May 19, 2017 by Species Ecology
The Elusive and Iconic Monkeys under Pressure in Udzungwa Mountains National Park, Tanzania.
The Udzungwa Mountains of South Central Tanzania (10,000 km2) are one of the most important mountains in Africa for conservation of biodiversity and, specifically, the one containing the largest forested blocks, and the richest in endemism levels, of the Eastern Arc Mountains of Kenya and Tanzania. This importance is particularly well reflected in the mammalian fauna. It is figuratively named as ‘Galapagos of Africa’ due to its unique flora and fauna.
The Udzungwa Mountains National Park lies between longitude 36⁰41’ and latitude 7⁰48’ in the Southern-Central parts of Tanzania. The Selous Game Reserve is found in the east, beyond the Kilombero Valley Floodplain (Ramsar site) and Mikumi National Park to the Northwest.
The climate of the area is described as tropical to sub-humid and receives the bulk of its annual rainfall from November to May, and the longer rain period of March and May. The dry season reaches its peak in September and October. The mean annual rainfall in the southeast of the Park, which is often covered by mist, is around 2000mm per year. In the northwest however only 600mm of rain falls per year is recorded.
The magnificent landscape of the Park is a refuge for endemic (native to continent) Iringa-Red Colobus Monkey Piliocolobus gordonorum and Sanje Crested Mangabey with taxonomic reckoning of Cercocebus sanjei. The Iringa Red Colobus feeds mainly on foliage leaves of many trees found in the Park, hence named as folivorous (leaf eating herbivores). It supplements their remaining diet by eating unripe fruits: members of colobinae primate never feeds on ripen fruits as they are not able to transform complex sugar into simple chemical form during digestion. On the other hand, the mangabey are omnivorous―and thus feeds on various materials such as mushrooms, insects, leaves, and fruits. Considering the significant gap in diet between these two endemic primates, it is no surprise that there is little or no competition between these species in terms of their resource utilization patterns. The harmonious co-existence between the Red-Colobus and the Sanje Crested Mangabey is apparent and they do show show remarkable niche segregation in terms of their resource partitioning mechanism and diet.
The increasing population in villages adjacent to the Park (due to high population growth and immigration), as well as expansion of commercial-agricultural activities in the vicinity of the ‘Galapagos of Africa’ would turn the future of these mysterious monkeys into jeopardy. The rain have been more erratic in the region and for the last 2-3 years the park has been receiving less rainfall than the previous years’ when average precipitation rate was primate friendly. This might have an impact on monkey’s diet as there may be less green leaves and relatively poor quality of their habitats hence forcing the primates to feed on ‘fall-back-food’ which is less nutritious and of course non-palatable. If this scenario continues to remain prevalent at its current pace then it may very well hamper the reproduction rate which in-turn would attribute to small population size. On the other side, more than 100,000 people are residing in a narrow strip between the park and the commercial agricultural farms and consequently trigger anthropogenic pressure to the fragile ecosystem of Udzungwa Mountains National Park. These forest dwelling local communities often seeks both domestic fuel (dead logs and twigs from the forest) and other tangible resources like grasses (thatches for roofing), timber as well as traditional medicines. These forms of resource exploitations can pose detrimental impact on primate population and negatively influence the monkeys’ diet one way or another.