Anyone who has traveled in the tropics in search of wildlife can tell you that disappointment comes easy. But Costa Rica is one place that lives up to its reputation. Costa Rica is nature’s live theater—and the actors aren’t shy. The scarlet macaws are like rainbows, the toucans and hummingbirds like the green flash of sunset. The tiny poison-dart frogs are bright enough to scare away even the most dim-witted predator. And the electric-blue morphos, the neon narcissi of the butterfly world, make even the most unmoved of viewers gape in awe.
Then there are all the creatures that mimic other things and are harder to spot: insects that look like rotting leaves, moths that look like wasps, the mottled, bark-colored machaca (lantern fly), and the giant Caligo memnon (cream owl) butterfly, whose huge open wings resemble the wide-eyed face of an owl.
Much of the wildlife is glimpsed only as shadows. Well-known animals that you are not likely to see are the cats—pumas, jaguars, margays, and ocelots—and tapirs and white-lipped peccaries. With patience, however, you can usually spot monkeys galore, as well as iguanas, quetzals, and sloths that get most of their aerobic exercise by scratching their bellies and look, as someone has said, like “long-armed tree-dwelling Muppets.”
Identifying the species is a prodigious task, which every day turns up something new. Insects, for example, make up about half of the estimated 500,000 to one million plant and animal species in Costa Rica. The country is home seasonally to more than 850 bird species—10 percent of all known bird species (the U.S. and Canada combined have less than half that number). There are 5,000 different species of grasshoppers, 160 known amphibians, 220 reptiles, and 10 percent of all known butterflies (Corcovado National Park [1] alone has at least 220 different species).
About three million years ago, the Central American isthmus began to rise from the sea to form the first tentative link between the two Americas. Going from island to island, birds, insects, reptiles, and the first mammals began to move back and forth between the continents. During this period, rodents of North America reached the southern continent, and so did the monkeys, which found the tropical climate to their liking.
In due course, South America connected with North America. Down this corridor came the placental mammals to dispute the possession of South America with the marsupial residents. Creatures poured across the bridge in both directions. The equids used it to enter South America, the opossums to invade North America. Only a few South American mammals, notably armadillos, ground sloths, and porcupines, managed to establish themselves successfully in the north. The greatest migration was in the other direction. The mammals soon came to dominate the environment, diversifying into forms more appropriate to the tropics. In the course of this rivalry, many marsupial species disappeared, leaving only the tough, opportunistic opossums.
The isthmus has thus served as a “filter bridge” for the intermingling of species and the evolution of modern distinctive Costa Rican biota, resulting in a proliferation of species that is vastly richer than the biota of either North or South America.
Links:
[1] http://www.moon.com/destinations/costa-rica/golfo-dulce-and-the-osa-peninsula/the-osa-peninsula/corcovado-national-park