Environmental Engineering Reference
In-Depth Information
Grasslands have mammalian herbivores ranging from small rodents to the largest
terrestrial mammals, and the dominant ungulates are larger than their predators:
killing one of those animals provides a large amount of meat. In contrast, in tropical
rain forests most of the vertebrate grazers are small and folivorous (mostly monkeys)
and hence present much less rewarding targets for hunts, and their numbers are
ultimately controlled by larger predators (leopards, eagles). And, as already noted,
in marine ecosystems many herbivores are much larger than the planktonic auto-
trophs, and secondary and tertiary consumers are larger still, presenting rewarding
opportunities for killing and capture.
Not surprisingly, the most commonly hunted animals were those that combined
fair size with relatively high productivity and high territorial density. Wild pigs (adult
body mass of up to 90 kg), deer, and antelopes (the smallest animals at less than 25
kg, the large male eland well over 600 kg) are perfect examples of such species.
Before the domestication of dogs, persistence hunting (made possible by the superior
endurance running and cooling abilities of our species) was an efi cient way to bring
down these animals (Liebenberg 2006). With simple tools (spears, bows and arrows)
they could be hunted with much less effort. In contrast, hunting of the largest her-
bivores required cooperative effort and often some elaborate strategies: perhaps
most notably, herds of buffaloes were chased over cliffs, their bodies smashed
by the fall. Head-Smashed-In buffalo jump near Fort McLeod, Alberta, is one of
UNESCO's world heritage sites.
In all afl uent countries, hunting has been transformed from a quest for food to
an often expensive pastime, but the killing of wild animals for food goes on in many
countries in Asia, Africa, and Latin America. China's omnivory creates particular
problems, as the traditional preference for exotic foods has been combined with
rising disposable incomes, resulting in a growing demand for shark i ns, sea cucum-
bers, turtles, and even tigers. The African bush meat trade is also very strong, and
the chunks of fresh or roasted meat offered for sale are not only from the abundant
rodents and small grazers but also from gorillas and chimpanzees.
Since animals selected for domestication had to combine a fair body size with a
relatively high productivity, the third important factor was their demand for feed,
in respect to both quantity and quality. No large carnivorous animal could be reared
proi tably for meat production. Omnivorous pigs had yet another advantage: their
basal metabolic rate is slower than that of sheep, goats, or cattle, and hence they
convert feed into muscle and fat with higher efi ciency. On the other hand, ruminants
can digest cellulosic tissue that is indigestible by other animals and hence are able
to survive entirely by grazing. But in places with longer winters and plenty of snow
