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Costa Rica is home to approximately 150 species of amphibians and more than 200 species of reptiles, half of them snakes. The most common reptile you'll see is the dragonlike, tree-dwelling green iguana, which seems to have little fear of man and can grow to two meters in length. You'll spot it often in moist deciduous habitats, crawling through the forest leaf litter or basking on branches that hang over water, its preferred route of escape when threatened. There's no mistaking this reptilian nightmare for any other lizard. Its head--the size of a man's fist--is crested with a frightening wig of leathery spines, its heavy body encased in a scaly hide, deeply wrinkled around the sockets of its muscular legs. Despite its menacing One Million Years B.C. appearance, it is quite harmless, a nonbelligerent vegetarian. Local gourmands, for reasons you may not wish to know, call the iguana the "tree chicken." Its cousin, the ctenosaur (iguana negra) is considered more edible, and you may see them on sale in mercados of major cities.
Another miniature dinosaur is Basilicus basilicus, or Jesus Christ lizard, a Pacific lowland dweller common in Santa Rosa, Palo Verde, and Corcovado national parks. These, too, have large crests atop their heads, backs, and tails, and use water as their means of escape; they run across it on hind legs! (Hence their name.)
Terrestrial turtles are also common in Costa Rica, particularly in the Caribbean lowlands, where they can be seen going about their business in the midmorning hours and after heavy rains. One species--the red turtle, found in northern Pacific lowlands--is particularly easy to spot: its high-domed carapace is gaudily patterned in oranges, reds, yellows, and blacks. Several species of aquatic turtles also frequent the swamps and creeks. Look for them squatting on partially submerged logs.
The amphibians are primarily represented by the dozens of species of frogs and toads, most of which you're probably more likely to hear than to see. That catlike meow? That's Boulenger's hyla (see "Poison-Arrow Frogs," below). That sharp tink, tink that is usually the most prominent sound on damp nights in Costa Rica's midelevation rainforests? That's the tiny tink frog, of course. That insectlike buzz is probably two bright-red poison-arrow frogs wrestling belly-to-belly for the sake of a few square feet of turf. And the deafening choruses of long loud whoops which resound through the night in Nicoya and the adjacent lowlands of Guanacaste? That's an orgiastic band of ugly, orange and purple-black Mexican burrowing toads doing their thing. Should you locate them--the sound carries for miles--don't be surprised to find the horny toads floating like balloons with legs outstretched, emitting their lusty whoops. Love's a strange thing!
CROCODILES AND CAIMANS
Many travelers visit Costa Rica in the hope of seeing crocodiles and caimans, modest-sized relatives. One of the smallest of western crocodilians--no more than two meters long--and possibly the most abundant in existence today, the speckled caiman is still relatively common in parts of wet lowland Costa Rica on both the Atlantic and Pacific coasts. Palo Verde and Tortuguero are both good places to spot them in small creeks, playas, and brackish mangrove swamps, or basking on the banks of streams and ponds.
The scales of the caiman take on the blue-green color of the water it slithers through. Such camouflage and even the ability to breathe underwater, through raised nostrils, have not protected the caiman. Their nests are heavily disturbed by dogs, foxes, tegu lizards, and humans. And increasingly they are being sought for their skins, which are turned into trivia. Ironically, this is easing the pressure on the crocodiles, which are fast disappearing as humanity takes their hides and habitats.
The crocodile exists in precariously low numbers along both coasts, and the only healthy population is in Corcovado National Park, in the Pacific southwest. Only three species of crocodiles--the saltwater croc of Southeast Asia, Africa's Nile crocodile, and the American alligator--are considered man-killers, but it's still a wise idea to check with locals or park rangers before swimming in coastal estuaries and lagoons.
For all their beastly behavior, crocodiles are devoted parents. And despite being relics from the age of the dinosaurs, croc brains are far more complex than those of other reptiles. Perhaps because crocodiles have ugly toothy leers and a stigma of primeval wickedness, there isn't the same love of crocs that has brought international support for the turtles, and their future is much less secure. As biologist David Janzen says: "We may never again see the huge four-meter animals that used to terrify the campesinos and eat their dogs."
Of all Central America's exotic species none are more colorful--literally and figuratively--than the "poison-arrow" frogs, of the type from which Indians extract deadly poisons with which 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, or poison-arrow frogs, which are confined to Costa Rica--produce among the most potent toxins known: atelopidtoxin, bufogenin, bufotenidine, and bufotoxin. Pity the poor snake that gobbles up Dendrobatis granuliferus, a tiny, bright green, red, and black frog which inhabits the lowland forests of the Golfo Dulce region (it is commonly seen on forest floors of Corcovado National Park). Another species, Bufo marinus, can even squirt its poison in a fine spray. And 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, many 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 not night, moving boldly around the forest floor, "confident and secure," says one writer, "in their brilliant livery."
Perhaps the most famous poison frog species is the rare golden toad, found only in the Monteverde Cloud Forest Reserve. In fact, the montane rainforest reserve owes its existence in part to the discovery of Bufo periglenes. This brilliant, neon orange arboreal toad--discovered in 1964 and so stunning that one biologist harbored "a suspicion that someone had dipped the examples in enamel paint"--is not easily seen, despite being one of the most brightly colored animals in the world. The golden toad is so seldom seen that some naturalists speculate that it may now exist only on the cover of tourist brochures.
April through May, golden toads go looking for love in the rainpools of scarlet bromeliads that festoon the high branches. They're easily distinguished: the males are the orange ones; females are yellow and black with patches of scarlet. Here, high in the trees, tadpoles of arboreal frogs wriggle about.
Few Costa Rican frog species breed in permanent bodies of water, where fish predation is intense. Above 1,500 meters, where there are no native fish species, stream breeding is more common (although the introduction in recent years of trout into upland streams already threatens whole frog populations).
The frogs instead have evolved away from dependence on bodies of permanent water. Many species, particularly the 39 species of hylids, spend their entire lives in the tree canopies where they breed in holes and bromeliads. (The hylas have enlarged suction-cup pads on their toes. They often catch their prey in midair leaps: 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.
Some rainforest species, such as the diminutive and warty eleutherodactylus--its name is longer than its body--live on the ground, where they lay their eggs in moist cups of leaves. The tadpole develops fully within the egg sac before emerging as a perfect, if tiny, replica of its parents: it and 12 of its siblings could easily fit on a man's fingernail. Some tadpole species--the Hyla zeteki, for example--are carnivorous: they eat other frogs' tadpoles. Others, like the smoky frog (Leptodactylus pentadactylus) are even cannibalistic! This aggressive giant (adults can grow up to eight inches long) can eat snakes up to 20 inches long. It, too, can emit a poisonous toxin, to which some snakes are immune. If the smoky frog's loud hissing, inflated body, and poisonous secretions don't manage to scare off its predator, it has another ingenious defense: when captured it emits a loud scream.
Although rarely seen by the casual tourist in Costa Rica, snakes make up almost half of all reptile species in the nation (135 species, 17 poisonous). It is a fortunate traveler indeed who gets to see in the wild the fantastically elongated, I-beam-shaped chunk-headed snake, with its catlike elliptical eyes; the slender, beak-nosed bright green vinelike vine snake; or the relatively benign boa constrictor. Many neotropical snake species inhabit a wide range of Costa Rican environments, and wherever you are in the country there are sure to be snakes about. Not that you should worry. Fewer than 500 snakebites are reported each year, and less than three percent of these are fatal. Most bites occur among farmworkers.
Still, caution is always the watchword. Never reach into holes or under rocks, debris, or forest-floor leaf litter without first checking with a stick to see what might be quietly slumbering there. And remember that many snakes are well-camouflaged arboreal creatures which snooze on branches, so never reach for a branch without looking. You should even be cautious when peering inside bromeliads: the dark-colored chunk-headed snake likes to doze inside the moisture-collecting plants during the dry season.
Among the more common snake species you are likely to see are the wide-ranging boas which, with luck, you might spot crawling across a cultivated field or waiting patiently in the bough of a tree in wet or dry tropical forest, savannah, or dry thorn scrub. Wild boas vary in temperament and some are aggressive. Though not poisonous, they are quite capable of inflicting serious damage with their large teeth and will not hesitate to bite. Heaven forbid a full-grown adult (three meters or more) should sink its teeth in sufficiently to get its constricting coils around you!
A species of tropical rattlesnake is also found in Guanacaste and a few relic areas of the Meseta Central. It produces a venom considerably more toxic than its North American cousin--blindness and suffocation are typical effects on humans--and it rarely uses its well-developed rattle to warn off the unwary.
Among the more colorful snakes are the four species of coral snakes, with small heads, blunt tails, and bright bands of red, black, and yellow or white. These highly venomous snakes (often fatal to humans) exhibit a spectacular defensive display when approached: they flatten their bodies and snap back and forth while alternately hiding then swinging their heads side to side and coiling and waving their tails.
Along the Pacific beaches, you may sometimes encounter venomous pelagic sea snakes, a yellow-bellied and black-backed serpent closely related to terrestrial cobras and coral snakes. This gregarious snake has developed an oarlike tail to paddle its way through the ocean. It tends to drift passively with its buddies among drift-lines of flotsam, where it feeds on small fish.
The most talked-about snake in Central America is the fer-de-lance, much feared for its aggressiveness and lethal venom. One of several Central American pit vipers--another is the bushmaster--the fer-de-lance can grow to a length of three meters and is abundant throughout the country, particularly in overgrown fields and rivercourses in drier lowland regions. Costa Ricans call this lethal creature terciopelo, Spanish for "velvet." As juveniles, fer-de-lance are arboreal critters that feed on lizards and frogs, which they attract with a yellow-tipped tail. As adults, they come down to earth, where they move about at night and, by daylight, rest in loose coils of burnished brown on the forest floor.
Give the fer-de-lance a wide berth! Unlike other vipers, the fer-de-lance will bite with little provocation. The snake's powerful venom dissolves nerve tissue and destroys blood cells and artery walls; those fortunate enough to survive may suffer paralysis or tissue damage so massive as to require amputation of the bitten limb.
The Serpentario in San José is a good place to learn to identify snakes and their habits and habitats (see p. 196). There is also a snake laboratory at the Clodomiro Picando Institute in Coronado, where you can watch snakes being milked for venom (see p. 262).
Six of the world's eight species of marine turtles nest on Costa Rica's beaches, and you can see turtles laying eggs somewhere in Costa Rica virtually anytime of year. In "season," turtles can vastly outnumber tourists.
Tortuguero National Park, in northeastern Costa Rica, is one of fewer than 30 places in the world that the green turtle considers clean enough and safe enough to lay its eggs. Although green turtles were once abundant throughout the Caribbean, today there are only three important sites in the region where they nest: one on Aves Island, 62 km west of Montserrat, a second at Gandoca-Manzanillo (and occasionally on beaches north towards Cahuita), and another at Tortuguero, the only major nesting site in the western Caribbean. July through September, more than 5,000 greens swim from their feeding grounds as far away as the Gulf of Mexico and Venezuela to lay their eggs at the eons-old nesting site on the oceanside 21-kilometer stretch of beach on Tortuguero's barrier island.
On the Pacific coast, the most spectacular nestings are at Playa Nancite, in Santa Rosa National Park, and Ostional Wildlife Refuge, where tens of thousands of olive Ridley turtles come ashore July-Dec. in synchronized mass nestings known as arribadas. Giant leatherback turtles, which can weigh as much as 2,000 pounds and reach a length of three meters (the largest reptile in the world), nest at Playa Grande, near Tamarindo, Oct.-March. Hawksbills, ridleys, leatherbacks, Pacific greens and occasionally loggerheads (primarily Caribbean nesters) can be seen in lesser numbers at other beaches along the Pacific coast.
One hundred years ago, green turtles were as numerous as the bison on the North
American plains. They were highly prized for their meat by Central American and
Carib Indians, who netted and harpooned them. And British and Spanish fleets,
buccaneers, and merchantmen counted on turtle meat to feed their crews while
cruising in New World waters. Green turtles are as big as heifers (an average
adult green weighs 250 pounds), easy to catch, and easy to keep alive for weeks
on their backs in a space no bigger than the turtle itself. ("Turtle
patrolled nesting beaches, where they wrestled female turtles on to their backs to be picked up next day.)
The end of colonialism offered no respite. Large-scale green turtle export from Tortuguero, for example, began in 1912 when turtle soup became a delicacy in Europe. And the recurrent massing of olive ridley turtles at a few accessible beaches fostered intensive human exploitation. Despite legislation outlawing the taking of turtle eggs or disturbance of nesting turtles, nest sites continue to be raided by humans (encouraged by an ancient Mayan legend that says the eggs are aphrodisiacs).
When not nesting in Costa Rica, Pacific ridleys congregate in Mexican and Ecuadorian waters, where commercial exploitation continues in earnest (in 1968, Mexican fishermen harvested over one million turtles for the leather trade). Turtle oil is used in the manufacture of cosmetics and perfumes, the shells used in jewelry and ornaments, and the offal dried and processed as fertilizer. Hawksbills, which rarely exceed 125 pounds, are hunted illegally for the tourist trade: one occasionally still sees stuffed turtle specimens for sale.
Mother Nature, too, poses her own challenges. Coatis, dogs, raccoons, and peccaries dig up nest sites to get at the tasty eggs. Gulls, vultures, and hungry frigate birds, with their piercing eyes and sharp beaks, pace the beach hungrily awaiting the hatchlings; crabs lie in wait for the tardy; and hungry jacks, barracudas, and sharks come close to shore for the feast. Ridley hatchlings have even been found in the stomachs of leatherback turtles. Of the hundreds of eggs laid by a female in one season, only a handful will survive to reach maturity. (As many as 70% of the hatchlings are eaten before they reach the water.)
Most of the important nesting sites in Costa Rica are now protected, and access to some is restricted. Still, there is a shortage of undisturbed beaches where turtles can safely nest. Most turtle populations continue to decline due to illegal harvesting and environmental pressures, despite the best efforts of conservationists inspired by Dr. Archie Carr, of the University of Florida, who has written and lectured indefatigably on behalf of turtle protection (see "Tortuguero," in the "Caribbean Coast" chapter).
Turtles have hit on a formula for outwitting their predators, though, or at least for surviving despite them. Each female turtle normally comes ashore two to six times each season and lays an average of 100 eggs on each occasion. Some marvelous internal clock arranges for most eggs to hatch at night when hatchlings can make their frantic rush for the sea concealed by darkness. Often, baby turtles will emerge from the eggs during the day and wait beneath the surface of the beach until nightfall. The young hatch together and dig their way up out through up to a meter of sand as a kind of "simple-minded, cooperative brotherhood," says Archie Carr, "working mindlessly together to lower the penalties of being succulent on a hostile shore." They are programmed to travel fast across the beach to escape the hungry mouths. Even after reaching the sea they continue to swim frantically for several days--flippers paddling furiously--like clockwork toys.
No one knows where baby turtles go. They swim off and generally are not seen again until they appear years later as adults. Turtles are very slow growing; most immature turtles of all species increase in carapace length by less than one inch a year. In fact, little is known about the lives of adult marine turtles. In captivity, a turtle can grow to the size of the smallest fertile nester in about 10 years; in the wild, they grow much slower.
Turtles are great travelers capable of amazing feats of navigation. Greens, for example, navigate across up to 1,500 miles of open sea to return, like salmon, to the same nest site. Guided presumably by stars and currents, thousands of greens arrive at Tortuguero every year from their faraway feeding grounds. (Most Tortuguero greens apparently arrive from the Miskito Bank feeding area of Nicaragua.)
One of the few things known about the intervals between females' trips to the nesting beaches is that a lot of strenuous romance goes on out in the surf. There is no pair-bonding between individual turtles, and each female may be courted by as many as 10 males.
"Sea turtles in love are appallingly industrious," according to Archie Carr. "The male turtle holds himself in the mating position on top of the smooth, curved, wet shell of the wave-tossed female by employing a three-point grappling rig [consisting] of his long, thick, curved, horn-tipped tail and a heavy, hooked claw on each front flipper . . . The female generally stays coy and resistant for what seems an unnecessarily long while. Other males gather, and all strive together over the female in a vast frothy melee." In the frenzy of mating, intelligence seems sadly lacking. Females have been mounted by a male who in turn is mounted by another male while several more jealous males jostle and bite one another to dislodge the successful Casanova.
Most females make their clumsy climb up the beach and lay their eggs under the cover and cool of darkness (loggerheads and ridleys often nest in the daytime, as they seem less timid). They normally time their arrival to coincide with high tide, when they can swim in over the coral reef and when they do not have to drag themselves puffing and panting across a wide expanse of beach. Their great weight, unsupported by water, makes breathing difficult. As a turtle drags her ponderous bulk up the beach, her progress is slow and punctuated by numerous halts in order to breathe. Some turtles have even been known to die of heart attacks brought on by the exertions of digging and laying.
Once she settles on a comfortable spot above the high tide mark, the female scoops out a large body pit with her front flippers. Then her amazingly dexterous hind flippers go to work hollowing out a small egg chamber below her tail and into which white, spongy, golf-ball-size spheres fall every few seconds. After shoveling the sand back into place and flinging sand wildly about to hide her precious treasure, she makes her way back to sea. Note: when near nesting sites, respect the turtles' need for peace and quiet. Nesting turtles are very timid and extremely sensitive to flashlights, sudden movements, and noise, which will send a female turtle in hasty retreat to the sea without laying her eggs. Sometimes in desperation she will drop her eggs on the sand without digging a proper nest.
The eggs normally take 6-8 weeks to hatch, incubated by the warm sand. The sex of the hatchling is determined by the temperature of the sand: males are predominantly produced in cooler sand; a difference of two to three degrees Celsius will produce females. Thus, hatchlings from any one nest site are usually siblings of the same gender.