Osman Hill's mangabey

Description

Osman Hill's mangabey is a medium-sized lanky, arboreal, dark furred monkey. The sexes are similar in colour and markings but males are far larger than females, the size difference being especially arked in this species compared to the other mambers of the grey-cheeked mangabey superspecies. Thet have long, loose fur which is mainly blackish-brown, and a rufous tinged mane of longer hairs over the shoulders which is more noticeable in the males. The head shows a tuft on the crown and smaller tuftd above the eyes, although these may not always be present, the cheeks are pale. The long tail is frequently held arched over the monkey's back. The two ischial callosities are bare and for a "C" shapes which are complete in the male but often broken in the females. The bare skin on such places as the palms and soles is pink in newborns but darkens as the get older and is normally black by nine momnths of age. A single male speciemn has been measured and he had a head and body length of 610mm and a tail length of 920mm.

Distribution

Osman Hill's mangabey has a very small range from the Cross River in south eastern Nigeria to the Batouri district of south eastern Cameroon.

Habitat

Osman Hill's mangabey occurs in low to medium altitude tropical rainforest where it is highly arboreal and can be seen in the camopy and emergent layeres. It is rarely observed on the ground or in secondary or savanna habitats. The hightes densities are found in swamp forest and flooded forest.

Habits

This species and its close relatives have cheek pouches which they cann use to store food to be eaten or processed later. The males have inflatable throat pouches which they use as resonators to amplify their loud low pitched calls which can be hear over a kiometre away from the calling male. They have powerfil jaws, hans and arms which makes it possible for them to extract seeds from harder fruits, e.g. those of Monodora myristica than similarly sized monkeys. They are omnivorous, althopugh fruit is the most omportant part of their diet, and they may locate fruiting trees by following the calls of frugivorous birds such as hornbills. Important fruit tree species for Odsman Hill's mangabey include Erythrophleum suaveolens and Enantia chlorantha. They also spend a lot of time splitting dead wood, excavating bark and searching through liana tangles and epiphyte masses searching for invertrebrates.

Osman Hill's mangabey is a social species living in groups of 10-20 individuals which consist of a few males, several females and their dependant young. These groups ofetn associate with groups of other monkey species, and even occasioinally with troops of chimpanzees. Contact calls are grunts, alarm calls are staccato barks and the males make a loud "whoop gobble" to co-ordinmate the group and to set spaces bewtween different groups. This call can be made by females but very infrequently. The groups are fluid and will mix but this can lead to increased aggression among the adults, although the young will play. Females in oestrus may attract additional males. The dominant male usyually guards receptive females but she will try and mate with other males when she can.

Taxonomy

Osman Hill's mangabey used to be considered a subspecies of the grey-cheeked mangabey, L. albigena.

Etymology

Osman Hill's mangabey was named after William Charles Osman Hill, a primatologist, anthropologist, and anatomist from the 20th century.