibit. Ripley, still young at the time, picked

it up and began to run about. Pandora, when offered an edible treat by the keepers, approached him, took the screwdriver, and

handed it to the keepers.

Figure 11: Pandora, highest-ranking

female and potential leader of the LA

Zoo group (Kaplan).


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The chimp community of the St. Louis Zoo originally had another “alpha by default”: Smoke, who was actively

dethroned by the next male to reach maturity, Hugo.

Sam, a wild-born male chimpanzee at the Sacramento Zoo, had grown up in contact with only two other

chimps. After their deaths he was introduced to another male, whose dominance he immediately accepted and never

challenged. When they fought, Sam always lead the reconciliation and seemed to act as peace-keeper between all

chimps in the group. (King 2006)

Conclusion

When I began this paper, I had no expectation of finding a succinct “answer” to the “problem” of the LA

Zoo’s hierarchy. I had hoped to determine the alpha at the LA Zoo, or to construct a captive dominance model –

both of which, it soon became apparent, were overly ambitious. Difficulties in obtaining and analyzing the data

from the Research Department, combined with my experiences in Mahale, impelled me to change direction. At the

ChimpanZoo Conference I became aware that “our problem” was common. The conference focused on the

difficulties of integrating psychologically-impaired chimps into social groups26

and behavioral differences from the

models were noted with worry; though several speakers noted that the aberrations of their chimps presented little

distress to their populations. When it was posited that simple “ignorance” was the key and that the idiosyncratic

chimps “simply didn’t know better” I began to wonder if what we were noticing were truly discrepancies or

whether a fundamental problem existed with the application of a dominance model to captive communities, i.e.

dominance defined by wild chimpanzees. At the time this idea was simply an inarticulate ramble in the margin of

my notes. After reviewing and analyzing both the original models and the captive situations, I am confident that

cultural adaptation has, and is, occurring.

In captivity, chimps neither hunt nor engage in skirmishes with foreign communities, resulting in the

decreased significance of male power reflected by the laxity of captive alpha males. Excellent diet and medical care

26

There are a large number of “professional” chimps due to the fact that the only chimps listed as endangered are those in

Africa; captive chimps are therefore not endangerd. While both professions require early retirement, neither involve any plans

or funds to retirement. As a highly cognitive and social species even the best of “working” situations leave the chimps

incapable of easy assimilation into a social group while the worst situations involve serious medical plight. (Conlee 2005)


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moderates the sexual dimorphism and differentiation, enabling females to hold greater authority and influence in

captive groups performing many of the alpha duties. Females more often demonstrate the skills significant to a

captive community, particularly affiliation with new and strange members. Frequent changes in group composition

necessitate the sharing of interventional authority.


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Appendix 1: Chimpanzees mentioned

Since Jane Goodall refused to comply with the ethological standard and refer to the chimps she studied at Gombe

by numbers, chimpanzees have been given names. To help clarify I have provided a list of all chimps mentioned in

this paper. Sibling relationships listed are maternal.

Arnhem Zoo

Luit: male, former alpha

Mama: Arnhem Zoo, oldest and highest ranking

female

Nikkie: Arnhem Zoo, male, current alpha

Yereon: Arnhem Zoo, high-ranking male,

former alpha

Gombe Stream National Park

Faben: male, older brother of Figan

Figan: male, alpha following Humphrey

Goliath: male, alpha preceding Mike

Humphrey: male, alpha following Mike

Mike: male, alpha following Goliath

LA Zoo

Bonnie: female, died 2006

Glenn: male, contender for rank, brother to

Shaun

Jake: male, born to Regina 1999

Jean: female, born to Gracie 1999

Jerrard: male, former/potential alpha

Pandora: highest ranked female, mother of

Jerrard, Gracie, and Ripley

Ripley: male, potential contender for rank,

brother to Jerrard

Shaun: male, potential contender for rank

Toshi: born to Yoshi in 1999 and killed by

Jerrard

Zoe: female, born in Florida

Mahale Mountains National Park

Alofu: M-group, male, current alpha

Darwin: M-group, male, adolescent

Kasonta: K-group, male, alpha

Kalunde: M-group, male, nicknamed “the

Kingmaker”

Sacramento Zoo

Joey: Sacramento Zoo, male

Sam: Sacramento Zoo, male

Sedgewick County Zoo

Bahati: male, former alpha

Gomez: male

Holly: female, died 2005

Mahati: male

Marbles: male, former alpha

Moshi: male

St. Louis Zoo

Hugo: male

Smoke: male

Washoe: at Central Washington University,

female, famous for ASL fluency


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Appendix 2: Notes on aggressive behavior

Aggression occurs for a variety of reasons in conflict situations. Fedigan cites Hamburg’s

identification of twelve main causational categories: protection of infants, competition for resources,

defense against predators, hunting other species, painful injury to an animal, long term changes in

dominance, daily dominance transactions, redirection downwards through the hierarchy, meeting an

unfamiliar animal, exploration of strange areas, and the crowding of strangers. The first four conflict

situations, while undeniably involving aggressive behaviors, have nothing to do with internal conflicts of

the sort necessary for evaluating dominance.

While the functions of aggressive interactions are clearly defined, the quantity and severity are

still not fully understood. Until 1972, primates were considered extremely vicious and dangerous. Jane

Goodall’s work at Gombe in Tanzania, among many other less prominent researchers, opened a new era

of primate ethology. The peaceful and intelligent aspects of chimpanzee behavior were observed and

emphasized. It was understood that the chimpanzee’s previous reputation of belligerence was built from

exaggerated and projected traveler’s tales and incomplete studies concerning out-of-context behavior in

extremely stressful situations.

As data continued to grow, however, and reports of isolated but continuing incidents of violence

came to light our understanding has become progressively less clear and more complex. Ironically, the

greatest and most sensational reports of violence stem from Goodall’s work at Gombe including the

“war” between the two groups in which males hunted, attacked, and killed members of the other group,

and the brief cannibalism of two females. While the violence at Gombe has continued to increase over

time, observations at the reserves at Budongo, Uganada and Mahale, Tanzania however, revealed

chimpanzee cultures far more peaceful. The major difference between the studies in the wild is the degree

of interaction with humans. At Gombe, in order to entice the chimpanzees to the camp, Goodall left out

bananas. The availability of food changed the Gombe chimpanzees’ social life as they began spending far

more time together in close proximity with a motive for competition. The effect of one such variable upon

the nature of their behavior is remarkable; chimpanzees in captivity, furthermore, spending 100% of their

time together, had adapted various other social conventions different from how they might behave in the

wild. Various observations in zoos helped reveal the great variability of chimpanzee social structures and

behaviors, which makes it even more important that each group be studied and observed individually.


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differences in social hierarchies in wild vs captive chimp communities: cultural adaptation

Documents

captive chimpanzee communities

wild chimpanzee communities

captive chimpanzee populations

wild communities

chimpanzee social behaviors

wild environments

social hierarchy

fundamental differences