Biology Reference
In-Depth Information
Sue and her associates had been the first to acclimatize troops of bald-faced saki monkeys
to human presence and watch them every day for hours on end. Eventually, the primates be-
came comfortable enough to act without visible concern about their presence. That allowed
her to focus on the contributions of her sakis to the rain forest ecology. Sakis seemed to be
everywhere but nowhere at the same time, she noticed. A distribution map of the saki indic-
ates the species is found throughout Madre de Dios, but when one tries to find them, the mon-
keys' presence seems irregular and unpredictable, what biologists call “patchy.” Why should
that be so when all of that forest looks so similar to us?
Monkeys may be hard to spot, but they glow like neon compared with jaguars. Few veteran
tropical biologists have ever met a wild jaguar; according to those who have, a prolonged en-
counter is usually a once-in-a-lifetime event. The cat's exquisite pelage of black rosettes on
an amber background stands out in animals on display in zoos and on wall calendars, but that
coat camouflages them in the dappled light of the forest understory.
Many biologists who attempt to study rain forest mammals eventually give up and shift
to some other project. It is not for lack of trying. Rain forest mammals shrink from plain
view. Many are nocturnal and diminutive; they scurry under leaves or, like the most abundant
group—bats—roost in caves or shelter under dense boughs until nightfall. But even large
vertebrates that are active by day are expert at staying out of sight, especially where hunters
stalk them.
George's two target cats—jaguars and pumas—are among the most wide-ranging mam-
mals in the region. The jaguar roams from Arizona to Argentina, but unlike many tropical
rain forest denizens it can live in desert conditions. Like most large predators, however, it
always occurs in low densities. The puma, also known as the mountain lion or cougar, can be
found from the Yukon south almost to the tip of South America in the mountains of Tierra
del Fuego. Like the jaguar, the puma has many ecological addresses, from the edge of arctic
tundra to tropical wet mangroves, but never exists in large numbers. Unlike jaguars, pumas
are one of the most studied of all large cats, except in the Amazon. Here, their ecology re-
mained a mystery until George became intrigued by them.
How do the two big cats fit together in this ecological puzzle? “I began to wonder,” George
told me, “do the smaller pumas share space with jaguars under the rain forest canopy? Do
they hunt the same areas for prey?” Reduction of prey by another top predator would only
boost the total area needed to support a pair of breeding jaguars, say, and make the answer to
“How much is enough?” frighteningly large. Of course, from the perspective of a territorial
male jaguar, even one nearby male jaguar or puma might be too close for comfort.
Since these questions all related to what rarity is, I began to wonder about the relativity
of our definition and how we understand the concept. Do jaguars and pumas even qualify as
rare species? Some biologists point out that when it comes to rarity, both of these big cats,
as well as the lion and the tiger, have such a widespread distribution that it may compensate
