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Inland Norway University of Applied Sciences (2016)

Browsing by giraffe in heterogeneous savanna

Mahenya, Obeid John

Titre : Browsing by giraffe in heterogeneous savanna

Auteur : Mahenya, Obeid John

Université de soutenance : Inland Norway University of Applied Sciences

Grade : Doctor of Philosophy (PhD) 2016

Understanding foraging behaviour of wild animals is an important step for wildlife management and conservation and for learning the animal’s role in the ecosystem. I used Maasai giraffe (Giraffa camelopardalis tippelskirchi Matschie) as a study animal to see how foraging decisions of giraffe varied in three study sites ; Arusha National Park , Mikumi National Park and Serengeti National Park, Tanzania, with focus on Arusha National Park (from here on referred to by names). My focus was on how giraffe make foraging decisions matching the vegetation in a heterogeneous savannah. I set up the following specific questions ; (i) does selection criteria differ with hierarchical scales ?, (ii) how do giraffe browse in relation to the trade-off between intake rate and quality selection (iii) which activities are most important for giraffe, and how and why do activities vary in time ? (iv) do foraging decisions differ between sexes and environments ? Visual observations were used to collect data on foraging behaviour in both dry and wet seasons in the year 2013 and 2014. In the first study, our results showed that in Arusha occurrence of Acacia xanthophloea was the main determinant of foraging decisions used by giraffes across all scales. In the second study in Arusha giraffe fed mainly from spinescent trees, such as Acacia xanthophloea, giving lower intake rate than the spineless trees, but assumed to be nutrient-rich. The third study, also in Arusha, focused on how giraffe allocated time into different activities, and found that time spent on feeding, resting and socializing was influenced by season but did not relate to each other. The fourth study compared sexual segregation in giraffe between Arusha, Serengeti and Mikumi, and focused on whether foraging decisions of giraffes differ between sexes in the nutrient rich and nutrient poor environments. We found that female and male foraging patterns were influenced by variation in tree chemistry and differences in the competing herbivore communities.


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