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Wageningen Universiteit (2000)

Wildlife dynamics : an analysis of change in the Masai Mara ecosystem of Kenya

Ottichilo, W.K.

Titre : Wildlife dynamics : an analysis of change in the Masai Mara ecosystem of Kenya

Auteur : Ottichilo, W.K.

Université de soutenance : Wageningen Universiteit

Grade : PhD thesis 2000

Résumé partiel
This thesis deals with the dynamics of large herbivores in the Masai Mara ecosystem in Kenya. The study area is famous for the annual migration of wildebeest and common zebra from and back to the Serengeti in Tanzania. In this study we made a distinction between these two migratory species and the other non-migratory wildlife species. The results reported are based on animal population estimates derived from counts made on board of small light aircraft. The study covers the period from 1977 to 1997. The total of non-migratory wildlife species in the Masai Mara ecosystem declined by 58% in the last 20 years. The decline ranged from 49% in small brown antelopes to 72% in medium brown antelopes. In individual species, the decline ranged from 52% in Grant’s gazelle to 88% in the warthog. The population sizes of the elephant, impala and ostrich remained constant during the analysis period. There was no significant difference in the decline of wildlife inside and outside the Masai Mara National Reserve except for Thomson’s gazelle and warthog. The population sizes of all livestock species except for the donkey did not significantly change during the entire analysis period. A large proportion of wildebeest migrates between the Serengeti and the Masai Mara ecosystem. A smaller population migrates between the Masai Mara National Reserve and the Loita plains in the north. Statistical analysis revealed that the size of this so-called "resident" wildebeest population declined by 81% over the last 20 years. Further analysis revealed a remarkable association between the decline in resident wildebeest population and the expansion of wheat farming into prime and original wildebeest habitat in the Loita plains. We therefore conclude that loss of former wildlife habitat to agriculture was responsible for the drastic decline of this resident wildebeest population. Apart from habitat loss to agriculture, droughts, poaching and possibly competition between wildlife and livestock may have further contributed to the decline. We argue that these factors and agricultural encroachment may have been responsible for the reported decline of the non-migratory species as well. In the last chapter of this thesis we studied a number of environmental factors that could be associated to the migration of wildebeest and common zebra. We found a significant relationship between wet season rainfall in Kenya and the size of the wildebeest and zebra population migrating into the Masai Mara ecosystem. We also found a significant relationship between dry season NDVI and the size of wildebeest population migrating into the Masai Mara ecosystem. We concluded that wet season rainfall and availability of food in the dry season influence the migration into the Masai Mara ecosystem. We also concluded that NDVI could be used for monitoring and predicting the movements of migratory wildebeest populations in the Serengeti-Mara ecosystem.

Mots clés : wildlife / surveys / remote sensing / population dynamics / herbivores / ecology / ecosystems / kenya

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Page publiée le 24 mars 2007, mise à jour le 2 février 2018