Background - A Short Safari Adventure Among Africa's Thorny Bushveld Wildlife - page 27

Poaching of elk and deer has increased in the USA partly because of the economic downturn
but also around Yellowstone due to of the wolf instigated population crash of elk by three
quarters.
Bugling Rocky Mountain Elk
Elk have been a major source of meat protein from many people. Many predict that we are
going into the 6 major extinction in wildlife and to what extent man has and will contribute to
extinction of wildlife is debated. Much of the debate revolves around the contribution of
climate versus man's predation that contributed to the mega herbivores extinction some ten
millennia ago in Northern Eurasia, South America, and Southern Africa. Norman Owen-Smith,
from the University of Witwatersrand has contributed to this debate based on both his topics on
herbivores and vegetation carrying capacities and also his presentations, including to the
American Museum of Natural History. In summary, the issue is that excessive predation results
in a demographic situation where predation exceeds the rate of recruitment of the population
by reproduction and the population may become extinct; unless the predators then switch to
other prey because of the rareness of the original prey, or the predator population cannot be
maintained, or prey can escape to a predator free space, for example as in the case of the
migrating wildebeest in East Africa. For extinction to occur either prey predation, even if the
population is rare, predation, like from humans, has to persist, or climatic conditions and
vegetation loss tips the balance toward extinction. If however the prey is in an area of low
density of predators, prey populations increase linearly until food resources limit population
growth and the carrying capacity is reached. Reproduction is usually highest at half the
carrying capacity and if lower than that it may be less because of less interaction between
males and females. If a predator is introduced it then reduces the population and a predator pit
model results. In this situation predators and prey reach equilibrium, however this is usually
one tenth of the carrying capacity set by food resources. This has important implications as we
will discuss later in connection with herbivore populations on our trip. Norman-Smith cites
the example that moose in North America could reach a density of 2 per square kilometer