four species of monkeys live in Costa Rica: squirrel, white-faced capuchin, howler, and spider monkeys. Reports of the night or owl monkey in southern Atlantic coastal forests so far have not been accepted as proof that it exists here. All are arboreal; they don't generally spend much time on the ground except to cross an open space-or, in the case of the white-faced monkey, sometimes to forage for insects. Monkeys migrated from South to Central America via the land bridge. I describe squirrel and howler monkeys here.


Squirrel monkey (Saimiri oerstedii), mono titi, mono ardilla This colorful, active creature has a captivating white face with black encircling its mouth and nose, a black cap, and orange-gold fur on back and limbs. Shoulders, hips, and tail (except for the black tip) are a yellowish green. The smallest monkey in Costa Rica, it's found only in the southern Pacific lowlands, south of the Tarcoles River. Scientists classify it as the Central American squirrel monkey, and many believe it was introduced here by humans because of its small range far from South America's squirrel monkeys. Don't confuse the squirrel monkey, with the white-faced capuchin. If you can't distinguish coloring, look at the tail. Capuchins coil theirs, while squirrel monkeys keep their tails straight.

A research project by Grace Wong, of the National University of Heredia's wildlife management program, focused on the titis in Manuel Antonio National Park, which are endemic to Costa Rica. Another subspecies farther south, such as those you might see on the Osa Peninsula, is endemic to Costa Rica and Panama, though few remain in Panama.

Wong's study identified 14 troops, totaling 681 individuals; six of the troops, varying from 15 to 65 individuals, ranged mainly inside the park. She found that from May to October, when fruit is abundant, the titis have more time to rest and play, but by November they spend most of the day looking for food. Up at 5 a.m., they retire for the night around 6 p.m. Young are born from the end of February to the end of March, one birth per pregnancy. Females bear young every two years. Babies are carried for their first three months, with other adults taking turns helping the mother.


When food is scarce, there is often competition between capuchins and titis. When they clash, the smaller titi leaves; Wong has seen a capuchin grab a titi and throw it to the ground. When food is plentiful, they eat together. In the park, natural enemies of the titi are mainly boa constrictors and tayras.

The increase in tourists and tourism infrastructure has reduced the habitat of monkeys and other animals living outside the park, in some cases isolating troops through destruction of forested corridors. Another impact of tourism is that monkeys near a trail or road where people stop to observe them spend more energy on guard and less time foraging. Natural events also influence habitat. Tropical Storm Gert in 1993 affected about 60 percent of the forest canopy (upper layer), reducing sites where monkeys look for insects and fruits. Although short-term effects are negative, Wong explained that long term results can be beneficial because of the mosaic of different types of forest that regenerates.

titi monkey

HOWLER MONKEYS (Allouatta palliata), mono Congo Howlers are all black except for a saddle-like mantle of long, brown or golden hairs on sides and backs; males have a white scrotum. Some field guides list them as mantled howler monkeys. The loud bass vocalizations of adult males reverberate over the tropical landscape from lowland dry forest to mountainous cloud forest. The roars carry about a mile (more than a kilometer). It is thought that these roars or barks not only allow members of the same troop to communicate with each other but also are territorial, advertising location to another troop to prevent feeding conflicts.

Since the average troop size is 10 to 20, keeping everybody together requires a system. Once in Monteverde I heard a big ruckus in the forest near the house. I stepped outside: howler calls told the story. The dominant male bellowed, and from a distance I heard what sounded like the distressed answer from one separated from the group. The calls moved closer to each other as I watched the progress from movement in the trees. Once the stray was back in the fold, the forest again fell silent.

If you get the chance, watch the dominant male through binoculars: see the threatening stance, mouth wide open as he roars. Daybreak and sunset are vocal times, but howlers also respond to thunder, loud noises, airplanes, other howlers' and even guides who imitate their call. But don't stand directly under the monkeys- they have been known to defecate. on people below.

Since howlers do not need large areas of forest, you may see them in the forest ribbons along streams, river, or roads. Strictly vegetarians, they feed on fruit, leaves, flowers, and leaf stems. They are the only monkey species in Costa Rica to eat significant amounts of leaves: specialized bacteria in their digestive tracts help break down cellulose, and they produce enzymes to counteract toxins in leaves, which many plants have developed to ward off herbivores. Research has shown that when presented with a variety of leaves, howlers choose those with highest nutrients and lowest toxicity.

Because of their low-energy diet, howlers are more sedentary than other monkey species. They spend long hours in the same tree resting, scratching, grooming, the adults draped over a tree branch while babies play. Adult males weigh up to 15 pounds.

Predators for adult monkeys are harpy and crested eagles and cats. Tayras, ocelots, and boas prey on the young.


GUATUSA, CHERENGA Though the agouti is a member of the rodent family, its body is shaped more like that of a miniature deer. It has no tail, but does have telltale rodent-like whiskers. Its generally reddish-brown coat can be more yellow on the belly and throat, and the lower legs are a darker brown. Inside the ears is a distinctive pink.

The agouti moves through the forest looking for seeds and fruits that have fallen on the ground: it eats seedlings, flowers, insects, and fungi. It's most active in late afternoon and early morning, though you may see it at any hour of the day. If you come upon an agouti at night, you know it must be extremely hungry.

In times of plenty, the agouti buries single large, hard-husked nuts so that when pickings get slim, it can return for them. It chooses nuts that will survive in damp soil. Because it doesn't dig up all the buried seeds, which then may sprout, the agouti is considered an important disseminator of some species of trees. The agouti sits on its haunches while eating, with the nut in the front paws, gnawing on one spot until it gets the nut open.

Usually solitary during the day, agoutis form monogamous pairs that sometimes travel together. Young are born in nighttime dens, which can be in hollow logs, under fallen brush, or in burrows. But the next day the mother leads the single offspring (occasionally twins) to a burrow where it lives for about eight weeks. The burrow's entrance is small to discourage predators, too small even for the mother to enter. She calls her offspring out every morning and evening to nurse and care for it. As a further precaution against predators, before nursing, the mother stimulates the offspring to urinated and defecate by licking its perineum; she then eats the wastes. Researchers say this probably also strengthens the odor bond between offspring and mother. The mother may give birth two or three times a year, but more than half of the offspring don't survive beyond the first few months of life. Adults can live three to five years.

A frightened agouti stamps its feet and sounds repeated high-pitched barks as it flees. A swift runner, it also has another defense-longer hair on the rump that can be raised so predators end up with a mouthful of hair instead of flesh. Predators include cats, large snakes (the boa and fer-de-lance), coyotes, coatis, tayras, owls, and eagles, some preying only on the young. Humans, of course, have been major predators-hunting agoutis for meat and also destroying their habitat.

Wary where hunted, agoutis can be easy to see in some protected reserves,even I where there are many people. Visitors to La Selva Biological Station, where rsearchers have worked for years, see agoutis foraging in open areas. In Monteverde they are seen crossing the road through town, and in Manuel Antonio and Cabo Blanco, they rustle leaves alongside trails.

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