Biology Reference
In-Depth Information
for their low density wherever the species occurs. Rarity, they argue, really depends on the
scale you are talking about. Other scientists argue that explaining the rarity of jaguars and
pumas is as simple as looking at a food pyramid, as Paul Colinvaux summarized in his aptly
titled 1979 topic
WhyBigFierce Animals AreRare
. It takes a lot of prey animals to support
a healthy population of large carnivores. Biologists refer to different levels of food gathering
by organisms as “trophic levels,” which can be visualized as a pyramid with the largest meat
eaters at the apex, followed by fruit and insect eaters, then plant eaters, and finally the plants
and fungi themselves at the base, supporting the whole structure. Species that occupy the top
of the food chain are always scarce, whether on land, in lakes or streams, or in the oceans.
Thus, in the rain forests of the Amazon, the Congo basin, or Asia, the largest flesh eaters,
as dictated by the laws of thermodynamics and energetics, have to be much fewer in number
than the large herbivores they eat. But how do the causes and consequences of rarity vary as
one moves down the tropical food chain, from big, fierce cats, large herbivores such as deer
and tapirs, monkeys, and macaws to the trees themselves, which give the forest its three-di-
mensional structure? The work of George, Sue, and other colleagues has brought these issues
to light.
Knowing something of the density of the cats' prey could help George to better understand
patterns of rarity among those that stalk them. Meet the forty-kilogram white-lipped peccary,
a shaggy, piglike forest specialist and a primary prey item of both jaguars and pumas. Unlike
the jaguar, a peccary moves in the company of hundreds of its family members and asso-
ciates. Peccaries are constantly on the go and travel long distances over the year; it is still
not clear whether they are nomadic or migratory. Unlike cats, peccaries make their presence
obvious. Rooting peccary groups leave conspicuous pockmarks and furrows in the soil and
announce their presence with grunts, screams, and tooth clacking. The sound track is accom-
panied by an overpowering barnyard cologne, an especially pungent odor that peccaries emit
when excited.
George and Sue chose the remote Madre de Dios area of the Amazon, and the Los Amigos
Biological Station in particular, for their studies. Los Amigos offered a rare chance to study
wildlife in a hunter-free zone. Somewhat like the Foja Mountains of New Guinea, Los Ami-
gos can be used as a control site for other studies conducted in places where hunting is in-
tense. At Los Amigos, George had the opportunity to study predator and prey populations,
and Sue could study monkey troops, where their subjects' numbers and behavior were less
influenced by human contact. For example, high densities of peccaries where they are neither
shot nor snared might offer different insights into the wanderings and densities of cats from
findings in locations where prey has been decimated by hunting, as it has been in a forest
area of Madre de Dios near Puerto Maldonado, southeastern Peru's regional population cen-
ter. These contrasting sites permitted George to study how wildlife responds to intrusion and
even invasion. Near town, machetes and chain saws were carving up this once isolated stretch
