Oddly enough, they occupy the same territory as another fierce predator, the mountain lion. When Kelly retrieves her film she sometimes finds that the same camera has snapped pictures of both mountain lions and jaguars. Whether that means that the two animals are on friendly terms, or just very good at avoiding each other, isn't known, she says.
It's hard to tell from the photographs because only one of the thousands and thousands of pictures shows an animal capturing its prey. And that's a photo of an ocelot, a smaller spotted cat, with a mouse in its mouth.
"That's the biggest kill I've gotten so far," she says, laughing.
She hopes to set up video cameras in the future to document the big cats at lunch, and that raises a serious question.
"Cats are the ultimate carnivores," Kelly says. Dogs can get by on all sorts of things, but cats, she adds, are "strictly meat eaters."
That's got to be a little disconcerting as she treks through the forest, but Kelly says the big cats aren't nearly as threatening as the wild pigs, or peccaries, that apparently think they are the real king of the jungle.
"They sometimes run in groups of 40 to 50 animals, and they are very aggressive," she says. Local people who work as guides are very fearful of the peccaries, she says, apparently because the thought of being nibbled to death by wild pigs is more troublesome than the unlikely chance of being ripped apart by a jaguar or mountain lion.
"We've come across wild pigs a few times, but never in a big enough group to pose a threat," she says.
It's worth the risk, she says, because that's the only way to learn about animals like jaguars. It may help save them from the fate suffered by the jaguars that once roamed parts of the southwestern United States. The jaguars disappeared years ago, apparently because of competition over their habitat, especially by humans.
But they may be heading back.
A photograph of a jaguar was captured a few months ago near the southern border of Arizona by wildlife researcher Jack Childs. It took him 4½ years to get the shot.
The photo convinced many wildlife experts that the big cats are flourishing so well to the south that some of them are being pushed north. But nobody is sure at this point.
So Childs and Kelly and about eight other researchers at various locations in Central America will continue to pursue the jaguar, toting their cameras into harms way to try to learn just a little bit more about these powerful cats.
Maybe they can talk more of them into coming back.
Lee Dye’s column appears weekly on ABCNEWS.com. A former science writer for the Los Angeles Times, he now lives in Juneau, Alaska.