Mandrillus

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Mandrillus
Mandril.jpg
A mandrill in captivity
Scientific classification Red Pencil Icon.png
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Primates
Suborder: Haplorhini
Infraorder: Simiiformes
Family: Cercopithecidae
Tribe: Papionini
Genus: Mandrillus
Ritgen, 1824
Type species
Simia sphinx [1] [2]
Species
Synonyms [3]
  • ChaeropithecusGray, 1870
  • DrillReichenbach, 1862
  • MaimonTrouessart, 1904
  • MandrilVoigt, 1831
  • MormonWagner, 1839
  • PapioP.L.S. Müller, 1773

Mandrillus is a genus of large Old World monkeys distributed throughout central and southern Africa, consisting of two species: M. sphinx and M. leucophaeus, the mandrill and drill, respectively. [4] Mandrillus, originally placed under the genus Papio as a type of baboon, is closely related to the genus Cercocebus . [5] They are characterised by their large builds, elongated snouts with furrows on each side, and stub tails. Both species occupy the west central region of Africa and live primarily on the ground. [6] [7] They are frugivores, consuming both meat and plants, with a preference for plants. [5] M. sphinx is classified as vulnerable and M. leucophaeus as endangered on the IUCN Red List of Threatened Species . [8] [9]

Contents

Taxonomy

Mandrillus is a genus within the tribe Papionini, which in turn is under the subfamily Cercopithecinae. This subfamily is classified under the family of Old World monkeys (Cercopithecidae) within the infraorder Simiiformes. [4] The Papionini tribe contains six other genera: baboons (Papio), macaques (Macaca), crested mangabeys (Lophocebus), white-eyelid mangabeys (Cercocebus), the highland mangabey (Rungwecebus) and Theropithecus . [10] [11]

Originally, both species were considered part of the Papio genus, as forest baboons, due to superficial similarities such as size and appearance, particularly in facial features. [12] However, studies conducted analysing anatomical and genetic differences between the current Mandrillus and Papio genera showed more differences than similarities resulting in the current taxonomic ranking. [13] [14] Furthermore, the studies showed Mandrillus are more closely related to the white eyed mangabeys, and diverged relatively recently (4 million years ago) from this genus. [5]

Species

ImageScientific nameCommon NameDistribution
Bei Jing Dong Wu Yuan De Shan Xiao .jpg Mandrillus sphinx Mandrill Southern Cameroon, Gabon, Equatorial Guinea, and Congo
Drill (Mandrillus leucophaeus).jpg Mandrillus leucophaeus Drill Cross River State in Nigeria, southwestern Cameroon (south to the Sanaga River), and on Bioko Island, part of Equatorial Guinea

Anatomy

Mandrillus leucophaeus skull Mandrillus leucophaeus 01 MWNH 297.jpg
Mandrillus leucophaeus skull

Both species of Mandrillus develop extremely large muzzles, prominent nasal ridges and paranasal swelling (swelling in the area adjacent to the nostrils). The size and colour of the paranasal swellings correlate to male dominance and rank, while the size of nasal ridges is a way of attracting mates. [15] Mandrillus teeth consist of two incisors, two premolars, one canine and three molars in each half of the upper and lower jaw, totalling 32 teeth. [5] Furthermore Mandrillus display larger premolars and extended canines; these dental traits are better adapted to crushing hard objects. This is due to a large part of their diet consisting of hard, dry nuts and seeds that require greater crushing power and the use of their teeth in ripping apart rotting wood to search for insects and other invertebrates. [16]

Mandrillus sphinx skull and shoulder blade Mandrillus sphinx MNHN.jpg
Mandrillus sphinx skull and shoulder blade

Within the shoulder and upper arm structures of the Mandrillus monkeys a deep scapular, broad deltoid plane, narrow stable elbow region and other skeletal features indicate the use of the forelimbs for climbing and foraging. [17] This is used by the monkeys to climb trees when searching for ripe fruit and in the aggressive foraging of the forest floor in search of food. [16] Mandrillus monkeys have developed an extremely broad and robust ilium, and a rounded tibial shaft. The development of these features can be attributed to the climbing of trees and quadrupedal locomotion. The largest toe is separated from the remaining toes for increased grasping power when climbing trees. [5]

Sexual dimorphism

Both species of Mandrillus demonstrate a great degree of sexual dimorphism in weight, anatomy and physical appearance. The mandrill displays the most extreme sexual dimorphism for weight among all primates, with a male-female weight ratio of 3.2 – 3.4 at eight to ten years of age. [18] Similarly, drills are one of the most sexually dimorphic primates for body weight, with a male growing up to 32 kg while a female grows to 12 kg. Sexual dimorphism is also displayed in the growth of the craniofacial bones of both species. [19] The males of each species have longer muzzles, much larger paranasal swellings and longer canines than their female counterparts. In a study of wild drills, female muzzles only grew up to 70% the length of the male muzzles. [5] [19] Furthermore, males have brightly coloured, saturated rumps unlike their female counterparts. [5] Both species also display the greatest visual sexual dimorphism within monkeys. On a scale based on rating the differences in physical features between genders, the mandrill obtained 32 whilst the drill obtained 24.5. [5] These ratings are based on features such as the saturation and colour of the rump (and face for mandrills), the paranasal swelling, the fatted rump and fur colouring. [5]

Distribution and habitat

Mandrillus monkeys have a very localised biographical region located in West central Africa. The two species are often considered allopatric, [15] [5] they occupy non-overlapping regions, and their regions are divided by a physical barrier, the Sanaga river in Cameroon. Mandrillus leucophaeus occupy the area above the river in North western Cameroon and southwestern Nigeria up until the Cross River, and Bioko Island (Equatorial Guinea) which lies off the coast. [15] [5] The mandrill occupies the area below the river line in Cameroon, Río Muni, Gabon and Congo. [15] The Mandrillus species occupy multiple sections of the Guinean forests of West Africa, including Cross-Sanaga-Bioko Coastal Forests and Cameroonian Highlands forests. [20] [15] The forests the monkeys occupy have a humid, tropical climate and rugged terrain. Deforestation has reduced the habitat of both Mandrillus species, reducing the distribution of each species, especially the drill. [5]

Behaviour

Diet

Both Mandrillus species are frugivores, consuming both plants and insects with a preference for fruits and nuts. Mandrillus species spend a large amount of their time foraging through the forest in search of food. [21] In a study conducted in Cameroon, approximately 84% of the faecal matter of mandrills consisted of fruit. [5] Similarly, a study done on drills in southwest Cameroon showed that the mean weight of fruit and seed in faecal matter was equal to or greater than 80%. [22] Seasonal changes can be seen within Mandrillus diet, during peak fruit season (September to March) their diet consisted mostly of fruit, pulp and seeds whilst during the fruit scarce season (June to August) there was a great increase in the consumption of insects, woody tissue and especially nuts. [23] [5] There was also an increase in the variation of the diet during the fruit-scarce season. [23] [24] Important fruit include but are not limited to, the fruit of the bush mango ( Irvingia gabonensis ), African Corkwood tree ( Musanga cecropioides ), Grewia coriacea, Sacoglottis gabonensis and Xylopia aethiopica . Invertebrates consumed include crickets, ants, caterpillars and termites. Rarely, Mandrillus monkeys will eat larger animals, such as rats and gazelles when presented with the opportunity. [21] [5] [24]

Social systems

The species of the genus exhibit great similarities in their social systems. Both generally form smaller groups, however the size of these groups is unclear. A study done on drills in southwest Cameroon found a mean group size of 52.3 [24] while another more recent report stated a figure of 25–40 on these smaller groups. [25] A study of mandrills done at Campo reserve in Cameroon found small groups contain 14 - 95 individuals. [5] These smaller groups, with stable social structures, often join to form larger "supergroups" of hundreds of individuals. [25] Some of the largest mandrill "supergroups" reported contained up to 845 individuals whilst some of the largest drill "supergroups" reported contained 400 individuals. [21] [5] There has been reports of solitary male Mandrillus monkeys, however this occurs very rarely. [5]

The social structures and social hierarchy of Mandrillus "supergroups" and groups is highly contentious. There are multiple older (1970s-1990s) sources referencing single male units, which contained a male and multiple female monkeys, as the smallest and most common stable social structure. However this has been disproved with the discovery of less colourful male Mandrillus and further observations of behaviour. [5] [26] [24] [27] Mandrillus leucophaeus social structures are unknown, due to low populations, and secluded habitats with dense forestry. [25] On the other hand, Mandrillus sphinx has had a variety of studies on social structure done in largely captive and semi-free ranging settings, with few studies on wild mandrills. The current studies on mandrills are inconclusive, and present different results. Various semi-free ranging studies conducted report a matrilineal social structure with a stable infant and female mandrill "supergroup". Male Mandrillus monkeys would disperse from this group when old enough and join other groups only during mating season. [26] [5] Further studies, also done in semi-free ranging settings, conclude that dominant females are central to group cohesion and connectivity (how close they remained). [5] [26] Conversely, a study on wild mandrills published in 2015 reported that a stable adult, male mandrill population of 5 - 6 was present year round in "supergroups". [28] This aligned with the social structures reported in other research papers done on wild mandrills, where stable multi-male and multi-female groups were found. [29] [28] [24] This difference in social structures between Mandrillus groups has been attributed to limitations in observing wild mandrills, differing habitats, and differing sample sizes. [26]

Male dominance and rank have been linked to the colouration and colour extension of the rumps, greater saturation and colour extension correlated to higher-ranking males. Males of higher ranking are more likely to associate with females, especially those with sexual skin swelling, and more likely to successfully mount females. [25] [5] Dominant, adult males practice mate guarding on adult females during times of maximal skin swelling; with their high competitive ability they are more likely to successfully reproduce. [25] Due to the tropical habitat, mating season coincides with the dry season (May to October) and birth season coincides with the wet season (November to April). [5]

Communication

Mandrill displaying silent baring of teeth Mandrillus sphinx (alpha male).jpg
Mandrill displaying silent baring of teeth

The Mandrillus genus uses both visual and vocal forms of communication, which are extremely similar or identical across both species. Both species have three identical long-range vocal communications: two-phase grunts, roars and "crowling". [5] The two-phased grunt is a low, two-syllable continuous sound used exclusively by adult males during calm group progression and mate guarding. [30] Roars are single low, single syllable sounds used exclusively by males in the same context as two-phase grunts. Crowling is used by infants and females during group movement or foraging to call together the dispersed group. [30] [5] [31]

They also use numerous short-range vocal sounds for various purposes. The "yak" and grinding of teeth are used during tense situations. The grunt is used in aggressive situations and screams are used to escape or while experiencing fear. The growl is used to convey mild alarm, the K-alarm is used to convey intense alarm and the "girney" is used for appeasement. [30] Both species use various facial expressions to communicate with each other. The silent baring of teeth is a positive visual signal conveying peaceful intentions, and it is often combined with a shaking head. [32] Staring open-mouthed is a display of aggression, frowning with bare teeth is used to encourage submission, staring with bare teeth can communicate aggression or fear, pouting signals submission and a relaxed open mouth encourages playing. [5]

Conservation status

The current conservation status of Mandrillus sphinx is vulnerable and that for Mandrillus leucophaeus is endangered. [9] [8] The greatest threats to the conservation of this genus are the severe loss and degradation of their habitat, and hunting. [33] [34] The loss of habitat is an ongoing threat that can be attributed to the expansion of human settlements as well as the clearing of forests for chipping factories and agriculture. Hunting and poaching of Mandrillus monkeys for meat or to protect crops is also major, ongoing threat to the population despite the implementation of hunting restrictions and sanctuaries. [8] [9] The drill population in Cameroon, which encompasses 80% of the drill's original habitat, has been fragmented into smaller, isolated populations with largest residing in Korup national park. [33] The mandrill population in south Cameroon and Equatorial Guinea are at great risk due to extensive forest loss. The majority of the mandrill population remains in Gabon and faces major threats from railroad construction and logging companies. [5] As of 2020, the mandrill population is in decline while the drill population is not able to be accurately determined. [8] [9]

Related Research Articles

Primate Order of mammals

A primate is a eutherian mammal constituting the taxonomic order Primates. Primates arose 85–55 million years ago first from small terrestrial mammals, which adapted to living in the trees of tropical forests: many primate characteristics represent adaptations to life in this challenging environment, including large brains, visual acuity, color vision, a shoulder girdle allowing a large degree of movement in the shoulder joint, and dextrous hands. Primates range in size from Madame Berthe's mouse lemur, which weighs 30 g (1 oz), to the eastern gorilla, weighing over 200 kg (440 lb). There are 190–

Black-and-white colobus Genus of Old World monkeys

Black-and-white colobuses are Old World monkeys of the genus Colobus, native to Africa. They are closely related to the red colobus monkeys of genus Piliocolobus. There are five species of this monkey, and at least eight subspecies. They are generally found in high-density forests where they forage on leaves, flowers and fruit. Social groups of colobus are diverse, varying from group to group. Resident-egalitarian and allomothering relationships have been observed among the female population. Complex behaviours have also been observed in this species, including greeting rituals and varying group sleeping patterns. Colobi play a significant role in seed dispersal.

Old World monkey Family of mammals

Old World monkey is the common English name for a family of primates known taxonomically as the Cercopithecidae. Twenty-four genera and 138 species are recognized, making it the largest primate family. Old World monkey genera include baboons and macaques. Common names for other Old World monkeys include the talapoin, guenon, colobus, douc, vervet, gelada, mangabey, langur, mandrill, surili (Presbytis), patas, and proboscis monkey. Phylogenetically, they are more closely related to apes than to New World monkeys. They diverged from a common ancestor of New World monkeys around 45 to 55 million years ago.

Mandrill Species of Old World monkey

The mandrill is a primate of the Old World monkey (Cercopithecidae) family. It is one of two species assigned to the genus Mandrillus, along with the drill. Both the mandrill and the drill were once classified as baboons in the genus Papio, but they now have their own genus, Mandrillus. Although they look superficially like baboons, they are more closely related to Cercocebus mangabeys. Mandrills are found in southern Cameroon, Gabon, Equatorial Guinea, and Congo. Mandrills mostly live in tropical rainforest and in very large groups. Mandrills have an omnivorous diet consisting mostly of fruits and insects. Their mating season peaks in July to September, with a corresponding birth peak in December to April.

Gelada Species of Old World monkey

The gelada, sometimes called the bleeding-heart monkey or the gelada "baboon", is a species of Old World monkey found only in the Ethiopian Highlands, with large populations in the Simien Mountains. Geladas are actually not baboons but the only living members of the genus Theropithecus. Theropithecus is derived from the Greek root words for "beast-ape". Like its close relatives the baboons, it is largely terrestrial, spending much of its time foraging in grasslands.

Olive baboon Also called the Anubis baboon, is a member of the family Cercopithecidae (Old World monkeys)

The olive baboon, also called the Anubis baboon, is a member of the family Cercopithecidae. The species is the most wide-ranging of all baboons, being found in 25 countries throughout Africa, extending from Mali eastward to Ethiopia and Tanzania. Isolated populations are also present in some mountainous regions of the Sahara. It inhabits savannahs, steppes, and forests. The common name is derived from its coat colour, which is a shade of green-grey at a distance. A variety of communications, vocal and non-vocal, facilitate a complex social structure.

Hamadryas baboon Species of baboon

The hamadryas baboon is a species of baboon from the Old World monkey family. It is the northernmost of all the baboons, being native to the Horn of Africa and the southwestern tip of the Arabian Peninsula. These regions provide habitats with the advantage for this species of fewer natural predators than central or southern Africa where other baboons reside. The hamadryas baboon was a sacred animal to the ancient Egyptians and appears in various roles in ancient Egyptian religion, hence its alternative name of 'sacred baboon'.

Guinea baboon Species of Old World monkey

The Guinea baboon is a baboon from the Old World monkey family. Some (older) classifications list only two species in the genus Papio, this one and the hamadryas baboon. In those classifications, all other Papio species are considered subspecies of P. papio and the species is called the savanna baboon.

Chacma baboon Species of baboon from the Old World monkey family

The chacma baboon, also known as the Cape baboon, is, like all other baboons, from the Old World monkey family. It is one of the largest of all monkeys. Located primarily in southern Africa, the chacma baboon has a wide variety of social behaviors, including a dominance hierarchy, collective foraging, adoption of young by females, and friendship pairings. These behaviors form parts of a complex evolutionary ecology. In general, the species is not threatened, but human population pressure has increased contact between humans and baboons. Hunting, trapping, and accidents kill or remove many baboons from the wild, thereby reducing baboon numbers and disrupting their social structure.

Cercopithecinae Subfamily of Old World monkeys

The Cercopithecinae are a subfamily of the Old World monkeys, which comprises roughly 71 species, including the baboons, the macaques, and the vervet monkeys. Most cercopithecine monkeys are limited to sub-Saharan Africa, although the macaques range from the far eastern parts of Asia through northern Africa, as well as on Gibraltar.

Mantled guereza Species of mammal

The mantled guereza, also known simply as the guereza, the eastern black-and-white colobus, or the Abyssinian black-and-white colobus, is a black-and-white colobus, a type of Old World monkey. It is native to much of west central and east Africa, including Cameroon, Equatorial Guinea, Nigeria, Ethiopia, Kenya, Tanzania, Uganda and Chad. The species consists of several subspecies that differ in appearance. It has a distinctive appearance, which is alluded to in its name; the long white fringes of hair that run along each side of its black trunk are known as a mantle. Its face is framed with white hair and it has a large white tail tuft.

Silvery lutung Species of Old World monkey

The silvery lutung, also known as the silvered leaf monkey or the silvery langur, is an Old World monkey. It is arboreal, living in coastal, mangrove, and riverine forests in Peninsular Malaysia, Sumatra, and Borneo.

Bioko drill Subspecies of Old World monkey

The Bioko drill is a subspecies of the drill, an old world monkey. It is endemic to Bioko Island, Equatorial Guinea, located off the west coast of Africa. The drill is one of the largest monkey species, and is considered endangered. The Bioko drill was separated from their mainland counterpart, due to rising sea levels after the end of the last ice age, around 10,000 years ago. The capital of Equatorial Guinea, Malabo, is on Bioko Island. The Malabo market is the primary point of sale for bushmeat on Bioko Island. The drill plays an important role in the cultural tradition of bushmeat consumption, and is locally considered to be tasty, and in some regions, a delicacy. The commercialisation of hunting on Bioko Island has made this practice unsustainable. Hunting of the Bioko drill is banned in most areas of Bioko Island, as they predominantly inhabit protected areas on the island, however the ban is considered ineffective and hunting remains the largest threat to the drill's population.

Papionini Tribe of Old World monkeys

Papionini is a tribe of Old World monkeys that includes several large monkey species, which include the macaques of North Africa and Asia, as well as the baboons, geladas, mangabeys, kipunji, drills, and mandrills, which are essentially from sub-Saharan Africa. It is typically divided into two subtribes: Macacina for the genus Macaca and its extinct relatives and the Papionina for all other genera.

Preusss red colobus Species of Old World monkey

Preuss's red colobus is a red colobus primate species endemic to the Cross-Sanaga Rivers ecoregion. An important population occurs in Korup National Park, Southwest Province, Cameroon, but the species' distribution is localized. The species is considered present in adjacent Cross River National Park - Oban Division in Nigeria and hunter reports suggest that few groups remain in Nkwende Hills and Nta Ali Forest Reserve in the broader Korup region. A population is also present in Ebo forest, Littoral Province of Cameroon.

Sexual dimorphism in non-human primates

Sexual dimorphism describes the morphological, physiological, and behavioral differences between males and females of the same species. Most primates are sexually dimorphic for different biological characteristics, such as body size, canine tooth size, craniofacial structure, skeletal dimensions, pelage color and markings, and vocalization. However, such sex differences are primarily limited to the anthropoid primates; most of the strepsirrhine primates and tarsiers are monomorphic.

Baboon Genus of mammals

Baboons are primates comprising the genus Papio, one of the 23 genera of Old World monkeys. There are six species of baboon: the hamadryas baboon, the Guinea baboon, the olive baboon, the yellow baboon, the Kinda Baboon and the chacma baboon. Each species is native to one of six areas of Africa and the hamadryas baboon is also native to part of the Arabian Peninsula. Baboons are among the largest non-hominoid primates and have existed for at least two million years.

Sexual swelling The swelling of genital and perineal skin in some mammals as a sign of fertility

Sexual swellings are enlarged areas of genital and perineal skin occurring in some female primates that vary in size over the course of the menstrual cycle. Thought to be an honest signal of fertility, male primates are attracted to these swellings; preferring, and competing for, females with the largest swellings.

Drill (animal) Species of primate

The drill is a primate of the family Cercopithecidae, related to baboons and even more closely to mandrills.

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