Central American Squirrel Monkey (Saimiri oerstedii) [FINAL]

This topic submitted by Lauren Reiter ( DiablozGirl@aol.com) at 12:06 PM on 5/16/04.

Jeremy touches a sea turtle at the wall break, 25 m deep, San Salvador, Bahamas.

Tropical Field Courses -Western Program-Miami University

Saimiri oerstedii

The human population has surpassed the six billion mark and is nearing seven billion. “Our relationship with nature is perhaps doomed to be strained and awkward because our population has already overwhelmed the planet. As we steadily creep across the landscape, we devour everything before us and put up barriers and boundaries where none has ever existed” (Greive). Since human beings have walked the earth, the rate of extinction has increased ten thousand times than that of any other major extinction in the history of the planet (Greive 57).

“Deforestation places Costa Rica’s rich biodiversity in danger. The country’s location on the cusp between North and South America and its abundance of tropical rainforests make it home to a great variety of species, many of them rare and threatened” (Encarta). “Clearing and using land for agriculture is one of the chief causes of the loss of plant and animal species,” reports Hillary Mayell. She claims, “If forest clearing continues at present rates, the world’s forests could lose more than half of their remaining species in the next 50 years.”

“Scientists equate the rapid loss of species due to human activities in the modern era to the massive extinction events evident in the geologic record. However, these two types of extinction events differ in important ways. In the extinction event in which we now live, humans make decisions about which species to save. We also decide, explicitly or implicitly, which species will go extinct…Understanding and formulating solutions to modern extinctions is the central concern of the field of biodiversity, a discipline that requires skills in the natural sciences, social sciences and the humanities” (Cummins). Furthermore, in a few compelling words, Bradley Trevor Greive says, “For endangered species we are both their greatest enemy and their only hope. These wonderful creatures will not argue their case. They will not put up a fight. They will not beg for reprieve. They will not say goodbye. They will not cry out. They will just vanish” (Greive 93).

“Costa Rica’s land is protected by one of the most ambitious conservation programs in Central America. Costa Rica was one of the first, and most active, countries to participate in debt-for-nature swaps, which cancel some national debt in exchange for the protection of a specified amount of land from environmental degradation” (Encarta).

“In an effort to bolster its economy while remaining responsible to the environment, Costa Rica has also established a booming ecotourism business. This form of tourism encourages travelers to learn more about the country’s natural wonders and to respect the environment in the course of their exploration” (Encarta).

Approximately two-hundred species of mammals can be found in Costa Rica, of which half are bats (Baker 46). Costa Rica has four monkey species, all of which are among the family Cebidae. The species include the Central American Squirrel Monkey, the White-Faced Capuchin Monkey, the Central American Spider Monkey, and the Mantled Howler Monkey (Rachowiecki 508). Weighing under one kilogram, this research paper will investigate Costa Rica’s smallest, rarest, and most endangered monkey; the Central American Squirrel Monkey (Rachowiecki 508).

Scientists have divided monkeys into two groups: New World monkeys and Old World Monkeys. “North and South American monkeys are called New World monkeys. Those found in Africa, Asia, and Europe are called Old World monkeys” (National Geographic Book Division 372). In addition, “The nostrils of most of the New World monkeys are round and set far apart on short snouts” (National Geographic Book Division 374).

No New World monkeys have cheek pouches or pads of tough skin on their rumps. Some New World monkeys have a prehensile tail, which can grasp objects and support the animal’s weight. Old World monkeys do not have this, nor do Central American Squirrel monkeys (National Geographic Book Division 375).

Carol B. Lutyk informs, “Although monkeys once thrived throughout Central America, their population has declined dramatically…In some areas they are hunted for food. And many people keep monkeys and other wild animals in captivity, even though it’s prohibited in Costa Rica.” Squirrel-Monkeys.com testifies, “Extensive deforestation that occurs due to agribusiness and tourist activities has led to the dramatic decrease in Squirrel monkey numbers.” The website also recounts to the 1980s when the species population was heavily lowered. Fortunately, Squirrel monkeys are easily maintained in captivity and reproduce successfully.

The Central American Squirrel Monkey is restricted to the Pacific lowlands in the part of the country (Janzen 427). “The eyes are dark, appearing quite large, surrounded by white “spectacles” and a black nose and mouth. Ears are white. Body hair is grayish with rich rufous on the back, arms and tail” (Kricher 297). In addition, “The shape of their skull is unique among primates, the brain case bulging out backwards beyond the point where the backbone joins it, and being larger in relation to the overall size of the animal than other monkeys” (Darrow).

Five species make up the genus Saimiri. They include the Bolivian squirrel monkey, the Red-backed squirrel monkey, the common squirrel monkey, the Gold-backed squirrel monkey, and the Black squirrel monkey (Mindy’s Memory Primate Sanctuary). However, emphasis will be placed on the two squirrel monkey species found in Costa Rica; the common squirrel monkey and the Red-backed squirrel monkey.

“There are two subspecies in Costa Rica that are distinctive and geographically separate. Those of the Osa/Golfo Dulce/Tiskita region near Panama (Saimiri oerstedii oerstedii) have black caps and are reddish over their backs, shoulders, and flanks. Squirrel monkeys of Quepos and the Manuel Antonio [National Park] region (Saimiri oerstedii citrinellus) have gray caps and reddish “saddles” over their backs and are grayish on their shoulders and flanks” (Henderson 457).

“The beautiful Red-backed Squirrel Monkey is the smallest and rarest primate in Costa Rica…It is the only monkey in this country without a prehensile tail” (Henderson 456). Gallery forests, lowland rainforest, and successional areas are desirable to Squirrel monkeys (Kricher 297). Primarily due to deforestation, as stated earlier, and the use of insecticides that kill their insect prey, the Red-backed squirrel monkey is listed as endangered by the 2000 IUCN Red List (BBC Science & Nature). Animal Planet’s Jeff Corwin discloses, “In the past, squirrel monkeys were used for biomedical research, though trade is now regulated.” In addition, the pet trade and electrocution from electric power lines have also contributed to their decline (Animal Info.org).

With all these major causes for declining numbers of squirrel monkey populations, “There is a twenty percent chance of extinction in twenty years or within five of its generations” (Mindy’s Memory Primate Sanctuary). Furthermore, “The Central American squirrel monkey rarely descends to the ground; therefore, any break in the forest, such as for roads or for telephone or electric power line rights of way, can severely fragment a troop’s habitat” (Animal Info.org). Animal Info.org presented a harsh but necessary statistic that said, “Long-term monitoring of isolated population of Central American squirrel monkeys indicated that local extinction was almost certain when a group contained less than 15 members and had less than about 30 hectares (75 acres) of available habitat”.

Squirrel monkeys are extremely social animals. However, the society is usually integrated by the adult females, as they form the core (Saimiri Breeding and Research Resource 2004). “Studies of these monkeys in Costa Rica indicate that they are highly egalitarian and non-aggressive, with neither males nor females appearing to be dominant over the other sex. These studies also indicate that female dispersal predominates, with females readily changing troops with no aggression from either resident male or female troop members” (Animal Info.org). Additionally, males stay close to the periphery of the group in the non-breeding season (Saimiri Breeding and Research Resource 2004).

Moreover, “Squirrel monkeys’ social relationships are very complex. They live in large groups, subdivided into adult male bands, mother-and-infant bands, and juveniles, except during the mating season” (Animal Fact File). The brief mating season for the Red-backed Squirrel Monkey takes place in January and February. “The yearly cycle has been shown in some field studies to be related to annual rainfall cycles and thus seasonal food availability with the birth season occurring at the period of greatest food availability insuring the female adequate nutrition post-parturition” (Saimiri Breeding and Research Resource 2004). After 170 days, the birth season will yield one young per female. “Females have their first young at two years [the age of maturity] and produce one young about every thirteen to fourteen months thereafter” (Henderson 457). “The mothers are very protective of their young, and caring for the young squirrel monkeys is a community affair” (Wilderness Classroom.com). In other circumstances, allomaternal care, or care of an infant in a maternal way given by someone other than the birth mother, has been documented in field studies with Squirrel Monkeys (Saimiri Breeding and Research Resource 2004).

In contrast to female squirrel monkeys, males mature at around five years (Singapore Zoological Gardens Docents 2000). Males take no part in caring for the infant (Animal Fact File). Nonetheless, “both sexes gain weight throughout the pre-breeding season attaining peak weights prior to breeding. Weight gain in males is associated with increased spermatogenesis in preparation for breeding” (Saimiri Breeding and Research Resource 2004). Squirrel monkeys can live up to twenty-one years. Predators include Boa Constrictors, Tayras, and Collared Forest-Falcons” (Henderson 457-9). In addition, people who hunt monkeys for food are the most dangerous enemies (National Geographic Book Division 379).

In conclusion, Bradley Trevor Greive best puts it into words when he conveys, “Anyone who has seen a sunrise, climbed a tree, smelled a rose, held a kitten or listened to a whale’s haunting love song knows, deep in their bones, just how amazing this planet really is. To preserve our home and the priceless creatures that dwell within it you need only see the world as it is and have a vision of how it could be. Then hold fast to this vision and let it guide your steps, your voice and your heart. If you can do that then there will be hope.” On a final note, Edward O. Wilson poses, “The biosphere promotes long-term material prosperity and health of the human race to a degree that is almost incalculable. But moral reasons, too, should compel us to take responsibility for the natural world” (Annual Editions 121).


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