Yellow Baboon (Papio cynocephalus)

MORPHOLOGY:
The average body mass for an adult male yellow baboon is around 23 kilograms, and for the female it is around 12 kilograms. This species exhibits sexual dimorphism, especially in body size.

RANGE:
The yellow baboon is found in the countries of Angola, Botswana, Kenya, Malawi, Mozambique, Somalia, Tanzania, Zaire, Zambia, and Zimbabwe. This species is mainly found in savanna and woodland habitats, although it can be found in scrubland, gallery forest, and semidesert.

ECOLOGY:
The yellow baboon is a frugivorous species, but leaves also constitute a major part of the diet. This species also eats flowers, roots, grasses, bark, twigs, sap, tubers, bulbs, mushrooms, lichens, aquatic plants, seeds, shoots, buds, invertebrates, and small vertebrates, such as gazelle. Females with infants mostly feed on the ground for grasses and on low bushes (Estes, 1991). Yellow baboons will sit on the ground and shuffle along as they feed for grasses and other food found on the ground (Richard, 1985). Group sizes are variable ranging from 7 to 200 individuals. This is a diurnal species.

LOCOMOTION:
The yellow baboon moves on the ground quadrupedally (Fleagle, 1988). When they run their style can be compared to the gallop of the horse (Hall, 1962).

SOCIAL BEHAVIOR:
The yellow baboon has a multimale-multifemale social system. This species has a promiscuous mating system. There is much aggression between males because of competition for females. Males disperse from their natal groups, and females are philopatric. A linear hierarchy exists within the group based on the matriline. Associations between males and females are important because when a male first tries to join a group he might have a difficult time, so an association with a female could help him. Male consorts with aid in the rearing of the infants in terms of carrying and grooming, and will come to the defense of their female when attacked by members of another troop (Estes, 1991). Male consorts will even become foster parents when the mother dies (Altmann, 1980). Adult males may act aggressively towards troop members if they lag behind when the troop is moving rapidly (Estes, 1991). Yellow baboons when threatened by predators such as leopards will mob them and sometimes the leopards are severely injured (Estes, 1991). Within the group younger males will take estrus females away from older males by solo aggressive attacks at night, while older males will take estrus females away from younger males by forming coalitions with other older males and attack during the day (Rasmussen, 1980; Collins, 1981; Smuts, 1985).

VOCAL COMMUNICATION:
two-phase bark: This is a deep, loud call which is repeated at 2 to 5 second intervals (Estes, 1991). This sounds like "wahoo" and is emitted by adult males (Estes, 1991). This call is emitted when a predator is near especially a feline one (Estes, 1991). This call is also heard when their is inter or intra group aggression between males (Estes, 1991). This call communicates male presence and arousal (Estes, 1991).

grunting: This sometimes resembles a two-phase "uh-huh" and generally is soft in nature (Estes, 1991). This call is emitted by the adult male, and this is a threat call and can occur before two-phase bark (Estes, 1991).

screeching: This call consists of high pitched screams which are repeated and may turn to a churring noise when the individual becomes caught (Estes, 1991). This call is emitted by all age classes and both sexes (Estes, 1991). This is given as a response to aggression especially by a dominant individual, and serves to inhibit aggression (Estes, 1991).

yakking: This call is short in duration and sounds like a sharp "yak" (Estes, 1991). Fear grimace often accompanies this call (Estes, 1991). This call is emitted by subadult and adult males and females, and is given by an individual who is withdrawing from a threatening animal (Estes, 1991).

clicking: This call is chirplike in nature and is emitted by infant and juvenile yellow baboons of both sexes (Estes, 1991). This is the equivalent of yakking (Estes, 1991).

ick-ooer: This is a two-phased call with the "ick" coming before the "coo" sound, and given with the lips pursed (Estes, 1991). This call is emitted by infants of both sexes, and is given as an expression of a low-level of fear or distress (Estes, 1991).

shrill bark: This call is a sound which is single, sharp, and explosive in nature (Estes, 1991). This call is emitted by all yellow baboons except adult males, and functions as an alarm signal especially to a sudden disturbance (Estes, 1991). Other members of the troop will flee upon hearing this call (Estes, 1991).

rhythmic grunts: This call is low and soft and is given by all yellow baboons except infants (Estes, 1991). This call is given when one individual is approaching another and signals friendly intentions (Estes, 1991).

doglike bark: This call is high-pitched and has more quaver and is less staccato than shrill bark (Estes, 1991). This call is emitted by subadult and adult males and females, and is given when individual or subgroups are separated from the troop (Estes, 1991).

OLFACTORY COMMUNICATION:

VISUAL COMMUNICATION:
tension yawning: This is done by an adult male yellow baboons (Estes, 1991). This is when the mouth is opened fully to reveal the canines (Estes, 1991). This is done when a rival group or a predator is approaching (Estes, 1991).

staring: This display by the yellow baboon is used as a threat display (Estes, 1991). The eyes are fixed on the stimulus and the eyebrows are raised and the scalp is retracted, the facial skin is also stretched by moving the ears back (Estes, 1991). Underneath the eye lids the color is different which contrasts sharply with the surrounding facial color (Estes, 1991)

canine display: This display is performed by adult male yellow baboons, and is variation upon tension yawning (Estes, 1991). This display serves as a threat display and is given by a lower-ranking male against a higher-ranking one when the higher-ranking individual is with an estrus female or is eating meat (Estes, 1991). Often eyebrow-raising occurs with this display (Estes, 1991).

eyebrow-raising: This is when a yellow baboon will raise the eyebrows and this functions as an aggressive gesture (Estes, 1991).

penile display: This display is performed by an adult male, and he will sit with this erect penis in full view (Estes, 1991). This display is performed while the male is guarding and communicates to other males that an adult male is present in the troop (Estes, 1991).

fear grimace: The lips are retracted so that the teeth are shown; the teeth are clenched together (Estes, 1991). This display functions as an appeasement signal to reduce aggression in aggressive encounters (Estes, 1991).

tooth-grinding: This is when the mouth is closed and the teeth are grinded together (Estes, 1991). This is heard when two males are threatening each other at a close distance (Estes, 1991).

rapid-glancing: This is when a threatened yellow baboon will turn its head away and look in the opposite direction (Estes, 1991). This serves to decrease the tension in the situation.

lipsmacking: This is when the lips are protruded, then smacked together repeatedly. This is a reassuring display by the yellow baboon (Estes, 1991).

social presenting: This is like presenting, but is done by females and juvenile males towards higher ranking males (Estes, 1991). This is a submissive display and differs from presenting by the hindquarters being lower. This is also done by a female to another female with a black infant, and she will lip-smack while doing this (Estes, 1991).

TACTILE COMMUNICATION:
social grooming: This is when one individual removes parasites and dead skin with their hands from another individual. In this species it generally only occurs between same sex individuals. This is used to reinforce the social bonds.

nose-to-nose greeting: When two individuals meet each other they touch noses as a friendly sign (Estes, 1991).

social mounting: This is generally a response to social presenting and serves to signal a friendly reassurance (Estes, 1991). This is also seen during aggressive encounters (Estes, 1991).

REPRODUCTION:
The yellow baboon gives birth to a single offspring. During estrus the perineum of the female swells up and turns pink. Females generally have 1-3 consorts from whom she chooses to mate with.

presenting: This behavior is preformed by the female to elicit copulation from the male; this pattern tells the male that she is ready for copulation (Estes, 1991).

REFERENCES:
Altmann, J. 1980. Baboon Mothers and Infants. Harvard University Press.

Burton, Frances. 1995. The Multimedia Guide to the Non-human Primates. Prentice-Hall Canada Inc.

Collins, D.A. 1981. Social behaviour and Patterns of Mating Among Adult Yellow Baboons (Papio c. cynocephalus L. 1766). Ph.D. dissertation, Cambridge University.

Estes, R.D. 1991. The Behavior Guide to African Mammals. University of California Press.

Fleagle, John G. 1988. Primate Adaptation and Evolution. Academic Press.

Hall, K.R.L. 1962. Numerical Data, Maintenance Activities and Locomotion of the Wild Chacma Baboon, Papio ursinus. Proc. Zool. Soc. Lond., Vol. 139, 181-220.

Rasmussen, K.L.R. 1980. Consort Behavior and Mate Selection in Yellow Baboons (Papio cynocephalus). Ph.D. dissertation, University of Cambridge.

Richard, A.F. 1985. Primates in Nature. W.H. Freeman and Co., NY.

Smuts, B.B. 1985. Sex and Friendship in Baboons. Aldine, Hawthorne, NY.

Last Updated: October 12, 2003.
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