buffalo. In 1961 heavy rains caused the lake levels to rise and flood the open grass-
lands, a situation which remained for the rest of the 1960s. The wildebeest were forced
to use the savanna habitat, which they did not prefer, and after 4 years the popula-
tion went extinct. On the surface this appeared to be due to competition with buffalo.
Closer inspection of the situation showed that lions, whose densities were high because
of the high buffalo population, had eradicated the wildebeest. Wildebeest normally
escape predation by running, which they can do in habitats with short grass and
little cover for ambush by predators. Once wildebeest were confined to the savanna
they were less capable of avoiding lions. Buffalo, on the other hand, avoid predators
by hiding in thickets and defending themselves with their horns, and this they
could do in savanna but not on the open grassland. Thus, each prey species had its
own specialized antipredator habitat that allowed coexistence between the prey
species, as predicted by Holt’s (1977) “apparent competition” hypothesis. Once this
habitat partitioning broke down, the predator was able to eliminate one of the species.
The process of apparent competition explains these observations better than true
competition.There are a number of studies designed to detect whether there is competition between
livestock and wildlife. Thill (1984) recorded the seasonal diets of cattle and white-
tailed deer in three forested and two clear-cut sites in Louisiana pine forests. Woody
plants made up more than 85% of the diet of deer on the forest sites throughout the
year (Fig. 9.19). For cattle diets these plants made up less than 16% in summer and
fall but rose to 60% in winter and to 48% in spring. The overlap between the two
species in overall diet was highest in winter at 46% and lowest in summer at 12%.
In contrast, on cleared sites deer continued to eat mainly woody plants but cattle ate
more than 80% grass year round. Diet overlap was only 17% in summer and fell to
10% in winter. Since the two species were in the same habitat and there did not appear
to be predators, there could be a real possibility for interspecific competition if
cattle were confined to forest sites; in fact most of them stayed on the open sites. It
is possible that because cattle and deer have not evolved together we do not see the
expected decrease in overlap in winter, so that competition is increased rather than
avoided at this time.160 Chapter 9
9.10.3Competition
between domestic
species and wildlife
100806040200100806040200% of dietSummer WinterShrubs Grass Herbs Shrubs Grass Herbs
Food type Food type% of dietFig. 9.19The
percentage of the diet of
white-tailed deer (open
bars) and cattle (shaded
bars) made up of
shrubs, grasses, and
herbs. Diet overlap
increased in winter
when food was limiting.
(Data from Thill 1984.)