Lake Manyara National Park

The flora of Lake Manyara National Park is diverse, with over 670 flowering plant and fern species documented. Most are widespread species; there are few rare or endemic species.[14]

The park has a variety of diverse habitats. Rivers flowing off the escarpment and perennial springs below the rift wall support tall, evergreen groundwater forests dominated by Trichilia roka with Broad-Leaved Croton (Croton macrostachyus), sycamore fig (Ficus sycomorus), quinine tree (Rauvolfia caffra) and forest toad-tree (Tabernaemontana ventricosa).[6] Trees are densest in gorges, along the edge of streams and in areas where springs emerge.[13] Growing at the edge of the groundwater forest are dense stands of yellow fever trees (Acacia xanthophloea) and the palm Phoenix reclinata.[6]

A fever acacia in Lake Manyara National Park

Woodlands on the western shore of the lake dominated by Acacia and Commiphora species are also supported by groundwater. Trees are spaced irregularly; densest in zones of seepage and along drainage channels. The dominant tree, Acacia tortilis, grows to about 10m tall with a flat-topped canopy. There is a patchy and diverse understory shrub layer.[13]

Extensive swamps have formed where the Simba River and its tributaries flow into the north end of Lake Manyara[13] and smaller swamps have formed elsewhere, associated with the minor rivers flowing off the walls of the rift valley.[5] A number of aquatic species have been documented, including two species of water lily (Nymphaea caerulea and N.lotus) and extensive mats of water lettuce (Pistia stratiotes). Cattails (Typha sp.) forms pure stands in the northern swamps and various Cyperus species are found around the edges of the swamps. Cyperus immensus forms dense clumps in areas with flooding by fresh water. Cyperus laevigatus is prominent along the lake shore in areas where the alkaline water table is high, in areas of shallow lagoons enclosed behind sand ridges and flanking river deltas.[13]

Grasslands are dominated by Cynodon dactylon in dry locations, or by Sporobolus spicatus, often in association with Sporobolus consimilis on the alkaline lake flats. Sporobolus spicatus is dominant on exposed lakebed and can be very extensive during low lake levels, becoming restricted to a narrow zone above the high water mark when lake levels are high. There are extensive areas of Psilolemma jaegeri grasslands outside the park, along the eastern shore of the lake.[13] Vegetation on the escarpment is characterized by Ruellia megachlamys and African baobab trees (Adansonia digitata).[6]

An African Baobab in Lake Manyara National Park.

Southern ground hornbill at Lake Manyara National Park

Lilac-breasted roller

Lake Manyara National Park is known for flocks of thousands flamingos that feed along the edge of the lake in the wet season. In 1991 there were an estimated 1,900,000 non-breeding Lesser Flamingo (Phoeniconaias minor) individuals and 40,000 Greater Flamingo (Phoenicopterus roseus). Great white pelican (Pelecanus onocrotalus) can also be present in large numbers (an estimated 200,000 individuals in 1991) and in all there has been an estimated 1,000,000-2,499,999 individual water birds, however, only 78,320 birds were counted in 1994.[5] The groundwater forest to the north of the lake, and largely within the National Park, is a well-known breeding site for thousands of pink-backed pelican (Pelecanus rufescens) and yellow-billed stork (Mycteria ibis) along with smaller numbers of Marabou stork (Leptoptilos crumeniferus) and grey heron (Ardea cinerea).[5] Over 40 species of birds of prey are documented, including palm-nut vulture (Gypohierax angolensis) and Ayre's hawk eagle (Hieraaetus ayresii).[15] In all, more than 390 species of birds have been documented in the national park,[8] although in the dry season, flamingos and other water birds are usually found only in small numbers.

Populations of large migratory mammals that are concentrated primarily in Tarangire National Park, but also move through Lake Manyara National Park include wildebeest, zebra, Thomson's gazelle and Grant's gazelle. Large herds of wildebeest and other plains game from the Mto wa Mbu Game Controlled Area enter the park from the north for short periods.[15] Wildebeest exclusively graze the alkaline grasslands around the lake, and numbers are highest during the dry season, dropping to small resident populations in the wet season.[3] Herbivores of Lake Manyara National Park include zebra, bushbuck, waterbuck, Grant's gazelle, impala, Thomson's gazelle, Cape buffalo, giraffe, hippopotamus, baboon, warthog, and elephant.[3]

Studies in the 1980s found this to be one of the areas with the highest wildlife biomass in Africa,[1] but elephant numbers had fallen by 75% between 1985 and 1991 as a result of illegal hunting, with numbers rebounding to around 200 in 1996.[3] Lake Manyara was also once known for its high population of black rhinoceros,[15] but none were present by 1996. Similarly, reedbuck were present in 1984, but no individuals were found in a 1996 census. Predators of Lake Manyara National Park include lion, leopard, African wild cat, spotted hyena, black-backed jackal, bat-eared fox, serval, honey badger, African civet, genet (Genetta) species and several mongoose species. Cheetah and African golden cat are sighted occasionally.[3]

Lake Manyara is the type locality for the endangered fish Oreochromis amphimelas, a species of in the cichlid family. It is endemic to Tanzania, and also lives in a few more saline lakes with closed basins. Exploitation is prohibited in the parts of Lake Manyara within the National Park and the protected park areas provide important seed stock for the replenishment of fished populations.[16]

Over 180 species of butterflies have been documented in the park.[17]