Scientists were thrilled this past April when a jaguar walked by a surveillance camera on Panama's Barro Colorado, a scrap of rainforest that became an island after creation of the Panama Canal nearly a century ago.
Researchers hadn't recorded jaguars—the largest wild cat species in the Americas—on Barro Colorado since 1983, the cats' absence the apparent result of poaching, habitat shrinkage, and prey loss. Mountain lions and ocelots, smaller than jaguars, have since gone missing, too. But the return of such keystone species could help to restore a fragile ecosystem that has also been losing its North American soungbirds.
The nine-square-mile island has been a Smithsonian Institution research station for 63 years and fully protected since 1923. The historical records of its local flora and fauna are extensive—a single ornithologist once counted 230 bird species there and scientists note an abundance of small mammals, including monkeys, peccaries, coatimundis, pacas, rats, and agoutis at levels two to 10 times their normal central Panama concentration.
By 1970, the island was changing. An estimated 45 bird species had disappeared, due in part to an increase in the density of omnivores, which ate the fruits and nuts the birds preferred. (Even in undisturbed rainforest, fewer than one percent of seedlings reach adulthood.) As another consequence of the predator imbalance on Barro Colorado, meadows and forest edges shrunk, offering fewer opportunities for the birds and other animals that depend on these niche habitats.
An estimated 51 percent of all North American migrant avian species winter in the neotropics, including Panama and other Central American countries. Thus, Barro Colorado's birds—including many songbirds and waterfowl—are to a great extent, our birds. And the loss of large felines does not bode well for those creatures (and plants) that rely on them to help maintain fragile ecosystems.
The jaguar photographed this past spring was likely a transient that swam to the island and moved on. Barro Colorado is too small (and busy, with 200 human researchers visiting each year) to support even a single jag year round. But the presence of the interloper offers hope, suggesting such cats are hanging on locally, perhaps even flourishing in a rainforest highly fragmented by agriculture and crisscrossed by a nearby canal, railroad, and highway.
If jaguars can make a comeback at Barro Colorado, perhaps the rainforest has greater restorative powers than previously believed. If so, it will mark the welcome the return of displaced bird species, including migrants that shuttle annually between the U.S. and Panama.