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Why do some African thorn trees (Acacia spp.) have a flat-top: a grazer-plant mutualism hypothesis?

The quintessential African savanna tree is the flat-topped Acacia. However, the reason for the architecture occurring in sparse-canopied small-leafed tree species from well-lit, often mesic, environments is unclear. Brown (1960) suggested that it reduced feeding by the distinctly African herbivore, the giraffe. Escaping recaptured herbivore and/or fire damage is crucial for palatable savanna trees such as acacias. The impact of fire depends on the fire intensity (mainly due to under-canopy dead grass biomass and weather conditions) and on woody plant

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Seasonal density estimates of common large herbivores in Hwange National Park, Zimbabwe

The monitoring of ecosystem processes and states is a critical step in the management of protected areas. It allows for the assessment of the success or failure of practices ranging from ‘laissez-faire’ to strong hands-on policies. Much effort is for instance devoted to the monitoring of wildlife abundance, particularly when associated with large ecological influence or socio-economical values. In Africa, the diversity of large herbivores represents both a major asset of protected areas and a global conservation target as a

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Structure and composition of Acacia xanthophloea woodland in Lake Nakuru National Park, Kenya

The woody vegetation of Lake Nakuru National Park occurs along rivers, lakeshores and flood plains. Four different sites within the Acacia xanthophloea woodlands were selected for the study. Vegetation structure was not significantly different in the four woodlands used for the study, but these sites differed in the relative density of Acacia trees. Regeneration of A. xanthophloea differed in each site, with the highest regeneration rates found in the nonfenced plots where browsing took place.

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Effect of low rainfall and browsing by large herbivores on an enclosed savannah habitat in Kenya

Savannah ecosystems in East Africa are rarely stable and can experience rapid local changes from dense woodlands to open plains. In this 3-year study there was a reduction of 16.3% in a height-stratified sample of nearly 1000 individually marked Acacia drepanolobium trees. The study was carried out in an enclosed fire-free wooded grassland habitat in the Laikipia region of Kenya. The trees were monitored from 1998 to 2001, a period that included 12 months when rainfall was 60% below average.

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Use of PCR-DGGE to characterize the distribution of bacterial populations in feces of reticulated giraffes (Giraffa camelopardalis reticulata), African elephants (Loxodonta africana) and white rhinoceros (Ceratotherium simum)

The gastrointestinal microbiota play a vital role in overall health of people and animals by helping break down and digest food, producing vitamins and hormones, training the immune system and preventing pathogenic bacterial overgrowth. Little is known, however, about the ecology of microbiota of large exotic herbivores and basic questions need to be answered. The objectives of this study were to evaluate whether bacterial populations are evenly distributed throughout fecal excretions in three exotic herbivore species and to compare the

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