The socioecology and conservation of the Samango monkey (Cercopithecus mitis erythrarchus) in Natal.

Abstract

The samango monkey (Cercopithecus mitis erythrarchus) is the southern most

representative of the polytypic mitis group. The samango is also the only truly arboreal

guenon to have radiated as far as 30°S. At southern latitudes a greater seasonality of

climate and an attendant seasonal shift in food availability is expected to restrict the

foraging strategy of the arboreal guenon. In the absence of arboreal congenerics and

few frugivorous bird and bat species, the samango experiences a level of competitive

release at Cape Vidal not found in other equatorially located mitis populations. In this

thesis I examine and contrast the diet and feeding behaviour of the mitis species group.

In this way I illustrate the consequences of seasonality of food abundance and

competitive release on the foraging strategy of the samango, and provide an explanation

for the unique distribution of the samango monkey as the only arboreal guenon in

southern Africa.

Despite seasonality in climate and abundance of food resources, my data show that, in

general, samango monkeys at Cape Vidal are not food limited. For this reason Cape

Vidal samangos have large troop sizes (25+), use small home ranges (15 ha) and have

the highest density (2.02 ind/ha) of any C. mitis population researched to date. Fruit

forms an important part of the diet year-round and therefore, energy and carbohydrate

are abundant. There is very little intra-group aggression for food, although interindividual

distances are greatest when feeding. There are age-sex differences in the diet, and adult

males eat more fruit while females eat more leaves than other age-sex classes.

The most important aspect of the feeding strategy of the samango is concerned with

obtaining adequate protein in the diet, and throughout the range of the mitis group,

populations differ most in feeding strategies used to secure protein-rich foods, such as

young leaves, flowers and invertebrates. In this respect seasonal nutrient (protein)

availability, rather than seasonality of food abundance per se, is the most limiting

component of the forest environment.

Unlike equatorial populations of mitis that derive most of their protein from insects,

samangos are unable to adopt a similar strategy. Insects were available to the monkeys,

and then only in low numbers, in the wet summer season at Cape Vidal. Samango monkeys, therefore, make greater use of a wider variety of plant items for protein

acquisition. During the wet summer months, insects, flowers and young leaves are used

by samangos to obtain sufficient protein for important reproductive activities, such as

lactation, and initial growth of the infant. During the drier winter months only mature

leaves and small quantities of young leaves are available as protein resources,

consequently samangos use more mature leaf in the diet than other C. mitis populations.

Adaptations of the gut and specialized gut microflora permit this high degree of folivory

in the diet (Bruorton and Perrin 1988) of the samango monkey. This is a characteristic

that does not appear to be shared with other arboreal guenons. In so far as protein is

essential for reproduction, folivory in c. mitis has been important in permitting this

arboreal guenon species-group to radiate into southern latitudes where protein is more

seasonally available. The ability of samango monkeys to eat large quantities of leaves at

anyone time, accounts for their unique position as the only arboreal guenon species in

southern Africa.