Tracing the Source of the Elephant And Hippopotamus Ivory from ...

unlikely that many were actually eaten” (1999: 79). However, Mugangu and Hunter
(1992) observed hippos foraging on aquatic vegetation in Lake Rutanzige in Virunga
National Park, Zaire, during the dry season of 1989. They found that the grasses, other
than Panicum repens, did not produce adequate levels of crude protein to adequately
nourish the hippos, and therefore aquatic plant consumption was likely a response to food
shortage (Mugangu and Hunter 1992: 345). Measuring the percentage of crude protein in
the diet of animals is means of determining food quality. The specific aquatic species
consumed included Nile salad (Pistia stratiotes, approx. 70% coverage in Lake
Rutanzige), a grass (Leersia hexandra) and a sedge (Cyperus sp.) (approx. 10% coverage
each). However, the hippo foraged more on the sedge and grass than the Nile salad
(Mugangu and Hunter 1992: 346, contra Field 1970). The hippos were also seen eating a
creeping vine (Ipomoea cairica) and two herbs (Justicia flava and J. cynorensis) along
the river bank.
Carnivory in hippos, on the other hand, is an even rarer occurrence. Dudley
(1996: 486-487) reported instances of carnivory in Hwange National Park, located in the
Zambezi of southern Africa, during the 1995 winter dry season. Drought conditions had
been instigated by low rainfall and high grazing animal density. Dudley (1998) later
detailed further incidents reported to him or personally witnessed in the years following
his first publication. Eltringham (1999: 82-84) even gives an account of an episode of
cannibalism! Nevertheless, carnivory (and most decidedly cannibalism) are likely the
consequence of scavanging due to severe nutritional stress and not predation. As such,
the hippopotamus will not be treated as a carnivore in the interpretation of the stable
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