|Journal||These pour Docteur de l'Universite Abdou Moumouni de Niamey|
The giraffes of Niger (Giraffa camelopardalis peralta) live freely in an environment highly colonized by man called, the zone of transition of the Reserve of Biosphere of the W Regional Park of Niger. The agricultural practices in synergy with the high demographic pressure and the recurring droughts infer an accelerated degradation of the natural forest of this zone, and consequently a fragmentation of the giraffe habitat will even change its behavior. Therefore, an exponential growth of the population of giraffes will make the space occupation more and more conflicting space, threatens the survival and the growth of the giraffe in a permanent search of food and refuge. The present thesis which enters within the framework of the preservation and of the sustainable management of the last herd of giraffes in western Africa, aims at establishing the scientific bases of a rational management. The diachronic analysis of satellitales images Landsat ETM + (on 1986 and 2003) allowed appreciating the state of degradation of the habitat of the giraffe. Indeed, modifications such as regression of the tiger bush for the benefit of the agriculture and an appearance of new units (bear ground, degraded arbustive steppe) were revealed. The headway of the agricultural front, the overgrazing, the repetitive droughts, the density of the road network and the uncontrolled cutting of wood-energy were considered as factors responsible for this degradation. The data from 170 phytosociological releves realized according to the sigmatiste method of Braun-Blanquet and subjected to multivariates analyses allowed to individualize six plant groupings. The geomorphology, the soil occupation and the texture of the soil are the discriminating environmental variables presenting a significant effect on the structure of the vegetation. The specific richness of the groupings varies from 62 in the fallows to Mitracarpus scaber to 83 in the millet farms and the coefficient of variety of Shannon, from 3,4 to 5,46 bits. The équitabilité of Pielou varies from 0, 57 to 0,9. The demographic structure of ligneous determined according to the railing of Peters highlighted 2 big groups: the species with low dynamics (Boscia senegalensis, Boscia angustifolia B. and Combretum nigricans) and those in remarkable dynamics (Guiera senegalensis and Combretum micranthum). This structure is affected by the ecological requirements and the human pressures. As for the annual follow-up of the growth in diameter in the snare of Combretum micranthum and Guiera senegalensis species characteristics of the tiger bush. It shows a variation of the dynamics according to sites, species and types of age group. The study of the eating habits of the giraffe, based on the direct observation and the faecal analysis, reveals a food spectrum composed essentially of 30 botanical species with ascendancy of Leguminosae-Mimosoideae and of Combretaceae. The seasonal variations of the diet observed which the giraffe is explained largely by the preference of the giraffe for a botanical species according to the phenological stage. To estimate the interaction "Man - Giraffe ", a survey was carried out withn about 218 persons of 12 villages distributed on 2 sites of distribution of the giraffe. The comparison of the data between villages and sites of herd of giraffes shows in ascending order, the main current constraints in the self-fulfillment of the giraffe in its habitat: wood cutting energy (25,1 %), lack of feed (21,9 %), advanced agricultural front (20,9 %) and disturbance (19,6 %). It is to be noted as well as the giraffe commits more and more damages on the agricultural crops.
Keywords : Giraffe, Diet, habitat, Phytosociology, Ligneous structure, Niger
Author: Morou Boube
Journal: These pour Docteur de l'Universite Abdou Moumouni de Niamey
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