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University of KwaZulu-Natal (2005)

The effect of habitat alteration by elephants on invertebrate diversity in two small reserves in South Africa.

Govender, Navashni.

Titre : The effect of habitat alteration by elephants on invertebrate diversity in two small reserves in South Africa.

Auteur : Govender, Navashni.

Université de soutenance : University of KwaZulu-Natal

Grade : Master of Science (MS) 2005

Résumé partiel
Balancing increasing elephant numbers with biodiversity conservation in small reserves has become a concern for many protected area managers. Elephants are considered important agents of disturbance creating heterogeneity and thus contributing to the maintenance of biodiversity. However elephants also damage vegetation through their destructive feeding habits, and this has led to pressure to reduce elephant populations in many reserves. Quantitative data on the impact of elephants on invertebrates, the main component of biodiversity at the species level, are lacking. The aim of this project was to assess the effect that habitat alteration by elephants has on the diversity of selected ground-dwelling invertebrates (ants, centipedes, millipedes, spiders, scorpions and termites) through the provision of logs and dung as a potential refuge niche for these invertebrate communities, and to determine the effect of spatial (vegetation types) and temporal (season and age of dung) variation on the invertebrates using these refugia. Variation in impacts was considered important because savanna is not homogenous and the impact of the refugia is likely to be dynamic in terms of seasonal trends in invertebrate populations, and in terms of changes in the environmental conditions offered by the refugia. Elephant impact on vegetation, quantity of refugia (logs and dung) produced and invertebrate diversity associated with refugia were determined for 115 transects within Madikwe Game Reserve in the North Western Province, South Africa. Invertebrate abundance, species richness and diversity were always higher under refugia than in areas without refugia. Vegetation utilisation, frequency of refugia production and invertebrate diversity showed strong temporal variation (seasonal) ; elephant impact and production of logs were higher in winter than in summer because elephants are more likely to feed on woody vegetation in winter when grass nutrient levels are low. Invertebrate diversity under the logs was higher in summer than in winter, and this probably reflected the higher abundance and diversity of invertebrates that are usually associated with the warmer, wetter summer months.

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