Costa Rica hosts approximately 160 species of amphibians, primarily represented by the dozens of species of frogs and toads. That catlike meow? That’s Boulenger’s hyla, one of Costa Rica’s more than 20 kinds of toxic frogs. That insectlike buzz is probably two bright-red poison-dart frogs wrestling belly-to-belly for the sake of a few square meters of turf. And the deafening choruses of long loud whoops that resound through the night in Nicoya and the adjacent lowlands of Guanacaste? That’s an orgiastic band of orange and purple-black Mexican burrowing toads getting it on.

Of all Central America’s exotic species, none are more colorful than the poison-dart frogs, from which indigenous people extract deadly poisons to tip their arrows. Frogs are tasty little fellows to carnivorous amphibians, reptiles, and birds. Hence, in many species, the mucous glands common in all amphibians have evolved to produce a bitter-tasting poison.

In Central and South America at least 20 kinds of frogs have developed this defense still further: Their alkaloid poisons are so toxic that they can paralyze a large bird or small monkey immediately. Several species—the dendrobatids—produce among the most potent toxins known. Some species’ eggs and tadpoles even produce toxins, making them unpalatable, like bad caviar!

Of course, it’s no value to an individual frog if its attacker dies after devouring the victim. Hence poison-dart frogs have developed conspicuous, striking colors—bright yellow, scarlet, purple, and blue, the colors of poison recognized throughout the animal world—and sometimes “flash colors” (concealed when at rest but flashed at appropriate times to startle predators) that announce, “Beware!” These confident critters don’t act like other frogs either. They’re active by day, moving boldly around the forest floor, “confident and secure,” says one writer, “in their brilliant livery.”

In April and May, toads go looking for love in the rain pools of scarlet bromeliads that festoon the high branches. Here, high in the trees, tadpoles of arboreal frogs wriggle about. Many species, particularly the 39 species of hylids, spend their entire lives in the tree canopies, where they breed in holes and bromeliads. (The hylids have enlarged suction-cup pads on their toes. They often catch their prey in midair leaps, and the suction discs guarantee surefooted landings.) Others deposit their eggs on vegetation over streams; the tadpoles fall when hatched. Others construct frothy foam nests, which they float on pools, dutifully guarded by the watchful male.