Given the rich diversity of Costa Rica’s ecosystems, it may come as a surprise that only 200 mammal species—half of which are bats—live here. Several species of dolphins and seven species of whales are common in Costa Rican waters, but there are no seals. And the only endemic marine mammal species of any significance is the endangered manatee.
Before man hunted them to extinction, there were many more mammal species. Even today all large—and many small—mammal populations are subject to extreme pressure from hunting or habitat destruction.
The mostly nocturnal and near-blind nine-banded armadillo (cusuco) will be familiar to anyone from Texas. The animal can grow to almost one meter long. They are terrestrial dwellers that grub about on the forest floor, feeding on insects and fungi. The female lays a single egg that, remarkably, divides to produce identical triplets. Its smaller cousin, the naked-tailed armadillo, is far less frequently seen.
The dog family is represented by the brown-gray coyote and nocturnal gray fox, both found mostly in the dry northwest.
The marsupials—mammals whose embryonic offspring crawl from the birth canal and are reared in an external pouch—are represented by nine species of opossums. The blunt-nosed, short-spined, prehensile-tailed porcupine (puerco espín) is nocturnal and arboreal and rarely seen. There are also two species of rabbits (conejos).
Anteaters are common in lowland and middle-elevation habitats throughout Costa Rica. Anteaters are purists and subsist solely on a diet of ants and termites, plus a few unavoidable bits of dirt. There is no doubt about what the best tool is for the job—a long tongue with thousands of microscopic spines. The anteater’s toothless jaw is one long tube. When it feeds, using its powerful forearms and claws to rip open ant and termite nests, its thong of a tongue flicks in and out of its tiny mouth, running deep into the galleries. Each time it withdraws, it brings with it a load of ants, which are scraped off inside the tunnel of its mouth and swallowed, ground down by small quantities of sand and gravel in its stomach.
The most commonly seen of Costa Rica’s three anteater species is the tree-dwelling lesser anteater (or tamandua locally), a beautiful creature with a prehensile tail and the gold-and-black coloration of a panda bear. It can grow to 1.5 meters and weigh up to eight kilograms.
The critically endangered giant anteater, with its huge, bushy tail and astonishingly long proboscis, is now restricted to the Osa Peninsula. It can grow to two meters long and when threatened rears itself on its hind legs and slashes wildly with its claws.
At night you may, with luck, see the strictly arboreal cat-sized silky anteater, which can hang from its strong prehensile tail.
The most numerous mammals by far are the bats (109 species). You may come across them slumbering by day halfway up a tree or roosting in a shed or beneath the eaves of your lodgings. In true Dracula fashion, most bats are lunarphobic: They avoid the bright light. They suspend foraging completely while the moon is at its peak, probably for fear of owls.
Many bat species—like the giant Jamaican fruit bat (murciélago frutero), with a wingspan of more than 50 centimeters—are frugivores (fruit eaters) or insectivores. Quite harmless, they play a vital role in pollination, seed dispersal, and mosquito control.
The three species of vampire bats (Ticos call them vampiros)—which belong to the neotropics, not Transylvania—are a different matter: They inflict an estimated $100 million of damage on domestic farm animals throughout Central and South America by transmitting rabies and other diseases. Two species feed on birds; the third on mammals, with a modus operandi almost as frightening as the stuff of Bram Stoker’s Dracula. It lands on or close to a sleeping mammal, such as a cow. Using its two razor-sharp incisors, it punctures the unsuspecting beast and, with the aid of an anticoagulant saliva, merrily squats beside the wound and laps up the blood while it flows.
The most interesting of bats, however, and one easily seen in Tortuguero, is the fishing bulldog bat (murciélago pescador), with its huge wingspan (up to 60 cm across) and great gaff-shaped claws with which it hooks fish.
Costa Rica boasts six endangered members of the cat family. All are active by day and night, but are rarely seen. Cats are primarily solitary and nocturnal and spend the greater part of the day sleeping or hidden in dense vegetation. Although they are legally protected, hunting of cats still occurs in Costa Rica. However, the main threat to the remaining populations is deforestation.
One of the most abundant of cats is the jaguarundi (called león breñero locally), a spotless dark-brown or tawny critter about the size of a large house cat. It has a long, slender body, short stocky legs (its hind legs are taller than its forelegs), long tail, and a venal face with yellow eyes suggesting a nasty temperament. It is more diurnal than its cousins and is sometimes seen hunting in pairs, preferring lowland habitats.
Pumas (león) also inhabit a variety of terrains, though they are rarely seen. This large cat—also called the “mountain lion”—is generally dun-colored, though coloration varies markedly among individuals and from region to region.
The spotted cats include the cute-looking, house-cat-sized margay (caucel) and its smaller cousin, the oncilla. Both wear an ocher coat spotted with black and brown spots, like tiny leopards. Their chests are white. The solitary and strongly nocturnal margay, which can weigh up to six kilograms, has a very long tail in relation to its body size, which, combined with its ability to turn its hind feet by 180 degrees, provides monkey-like climbing abilities. It is found only in primary or very little-disturbed forests. The oncilla or tiger cat has black ears and is distinguished from the margay by its face (closely resembling that of a domestic cat), its shorter tail, and more slender body shape. This solitary animal prefers montane cloud forest.
The most commonly seen cat is the ocelot (manigordo), which is well distributed throughout the country and among various habitats. The ocelot is the biggest (males can weigh up to 15 kg, the females up to 11 kg) of Costa Rica’s “small” cats and has short, dense fur with brown spots and rosettes with black edges, arranged in parallel rows along its body length, with a background of grayish-yellow. It has a characteristic white spot on each ear, and black stripes on both cheeks and forehead.
Worshiped as a god in pre-Columbian civilizations, the jaguar is the symbol of the Central American jungle. Panthera onca (or tigre to locals) was once abundant throughout Central America. Today this magnificent and noble beast is an endangered species, rare except in parts of the larger reserves: Santa Rosa, Tortuguero, and Corcovado National Parks, and the Cordillera Talamanca. When roads penetrate the primeval forest, the jaguar is among the first large mammals to disappear. While a few of the famous black “panther” variety exist, most Central American jaguars are a rich yellow, spotted with large black rosettes. Jaguars are the largest and most powerful of the American members of the cat family—a mature jaguar measures over two meters, stands 60 centimeters at the shoulders, and weighs up to 90 kilograms. The animal’s head and shoulders are massive, the legs relatively short and thick. An adept climber and swimmer, the beast is a versatile hunter, at home in trees, on the ground, and even in water. Like all wild cats, jaguars are extremely shy and attack humans very rarely.
Costa Rica has two species of deer: the red brocket deer (called cabro de monte), which favors the rainforests, and the larger, more commonly seen white-tailed deer (venado), widely dispersed in habitats throughout the country, but especially Guanacaste. The former is slightly hump-backed and bronze. The latter varies from gray to red, normally with a white belly and a white dappled throat and face.
Anyone venturing to Tortuguero National Park  or Gandoca-Manzanillo National Wildlife Refuge  will no doubt hope to see a West Indian manatee (manati). This herbivorous marine mammal looks like a tuskless walrus, with small round eyes, fleshy lips that hang over the sides of its mouth, and no hind limbs, just a large, flat, spatulate tail. The animals, sometimes called sea cows, can grow to four meters long and weigh as much as a ton. Now endangered throughout their former range, these creatures once inhabited brackish rivers and lagoons along the whole coast of Central America’s Caribbean shoreline. Today, only a few remain in the most southerly waters of the United States and isolated pockets of Central America and the Caribbean Isles. Tortuguero, where the animals are legally protected, has one of the few significant populations.
They are not easy to spot, for they lie submerged with only nostrils showing. Watch for rising bubbles in the water: Manatees suffer from flatulence, a result of eating up to 45 kilograms of water hyacinths and other aquatic flora daily.
Costa Rica has four species of monkeys: the white-faced (or capuchin), howler, spider, and squirrel. Along with approximately 50 other species, they belong to a group called New World monkeys. They inhabit a wide range of habitats, from the rainforest canopy to the scrubby undergrowth of the dry forests, though each species occupies its own niche and the species seldom meet. Together, they are the liveliest and most vocal jungle tenants. Beyond the reach of most predators, they have little inhibition in announcing their presence with their roughhousing and howls, chatterings, and screeches.
The distinctive-looking capuchin, or white-faced monkey (mono cara blanca), is the smartest and most inquisitive of Central American simians. It derives its name from its black body and monklike white cowl. They’re the little guys favored by organ grinders worldwide. Capuchins range widely throughout the wet lowland forests and the deciduous dry forests of the northwest Pacific below 1,500 meters. Two excellent places to see them are Santa Rosa and Manuel Antonio National Parks, where family troops are constantly on the prowl.
These opportunistic feeders are fun to watch as they search under logs and leaves or tear off bark as they seek out insects and small lizards. Capuchins also steal birds’ eggs and nestlings. While their taste is eclectic, they are fussy eaters: They’ll meticulously pick out grubs from fruit, which they test for ripeness by smelling and squeezing.
The howler (mono congo) is the most abundant as well as the largest of Central American monkeys (it can weigh up to 5 kg). It inhabits both lowland and montane forests throughout Costa Rica and can be found clinging precariously to existence in many relic patches of forest.
The stentorian males greet each new day with reveille calls that seem more like the explosive roars of lions than those of small arboreal leaf-eaters. The hair-raising vocalizations can carry for almost a mile in even the densest of jungle. The males sing in chorus again at dusk (or whenever trespassers get too close) as a spacing mechanism to keep rivals at a safe distance. Their Pavarotti-like vocal abilities are due to unusually large larynxes and throats that inflate into resonating balloons. Females generally content themselves with loud wails and groans—usually to signal distress or call a straying infant. This noisy yet sedentary canopy browser feeds on leaves and fruit.
The smallest and most endangered Costa Rican primate, the squirrel monkey (mono titi) grows to 25–35 centimeters, plus a tail up to 45 centimeters. Fewer than 2,000 individuals are thought to exist. It is restricted to the rainforests of the southern Pacific lowlands. Always on the go, day and night, they scurry about in the jungle understory and forest floor on all fours. Squirrels are more gregarious than most other monkeys; bands of 40 individuals or more are not uncommon. The golden-orange titi (with its face of white and black) is the arboreal goat of the forest. It will eat almost anything: fruit, insects, small lizards. The titi is well on its way to extinction.
The large, loose-limbed spider monkey (mono colorado)—the supreme acrobat of the forest—was once the most widespread of the Central American monkeys. The last few decades have brought significant destruction of spider monkey habitats, and land clearance and hunting have greatly reduced spider monkey populations throughout much of their former range.
These copper-colored acrobats can attain a length of 1.5 meters. They have evolved extreme specialization for a highly mobile arboreal lifestyle. Long slender limbs allow spider monkeys to make spectacular leaps. But the spider’s greatest secret is its extraordinary prehensile tail, which is longer than the combined length of its head and body. The underside is ridged like a human fingertip for added grip at the end of treetop leaps (it is even sensitive enough for probing and picking). You might see individuals hanging like ripe fruit by their tails.
Gregarious by night (they often bed down in heaps), by day they are among the most solitary of primates. The males stay aloof from the females. While the latter tend to their young, which they carry on their backs, the males are busy marking their territory with secretions from their chest glands.
These myopic, sharp-toothed wild pigs are potentially aggressive creatures whose presence in the rainforest may be betrayed by their pungent, musky odor and by the churned-up ground from their grubbing. Gregarious beasts, they forage in herds and make a fearsome noise if frightened or disturbed. Like most animals, they prefer to flee from human presence. Occasionally, however, an aggressive male may show his bravado by threatening to have a go at you, usually in a bluff charge. Attacks by groups of a dozen or more peccaries sometimes occur. Rangers advise that if attacked, you should climb a tree or stand absolutely still. Don’t try to frighten them away—that’s a sure way to get gored.
The more common collared peccary (saino) is marked by an ocher-colored band of hair running from its shoulders down to its nose; the rest of its body is dark brown. The larger white-lipped peccary (cariblanco), which can grow to one meter long, is all black, or brown, with a white mustache or “beard.”
Raccoons, familiar to North Americans, are present throughout Costa Rica, where they are frequently seen begging tidbits from diners at hotel restaurants. The northern raccoon (mapache to Ticos) is a smaller but otherwise identical cousin of the North American raccoon and can be found widely in Costa Rica’s lowlands, predominantly in moist areas. Its cousin, the darker-colored crab-eating raccoon, is found only along the Pacific coast.
A relative, the long-nosed coatimundi (called pizote locally), is found throughout the country. Coatis wear many coats, from yellow to deepest brown, though all are distinguished by faintly ringed tails, white-tipped black snouts, and panda-like eye rings. They are gregarious critters and often seen in packs.
Another raccoon family member is the small and totally nocturnal kinkajou (known to Ticos as the martilla), with its large limpid eyes and velvet-soft coat of golden brown. It’s a superb climber (it can hang by its prehensile tail) and spends most of its life feeding on fruit, honey, and insects in the treetops. Its smaller cousin is the much rarer grayish, bug-eyed olingo (cacomistle), with panda-like white spectacled eyes and a bushy white tail ringed with black hoops.
The agouti (guatusa to Ticos) is a brown cat-size rodent related to the guinea pig. It inhabits the forests up to 1,980 meters elevation and is often seen by day feeding on the forest floor on fruits and nuts (the wet-forest agoutis are darker than their chestnut-colored dry-forest cousins). It looks like a giant tailless squirrel with the thin legs and tiptoeing gait of a deer, but it sounds like a small dog. They are solitary critters yet form monogamous pairs.
Agoutis have long been favored for their meat and are voraciously hunted by humans. Their nocturnal cousin, the paca (called tepezcuintle by locals), also makes good eating. It can grow to a meter long and weigh 10 kilograms, three times larger than the agouti; it is favored by a wide variety of predators. It is brown with rows of white spots along its side. Both are easily captured because of the strong anal musks they use to scent their territories and because of their habit of running in circles. If you disturb one in the forest, you may hear its high-pitched alarm bark before you see it.
Costa Rica also has five squirrel species and about 40 species of rats, mice, and gophers.
Ask anyone to compile a list of the world’s strangest creatures, and the sloth (locally called perezoso, which means “lazy”), a creature that moves with the grace and deliberation of a tai chi master, would be right up there with the duck-billed platypus.There are six distinct species, of which Costa Rica has two: the three-fingered sloth (Bradypus variegatus or perezoso de tres dedos) and the nocturnal Hoffman’s two-fingered sloth (Choleopus hoffmani or perezoso de dos dedos). The animals are commonly called “three-toed” and “two-toed,” but in fact both species have three toes.
The two species are only faintly related and belong to two different families. Both grow to the size of a medium-size dog. The three-fingered sloth has a small head and flat face with snub nose; the two-fingered sloth has a tapered nose. Both have beady eyes, and seemingly rudimentary ears (its reputation for poor hearing is entirely incorrect). Sloths have long arms with curving claws that hook over and grasp the branches from which they spend almost their entire life suspended upside down. The creatures spend up to 12 hours daily sleeping curled up with their limbs drawn close together and their heads tucked between the forelimbs.
The sloths shaggy fur harbors algae, unique to the beast, that make sloths greenly inconspicuous—wonderful camouflage from prowling jaguars and keen-eyed eagles, their chief predators. Communities of moths live in the depths of the fur and feed on the algae as well.
There’s a very good reason sloths move at a rate barely distinguishable from rigor mortis. A sloth’s digestion works as slowly as its other bodily functions, and food remains in its stomach for up to a week. Hence, it has evolved a large ruminant-like stomach and intestinal tract to process large quantities of relatively indigestible food. To compensate, it has sacrificed heavy muscle mass—and, hence, mobility— to maximize body size in proportion to weight. Sloths need warm weather to synthesize food. During long spells of cold weather, the animals may literally starve to death.
Sloths live up to 20 years or longer and reach sexual maturity at three years. Females screech to draw males, which have a bare orange patch on their back with unique sexual markings. Females give birth once a year and spend half their adult lives pregnant. When the juvenile reaches six months of age, the mother simply turns tail on her youngster, which inherits her home range of trees.
An easy way to find sloths is to look up into the green foliage of cecropia trees, which form one of the sloth’s favorite food staples. The sight of a sloth languishing in open cecropia crowns is a heavenly vision to harpy eagles, which swoop in to snatch the torpid creature like plucking fruit.
Another symbol of the New World tropics is the strange-looking Baird’s tapir (danta locally), a solitary, ground-living, plant-eating, forest-dwelling, ungainly mixture of elephant, rhinoceros, pig, and horse. The tapir uses its short, highly mobile proboscis—an evolutionary forerunner to the trunk of the elephant—for plucking leaves and shoveling them into its mouth. Tapirs live in dense forests and swamps and rely on concealment for defense. They are generally found wallowing up to their knees in swampy waters, to which they rush precipitously at the first sign of danger.
This endangered species is the largest indigenous terrestrial mammal in Central America. Like its natural predator the jaguar, the tapir has suffered severely at the hands of humans. The animal was once common in Costa Rica and ranged far and wide in the lowland swamps and forests. Hunters have brought it to the edge of extinction. Today, tapirs are found only in national parks and reserves where hunting is restricted, with the greatest density in Corcovado National Park .
Costa Rica boasts seven members of the weasel family. The most ubiquitous is the skunk (zorro in local parlance), one of the most commonly seen mammal species, of which Costa Rica has three species. The black striped hog-nosed skunk, with its bushy white tail and white stripe along its rump, will be familiar to North Americans. The smaller spotted skunk and hooded skunk are more rarely seen. Their defense is a disgusting scent sprayed at predators from an anal gland.
Costa Rica is also home to the badger-like grison, another member of the weasel family that can weigh three kilograms and is often seen hunting alone or in groups in lowland rainforest during the day. The grison is gray, with a white stripe running across its forehead and ears, white eye patches, and a black nose, chest, and legs. Meter-long otters (perro de agua, or water dog, to locals) are commonly seen in lowland rivers, especially in Tortuguero.
A cousin, the sleek, long-haired, chocolate-brown tayra (locals call it tolumuco)—a meter-long giant of the weasel family—resembles a mix of grison and otter. It is often seen in highland habitats throughout Costa Rica.