The ecosystem is defined by the main migration routes of several species. As in many African national parks, much of the wildlife moves across park boundaries along traditional migration routes, searching for food and water as the seasons change.

Most animals leave the area near the Tarangire River at the beginning of the short rainy season in October/November. The first to move are the numerous wildebeest and zebras, soon followed by Grant's and Thomson's gazelles, buffaloes, eland, elephants, oryx and hartebeest. Only the resident species, which include waterbuck, impalas, warthogs, dikdiks, giraffes, rhinos and lesser kudus stay behind.

The second rainy season begins in March and at its peak the Tarangire animals are spread over an area of more than 20,500 sq/km of Maasai country. At the beginning of June the long rains end, the Maasai steppe dries up rapidly and the migratory species return to the Tarangire River.

As in all ecosystems the vegetation and the types of animals are closely correlated. Giraffes need trees to browse and won't be found in open grasslands. Lions, which usually follow the migrating antelopes and waterbirds, will be found on the flood plain. It is impossible to say exactly when and where different species will occur, but it is possible to build up a picture of the most likely species to be found in any area at a particular time.

Over 300 species of birds have been recorded in the Park, some of them Eurasian migrants which are present from October to April.

Tsetse flies are found in Tarangire and have played a major role in the land- use of the area. Tsetses carry trypanosomiasis, a form of sleeping sickness to which domestic stock are highly susceptible. This has meant that Tarangire has not been used as a dry season rangeland by the Maasai and wildlife has remained undisturbed.

The wild animals here have, over a long period, built up a resistance to 'tryps' end can survive in a tsetse-infested area. Large areas in Africa contain no human settlements because of the small tsetse fly, but recent projects to eradicate tsetses and open up these areas threaten the existence of large populations of wild animals and their natural habitats.