Biology Reference
In-Depth Information
resulted in a massively biased colonization. North American mammals flooded into South
America and are now major components of the fauna (the maned wolf among them). Many
fewer South American mammals became established in North America, and today only three
species—the Virginia opossum, the porcupine, and the nine-banded armadillo—still survive
there. Interestingly, two of the three species of our focus in this chapter—anteater and arma-
dillo—are remnants of that native South American fauna.
When the renowned paleontologist George Gaylord Simpson came out with his 1980 clas-
sic
Splendid Isolation: The Curious History of South American Mammals
, he highlighted
the divergent route South American mammals took in evolution because of physical barriers
posed by the oceans and the flooded isthmus, as well as by the Andes, high deserts, and rain
forests. These virtual fences prevented the mixing of the fauna. Thirty years after the pub-
lication of his work, intensive human activities including agricultural expansion, settlement,
and transportation infrastructure, rather than mountain ranges or large rivers, have become
the great isolators. The results, too, threaten millions of years of evolution. The IUCN Red
List now includes many formerly common species that cannot persist in human-dominated
landscapes, such as many antelope species and other large, hoofed mammals that used to mi-
grate across large grasslands.
I asked Leandro and Carly to assess which of the mammals they were studying would sur-
vive in the face of expanding agriculture. I wondered if it was an ecological stretch for the
grassland-loving mammals to occupy soybean fields, should landowners happen to allow it.
Alternatively, I wondered whether some might be preadapted to colonize and persist in an-
other open habitat, albeit one with a monoculture of soy, or on cattle ranches where the grass
was cropped to the ground.
Carly's scat data showed that the answer varied, depending on the species. Maned wolves
preferred Emas's grasslands and avoided closed-canopy forests inside and outside the park.
Surprisingly, maned wolf scats were quite common out in the soy, however. She attributed
the presence of the species there to the abundance of rodents, its dietary staple. Soy acted like
natural vegetation and gave the rodents shelter. As long as they could go a-ratting, the wolves
seemed to do fine in the croplands. Carly noted, “In spite of its shy nature, the maned wolf
is adapting to expansion of agriculture.” Maned wolves are common in Brazil's agriculture-
dominated landscapes, at least those of soy, it seems, because they are not persecuted as is
the gray wolf in northern climes. Maned wolves tend to avoid cattle ranchlands, though, as
those lands are too bare even for rats.
In contrast, the giant armadillo had no use for soy plantations. Giant anteaters also avoided
the agricultural fields, but they visited the cattle pastures because these appeared to have
greater populations of ants and termites. Ranchers often left the termite mounds and ant nests
intact, and the long-snouted opportunists showed no hesitance in excavating their dinner in
man-made habitat. Giant anteaters were also more common where ranchlands abutted ri-
