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Accueil du site → Doctorat → Royaume-Uni → 2002 → Factors limiting the abundance and distribution of hirola (Beatragus hunteri) in Kenya

Newcastle University (2002)

Factors limiting the abundance and distribution of hirola (Beatragus hunteri) in Kenya

Andanje, Samuel A

Titre : Factors limiting the abundance and distribution of hirola (Beatragus hunteri) in Kenya

Auteur : Andanje, Samuel A

Université de soutenance : Newcastle University

Grade : Doctor of Philosophy (PhD) 2002

Résumé partiel
This study investigates the factors limiting the abundance and distribution of hirola, or Hunter’s antelope, (Beatragus hunteri), in Kenya’s Tsavo East National Park (ex-situ population) and Garissa (in-situ popUlation). The hirola is widely recognized as the most severely threatened monotypic species of antelope in sub-Saharan Africa. Data were collected between 1996 and 2000 on the ex-situ population, with occasional comparative sampling of the in-situ population. The study was carried out almost entirely in the field. Hirola were located by ground searching, by radio tracking and occasionally using aircraft ; animals were observed from a landrover. In Tsavo NP the population was found to be static (71.1±9.3 in 844 km2 range), while the Garissa population was declining with about 672 animals remaining in a 5,171 km2 range. Calving in Tsavo took place between August and March, with the peak occurring in late October and early November. About 69.8% of calves died or disappeared within the first 6 months of life and about 18.0% survived to the age of 2 years. Mortality in Tsavo was predominantly associated with predation, while in Garissa, mortality was associated with disease and poaching. Hirola occurred in 8 distinct family groups in Tsavo, each with an adult male and a number of females and their offspring ; temporary separations involving the adult male, or females with young, were also recorded. Remarkably, offspring left their natal groups at about 6-15 months of age and spent a period isolated or with other young animals ; females eventually rejoined a family group or joined a lone male to form a new group. Young males generally formed bachelor groups and eventually separated as adults to become solitary. Hirola were most active in the early morning hours and late evening when it was cool ; hot times of the day were spent resting in the shade of trees and bushes. Densities of other ungulate species within the hirola range varied seasonally, being more abundant in the wet season. Controlling for the relative abundance of other herbivore species, hirola in Tsavo were found to associate predominantly with Grant’s gazelle (Ga ella granfii), while in Garissa they associated mainly with topi (Damaliscus korrigwn). The presence of fewer associates and fewer alternative prey in the dry season appears to have increased the risk of predation to hirola, perhaps due to reduced detection and dilution effects.


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