Our Monkeys

The Peaceful Primates

Costa Rica's squirrel monkeys are adorable, charismatic, sexy and critically endangered

Squirrel monkeys are becoming an important symbol for wildlife in Costa Rica. They delight researchers who study them, and weighing in at just one and a half pounds, with beautiful orange fur and expressive faces, they are irresistible to tourists. Sue Boinski, a professor of anthropology and comparative medicine at the University of Florida, has spent the past 20 years observing squirrel monkeys in Central and South America. Her research has revealed that Costa Rica's squirrel monkeys are among the most egalitarian and least aggressive primates in the world. She describes them as the peaceful primate in the peaceable kingdom. "I think they are like the tourists who love to come here to the tropical beaches," she says with a smile. "They're just looking for good food and sex."

But the future of these winsome primates is in doubt. Their forest habitat is being destroyed at an alarming rate by agribusiness, including the raising of crops such as palm oil trees and bananas. The tourist industry is also booming, resulting in new construction and an increasing human population. The second-growth forest that squirrel monkeys prefer for the plentiful soft fruits and insects is rapidly disappearing. If we don't intervene soon to protect Costa Rica's squirrel monkeys, Boinski warns, the survival of these endearing primates cannot be assured.

Costa Rica’s squirrel monkeys are adorable, charismatic, sexy and critically endangered By charles bergman

Few moments in the forest compare with the thrill of hearing a troop of squirrel monkeys approaching through the trees. There is the subtlest hint of their arrival, a peep perhaps, barely distinguishable from the calls of forest birds. Suddenly, branches are breaking and trees are alive. With a feeling of sweet anticipation, such as precedes all good arrivals, I realize the monkeys are coming.

The squirrel monkeys of Costa Rica bring a special delight for my forest guide, Sue Boinski, a professor of anthropology and comparative medicine at the University of Florida. She has spent the past the past 20 years studying squirrel monkeys in Central and South America. I watched her face grow animated as she heard them coming. Though spectacularly colored, they are surprisingly invisible and fade into the foliage."But once you find them," Boinski laughed, "squirrel monkeys on the move are about as subtle as a high school marching band."     It was easy to see why she is so attracted to them. These small (weighing about one and a half pounds), adorable and charismatic creatures are becoming an important symbol for wildlife in Costa Rica, and their unusual social behavior makes them remarkable primates. Boinski and I were in Manuel Antonio National Park near the old fishing village of Quepos, Costa Rica, where she had returned to gather more data on the behavior of squirrel monkeys during mating season and to collect DNA material. Her work is urgent because this species, Saimiri oerstedii, is critically endangered. As the monkeys worked their way toward us, they grabbed small red fruits called guayabón, a type of wild guava. Scampering dexterously across small branches, a band of juveniles saw us and came closer. One youngster swung onto a curving vine, and stretched his body and plucked a huge grasshopper from bromeliads from a nearby tree trunk just a few feet away, plopped down in front of us and looked us straight in the eye. As surely as we were studying him he seemed to be studying us.

Though squirrel monkeys are increasingly rare, such encounters with them in Costa Rica are not unusual. Troops often approach tourists in this popular resort area. They are inquisitive and friendly, and their golden beauty makes them everyone’s favorite.
Of the four species of primates in Costa Rica, the squirrel monkey is certainly the most beautiful. It’s also, well, "squirrely", with its rapid movements and flowing tail, which it wraps around itself for warmth as it naps in the tree. The creatures most striking feature, though, is the vibrant pumpkin orange fur on his back. Its face is dramatic, too, topped by a black or gray cap with a window’s peak that frames with fur, pink skin and huge eyes. A splotch of black skin covers its mouth like face paint, accentuating its expressiveness.
In Central America, the squirrel monkey is confined to small pockets dispersed over the southern half of the Pacific coastline. Manuel Antonio National Park and the area around it marks its northernmost boundary. A closely related subspecies occurs farther south, in Corcovado National Park. There was once a population in Panama, but it has disappeared as the forests have been decimated. (Tiny relict populations have recently been discovered near the Costa Rican border.) Squirrel monkeys are lowland creatures who thrive in the tropical forests, where they forage for soft fruits and juicy bugs. The troop of monkeys Boinski and I were observing lives in the forest adjacent to one of the park’s most spectacular beaches.
The area’s beauty makes Manuel Antonio one of the most popular national parks of Costa Rica. This fertile part of the country is also desirable for agribusiness, particularly for raising bananas and palm oil trees.

Tourism and farming have negatively affected Costa Rica’s fragile and isolated population of squirrel monkeys. The creatures are separated from squirrel monkey species in South America by about 600 miles, and how they got here has been a matter of speculation and controversy. Their isolation has made them vulnerable, and in recent decades their numbers have crashed dramatically. All of Costa Rica’s squirrel monkeys are endangered, but the subspecies around Manuel Antonio (Saimiri oerstedii citrinellus) is nearly gone. Fewer than 1,000 monkeys survive from a population that Boinski estimates was about 5,000 some 30 years ago.
"Without intervention they are most certainly drifting towards extinction," she said. "Deforestation is the major problem. The answer is to buy land, to protect it and manage it to maintain second-growth forests because of the plentiful supply of their favorite insects and fruits.
The friendliness of the monkeys as they swirled close about us in the trees gave me a hint of their remarkable behavioral adaptations. Due to their geographic isolation, the monkeys have evolved in unique ways. They are probably the most egalitarian of the primate species that form groups consisting of large numbers of both sexes. The males show aggression so infrequently among themselves that researchers can’t discern any dominance hierarchies. According to Boinski, there is no less aggressive primate society.

One of Boinski’s delightful qualities is her skill of condensing, like a good teacher, the technical language of primatology and animal behavior into colorful everyday terms. With a smile and a kind of pride in the monkeys, she said, " This is the peaceable kingdom. They are the peaceful primate." Indeed, the juvenile that had approached us had seemed wonderfully calm as he peered at us.
" I think they are like the tourists who love to come here to the tropical beaches," Boinski said, smiling. "They’re just hanging out, playing and looking for good food and sex."
With her bright clothes, Boinski does not have the look of a field researcher. "But I love to spend lots of time here in the jungle," she continued." I try to be a fluent listener, and after a while, it’s like the forest forgets I’m here. Then, anything can happen."

Through thousands of hours of painstaking fieldwork, Boinski has assembled data not only on the squirrel monkeys in Costa Rica but also on their near cousins in South America. She has spent up to 18 months at a stretch in the wet tropics living on rice and beans. In gathering data she documents numbers of animals and their behaviors.
After spending several days with Boinski, I realize that her knowledge of these monkeys is so intimate that she almost sees the landscape through their eyes. She showed me this landscape as we imitated the monkeys foraging, gingerly unwrapping dead leaves of cecropia trees to find the wolf spiders and cockroaches that they eat. They suck ripe berries, she explained, because their jaws are too weak for hard fruits or nuts.
But the most compelling part of Boinski’s studies reveals the squirrel monkeys’ peaceful social behavior within their society, particularly their mating behavior, sexual relationships and birthing patterns.
One of the males in the troop we were observing suddenly stepped forward, climbed up a dead tree trunk and emerged into full view standing erect. Framed by green leaves, he turned golden in the soft light.
"Look at that beautiful boy," Boinski exclaimed. "See how huge he is!"
He looked like a squirrel monkey on steroids. Through his chest, shoulders and haunches, he had the "puffy" look typical of males during the mating period. Between July and September, the males "fatten," increasing in body size by 20 percent. This male seemed to be posing in a way that exposed his genitals. His testicles were double their normal seize.
The mechanism causing the swelling is unique to this genus of primates; it is also strange. During mating season, the males convert their testosterone into estrogen, which causes to retain water and thus gain body size. The more testosterone the males have, the more estrogen, and the bigger they swell. These engorged males look like buffed teenagers. Boinski calls them "diminutive bulked-up linebackers."
The male body size is crucial during mating. It is characteristic of sexual selection, and the females apparently find these swollen males alluringly sexy, and the bigger the better. Boinski has documented that the largest male in the troop gets 70 to 90 percent of the mating in any given year. Since size determines who mates, males do not fight for dominance or compete for the females.
"Look at these males," Boinski said. "Several of them are just hanging around, and see how young males gather near the biggest ones. This behavior is rare in primates. The males like to be together. And when it comes to mating, they even help each other."
Squirrel monkeys begin courtship by genital sniffing. Generally, a group of two or three males approaches a female, mobs her, immobilizes her, and takes turns sniffing her bottom to determine if she’s in estrus.

In the years Boinski has observed the monkeys, though, she has never witnessed males forcing females to copulate. Rather, ultimately, the females choose their mate. Since one of the males may have sired nearly all the babies during the year, most of the males in a troop are likely related. "All these males," Boinski said, "may be half brothers, making it even more likely that they cooperate. That is why they are so buddy-buddy."
Recognizable by their smaller size and darker black cap, the females we observed typically sat apart, solitary, and spent their time foraging. The males lounged nearby, in loose groups. Many females were still nursing their young of the year. The youngsters frolicked vigorously in a rough-and-tumble play that is the most aggressive behavior that squirrel monkeys display within the troop.

These monkeys are also remarkable among primates because they give birth the same time every year. Called "birth synchrony," their birth periods are "unusually predictable," Boinski said. They occur over a two-month period, between early February and early April, peaking during a five-day period in mid-February. "The babies are popping out like popcorn during that single week," she laughed.
Although many monkeys have birthing peaks that correspond to food availability, the peak time of squirrel monkeys is unusually tight, Boinski explained. Such highly synchronized birthing reduces infant mortality. Most of the young born prior to the peak birth week die, and about 50 percent of all the infants die within six months of birth. The infants are especially vulnerable to predators, including hawks and falcons. Boinski has seen toucans scrape baby monkeys off their mothers’ backs. The only time females associate closely with one another is when the mothers form protective alliances among themselves to watch for predators. Boinski describes this behavior as "glomming."

The female squirrel monkeys of Costa Rica also emigrate from one troop to another, again unusual among primates; in most species the males transfer. When they are about 2 years old, the females leave their natal troop to find another, where they mate with the males. The females are always accepted by the new group. While we were watching another troop farther into the park, near a popular beach, we actually saw a collared forest falcon attack a group of monkeys. Toward dusk, the group was moving slowly among the branches of the huge almond and cecropia trees to return to its sleeping tree. About 50 feet above, several monkeys stopped to rest and play on the branches. The falcon, distinctive with its white belly and dark body, sliced through the canopy, cruising the troop. Suddenly, about half the group let out a earsplitting screech. It was a signal, and the monkeys reacted immediately, scattering in all directions. Several of them dropped as if they’d been shot. Others leapt into the air, scrambling for branches to grasp as they plummeted to the ground.
The tiny squirrel monkeys avoid predators by sleeping on the ends of palm tree fronds at night. Even in the heavy rains the fronds shake at the slightest movement.
When the monkey detect an intruder, "they just let go," Boinski explained. "They fall out of the trees like apples."
When Boinski first arrived in Costa Rica, she was a 23-year old graduate student hoping to study the foraging strategies of these monkeys. Though squirrel monkeys are the second-most common primate used in medical research in the United States (only rhesus macaques outnumber them), they had been poorly studied in the wild. All that was known was learned from the notoriously aggressive captive animals originating from the South American population, which has strong social hierarchies.
"On my first trip to Costa Rica," Boinski explained," I set up my tent and found a troop right next to it." The monkeys came very close. To identify individuals she squirted them with black dye to mark them.
"I thought my project was going to be easy," Boinski reflected. But there was one big problem. I wasn’t seeing any aggression or hierarchies. The monkeys just weren’t doing what they were supposed to do. I thought I was a failure. But what I did learn," she continued, "is to trust my data."
Her data helped her see the divergent evolution of the social behavior of the squirrel monkeys. She observed that Costa Rica’s squirrel monkeys were very different from those in South America, where most of the research animals were captured. As Boinski pieced together the social behavior of her squirrel monkey troops, she compared her data with the characteristics of two South American species, both of which are abundant.
The three species are closely related, yet each has evolved a different social structure. In the Peruvian species, Saimiri boliviensis, the females are dominant and very aggressive. They form alliances with female relatives to defend their food patches, and only the males emigrate to other troops. A second South American species, Saimiri sciureus, is found from Suriname down to Brazil. The males are dominant, and both sexes are aggressive and fight each other ferociously. Both species differ greatly from Costa Rica’s nonhierarchical and gender-equal squirrel monkey.
"There is no other primate genus in the world in which three separate species are so similar morphologically in body size, shape and diet specializations," Boinski says, "yet display such divergent social adaptations."
When she looks at these monkeys, Boinski sees evolution in action. Her current studies focus on understanding why these species, so closely related, are so different socially.
What is becoming clear to her is that the social organization of primates, especially in regard to gender, is more complex then we know. Past theory has focused on tight male bonds and male aggression, but these three species of squirrel monkeys suggest that there are alternate social strategies within and among species.
Another aspect of Boinski’s study is the molecular variation among the species of squirrel monkeys. Scientists debate how Costa Rica’s monkeys came to Central America, from South America. One theory suggests that several species came north with pre-Columbian traders no earlier than 30,000 years ago. If so, the squirrel monkeys in Costa Rica are not a true species but a hybrid population.

Boinski believes she has proved this theory wrong. Not only does squirrel monkey behavior argue against it but so does DNA. She and another researcher, Susan Cropp, at the University of Chicago, have conducted studies with DNA, comparing the three species. The results are just being published.
They have demonstrated a distinction between the species on a molecular genetic level, as well as on a behavioral level. The monkeys in Costa Rica were not introduced by humans. The DNA analysis indicates they came there perhaps millions of years ago and have been evolving separately ever since.
Doubt as to whether the Central American squirrel monkey is a true species has hindered conservation efforts; the government is reluctant to commit funding to protect a non-native hybrid. With Boinski’s new genetic research giving solid evidence of the species’ authenticity, she expects to see more interest in conservation.
Boinski and I visited Jardín Gaia, a private animal rescue center near Manuel Antonio. Dario Castelfranco who founded and runs the shelter, is a vigorous political advocate for squirrel monkeys. His mayor concern is that the habitat for the monkeys is dangerously fragmented, and at only 2 and a half square miles, Manuel Antonio Park is much too small to harbor more than the three troops that live there-about 100 monkeys in all.

The rest must live in unprotected and increasingly developed habitat on the periphery of the park, where the monocultures of agribusiness are filled with pesticides, and there is little food.
During our visit with Castelfranco, the body of an old male squirrel monkey was brought in for autopsy. The animal had been electrocuted on the power lines that primarily support tourist and agricultural development in the region. It’s a common cause of death for the squirrel monkeys, who use the wires to cross the roads that dissect their territories.
A passionate and feisty Italian, Castelfranco is a one-man conservation force. "I used to be an idealist," he said. "I didn’t see how we could lose. We have all the arguments. It is a flagship species, a wonderful animal. So cu-u-u-u-te, and they eat insects, so farmers like them.
But the monkeys themselves may unwittingly contribute to the difficulty in convincing people they need protection. Their friendly nature brings them face-to-face with tourists in local hotels and restaurants. The resort owners know what an attraction these animals are, so they feed them bananas to lure them.
"Squirrel monkeys would sell their tails for a banana," Boinski said.
One evening, we went to a restaurant that feeds the monkeys. Their arrival was quite different from the one we experienced our first morning in the forest. At the restaurant, we could set our watches by their entrance at dinnertime. They are completely habituated to strangers. The monkeys climbed onto the open-air railings, scampered across tile floors and sneaked onto dinner tables. One monkey, looking for a banana, strutted up on his hind legs to some patrons who were drinking beer.
The tourists squealed with delight. The monkeys squealed, too. The scene was full of energy and emotion. "I want to kiss one," a woman screeched. "I want to take one home with me," a man offered. "I bet I could get a thousand bucks for one," another man joked.
The scene confirmed Boinski’s point. The monkeys appear so abundant that it is difficult to convince anyone, locals or tourists, that these creatures are extremely endangered.
Swollen and swaggering machostyle, one of the largest males leapt onto the railing and loaded up with banana handouts. With his mouth stuffed, he scurried off with all he could carry. Perhaps the bananas are harmless, but we need to offer these peaceful and pleasing monkeys something more - help to survive. Charles Bergman teaches at Pacific Lutheran University in Washington and last wrote for Smithsonian about Hawaii’s monk seals.

Abstract of an article by Charles Bergman, originally published in the June 1999 issue of Smithsonian. All rights reserved.

Click here for the article from Yakima Herald Republic

Manuel Antonio National Park

Parque Nacional Manuel Antonio is a small biological oasis weighted down under the pressure of many and conflicting local enterprises such as agriculture , livestock and a highly developed tourism. This national park contains some of the most beautiful scenery in the country .This humid tropical forest ,is home to may species of flora and fauna that area in danger or extinction.
At one time ,much of this was area logged using a system called selective extraction to cut high quality lumber without clear cutting . Now, these areas of the forest area in a regeneration process.

General Information

This wilderness area on the pacific coast of Costa Rica in the province of Puntarenas , is located 157km (98miles) south of San Jose , by highway and 7km (4.5 miles) south of the city of Quepos.
The park was established on November 15,1972.Its area encompasses 683 hectares(1.700 acres)of land mass and 55.000 hectares (135.905 acres) of marine reserve.
This region was once inhabited by the Quepos Indians from which comes the name of the city of Quepos. With the arrival of Europeans, the region was converted into cultivated cropland which later was purchased by the United Fruit Company.
The area which constitutes the park today, was acquired by foreigners who prohibited local people entering. This precipitated the formation of a pro-national park committee which convinced the municipal and national authorities to declare this area a national park.
The park is located in a region of high precipitation and temperature. The average annual rainfall is 3.875mm(151 inches).The dry period is January through march while the rainiest months area August through October .The average annual temperature is 27C (81F) with a minimum of 20C (68F) .

Flora and Fauna

Parque National Manuel Antonio is situated in a humid tropical forest life zone .It protects primary and secondary forests ,mangroves ,beach vegetation and marine resources. The most characteristic species of flora in the primary forest are the guácimo Colorado ,bully tree ,cedar ,locust SURA black locust a tree in danger of extinction, cow tree, madroño , cenízaro , and silk cotton tree.
The mangrove swamp which covers 18 hectares (44.5 acres) is composed of three species red mangrove ,buttonwood mangrove and white mangrove.
The beach vegetation consists mainly of manzanillo which produces a milky extract ,latex and poisonous berries, almond mayflowers and coconut.
Within the wildlife ,some of the most common, but impressive species are the raccoon, whit nosed coatis , agouties, the two toed sloth ,white faced capuchin monkey and squirrel monkeys,(a subspecies of the park ,which is in danger of extinction due to the destruction of this habitat and its exploitation as mascot).
In this area you can also observe birds such as the tucancillo , fiery billed acari , brown pelican ,laughing falcon ,blachcollared hawk ,green kingfisher and the northern jacana. As well Iguanas, giant lizard, snakes and thousands of insects abound.

Outstanding sights

In addition to the flora and fauna ,one of the main features of this area is an overwhelming beauty of the following attractions

*Playa Espadilla Sur
Extends between the northern limit of the park and Punta Catedral (Cathedral Point).During low tide it has a long wide beach, great for strolling or sunbathing. And although the surf can be quite strong . It poses no real danger to swimmers.

*Playa Escondida
Is a small beach ,that can be found south of the administration building. Because one has to wade through some areas bounded by steep cliffs, accessibility to the beach depends on the tides. Please inquire with the park guards as to the when and whether you should enter.

*Punta Catedral
Is an interesting geological phenomena. It once was and island, and with the accumulation of sediments, over time ,it united with the continental landmass forming a sandy strip called a tómbolo .
The interior boats primary and secondary growth forest and excellent lookout points from which to view the various islands off the coast .Playa Blanca (white beach),and the exquisite turquoise sea.

Recommendations

"So that you and the other visitors enjoy day in park, follow these recommendations to further enrich your experience with this marvellous word."

*If you need help or have questions ,please ask the rangers, they are pleased and prepared to help you.
*All the living things, plants and animal alike ,share this planet with you. Please respect them.
*Enjoy the peace and natural sounds of the forest. Do not play radios or make loud noises which could disturb the tranquillity found here.
*Please keep to the trails. The signs are these for the benefit of all, do not deface or destroy them.
*This area is a natural preserve. We invite you to observe , enjoy and take as many pictures you like .But please do not remove plants ,animals, stones or other material as souvenirs.
*Please collect your garbage and deposit it in the appropriate containers.
*Do not feet the wildlife. They can suffer serious health problems if they eat people food.
*In spite of its biological diversity, many animals living in Costa Rica area hard to observe because of their migratory or reproductive habits, because they are nocturnal or because the forest is too dense to see them clearly. Move quietly and sharpen your observation skills in order to better appreciate the richness of the area.
*All protect wildlife areas have rules which regulate the protection of resources and the activities of visitors. This park operates under these rules for public use and it is obligation of all visitor to respect them.