Seasonal Foraging Behaviour Of The Plains Zebra And The African Elephant In Relation To The Occurrence Of Anthrax In Etosha National Park, Namibia

ABSTRACT

It is generally assumed that herbivores acquire gastrointestinal anthrax by ingesting

spores, hence information on foraging behaviour of ungulates can be a fundamental

component in understanding epidemiology of anthrax. This study investigated seasonal

foraging behaviour in relation to the timing of anthrax mortalities in zebras (wet season,

anthrax peak) and elephants (dry season, anthrax peak) in Etosha National Park. Zebra

diet composition and foraging efficiency was determined using video playbacks of focal

animals and elephant diet quality and soil ingestion was studied using faecal analysis.

The results show that zebras forage more intensively in the wet season, taking on average

3.5 bites per step in wet season versus 1.8 bites in the dry season. Nineteen grass species

and six shrub species were consumed by zebras in the study areas (Okaukuejo and Halali)

plains and zebras tended to eat short grass species in the wet season and tall grass species

in the dry season. Elephant faecal crude protein (CP), phosphorus (P) and crude fiber

(CF) was significantly higher in the wet season (CP 5.2%, P120mg/100g and CF 34%)

than the dry season (CP 4.3%, P 80.1mg/100g and CF 49.5%) and the amount of soil in

elephant faeces was significantly higher in the wet season (4.9%) than the dry season

(0.8%). It was concluded that foraging behaviour can be a powerful tool for

understanding host interactions and contact with B. anthracis spores in the environment;

however an understanding of anthrax transmission built around foraging behaviour alone

will remain speculative until we consider other aspects of the host–B. anthracis

interaction.