A Dynamic Process in the Open Savannah

When dealing with an area that is about km² counting wild game is easier said than done!

The animals occur over a diversity of habitats all with differing degrees of visibility, they move over space and time, often sporadically, and accessibility to certain areas is sometimes difficult. Grumeti Reserves is part of an open system so animals are always moving in and out of the area.

To be able to compare trends over time, consistency in the counting method is very important. Using helicopter counts, every year in August, game are counted using the DISTANCE sampling method.

By using DISTANCE, you do not have to see all the game. It is more important to record the distances at which game are seen accurately. The program then works out a density and area estimate. However, it is important to have a good number of sightings per species, at least 60, to develop more accurate estimates.

The below table shows species trends for the period 2003-2008. These figures are estimates – the data reported is not a total count but rather the mean estimates for the species.

Wildebeest and zebra are the primary migratory species in the Serengeti ecosystem. While the general migration pattern is relatively consistent, how they move over this vast landscape shifts slightly each year. This accounts for the variation in numbers counted each year. Higher counts are likely to contain a component of the migration, while lower counts are more reflective of resident populations.