South American animals in U.S. zoos

An island continent

For tens of millions of years after the breakup of Gondwana, South America drifted on its own, and many separate animal lineages evolved there. That isolation ended two to three million years ago when the Isthmus of Panama formed. The Great American Interchange followed. Opossums and armadillos moved north, the ancestors of llamas moved south, and many South American species died out, mostly outcompeted by northern arrivals.

The survivors remain the continent's signature animals. Sloths, anteaters and armadillos, the xenarthrans, are among its most characteristic evolutionary radiations. The giant anteater is the largest of the four living anteaters and, unlike its relatives, lives mostly on the ground. The capybara, the world's largest rodent, belongs to the caviomorphs, a rodent group that also includes guinea pigs and the chinchilla. The maned wolf is neither a wolf nor a fox and is the largest canine native to the continent.

From the Amazon to the Andes

South America holds the Amazon rainforest, the Andes, the Pantanal wetlands, the Cerrado savannas, the Atacama Desert and the Patagonian steppe. The Neotropical realm has more tropical rainforest than any other realm. Andean animals are built for altitude: the Andean condor ranges over grassland and rock up to 5,000 m (16,000 ft) and is the heaviest living flying bird. The maned wolf's long legs probably suit the tall grasses of the Cerrado.

Rivers and wetlands are just as rich. More than 5,600 freshwater fish species are described from the continent, which covers less than 12 percent of Earth's surface. The red-bellied piranha is widespread in the Amazon, Paraguay, Paraná and Essequibo basins and is among the most common fish in parts of its range. The green anaconda, the largest snake native to the Americas, hunts in swamps and slow rivers.

Birds and frogs

With more than 3,400 species, South America has more birds than any other continent. The Neotropical realm has 31 endemic bird families, over twice as many as any other realm, among them toucans, rheas and seriemas. The greater rhea is the largest native bird in the Americas. The continent is also a global center of amphibian diversity, from glass frogs in Andean cloud forest to poison dart frogs such as the blue poison dart frog, which takes its skin toxins from the insects it eats.

Pressures and recoveries

Deforestation, mining, agriculture and climate change are cutting into habitats, and large parts of the Amazon, Atlantic Forest and Cerrado are under threat. The giant anteater is Vulnerable after a decline of more than 30 percent over three generations. Wild chinchillas, hunted heavily for fur, are now known only in Chile.

Conservation can reverse a decline. The golden lion tamarin of Brazil's Atlantic coastal forest recovered from a few hundred animals to roughly 4,800. The work combined reintroduction of zoo-born tamarins, moving wild groups out of small forest fragments and replanting forest to reconnect habitat.