Themandrill (Mandrillus sphinx) is a largeOld World monkey native to west central Africa. It is one of the most colorful mammals in the world, with red and blue skin on its face and posterior. The species issexually dimorphic, as males have a larger body, longer canine teeth and brighter coloring. It is the largest monkey in the world. Its closest living relative is thedrill, with which it shares thegenusMandrillus. Both species were traditionally thought to bebaboons, but further evidence has shown that they are more closely related towhite-eyelid mangabeys.
Mandrills mainly live intropical rainforests but will also travel acrosssavannas. They areactive during the day and spend most of their time on the ground. Their preferred foods are fruit and seeds, but mandrills will consume leaves,piths, mushrooms, and animals from insects to juvenilebay duiker. Mandrills live in large, stable groups known as "hordes" which can number in the hundreds. Females form the core of these groups, while adult males are solitary and only reunite with the larger groups during the breeding season. Dominant males have the most vibrant colors and fattest flanks and rumps, and have the most success siring young.
The wordmandrill is derived from the English wordsman anddrill—the latter meaning'baboon' or'ape' and being West African in origin—and dated to 1744.[3][4][5] The name appears to have originally referred tochimpanzees.[6] The first scholar to record the name for the colorful monkey wasGeorges-Louis Buffon in 1766. It was called the "tufted ape", "great baboon" and "ribbernosed baboon" byThomas Pennant inA Synopsis of Quadrupeds (1771) andA History of Quadrupeds (1781).[7]
Historically, some scientists placed the mandrill and the closely relateddrill (M. leucophaeus) in the baboon genusPapio.Morphological andgenetic studies in the late 20th and early 21st centuries found a closer relationship towhite-eyelid mangabeys of the genusCercocebus. Some have even proposed that the mandrill and drill belong toCercocebus.[10] Two genetic studies in 2011 clarifiedMandrillus andCercocebus as separatesister lineages.[11][12] The two generasplit around 4.5 million years ago (mya) while the mandrill and drill split approximately 3.17 mya. Fossils ofMandrillus have not been found.[13]
Some authorities have divided mandrill populations intosubspecies: the northern mandrill (M. s. sphinx) and the southern mandrill (M. s. madarogaster). A proposed third subspecies,M. s. insularis, was based on the mistaken belief that mandrills are present onBioko Island.[14][15] The consensus is that mandrills belong to one subspecies (M. s. sphinx).[16]
Skull of male mandrill, showing the long canines and ridged bone swellings
The mandrill has a stocky body with a large head and muzzle, as well as a short and stumpy tail.[19] The limbs are evenly sized and the fingers and toes are more elongated than those in baboons,[20] with a more opposable big toe on the feet.[21] The mandrill is the mostsexually dimorphic primate,[22] and it is the largestmonkey.[23] Females are less stocky and have shorter, flatter snouts.[19] Males have a 70–95 cm (28–37 in) head-body length and weigh 19–30 kg (42–66 lb) while females have a 55–70 cm (22–28 in) head-body length and weigh 10–15 kg (22–33 lb).[24] Most of the teeth are larger in males,[25] and the canine teeth reach up to 4.5 cm (1.8 in) and 1 cm (0.39 in) long for males and females respectively.[22] Both sexes have 7–10 cm (2.8–3.9 in) long tails.[24]
Male and female mandrills, showing size and color dimorphism
Thecoat of the mandrill is primarily grizzled orbanded olive-brown with a yellow-orange beard and sparse, light hairs on its underside.[19][24] The lips are surrounded by stiff whitewhiskers, and white bare skin exists behind the ears. Male mandrills have a "crest" of long hairs on the head and neck, while both sexes have chest glands which are covered by long hairs. The face, rump and genitals have less hair.[26] The mandrill has a red line running down the middle of their face which connects to their red nose. On either side of the line, the skin is blue and grooved.[24][27] In males, the blue skin is supported by ridged bone swellings. Females have more subdued facial coloring, but this can vary between individuals with some having stronger red and blue hues and others being darker or almost black.[28] In males, the rump and areas around the genitals are multi-colored, consisting of red, pink, blue and purple skin,[20][28] with a red penis shaft and violet scrotum. The genital and anal areas of the female are red.[29]
The mandrill is among the most colorful mammals.Charles Darwin wrote inThe Descent of Man: "no other member of the whole class of mammals is coloured in so extraordinary a manner as the adult male mandrill".[30] The red coloration is created by blood vessels near the surface of the skin,[31] while the blue is a form ofstructural coloration caused by parallel arrangements ofcollagen fibers.[32] The blue ridges on males contrast with both the red facial hues and the green foliage of their environment, helping them stand out to other individuals.[33] The darker and more subdued coloring of female faces is caused bymelanin.[34]
The mandrill is anomnivore. The core of its diet consists of plants, of which it eats over a hundred species.[38] One study found the mandrill's diet was composed of fruit (50.7%), seeds (26.0%), leaves (8.2%),pith (6.8%), flowers (2.7%), and animal matter (4.1%), with other foods making up the remaining 1.4%.[39] During the wet season, mandrills forage in continuous forest, when fruit is most available, while during the dry season they feed in gallery forests and at the borders of savannas and forests.[40]
The rest of a mandrill's diet is largely made up of invertebrates, particularlyants,termites,crickets,spiders,snails, andscorpions. They also eat birds and their eggs, frogs and rodents.[38][41] Mandrills have been recorded preying on larger vertebrates such as juvenilebay duikers. Such prey is killed with a bite to the head followed by pulling off the hind limbs and tearing open the belly. Individuals may cooperate during hunting and share kills.[41]
Predators, parasites and pathogens
Leopards may prey on mandrills, as traces of mandrill have been found in their feces.[42] Other potential predators includeAfrican rock pythons,crowned eagles and chimpanzees.[36][43] Leopards are a threat to all individuals, while eagles are only threats to the young.[44][43] In a study where a mandrill group was exposed to models of leopards and crown eagles, the leopard models tended to cause the mandrills to flee up trees while the eagles were more likely to drive them to take cover. The dominant male did not flee from either model types; in the case of the leopards, he paced around while looking in their direction.Alarm calls were more commonly heard in response to leopards than eagles.[44]
Mandrills can become infected with gastrointestinal parasites, such asnematodes andprotozoa.Tumbu fly larvae may live under the skin and individuals that walk though grassland can get infested withticks. Blood parasites include themalaria-causingPlasmodium and the nematodeLoa loa, which is transmitted by bites fromdeer flies.[45] Wild mandrills have tested positive for SIV,enteroviruses of the speciesEV-J andastroviruses, including a human variant.[17][46]
Mandrills are mostlydiurnal and are awake around 10 hours per day from morning to dusk.[38][47] They often pick a new tree to sleep in every night.[38] Mandrills have been observedusing tools; in captivity, they use sticks to clean themselves.[48] In the wild, mandrills appear to live 12–14 years, but captive individuals can live 30–40 years.[49]
Social structure
Mandrills live in large "supergroups" or "hordes" that can contain hundreds of individuals.[40][50][51] These large groups are fairly stable and do not appear to be gatherings of smaller ones. At Lopé National Park, Gabon, mandrill hordes were found to have an average of 620 individuals, and some groups were as large as 845, making them possibly the largest cohesive groups of wild primates.[51] Another study in Lopé found that a horde of 625 mandrills consisted of 21 dominant males, 71 less dominant and subadult males, 247 adult and adolescent females, 200 juveniles, and 86 dependent infants.[40] A mandrill horde of around 700 individuals in northern Lopé had a totalhome range of 182 km2 (70 sq mi), 89 km2 (34 sq mi) of which was suitable habitat. The supergroup would occasionally diverge into two to four subgroups before reuniting.[52] Another 15-month long study of a 120-member group found a home range of 8.6 km2 (3.3 sq mi) with an average traveling distance of 2.42 km (1.50 mi) per day.[47]
Hordes consist ofmatrilineal family groups, and females are important for maintaining social cohesion. Strong connections with their relatives may lead to support during conflicts, higher survival rate of offspring and a longer lifespan for females. Dominant females are at the center of the group network and their removal leads to fewer social connections in the group.[53] The social rank of a mother mandrill can contribute to the social rank of both her female and male offspring.[54] Mature males are not permanent members of hordes but join as females become sexually receptive and leave as their sexual cycle ends. As a result, the coloration of the male mandrill may be intended to attract attention in a social structure with no long-term relationships between mates.[51] Higher ranking males are found in the center of a social group while lower ranking males are more likely to occupy the periphery.[55] Females have some control over the males and coalitions can expel an unwanted male from a group.[56] Outside the breeding season, males are believed to lead a solitary life and all-malebachelor groups are not known to exist.[51]
Both male and female mandrills rub and mark trees and branches with secretions from their chest glands, though males (and especially dominant males) mark more than females. The chemicals in the secretions signal the individual's sex, age and rank. Scent-marking may also serve aterritorial function, captive alpha males will mark enclosure boundaries.[57] Mandrills willgroom one another, even when there is no benefit to be gained from doing so.[58] During grooming, subordinates prefer to pick at other mandrills from behind, in order to minimize eye contact and give them more time to flee if the more dominant individual attacks. The recipients of grooming will try to maneuver the groomer to pick at more "risky" areas.[59]
Reproduction and development
"Fatted" male mandrill showing colorful posterior
Dominant oralpha male mandrills have the most mating success. Upon gaining alpha status, males develop larger testicles, redder faces and posteriors, more secretion from the chest glands and fatter sides and rumps. When a male loses dominance, these physiological changes are at least partially reversed.[31] The blue facial skin is more consistent in brightness.[31][60] Higher ranking males tend to have more contrast between red and blue facial coloring.[33] Due to their distribution of fat, dominant males are also known as "fatted" males while subordinate males are known as "non-fatted" males.[61] Canine length also correlates with dominance, and males are less likely to sire offspring when their canines are under 30 mm (1.2 in).[22] In some individuals, the development ofsecondary sexual characteristics issuppressed in response to competition from other males.[55] Male mandrills tend to establish dominance with vocalizations and facial expressions, rather than fighting.[62]
Mating occurs mostly during the dry season, with femaleovulation peaking between June and September. Receptive females havesexual swellings on their posteriors,[63] and the red facial coloration can communicate age and fertility.[64] Males also appear to detect a female's reproductive state using thevomeronasal organ (known as theflehmen response).[65] Dominant males try to monopolize access to females by mate guarding, which involves the male tending to andcopulating with a female for days.[66] Dominant males tend to sire most of the offspring, but they are less able to monopolize access to the females when many females reachestrus at the same time. A subordinate male is also more likely to have reproductive success if he is closely related to an alpha male.[67] An ovulating female tends to allow the brightest colored males to come near her and touch herperineum, and is more likely to groom and solicit them.[68] The female signals her willingness to mate by positioning her posterior towards the male. Intercourse lasts no more than 60 seconds, with the male mounting the female and making pelvic thrusts.[69]
Mandrill infant perched on mother
Mandrill gestation lasts an average of 175 days with most births taking place between January and March, during the wet season. Gaps in between births range from 184 to 1,159 days with an average of 405 days.[70] and tend to be shorter in higher ranking females.[71] Infants are born at an average weight of 640 g (23 oz), and mostly bare-skinned with some white hair and a tuft of dark hair on the head and along the spine. Over the next two or three months, they develop their adult hair color on the body, limbs and head while the flesh-colored face and snout darken.[72] Dependent infants are carried on their mothers' bellies.[73][51] Young are typically weaned at around 230 days old. Males become more sexually dimorphic between four and eight years old, at which point females are already beginning to give birth.[54] Males start leaving their horde after they reach six years old.[51] Females reach their adult size around seven years while males do so at ten years.[54]
Communication
Female mandrill facepalming
Mandrills communicate with various facial expressions and postures. Threat displays involve open mouth staring, usually in combination with head bobbing, ground slapping andraised hair. These gestures are usually performed by dominant individuals towards subordinates, who respond with bared teeth grimaces, signaling fear and aggression. Both young and low-ranking females show submission and anxiety with a pouting "duck face". Playful intentions are communicated with a relaxed open-mouth face. Males approaching females display a "grin" or silent bared-teeth face and make lip-smacks. This display may also occur with teeth-chattering.[74] Mandrills can develop and pass on new gestures; captive individuals at theColchester Zoo, Englandfacepalm to discourage being disturbed, particularly while resting.[75]
Mandrills also produce several vocalizations, for both long and short distances. During group movements, adult males produce two-phase grunts and one-syllable roars, both of which are equivalent to the "wahoo" bark of baboons. Other group members produce "crowings", which last almost two seconds and start as a vibration and transition into a longer harmonic sound. Short distance vocals include the "yak", a sharp, repeating, pulse-like call produced by all individuals except for adult males and made in tense situations. Mandrills may also grunt during aggressive encounters. Growls are used to express mild alarm while intense alarms come in the form of a short, two-syllable sharp call known as the "k-alarm". A sharp, loud "K-sound" is produced for unknown reasons. Screaming is a signal of fear and made by individuals fleeing, while thegirney, a type of moan or purr, is made as a form of appeasement or frustration among females and young.[76][77] Individual voices are more similar among related animals, but unrelated mandrills can have similar voices if they regularly interact.[78]
Threats and conservation
As of 2019, theIUCN Red List lists the mandrill asvulnerable. Its total population is unknown but is suspected to have decreased by more than 30 percent over the last 24 years. Its main threats arehabitat destruction and hunting forbushmeat.[1] The mandrill appears to have suffered massive habitat loss in Equatorial Guinea and southern Cameroon, while its range in the Republic of the Congo is limited and its status is unknown.[79] In addition, while mandrills live in groups numbering in the hundreds, hunting in Cameroon and Equatorial Guinea appears to have led to smaller group sizes.[1] Gabon is seen as the most important remaining refuge for the species, and the country's low population density and vast rainforests make it a good candidate for mandrill conservation. Surveys have shown high population numbers for other primate species like chimpanzees and gorillas. A semi-wild population exists at theInternational Centre of Medical Research of Franceville.[80]
The mandrill is listed under Appendix I byCITES, banning commercial trade in wild-caught specimens, and under Class B by theAfrican Convention, which provides them protection but allows special authorization for their killing, capturing or collecting.[1][81][82] There is at least oneprotected area for mandrills within each of the countries they inhabit.[1] In Gabon, most of the rainforests have been leased to timber companies but around 10 percent is part of a national parks system, 13 of which were established in 2002.[83]
^abcSetchell, J. M.; Dixson, A. F. (2001). "Changes in the secondary sexual adornments of male mandrills (Mandrillus sphinx) are associated with gain and loss of alpha status".Hormones and Behavior.39 (3):177–184.doi:10.1006/hbeh.2000.1628.PMID11300708.S2CID7560147.
^abcSabater Pi, J. (1972). "Contribution to the ecology ofMandrillus sphinx Linnaeus 1758 of Rio Muni (Republic of Equatorial Guinea)".Folia Primatologica.17 (4):304–319.doi:10.1159/000155442.PMID4624917.
^abcdefgHoshino, J. (1985). "Feeding ecology of mandrills (Mandrillus sphinx) in Campo Animal Reserve, Cameroon".Primates.26 (3):248–273.doi:10.1007/BF02382401.S2CID12216632.
^abKudo, H.; Mitani, M. (1985). "New record of predatory behavior by the mandrill in Cameroon".Primates.26 (2):161–167.doi:10.1007/BF02382015.S2CID20928597.
^Mombo, I. M.; Boundenga, L.; Suquet, E.; et al. (2021). "Natural infection of free-ranging mandrills (Mandrillus sphinx) by enteroviruses and astroviruses in southern Gabon".Microbial Pathogenesis.150: 104659.doi:10.1016/j.micpath.2020.104659.PMID33249166.S2CID227236595.
^abBrockmeyer, T.; Kappeler, P. M.; Willaume, E.; Benoit, L.; Mboumba, S.; Charpentier, M. J. E. (2015). "Social organization and space use of a wild mandrill (Mandrillus sphinx) group".American Journal of Primatology.77 (10):1036–1048.doi:10.1002/ajp.22439.PMID26235675.S2CID38327403.
^White, E. C.; Dikangadissi, J.-T.; Dimoto, E.; et al. (2010). "Home-range use by a large horde of wildMandrillus sphinx".International Journal of Primatology.31 (4):627–645.doi:10.1007/s10764-010-9417-3.S2CID44740032.
^abcSetchell, J. M.; Lee, P. C.; Wickings, E. J.; Dixson, A. F. (2001). "Growth and ontogeny of sexual size dimorphism in the mandrill (Mandrillus sphinx)".American Journal of Physical Anthropology.115 (4):349–360.doi:10.1002/ajpa.1091.PMID11471133.
^abSetchell, J. M.; Dixson, A. F. (2001). "Arrested development of secondary sexual adornments in subordinate adult male mandrills (Mandrillus sphinx)".American Journal of Physical Anthropology.115 (3):245–252.doi:10.1002/ajpa.1079.PMID11424076.
^Setchell, J. M.; Knapp, L. A.; Wickings, E. J. (2006). "Violent coalitionary attack by female mandrills against an injured alpha male".American Journal of Primatology.68 (4):411–418.doi:10.1002/ajp.20234.PMID16534806.S2CID40486302.
^Setchell, J. M.; Dixson, A. F. (2002). "Developmental variables and dominance rank in adolescent male mandrills (Mandrillus sphinx)".American Journal of Primatology.56 (1):9–25.doi:10.1002/ajp.1060.PMID11793410.S2CID25762754.
^Charpentier, M. J. E.; Mboumba, S.; Ditsoga, C.; Drea, C. M. (2013). "Nasopalatine ducts and flehmen behavior in the mandrill: reevaluating olfactory communication in Old World primates".American Journal of Primatology.75 (1):703–714.doi:10.1002/ajp.22146.PMID23526642.S2CID25612927.
^Setchell, J. M.; Lee, P. C.; Wickings, E. J.; Dixson, A. F. (2002). "Reproductive parameters and maternal investment in mandrills (Mandrillus sphinx)".International Journal of Primatology.23:51–68.doi:10.1023/A:1013245707228.S2CID25158600.
^Kudo, H. (1987). "The study of vocal communication of wild mandrills in Cameroon in relation to their social structure".Primates.28 (3):289–308.doi:10.1007/BF02381013.S2CID1507136.
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