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University of Namibia (2021)

Effects of elephant carcasses on vegetation cover, herbivore behaviour, and potential Anthrax transmission in central Etosha National Park

Joel, Hendrina

Titre : Effects of elephant carcasses on vegetation cover, herbivore behaviour, and potential Anthrax transmission in central Etosha National Park

Auteur : Joel, Hendrina

Université de soutenance  : University of Namibia

Grade : Master of Science (Biology) 2021

Résumé partiel
Anthrax is primarily a disease of herbivores caused by a soil-borne, spore-forming and Grampositive bacterium, Bacillus anthracis. This study investigated the role large-bodied animal carcasses may play in anthrax transmission dynamics in an African savanna. Specifically, I examined how African elephant (Loxodonta africana) carcasses affected vegetation cover, soil pathogen concentrations, and herbivore behaviour at carcass sites over time in central Etosha National Park, Namibia. Carcass site soil and vegetation sampling was conducted three times over a growing season (January, April and July), while motion-triggered camera traps monitored activity at elephant carcass sites over a three-year period in central Etosha National Park. Elephant carcasses were placed into age classes for soil and vegetation sampling based on the time of death as follows : recent (0-2 years old), old (2-5 years old), and very old (>5 years old). This study i) measured the area of soil disturbance around the elephant carcass, ii) measured for vegetation cover at elephant carcass, iii) determined the concentration of B. anthracis spores in soils at zebra and elephant carcass sites, and iv) monitored animals activity at elephant carcass sites using motion sensing video camera. The area of soil disturbance at elephant carcass sites, while substantial in the year of death (up to 31.55m2), showed a sharp decline after the first year (to lessthan 1m2). Vegetation cover was generally highest near the centre of carcass sites and declined with increasing distance away, except for some of the younger sites (<2 years old) with more soil disturbance at the closest sampling distance. Among site ages, the 2-5 years old carcass sites had higher vegetation cover than younger or older sites. There was seasonal variation in vegetation cover that varied with site age, with cover at older carcass sites dropping off considerably in the dry season. Although B. anthracis spore concentrations showed a declining trend with site age for elephant and zebra carcass sites, these trends were not statistically significant. Over 35 trap months, the video cameras recorded a total of 31,068 videos of which 12,728 were mammals and the rest by wind, rain and birds. Video recordings at elephant carcass sites showed that 21 animal species (ungulate herbivores, carnivores and small mammals) visited these sites.

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Page publiée le 28 novembre 2022