As we moved on, nothing could have prepared us for the next sighting. In a grassland to our left, Edson’s sharp eyes spotted a hovering bird. It was the most dashing of raptors, an aplomado falcon. The aerial predator was preoccupied, following something gliding through the tall grass. Then a head with pointed ears emerged. The maned wolf looked around for a second and moved on. The falcon persisted, perhaps planning to feast on the large insects or birds scared up during the terrestrial predator’s afternoon hunt.
Shadows fell over the rugged escarpment in the distance as the afternoon wore on. We drove out of the park and entered the agricultural zone—“the Ag,” for short. An hour later, our magical sightings of the wolf and the falcon, the merganser and giant anteater, began to feel like a dream. This had been only a first taste of the Cerrado’s wildlife. To learn more about how these animals navigated the last natural pockets embedded in a landscape of soy and cattle would require a longer stay, and for that I had decided to join an unlikely pair of long-term researchers.
March 2008. The sea of grasses undulated in the warm, dry breezes. A tall, blond woman dressed in khakis and field vest reached down to release her dog from its leash. “Okay, Mason, let’s go to work!” The dog dashed into the tall grass of Emas National Park. Every so often a grassy wave broke over the upright tail of the black Labrador retriever as he bounded through a large marshy area bordering a palm glade. The tail zigged and zagged through the wet pampa. Carly Vynne, then a PhD candidate at the University of Washington in Seattle, kept her eye on the dog. Within minutes, Mason returned with a look of great urgency. “What is it, Mason? Let’s go look.” Having grabbed her attention, Mason led us back through the muck and stood with his nose pointed toward the base of a grass clump.
At first we couldn’t see anything. Then we bent down and noticed a cylindrical dropping half submerged below the tussock. Bingo. In a vast expanse of grassland filled with thousands of smells, Mason had detected the scent of rarity: he had sniffed out the droppings of a giant anteater. Carly could barely contain her excitement. Gathering herself, she placed a sample of anteater dung in a vial of preservative to protect the scat sample and the precious strands of DNA it contained from further degradation. Those convinced that dogs are superior to humans praise their loyalty, good nature, and capacity for unconditional love. Scientists appreciate another canine advantage—dogs have an uncanny sense of smell, surpassed only by that of bears and, by coincidence, the giant anteater. The homely bloodhound, with the keenest nose of any dog, possesses a sense of smell 300 times more acute than that of its handlers. Bloodhounds can detect a scent nearly two weeks old, but they are a lot harder to train than Labradors.
Sniffer dogs have recently been recruited for biological field studies because they excel at locating the fecal tidings of rare mammals. Carly had invited me to join the last year of her fieldwork in her study of a group of rare South American mammals in the Cerrado. The maned wolf, jaguar, puma, giant anteater, and giant armadillo of the continent’s pampas and central savannas are vestiges of a rich Serengeti-like fauna that flourished in the Pleistocene epoch, 15,000 years ago. Today, their secretive behavior, low population densities, and ability to hide in the waist-high grass make sightings of these charismatic vertebrates quite rare. Their presence in the agricultural landscape remained an open question. The small size of the existing Cerrado parks and the wide-ranging nature of these species probably meant that some of them lurked out there in the ranchlands as well.
Field biologists who study the habitat use of rare mammals look for any sign: a scrape, a footprint, or the unexpectedly precious gift, a dropping. Miraculous advances in molecular biology have enabled researchers to extract strands of DNA and hormones from animal droppings, transforming the lowly fecal deposit into a gold mine of information. A scat sample can reveal the species of the depositor, individual identity, sex, reproductive status, diet, and health. Moreover, accumulated droppings from any single species, giant anteater or jaguar, yield the most prized data of all for rarities—density, home range, and population size.