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

In the Ngorongoro Crater of northern Tanzania, Kabigumila (1993) considered
this seasonal variation in the diet of African elephants. The Ngorongoro Crater is
grassland, with some areas of swamp and closed canopy Acacia forest. He found that the
elephants’ diet in this area consisted of at least 36 different plant species, with an
emphasis on high-quality vegetation such as forbs and grasses during the wet season, and
sedges and tree-browse during the dry season. Moreover, the shoots, leaves, and
inflorescences of the most important plant species, the sedge Cyperus immensus, were
targeted in the wet season while the bark, wood, and twigs were ingested in the dry
season, showing seasonal preferences for plant parts within a species. Sedges such as C.
immensus are generally considered to be a low quality vegetation, with a 5.8-7.0% crude
protein content.
Indeed, with the advent of the dry season and subsequent drying out of the grasses
and forbs in the grasslands, elephants concentrated their feeding on twigs of trees and
sedges from the Lerai forest. Thus the proportion of browse in the diet was higher during
the dry season. Field (1971, cited by Kabigumila 1993: 162) suggested that elephants
browse more during the dry season because a) browse has a higher crude protein content
than grass, and b) grasses are less palatable because they become more fibrous and
accumulate tannins. Kabigumila also found that there was a significant increase during
the wet season in the number of elephants using the Crater.
Ranging behavior was the focus of the studies by Barnes (1983) in Ruaha
National Park, located in south-central Tanzania, and Leuthold (1977) in Tsavo National
Park in Kenya. Leuthold (1977) established that range size is dependent on the quality of
the environment. In Tsavo East, an area with comparatively poorer habitat, the elephants
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