Biology Reference
In-Depth Information
to that point to retrieve the TrackTag.” After returning it to Peter Brown, George would re-
ceive a computer file with all locations that the jaguar or puma had visited while wearing the
TrackTag.
“Couldn't you learn the same thing from the VHF signals you pick up by flying each
month, even with fewer locations?” I asked. “Take a look at this,” George responded, indicat-
ing an image on his laptop. Since the beginning of the radio tracking, he had been religiously
plugging his jaguar locations into a database. On the screen were the location points, collec-
ted during all the flights, for Paya, a female that had recently been killed by another jaguar.
The seventeen VHF fixes George had for Paya, when connected, outlined a large triangular
home range of about 230 square kilometers overlaid on a map that covered vast sections of
upland forest in addition to the Tambopata River.
“Now watch,” George said. He keyed in a few commands and displayed the TrackTag loc-
ations—literally hundreds of yellow dots—on top of the triangle created by the seventeen
VHF fixes. “Quite a revelation, huh?” he said with a laugh. The TrackTag locations, recorded
during the same period from the same animal, showed exactly the opposite pattern: Paya
hugged the fifty kilometers of the river system lying within that large triangle. “She actually
avoided the upland forests!” George exclaimed. “I had a hunch that the sparse VHF locations
might be misleading us about how jaguars use Amazonian forests. Now we know.”
When George uploaded TrackTag results from other animals, it was clear that Paya was
not the only big cat to follow that pattern. Other females largely avoided the much more
abundant uplands and patrolled the riparian forest instead. Although the TrackTag evidence
was indisputable, the behavior was mystifying, since rivers have been the center of human
development in this region for hundreds or even thousands of years. Why did the jaguars live
so close to the water's edge? What was attractive enough to override the real threats posed
by a growing human presence? In the pioneer days, the threat had been boatloads of pelt
hunters. Today, the threat is thousands of gold miners and their followers who provide them
with food, lodging, and pleasures. And still the jaguars hang on.
As I write, those questions remain unanswered and George still labors to crack the mystery.
The evidence so far, however, casts doubt on his original assumption, that the jaguars have
a taste for river-dwelling food items. Using modern DNA-sequencing techniques to analyze
the jaguars' scat and identify their prey, his team has found no sign of fish or turtles or
caimans. Instead, white-lipped peccaries are the primary prey. Tracking results for those an-
imals showed that the peccaries range widely throughout the floodplain, so a steady diet of
these wanderers gives no obvious clue to why the females are so attracted to river edges. Per-
haps the question will remain unanswered until a researcher figures out how to add digital
cameras to the TrackTag equipment in order to monitor how and where the female jaguars
capture their prey. One theory holds that it is easier for cats to kill peccaries along the flat
riverbanks than in the broken terrain of the uplands.
