Feeding choices and impacts of extralimital giraffe on two keystone tree species in the Kgalagadi National Park

Koedoe - African Protected Area Conservation and Science

Field Value
Title Feeding choices and impacts of extralimital giraffe on two keystone tree species in the Kgalagadi National Park
Creator February, Edmund Shadwell, Eleanor Viljoen, Storme Hattas, Dawood
Subject Ecology, Conservation, Environmental management Rewilding; megaherbivore; reshape canopy structure; reproductive potential; physical and chemical defences; leaf nutrient status
Description In this article we determine the effect of an extralimital megaherbivore on the reproductive potential and vegetation structure of two keystone tree species in the Auob River in the south western Kalahari Desert of southern Africa. Using spoor and dung counts we establish the presence of giraffe in three predetermined density zones by walking 50 transects across the river in each zone. We also photographed six trees from each species in each zone and use these photographs to determine browse impact on reproductive potential, canopy volume as well as the percentage dieback on the extremities of the canopy. We then perform stable carbon and nitrogen isotope analysis on the leaves of the trees and compare these relative to the isotope ratios of giraffe dung to ascertain dietary preference. Crude protein was determined as a guide to nutritive value. Finally, we determine both chemical and physical defences for the two species. Our results show a significant negative impact of giraffe browse on tree canopies, no significant differences in recruitment and a noticeable decrease in flowers and pods at the giraffe browse height of 2 m – 5 m. No significant differences in crude protein or condensed tannins were found but significant differences in spinescence. Giraffe are not endemic to the Auob River and our study shows that the introduction of these animals is having a negative impact on the canopies of Vachellia haematoxylon. While there are, as yet, no significant impacts on reproductive potential we speculate that this will happen with time.Conservation implications: Our study shows that giraffe are significantly impacting the canopies of two common tree species in the Auob River in the arid Kgalagadi Transfrontier Park. Without management intervention an increasing population of giraffe will result in substantial changes to the plant community vegetation structure of the river.
Publisher AOSIS Publishing
Contributor Mellon Foundation, South African NRF
Date 2017-05-29
Type info:eu-repo/semantics/article info:eu-repo/semantics/publishedVersion — Correlative, survey, transects,
Format text/html application/epub+zip text/xml application/pdf
Identifier 10.4102/koedoe.v59i1.1454
Source Koedoe; Vol 59, No 1 (2017); 10 pages 2071-0771 0075-6458
Language eng
Relation https://koedoe.co.za/index.php/koedoe/article/view/1454/2054 https://koedoe.co.za/index.php/koedoe/article/view/1454/2053 https://koedoe.co.za/index.php/koedoe/article/view/1454/2055 https://koedoe.co.za/index.php/koedoe/article/view/1454/2045
Coverage Africa, Protected areas Holocene Period Total counts, partial counts, density
Rights Copyright (c) 2017 Edmund February, Eleanor Shadwell, Storme Viljoen, Dawood Hattas https://creativecommons.org/licenses/by/4.0