| dc.description.abstract | In his pioneer ecological study of the then Tarangire Game Reserve in northern Tanzaniat Lamprey (1964) found out that while wild ungulates •pent the dry season concentrated in the Tarangire at a high density of up to about 4o animuls/km2, during the wet season they dispersed over the Masai steppe at a low density of less than 1 animal/las2.
He further observed that other dry season habitats were being lost through human occupation* Since then, human settlement has continued to engulf more and more of the wildlife habitat particularly the wet season areas such as Ardai, Sanya* Kwa Kuchinja and Monduli Juu short grassland plains*
The Simanjiro Plains only 28 kilometres east of Tarangire has been mentioned before as part of the wet season habitat for migratory plains ungulates from the Tarangire (Naveh, 1963)* Before this study was started, Simanjiro was the only viable wet season habitat for plains game within the Tarangire ecosystem but expanding settlement from Arusha was creeping towards it rapidly*
There was therefore an urgent need for a study to assess the importance of the area as wet season r.Kt habitat for zebra and wildebeest within the Tarangire ecosystem and suggest ways of safeguarding it*
(xia.)
This study fulfilled this need.
Research work commenced at the beginning of January 1970. The study area was 570 km2 and was chosen so as to enclose the whole short grassland area located 64 kms southeast of Arusha.
In order to analyse the environmental factors constituting the habitat the vegetation was studied in detail as it is the main habitat component. The major vegetation types were classified according to terminology adopted for Bast African rangelands (Pratt et ala 1966). The types were then mapped and analysed in detail. The grassland was analysed with the list-count quadrat and line-interception methods which are described in various manuals (Oostlng, 1956) Greig-Smith 1957) Cain and Castro, 1959)* The woodland was analysed mainly with plot-less sampling method using an angle-gauge as described by Grosenbaugh (1952). The other vegetation types were analysed with other methods described in the thesis.
The major vegetation type is the Digitaria nacroblephara - Panicum coloratum short grassland. Other important grasses are Pennisetmn neaianun.
(xiii)
Themeda triandra and Bothriochloo radicanj,
Barleria ramulosa is a very widespread shrub.
The percentage cover is between 45-48#. Other quantitative details of dominance are given. The next vegetation type is the Acacia-Commiphora woodland with three subtypes. The bushland is dominated by Acacia stuhlmannii while vhe seasonally water-logged bushed grassland is dominated by Pennisetum mezianum in association with this Acacia. Quantitative measurements are given.
Soil samples taken show that the short grassland
and Acacia tortilla dominated woodland one associated with red sandy loam. Grey sandy clay is associated with Acacia nilotica asp. aubalata and Commiphora schimperi dominated sub-types. Both the bushland and seasonally water logged bushed grassland are associated with black clay. The topograpHy/soil/plant catenas are shown and explained. Rainfall records taken indicate a typical Masailand pattern as described by Griffiths and Gwynne (1961) with short rains falling from October to December and long rains from March to May. Also both permanent and seasonal surface water sources were mapped.
Important wild herbivores using the Simanjlro were zebra, wildebeest, eland. Grant's and Thomson's
(xiv)
^ V
A*
f*'
gazelles, ostrich, giraffe and impala, Domestic species were cattle, sheep and goats. Their populations were determined by monthly aerial counts using Method 2 of Jolly (1969)* The average maximum population sizes or numbers were zebra 6000, wildebeest 9000, eland 200, Grant's gazelle 700, Thomson's gazelle 150, ostrich 200, giraffe 150, impala 200, cattle 18,000 and goats and sheep 5000, Full transect data including densities, biomass, group structure, mortality and reproduction are given. Calving in wildebeest is synchronised and occurs between January and February, Although calving in other species is not synchronised most
species calve in the plains during the rains. Full
our*
data is shown.
Feeding observations were conducted and the results tabulated for the most important species. Occupation of different vegetation types by herbivores was worked out to determine habitat preferences using occupance and the Chi-square ( ) method similar to that used in Amboseli (Western, 1973)• Results show that the short grassland is the most utilized vegetation type because of the availability of grasses upon which the important herbivores feed as they are grazers. The other vegetation types supplement this besides providing food for the browsers. The mechanisms of ecological separation are shown. The effect of surface water on the distribution of herbi-rores is also assessed.
Migration between Slmanjlro and Taranglre was monitored by aerial reconnaissance supplemented by ground observations. There was an orderly progression of zebra and wildebeest from Tarangire to Simanjiro beginning at the onset of the rains continuing and ending during the long rains. There was an inverse relationship of herbivore populations between the two areas during the wet and dry seasons and the population sizes were comparable. Further observations showed limited migrations of plains herbivores from Taranglre to other areas. Postulated migrations within the Tarangire ecosystem were supped.
In the discussionv the implications of the habitat analysis findings are shown( together with the Importance of short grasslands in Bast Africa in supporting high animal biomass and providing high nutritional requirements needed in reproduction.
The various parameters of the herbivore population are compared to other similar areas and their implications analysed. Evidence of factors affecting the stability of the herbivore populations are analysed.
The study in all conclusively shows that the Simanjiro Plains provide over 90# of the wet season requirement* of zebra and wildebeest within the Tarangire ecosystem while at the same time providing grazing and water for a large cattle population and a small population of resident game animals* In order to safeguard the future of the area and hence that of the Tarangire National Park remedial measures are suggested* These include creation of a partial reserve in which human settlement is excluded besides livestock herding, increased anti*poaching work and carefully planned livestock management* The general aspects of the future of wildlife conservation are discussed | |
