Biology Reference
In-Depth Information
in the state. If striking a poor nine-banded would feel like rolling over a speed bump, hitting
a giant armadillo, which can weigh up to 60 kilograms, would be like smashing into a re-
taining wall. Fortunately, giant armadillos tend to stay clear of roads in the Cerrado, though
some are run over by passing vehicles anyway. Unlike the nine-banded, which ranges across
much of the southern and southeastern United States all the way to Argentina and parts of
the Caribbean, the giant armadillo is limited to South America. There it ranges widely into
the Amazon basin, where very little is known about its habits and needs. Most likely, though,
giant armadillos, which are both rare and considered by the IUCN to be threatened, thrive in
the drier portions of the range, in Venezuela, the Cerrado, and the Chaco region, which ex-
tends into Paraguay.
Carly and Mason found nearly sixty scats of this subterranean mammal. Together with
the data from Leandro's team, which was the first to radio-track the species, giant armadillo
ecology moved beyond the anecdotal phase. Even though tracked individuals proved to be
largely nocturnal, this armadillo turned out to be the most sensitive of the large mammals to
human disturbance. Not surprisingly, it shuns life in the soy fields. Leandro and his cowork-
ers found that the home ranges of five individuals were about 10 square kilometers and
put the density of armadillos in Emas proper at about 3.4 animals per 100 square kilomet-
ers, more akin to the densities of a top predator such as a jaguar than of a species that eats
more abundant ants and termites. “Just like the anteaters, giant armadillos also have low
birthrates,” Carly mentioned. In the scientific literature, low reproductive rate is not itself
viewed as an initial cause of rarity, but as we saw with the greater one-horned rhino, serious
depletion of a population hampers rapid recovery and can leave the species more vulnerable
to extinction.
At lunch, Carly and I discussed the peculiar habitats of the guild of ant- and termite-loving
mammals. Mammals that subsist on the social insects are few in number and restricted to
the tropics and subtropics, but their taxonomic spread is remarkable. Biologists call different
groups that feed in a similar way an example of “convergence”; the various species that fill
the termite-eating niche (or any analogous niche) are said to be “ecological equivalents.” In
South America, anteaters and armadillos, of the orders Pilosa and Cingulata, respectively, are
examples. Africa is home to the aardvark, the sole living member of the order Tubulidentata;
the aardwolf, a hyena relative; and pangolins, or scaly anteaters, also in their own order,
Pholidota. Asia also harbors pangolins and has the sloth bear, a true carnivore and a termite
connoisseur. Australia and New Guinea have the spiny anteaters or echidnas, which represent
the monotremes, and Australia's bandicoots represent the marsupials (though the most pre-
valent and species-rich termite-eating animals in Australia are not mammals but lizards).
Little is known about the ecology of pangolins, aardvarks, aardwolves, and sloth bears, but
evidence indicates that where there are termites, the density of termite eaters can be impress-
ive, even if their mostly nocturnal behavior makes them hard to see. Some, such as pangolins
