Earlham College –– Biology Department –

Understanding ecosystems is a crucial component of conserving them. Kakamega Forest is a complex and yet little understood forest system. This section discusses the basic ecology of Kakamega Forest.

Kakamega Forest is the eastern most remnant of a dense rain forest that in the past millenium stretched across the entire expanse of central Africa. It is the only rainforest in Kenya. Thus, Kakamega Forest is an island of immense biodiversity that has developed along its own unique evolutionary course for thousands of years and which shows a high level of endemism.

The reserve is at an altitude of 1,400-2,300 meters (4,000-7,000 ft.) and encompasses an area of 240 sq. kms. It is an area that is famous for its abundance of bird and butterfly life. Up to 20% of all Kenyan plant and animal species occur only here, including 75% of all butterflies. In addition there are over 350 species of birds that reside in the forest. Several primate species are also present such as the Black and White Colobus Monkey, Blue Monkey, Olive Baboon, Red-tailed Monkey, and the rare De Brazza's Monkeys. Plants, and especially orchids, are found in extremely high diversity. Over 380 species of plant have been identified in Kakamega Forest.

This enormous diversity has not been fully studied. Vast numbers of invertebrates have not been identified. The behavior of the majority of the megafauna is only minimally understood. Opportunities for scientific studies are abundant in Kakamega and are of crucial importance to the conservation of this unique ecosystem. We must understand the forest in order to adequately protect it.

This page discusses various aspects of the ecology of Kakamega Forest. Guide books for some of the sections (birds, invertebrates, reptiles and amphibians, mammals, and plants) can be found in our literature section under the heading Guide Books.

Geography and Geology

The bedrock substrate on which the forest sits consists of basalt, phenolites, and ancient gneisses. These rock formations are overlayed by a layer of clay-loam soils. These soils are dependent on the decomposition and reincorporation of dead organic matter. Fertility of the soils has dropped as wood has been increasingly removed by illegal loggers and local families.

Kakamega Forest receives approximately 200 centimeters of rain a year. This is nearly twice the rainfall of most temperate forests. Rainfall is heaviest in April and May (during the "long rains"), with a slightly drier June and a second peak of rain roughly in September to November (the "short rains"). January and February are the driest months. The temperature is fairly constant throughout the year, with mean daily minimums of about 11 C (52 F) and mean daily maximums of about 26 C (79 F).

Several different types of plant communities are found in Kakamega Forest. In addition to areas classified as "virgin" rain forest, there are several other classifications including: colonizing forest, disturbed forest, clearings made for pit-sawing and charcoal burning, plantation areas (usually tea), natural glades, swamps, and riverine forest.

Like rainforests elsewhere, the physical structure of Kakamega Forest is complex, consisting of multiple layers of vegetation. The trees are usually well buttressed at the base. Though a variety of hypotheses have been proposed, it is most likely that buttresses have the obvious function of supporting shallowly rooted trees. Also like other rainforests, Impatiens sp

diversity is high. There are over 150 documented species of woody trees, shrubs and vines, and 170 species of herbs of which 60 are orchids. Nine of these orchids are only found in Kakamega rainforest! In addition, there are 62 species of ferns. All totaled there are over 380 documented plant species (not counting the bryophytes and lichens). This remarkable diversity results in a forest landscape where trees are festooned with orchids, mosses, other epiphytes, and lianas (climbers, woody vines). Gaps in the forest canopy are frequent, which allows for succession and the maintenance of species diversity.

Other than the information given above, very little is known about the specifics of the community or ecosystem ecology of Kakamega Forest.

Primary Colonizers	2nd Colonizers	Understory Species	Canopy Trees
Acanthus sp.	Maesopsis sp.	Dracaena sp.	Aningeria altissima
Harungana sp.	Albizia sp.	Brillantasia cicatroza	Milicia excelsa
Bersama sp.	Polyscias sp.	Afromontanum sp.	Antiaris toxicaria
Trema sp.	Croton sp.	Impatiens stuhlmannii	Cordia abyssinica
		Coffea eugenioides	Olea capensis
			Croton megalocarpus
			Albizia gummifera
			Fagara mildbraedii
			Chrysophyllum albidum
			Markhamia lutea

350 species of birds have been recorded in the forest. Some of the more spectacular birds to be seen include the Great Blue Turaco, the Blue-headed Bee-eater, Jameson's Wattle-eye, the Pygmy Kingfisher, the Dusky Tit, the red-chested owlet, and many, many others. Birding is absolutely phenomenal within the forest and is important, not only to help document and understand the wealth of avian species, but also to provide an incentive for conservation of endangered bird species of the area. Some of the more well-known species that are disappearing from the forest include the African Grey Parrot, the Yellow-Crested Woodpecker, Yellow Mantled Weaver, and the Black-billed Turaco, among others.

For a thorough, concise, and beautifully illustrated bird guide, we highly recommend Birds of Kenya and Northern Tanzania by Zimmerman, Turner and Pearson. A full citation can be found in our literature section.

Mammals are abundant within the forest but are difficult to observe. In the past, elephants, buffalo, uganda kob, hippos, and bongos were fairly common in the forest. It is believed that buffalo were killed off by rinderpest while the other large mammals were either hunted out or dissappeared as human habitation increased. Hippos will still occasionally move up from the Yala River into the forest but they often are slaughtered for their meat when they do so. Leopards still live in the forest but are extremely secretive. The last confirmed sighting of a leopard was in 1991.

Some of the more common large mammals include the Blue Duiker and the Red Duiker, both forest antelope species. Bush Pigs are abundant in the forest but are not often seen because they are nocturnal. Finally, the Bushbuck, a medium sized antelope with white stripes and spots, can often be seen in forest thickets, although there is some evidence that its numbers are declining due to trapping outside of the forest.

There are many smaller mammals in the forest, too. The clawless otter lives in dens in river habitats and spends much of its time playing in the water although it will quickly dive under water at the first sound of approaching feet. Kakamega forest is also home to the Marsh Mongoose and the famous Giant Water (or Otter) Shrew. Within Kenya, the Giant Water Shrew only lives in Kakamega Forest, although it is found in other regions of Africa.

Several species of squirrel can be heard or seen in the tree tops. The Sun Squirrel and similar but larger Giant Forest Squirrel are fairly common. In the early mornings the deep booming call of the Giant Forest Squirrel may be heard. Rarely seen, but of exceptional interest, is the Scaly Tailed Flying Squirrel which can glide (mainly at night) up to fifty meters from tree to tree. In addition to squirrels, there also are porcupines, aardvarks and hedgehogs in the forest. The Tree Pangolin is present which is a semi-arboreal, nocturnal, solitary mammal about the size of a badger that has horny overlapping scales all over its body, and that can roll into a ball for protection when attacked.

There are numerous species of bats to be found in the forest. In Kenya, the Hammer-headed Fruit Bat is endemic to Kakamega Forest. This bat is the largest on the African continent with a wing span of almost one meter and a huge head. These bats can be idenitified not only by their enormous wing span but also by the distinctive loud call of males. The smaller Lesser Leaf-nosed bat and Yellow bellied bat are also common in the forest.

The most noticeable arboreal creatures in the forest are primates, especially the Black and White Colobus monkeys. The colobus monkeys live and move in troops of well-defined

social groupings and occupy small territories. Blue Monkeys are also abundant in the forest and are often seen near the colobus troops. Within the Blue Monkey troops, smaller Red-tailed Monkeys will often be seen. This interspecific association is believed to be a mutualistic one, with increased predator vigilance for both species and a sharing of food resource knowledge. Olive Baboons are abundant at the forest edge and are viewed as pests by locals as they raid maize, sugar cane and fruit crops. Extremely rare within the forest is the de Brazza's Monkey, with a population of only thirty individuals. These monkeys face extinction in other areas of Kenya as they are becoming increasingly isolated by habitat fragmentation. There is hope, however, as studies indicate that the Kakamega troops of de Brazza's are breeding well. Finally, several primate species can only be seen at night, including bushbabies and the Potto, a small, large-eyed mammal that crawls about searching for insects, snails and other forage.

To see snakes in the dense undergrowth of Kakamega Forest, one must have a discerning eye and a lot of patience. However, many snakes can be seen and identified. Most of these snakes are dangerous only when caught unawares, so when walking along paths it is recommended to walk heavily so the ground-dwelling snakes can slither out of your way. Many of the snakes in the forest are from West Africa including the Forest Cobra, the Black-lipped Cobra, Jameson's Mamba, the Bush Viper, the Rhinoceros-horned Viper and the Gaboon Viper. Two species that are endemic to the forest and that are in danger of extinction are the Gold's Cobra and Kaimosi Blind Snake.

Some of the common lizards included Jackson's Lacerta, Agama, Peter's Long-tailed Skink, Five-lined Skink, Common Skink, and the Common Chameleon. Less common is the two meter long Nile Monitor which can attack, kill and devour large prey by the unique ability of unhinging its lower jaw.

There are several species of Sedge Frogs and the Disk-toed Rana is abundant. Many reptile and amphibian species have not yet been identified including several species of terrapin turtles found in the forest ponds.

Kakamega Forest is famous for its butterflies and tours often focus solely on these invertebrates. Among the more flamboyant species are the Regal Swallowtail, the Black-lipped Diadem, the Forest Mother of Pearl, the Mocker Swallow-tail, the Amauris, and the

Broad Green-banded Swallowtail. In addition, Kakamega forest is home to many species of the butterfly genus Charaxes which contains the fastest flying butterflies in Africa, including the Large Blue-Spangled Forest Charaxes.

Other insects of note include the huge, shiny black, white or chestnut coloured Goliath Beetles which live off the fruits of the wild fig. In addition there are numerous species of stick and leaf insects which are extremely difficult to see due to their incredible camouflage.