These monkeys are highly sexually dimorphic. Males weigh around 23 kg and females around 12 kg. The head and body length ranges between 508 and 1,143 mm, with the tail adding an additional 456 to 711 mm to the total length. These animals have 32 teeth. The first lower premolar is modified and serves as a hone for the upper canine tooth. Males have large canine teeth, whereas the teeth of females are much smaller. There is significant geographic variation in average body size and skull size, as well as in the texture of pelage. The three forms most often described are Ibean baboons, Kinda baboons, and "typical" yellow baboons.
The orientation of the face in yellow baboons is normal, helping to distinguish them from Papio ursinus which has a downwardly flexed face. The post-orbital constriction of these animals is less pronounced than in anubis and chacma baboons. Ibean yellow baboons have large skulls. Typical yellow baboons have medium to large skulls. Kinda baboons are noted for their greatly reduced cranial size, associated smaller teeth, and weakly expressed temporal lines.
Pelage is characteristically a yellowish-brown. This overall color is produced by individual hairs which are yellow-brown for most of their length but have a black tips. In typical yellow baboons, both males and females are unmaned. However, in the Ibean form of this species, males have a weakly expressed mane. It is not at all comparable to the large mane found in Papio hamadryas, Papio anubis, and Papio papio. The head has a prominent crest on the top, produced by the longish hairs which grow upward toward the crest. This helps to distinguish this species from P. anubis which has a "flat" head. The pelage of typical and Kinda forms of this species is straight. The hair of Kinda baboons is reported to be very silky in texture. In contrast, the hairs of Ibean baboons are wavey and coarser than those of the other yellow baboons. All yellow baboons have hands and feet that are the same color as the rest of the body, and silver-colored fringes on the hands and feet.
Tail shape varies geographically. The tail of Ibean baboons resembles that of P. anubis, with the proximal portion extending straight out from the rump, and the distal 3/4 falling limp, as if the tail has been broken. Kinda baboons have a gracefully arched tail. Typical yellow baboons generally have the bent phenotype, but are variable, with some individuals showing the arched tail morphology.
In Ibean and typical yellow baboons, the natal pelage is black. This fur is replaced by the typical yellowish-brown by about 6 months of age. In sharp contrast, the natal coat of Kinda baboons is a reddish-brown color.
Yellow baboons have a somewhat "pointed" nose, and are thinner through the chest than are anubis baboons.
Average mass: males, 23 kg; females 12 kg.
Range length: head and body: 508 to 1,143 mm.
Other Physical Features: endothermic ; homoiothermic; bilateral symmetry
Sexual Dimorphism: male larger; ornamentation
- Napier, J., P. Napier. 1985. The natural history of the primates. Cambridge, Massachusetts: The MIT Press.
- Nowak, R. 1999. Walker's Mammals of the World, Sixth Edition. Baltimore: The Johns Hopkins University Press.
- Alberts, S., J. Altmann. 2001. Immigration and hybridization patterns of yellow and anubis baboons in and around Amboseli, Kenya. American Journal of Primatology, `53: 139-154.
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