The samango monkeys of Hogsback
(Cercopithcus mitis labiatus)
by Judith Masters
The samango monkeys of Hogsback belong to a species that is widely distributed in sub-Saharan Africa, Cercopithcus mitis, the blue monkey a.k.a. Sykes' Monkey or the Gentle Monkey.
There are two subspecies of C. mitis in South Africa: C. m. erythrarchus, ranging from north-eastern Zimbabwe to northern KwaZulu-Natal, Mozambique and Limpopo Province; and C. m. labiatus, distributed from the Eastern Cape to the KZN Midlands and southern Mpumalanga. Although these ranges seem large, patches of suitable habitat are not, and samangos are South Africa's only endangered primates.
C. m. erythrarchus inhabits a variety of forest types, from coastal lowland forest and thicket, to riverine, swamp, deciduous dry and coastal dune forest (Lawes, 1992). These animals are relatively common in the coastal reserves of Ezemvelo KZN Wildlife - Sodwana Bay and Cape Vidal are particularly good places to spot them. Our Hogsback subspecies, C. m. labiatus, by contrast, is a rather more particular beast; it only ever occurs in Afromontane forests. These habitats are, by definition, confined areas, patchily distributed across the eastern part of the country wherever the altitude and climate combine to support Afromontane vegetation.
This means the C. m. labiatus populations will be similarly restricted in size, and fragmented by vast tracts of inhospitable habitat. In recent years, this fragmentation has been exacerbated by the fact that logging and habitat destruction has become commonplace in Afromontane areas. Professor Mike Lawes (University of KwaZulu-Natal) believes that samango populations in some of the Afromontane areas of KwaZulu-Natal are already in irreversible decline. C. m. labiatus occurs on the IUCN (2007) Endangered list.
What distinguishes the subspecies?
C. m. erythrarchus: Yellowish-white ear tufts, back light grey to olive green; yellow, orange or reddish hairs on bottom, tail black.
C. m. labiatus: darkest of all C. mitis subspecies. Crown almost black, back dark grey, tummy white ashy grey; tail with dark band on top, buff colouring on sides and underneath; no red on bottom.
Behaviour and ecology
Samango monkeys have a remarkable repertoire of vocalisations that convey a range of messages. Adult males emit loud resonant "booms" involving large laryngeal air sacs that develop at puberty. Females keep contact by means of a series of grunts and "trills". People walking their dogs in the forest will often elicit group rallying calls and alarm calls: these are made up of a series of repeated "pyow" or "ka" noises. Females and juveniles also give bird-like chirps when disturbed.
Samango monkeys belong to the group of African fruit-eating monkeys generally referred to as "guenons". Guenon monkeys have cheek pouches within which they can store fruits while they are foraging, which are consumed later when they are in a less exposed place. Samangos have the most generalised diet of all the guenons. They prefer fruits rich in sugar, but will eat leaves, flowers, stems, bark, fungi, insects, and occasionally small vertebrates.
Their versatility lies in the fact that they can ferment food in both the fore- and the hindgut. Fruit gets digested in the foregut (stomach), while leaves, which take a lot longer, and require symbiotic bacteria for their digestion, get shunted into the caecum, a large pocket attached to the colon.
Since they appear to be so catholic in their tastes, it is indeed a puzzle as to why C. m. labiatus is confined to Afromontane forests; why can't they survive in other kinds of wooded habitats? This is a question a joint team from the Universities of Fort Hare and Palermo (Sicily) are hoping to answer in a collaborative research project.