Animal Info - Bonobo

(Other Names: Chimpancé Pigmeo, Chimpanzé Nain, Chimpanzé Pygmée, Dwarf Chimpanzee, Gracile Chimpanzee, Mokomboso, Pygmy Chimpanzee, Zwergschimpanse)

Pan paniscus

Status: Endangered


Contents

1. Profile (Picture)
2. Tidbits  
3. Status and Trends (IUCN Status, Countries Where Currently Found, Taxonomy, Population Estimates, History of Distribution, Threats and Reasons for Decline)
4. Data on Biology and Ecology (Size and Weight, Habitat, Age to Maturity, Gestation Period, Birth Season, Birth Rate, Early Development, Dispersal, Maximum Reproductive Age, Maximum Age, Diet, Behavior (Activity Patterns, Locomotion, Living in Trees, Sleeping, Intelligence), Social Organization (Group Structure and Composition, Inter-group Relations, Relations between Individuals), Age and Gender Distribution, Density and Range)
5. References


Profile

Pictures: Bonobo #1 (18 Kb JPEG); Bonobo #2 (21 Kb JPEG); Bonobo #3 (40 Kb JPEG) (Arkive) 

The bonobo is covered by black fur, which may turn to a grayish color in aged individuals. It has a black face and black ears. A white "tail-tuft" commonly remains in adults. Males are about 78 cm (31") tall and females are about 73 cm (29") tall. In most of its range, the bonobo occupies three kinds of forest: swamp forest, primary forest, and secondary forest resulting from clear-cutting. Fruits form the bulk of the bonobo's diet, but other plant parts, fungi, eggs, and invertebrates are also eaten. Bonobos have been observed to eat small mammals but have rarely been observed to actively hunt for meat. 

The bonobo is diurnal, arboreal, and terrestrial. It is generally active from dawn to dusk. Bonobos sleep in trees and do most of their feeding in trees, although they also forage on the forest floor.  Preparation for sleeping involves the construction of a flimsy day-nest and a sturdier night-nest. Sleeping nests are typically built in trees at 20 m (66') above the ground. Although the bonobo spends much of its time in the trees, eating and sleeping, it travels mostly on the ground. 

The bonobo has a "fission-fusion" social organization which is gregarious and generally mutually tolerant. Individuals belong to groups called "communities." While foraging and traveling, the community members generally break up into subgroups, called "parties." When parties from different communities meet each other, sometimes they are peaceful. At other times, there may be loud vocalizing, agonistic displays, and, occasionally, serious fighting. Social relations within bonobo communities are significantly affected by the species’ sexual behavior. Bonobos use sex to appease, to promote the sharing of food, to make up after fights, to gain favors, and generally to strengthen relationships. Sexual encounters are strikingly casual, almost more affectionate than erotic. 

Female associations seem to form the primary basis of the community, and it is the females that generally have the leadership role. If there is a female rank order, it is largely based on seniority rather than physical intimidation - older females generally have a higher status than younger ones. Dominant status among males is actively sought, and this leads to more fighting among males than among females. On the other hand, male bonobos also groom each other regularly. Adult females are dominant over males. Females sometimes form coalitions against males and can influence the males to behave submissively. Males are only rarely aggressive towards females.   

The bonobo has only been found in The Democratic Republic of the Congo. Within its range, the bonobo is absent or rare in many areas and is common only in a few scattered localities. Threats to the bonobo include loss and fragmentation of habitat due to increasing human population, agricultural expansion and logging. It also is hunted extensively by people for meat and for body parts used in religious rituals and traditional medicine. 


Tidbits

*** The bonobo is also called a "pygmy chimpanzee," but this is a misnomer. The bonobo has a more slender build than chimpanzees, but it weighs as much as one of the subspecies of chimpanzee. (Macdonald 2001) 

*** The bonobo has the only great ape families led by females. It has a sophisticated social structure that encourages cooperation and peace and settles disputes through sex. Bonobos coexist peacefully in large communities of over 100 members. (Focus 2005b)

*** The origin of the name "bonobo": In 1936, the German Zoo Director H. Heck bought two pygmy chimpanzees (as they were known at the time) from an African animal dealer. The dealer called them "bonobos". The origin of this term is unclear - some think that it may be a garbled version of "Bolobo", a town in The Democratic Republic of the Congo where scientists first found bonobos in the 1920's. Heck then coined this word as a German species name. (Kemf & Wilson 1997, Kortlandt 1998) 

*** Etymology of the scientific name of the bonobo: the genus name ("Pan") comes from the name of the Greek god of flocks, shepherds, and woods, who had a human torso, but the legs, beard, ears, and horns of a goat; the species name ("paniscus") is a diminutive (originating from when the bonobo was originally (and erroneously - see above) known as the "pygmy chimpanzee") (de Waal 1997). 

*** Although they are fundamentally similar in anatomy, there are a number of characteristics that can be used to distinguish the bonobo from the chimpanzee. The bonobo has a black face (the chimpanzee’s face is variable from pink to brown or black), a prominent white tail tuft which is retained by adults (chimpanzees only have one at the juvenile stage), and a slimmer body and relatively longer legs. Behavioral differences between the bonobo and the chimpanzee include: bonobos are sensitive, lively and nervous, whereas chimpanzees are coarse and hot-tempered; and physical violence almost never occurs in bonobos, yet is common in chimpanzees. From the standpoint of their social organizations, both bonobos and chimpanzees live in fission-fusion societies, but otherwise there are major differences. For example,  chimpanzee males are more dominance-oriented and "political" than bonobo males, and chimpanzee females have less social influence than their bonobo counterparts.  Furthermore, bonobos rarely perform the complex confrontations known among chimpanzees, in which one opponent recruits supporters against the other, thus forcing the latter to do the same, until entire sections of society oppose each other on the battle field. (de Waal 1997, Burnie & Wilson 2001, Macdonald 2001, WWF 2005)

*** The Bonobo and People:

  • Most of the scientific community now consider bonobos and chimpanzees to be humans' closest living relatives. Genetic evidence indicates that we last shared a common ancestor with them about 6 million years ago. (Macdonald 2001) 
  • According to DNA analyses, humans share over 98 % of our genetic material with both the bonobo and the chimpanzee (de Waal 1997)

Status and Trends

IUCN Status:

  • 1960's: Insufficiently Known 
  • 1970's - 1994: Vulnerable
  • 1996: Endangered 
  • 2000 - 2004: Endangered (Criteria: A2cd) (IUCN 2004)

Countries Where the Bonobo Is Currently Found:

2004: Occurs in The Democratic Republic of the Congo. (IUCN 2004)

Taxonomy:

In 1929 it was first suggested by some scientists that the anatomical differences between the bonobo and the chimpanzee were sufficient to warrant their classification as separate species.  The bonobo was still considered by others to be a subspecies of chimpanzee. However, recent evidence suggests that the two are distinct species. (de Waal 1997, Nowak 1999).

Population Estimates:

[Note: Figures given are for wild populations only.]

There are no reliable estimates of total numbers for the bonobo. Many years of civil unrest in The Democratic Republic of the Congo has meant that few recent surveys have been done. Distribution of bonobos within the country is very patchy, and total population estimates vary widely (from 10,000 to 50,000), reflecting our poor understanding of this ape. (WWF 2005)

History of Distribution:

The bonobo has only been found in one region of Central Africa: between the Zaire River, the Lomami River, the Kasai/Sankuru Rivers, and the Lake Tumba/Lac Ndombe region in The Democratic Republic of the Congo. It appears to be absent from the central part of this area between the Momboyo River and the Busira River. Within this large forest zone, totaling approximately 350,000 sq km (135,000 sq mi), the bonobo is absent or rare in many areas and is common only in a few scattered localities. (de Waal 1997, WWF 2005) 

Distribution Map #1 (14 Kb GIF) (Afr. Mamm. Databank)
Distribution Map #2 (25 Kb GIF) (Calvin 2005)

Threats and Reasons for Decline:

The bonobo is threatened by loss and fragmentation of habitat due to increasing human population, agricultural expansion and logging. It also is hunted extensively by people for meat and for body parts used in religious rituals and traditional medicine. Trapping by snares set for other animals is an additional threat. (Nowak 1999, Macdonald 2001)


Data on Biology and Ecology

Size and Weight:

Height: Male: 73 - 83 cm (29 - 33"); Female: 70 - 76 cm (28 - 30") (Macdonald 2001).

Weight: A survey of most of the world's captive bonobos in the 1990's put the average weight of males at 43 kg (95 lb) and the average weight of females at 37 kg (82 lb) (de Waal 1997).

Habitat:

In most of its range, the bonobo occupies three kinds of forest: 1) Swamp forest near the rivers includes relatively low trees, which are supported by prop roots, or by leaning against each other, because of the loose, muddy soil. 2) Primary forest grows on a firmer foundation and is darker because of the dense canopy and the much taller trees, including trees up to 50 m (160') high. The lack of light makes for relatively sparse undergrowth. 3) Finally, there is the secondary forest resulting from clear-cutting. After the loggers have left the area, vegetation soon covers their traces, but even when full-sized trees have returned, tree density remains below that of the primary forest. Thick patches of herbs grow at places where sunlight reaches the forest floor. In some parts of their range, the bonobo habitat alternates between forest, open woodlands, and grasslands. (de Waal 1997) 

The bonobo is found in the Southern Congo Basin Forests and Western Congo Basin Forests Global 200 Ecoregions. (Olson & Dinerstein 1998, Olson & Dinerstein 1999)

Age to Maturity:

Females reach sexual maturity at approximately 12 years of age and the first birth occurs at 13 - 15 years of age. A female bonobo reaches adult size at 14 - 16 years of age. (de Waal 1997, WWF 2005) The male bonobo reaches its full adult size at about 16 years of age, but it may be sexually mature well before this (Macdonald 2001).

Gestation Period:

The gestation period is 220 - 240 days.

Birth Season:

No seasonality in the bonobo's reproduction has been observed (Nowak 1999).

Birth Rate:

In the wild, there are single births about every 5 years (de Waal 1997). Females have between five and six offspring in a lifetime (WWF 2005).

Early Development:

After a period of clinging to its mother’s belly, an older infant rides on her back. Its mother takes it everywhere she goes. Even after 1 year of age, a bonobo infant does not walk or climb much, and it is very slow. The mother keeps it nearby. A young bonobo starts to play with others at about 1.5 years of age. The mother carries her youngster while traveling until it reaches at least 3 or 4 years of age. (de Waal 1997, Colbeck 1998) 

A young bonobo is weaned at about 3 years of age. The mother continues to protect, groom, and share nests with her offspring for another year or two after weaning.  A female juveniles gradually loosens her tie with her mother and travels farther away from her than does a son. Sometimes a young female is observed who stays alone, or is peripheral to a party, even if she is only 5 or 6 years of age. A son, however, is always near his mother. (de Waal 1997, Burnie & Wilson 2001) 

Dispersal:

An adolescent female bonobo disperses from her natal community before she has started to reproduce, generally at the age of 7, and joins a neighboring community. She has no further ties with her mother. Adult females occasionally transfer into another community, although this apparently is rare. A male stays in his mother’s community for life and maintains a permanent association with her. (de Waal 1997, Nowak 1999, Macdonald 2001, WWF 2005) 

Maximum Reproductive Age:

Estimated at 40 years (de Waal 1997).

Maximum Age:

A captive female bonobo was estimated to be around 40 years old (de Waal 1997). The lifespan of bonobos in the wild is unknown (WWF 2005).

Diet:

Fruits form the bulk of the bonobo's diet, but leaves, pith, flowers, bark, seeds, honey, fungi, eggs, and invertebrates (e.g. termites, caterpillars and earthworms) are also eaten. The bonobo has been observed to eat small mammals, including shrews, flying squirrels, and small antelopes such as young duikers. However, unlike the chimpanzee, the bonobo has rarely been observed to actively hunt for meat. It captures most animal prey individually and opportunistically, rather than during a group hunt. The bonobo does most of its feeding in trees, mostly in the crowns of large fruit trees, although it also forages on the forest floor. The main feeding activity, in the morning, is usually concentrated on fruits. In the afternoon the bonobo may switch to less energy-rich, more fibrous foods. (de Waal 1997, Kingdon 1997, Nowak 1999, Macdonald 2001, Burnie & Wilson 2001, WWF 2005) 

Behavior:

Activity Patterns: The bonobo is diurnal, arboreal, and terrestrial. It is generally active from dawn to dusk, a 12 - 13 hour period in its equatorial habitat. It feeds for at least half of this time unless food is plentiful, whereupon it may feed for only a third of the time. The bonobo begins feeding in a tree, frequently in the dense upper forest canopy, shortly after waking, rests, moves leisurely on the ground to the next food tree, becomes less active toward the middle of the day, and then repeats the pattern in the afternoon. Average daily movement is about 2.4 km (1.5 mi). (de Waal 1997, Kingdon 1997, Nowak 1999, Macdonald 2001)

Locomotion: The bonobo travels mostly on the ground, where it engages in quadrupedal "knuckle-walking," a form of locomotion it shares with the gorilla. The bonobo can stand upright and often does so when climbing or reaching for food, but its bipedal locomotion is awkward compared to our own. The bonobo, like other apes, does not swim (Therefore, wide rivers such as the Zaire River are barriers to the mixing of populations of apes on either side of the river.). However, the bonobo shows no hesitation in wading through shallow water. (Stuart & Stuart 1996, de Waal 1997. Macdonald 2001) 

Living in Trees: The bonobo has a body that is well adapted for arboreal activities. Its arms are considerably longer than its legs, its fingers much longer than those of humans, and its shoulder joints are highly mobile. These and other features of its skeleton and musculature enable it to hang from tree branches by its arms and make it adept at climbing tree trunks and lianas and at clambering in the crowns of trees. (Macdonald 2001) 

Sleeping: The bonobo sleeps in a tree. Preparation for sleeping involves the construction of a flimsy day-nest and a sturdier night-nest. Nests are commonly made close to the current feeding site, and the bonobo prefers to seek out flexible, multi-branched trees for this purpose. It draws in all reachable fronds and stuffs them into a wedging fork to form a springy, globular platform. Sleeping nests are typically built in trees at 20 m (66') above the ground. One study reported that the average height of 46 nests seen was 25 m (82‘). (MacKinnon 1976, Lee et al. 1988, Kingdon 1997, Macdonald 2001) 

Intelligence: The bonobo has a brain that, with a volume of 300 - 400 cc (18 - 24 cu in), is large both in absolute terms as well as relative to its body size. It does well on problem-solving tasks in laboratory settings, and it has shown some capability to engage in symbolic communication in captivity when given intensive training. Tool use in the wild has not been observed, but captives have been reported to construct ropes to swing from; to wipe themselves with leaves; and to use sticks to probe, rake, and pole-vault over water. (Nowak 1999, Macdonald 2001) 

Social Organization:

Group structure and Composition: The bonobo has a "fission-fusion" social organization which is gregarious and generally mutually tolerant. Individuals belong to groups called "communities" that have 15 - 150 members and that seem to be socially bonded. While foraging and traveling, the community members generally break up into subgroups, called "parties," that vary in size and composition on a daily and even hourly basis. All associations, except the one between mother and dependent offspring, are of a temporary nature.  Party size depends on the availability of food - parties grow larger if individuals can feed together, such as in large fruiting trees. Parties usually contain 2 - 15 individuals but may contain as many as 40. A party is usually based on a female and her male offspring plus adult female associations. Community members tend to gather at night ("fuse") in clusters of nests. In the morning, they break up again ("fission") into foraging parties. (de Waal 1997, Nowak 1999, Macdonald 2001, WWF 2005) 

Inter-group Relations: There is extensive overlap among community home ranges, but parties of one community avoid those of the other. When there is an encounter, sometimes they are peaceful. At other times, there may be loud vocalizing, agonistic displays, and occasionally serious fighting. But the boundary patrols and deliberate "lethal raids" of the chimpanzee have not been observed. (Nowak 1999, Macdonald 2001) 

Relations between Individuals: Adult females appear to have a tendency to come together in strongly bonded units, even though they usually are not close relatives. Such female associations seem to form the primary basis of the community, and it is the females that generally have the leadership role. A status hierarchy among females is not wholly absent, but it is very vague - there are no "high-ranking" females, only "influential" ones. If there is a female rank order, it is largely based on seniority rather than physical intimidation - older females generally have a higher status than younger ones.

Dominant status among males is actively sought, and this leads to more fighting among males than among females. On the other hand, male bonobos also groom each other regularly. Females support their adult sons in competition with other males and can influence their sons’ dominance ranking. A high-ranking mother confers high-ranking status on her male offspring. Whereas rank positions near the top, especially the position of alpha male, tend to be quite clear, mid-ranking and lower positions are not so well defined. 

Adult females are dominant over males. Females sometimes form coalitions against males and can influence the males to behave submissively. Furthermore, males commonly defer to females during feeding, rather than trying to take feeding spots or food items. Males are only rarely aggressive towards females. Even younger females sometimes dominate adult males. 

Social relations within bonobo communities are significantly affected by the species’ sexual behavior, which is used to manage and diffuse tension. When it comes to bonobo sex, no rules apply - everybody does it with everybody else. Bonobos use sex to appease, to promote the sharing of food, to make up after fights, to gain favors, and generally to strengthen relationships. Sexual encounters are strikingly casual, almost more affectionate than erotic. 

(de Waal 1997, Colbeck 1998, Nowak 1999, Macdonald 2001, WWF 2005) 

Age and Gender Distribution:

The total numbers of identified individuals in the best-known wild bonobo communities, together with the ratios of adult males to adult females, have been reported as follows (de Waal 1997)

  • Lomako Eyengo: 34, 6:12 
  • Lomako Hedons: 44, 8:14 
  • Lomako Rangers: 26, 5:8 
  • Wamba E: 75, 20:20
  • Wamba E1: 32, 7:9 
  • Wamba E2: 36, 8:11 

Density and Range:

Density

Estimates of bonobo density in The Democratic Republic of the Congo include (van Krunkelsven et al. 2000, Oryx 2001):

  • Lilunga: 0.43 bonobos/sq km (1.1 bonobos/sq mi)   
  • Lomako Forest: 2.98 bonobos/sq km (7.75 bonobos/sq mi) 
  • Salonga National Park: 1.15 bonobos/sq km (3.0 bonobos/sq mi) 
  • Wamba: 1.7 bonobos/sq km (4.4 bonobos/sq mi) 
  • Yalosidi: 0.45 bonobos/sq km (1.2 bonobos/sq mi) 

Generally a home range of bonobos has a density of approximately 2 bonobos/sq km (5 bonobos/sq mi) (Nowak 1999).

Range

Bonobo communities occupy home ranges of about 22 - 68 sq km (8.5 - 26 sq mi) (Nowak 1999).

References

Afr. Mamm. Databank, Arkive, Badrian & Badrian 1977, Burnie & Wilson 2001, Calvin 2005, Colbeck 1998, Cologne Zoo, Focus 2005b, IUCN 1966, IUCN 1994, IUCN 1996, IUCN 2000, Kemf & Wilson 1997, Kingdon 1997, Kortlandt 1996, Kortlandt 1998, van Krunkelsven et al. 2000, Lee et al. 1988, Macdonald 2001, MacKinnon 1976, Nowak 1999, Oates 1996, Olson & Dinerstein 1998, Olson & Dinerstein 1999, Oryx 2001, Rowe 1996, Stuart & Stuart 1996, Susman et al. 1981de Waal 1997. WWF 2005


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