studies have shown that each species of ungulate appears to have a 
yearlong preferred diet different from and complementary to the others. 
Some species of animals eat different classes of food. Giraffes 
(Giraffa Camelopardalis) for example, feed largely on trees; rhinoceros 
(Diceros bicornis) feed largely on brush; while wildebeests eat grass 
almost exclusively. 
But within the different classes of food the diets are also 
complementary either as to species of food plants eaten or to the stage 
of growth of a given plant. Red oats grass (Themeda triandra) for 
example, although not eaten by some ungulates, is the most important 
single item in the diets of wildebeests, topis, and zebras in western 
Kenya and Tanganyika. The wildebeests choose the fresh leaves of this 
grass until they reach about 4 inches in length. Stalks and seed 
heads are rarely taken and only 4 percent of the red oats identified 
in wildebeests' stomachs was dry. Zebras feed on red oats grass pri¬ 
marily when it is more mature. Most of the leaves eaten by them were 
over 4 inches long and stalks and heads were frequently taken. Zebras 
also avoided the grass when it was dry. Topis, on the other hand, 
showed a marked preference for dry red oats grass, and over 50 percent 
of the red oats in the stomachs of the topis examined were dry. Most 
of the rest were mature, about 20 percent stalks and heads. 
The individual diets of the wild herbivores differ from one 
another in various respects including crude protein, dry matter, and 
moisture content. They appear to provide the optimum nutrition for 
the animals involved. When the animals are denied their preferred 
diets they may still survive, but various lines of evidence -- includ¬ 
ing age of females at first breeding, timing and success of breeding, 
pre- and post-natal survival and differential sexual mortality of the 
young, resistence of population to drought stress, and biomass -- 
indicate that alternate diets provide a lower plane of nutrition 
(Talbot and Talbot, 1963a, 1963b). 
These nonduplicating food preferences result in the efficient use 
of virtually all the available vegetation to support the biomass of 
mixed wild herbivores; whereas when cattle, goats and sheep graze, only 
one class of food, grass, and only a few species within that class, are 
the preferred forage and most efficient source of nutrition (Heady, 1960). 
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