Squirrel monkey

"Si el Norte Fuera el Sur:
A Case of Squirrel Monkey Identities"

Karin Gastreich
Organization for Tropical Studies
Undergraduate Semester Abroad Program
Department of Biology, Duke University


This case was designed for BIO134, Fundamentals of Tropical Biology, which is part of a four-course semester field program accredited by Duke University and implemented by the Organization for Tropical Studies (OTS) in Costa Rica. Students who matriculate in the program are expected to have a basic understanding of ecology and evolutionary processes by the time they begin the program. Because our students come from several universities across the United States, the range of understanding of basic evolutionary processes is often wide at the start of the semester. In previous semesters, we have tried to address this issue by giving an introductory lecture to review evolutionary processes. Unfortunately, the lecture approach has not worked well. Students often "tune-out" because they have had ample exposure to terms like "directional selection" and "stabilizing selection." Therefore, they assume that they know the material, when in fact subsequent testing consistently demonstrates they have little understanding of how to apply their knowledge of these processes to real-world scenarios.

James A. Hewlett's case study "Trouble in Paradise: A Case of Speciation" (see http://ublib.buffalo.edu/libraries/projects/cases/paradise/paradise.html) provided a great idea as to how to approach this problem. While the basic scenario, objectives, and application of this case are similar to Hewlett's, I have introduced at least three important changes. First, I adapted his scenario to a Costa Rican problem by incorporating the Central American squirrel monkey, Saimiri oerstedii. This allows the evolutionary case to be used simultaneously to introduce students to specific aspects of Costa Rican fauna, geography, and conservation. Second, the exercise is introduced in the first week of our program, allowing students to review and apply what they have already learned about evolutionary biology prior to coming to Costa Rica. Finally, students work in small groups and present their results orally (as opposed to an individual written assignment). This encourages students to get to know each other and begin the exchange of ideas and knowledge during the very first week of the program. In addition, the oral presentation format allows me to identify misunderstandings about the evolutionary process and correct them with the help of the rest of the group as part of an interactive discussion.


This case study will allow the students to:

Student Preparation

In order to complete this case study, students will need to understand:

Successful completion of the case also depends on a basic familiarity with biogeography, comparative behavior, and comparative morphology. As stated earlier, students who participate in the program are expected to have a background in these areas before they arrive in Costa Rica. If necessary, the professor may choose to briefly review, via a discussion format, the species concept as well as the "Concept List" before students begin working on the case.

Because this case focuses on Costa Rica, it is useful for students to have an introduction to the geological history and climate of Central America in order to complete their stories. In BIO134, this information is provided to the students via lecture and reading assignments prior to the completion of the case. Appropriate background reading for this topic can be found in Janzen's (1983) Costa Rican Natural History and in Stiles and Skutch's (1989) A Guide to the Birds of Costa Rica (see references below for further bibliographic detail).


One model for presenting this case to a class is the following, which I have used successfully in BIO134:

Limiting each student group to three assigned concepts works in BIO134 because it ensures that all the concepts we want reviewed are included in one round of oral presentations. However, if the instructor wishes to give more creative freedom to the students, each group could develop its own set of evolutionary concepts to address. Important concepts that are left out in the round of oral presentations could then be covered at the discretion of the professor at some other time.

As a basic reference for evolutionary processes, we recommend students read chapters 5 and 6 of E.O. Wilson's The Diversity of Life. In addition to refreshing their memories, this reference provides a variety of evolutionary stories from which students may draw ideas. I also recommend having a basic evolutionary textbook on hand (such as Douglas J. Futuyma's Evolutionary Biology), as well as giving students ready access to additional squirrel monkey references from the primary literature. (In a typical university setting, students generally have an easier time accessing these resources on their own. However, at OTS field stations in Costa Rica, library and Internet resources are limited, making it necessary to provide basic reference material directly to the students.)

Not all scenarios need to be constructed in support of the hypothesis that the Osa and La Cusinga populations are two separate species. For example, in one presentation the students argued that the populations represented the same species, but were behaviorally isolated because females from the Osa did not recognize gray-capped males from La Cusinga as potential mates. Students reasoned this was a learned behavior, and proposed that if Osa females could be convinced to mate with La Cusinga males, their female offspring would learn to recognize both gray caps and black caps as belonging to potential mates in subsequent generations. In their scenario, they obtained a generous donation from Clairol, allowing them to dye the La Cusinga male monkeys' caps black and solve the problem!

Student Response to the Case

I have field-tested this case study once with OTS undergraduate students and the response was very positive. Even though they had just met each other, students worked together successfully to come up with a variety of plausible scenarios. Interestingly, all groups chose to dramatize their presentation, acting out the evolutionary scenario by playing the part of squirrel monkey protagonists.

In a brief informal evaluation of the activity, students consistently agreed that the case study provided an adequate, interesting, and creative review of evolutionary concepts. In addition, most students cited getting to know their classmates as an important component of the activity. All students enjoyed the opportunity to learn something about squirrel monkeys.

Concerns expressed by the students included the need for more information about the monkeys, as well as the need for adequate support material for defining evolutionary concepts. In response to these criticisms, I subsequently expanded this case to include more information about squirrel monkeys. I also included more explicit suggestions in the teaching notes regarding additional support material for the students. However, since one objective of the case is to have the students draw upon their own background knowledge, I chose not to include definitions of evolutionary concepts in the case handout itself. At the discretion of the professor, these can be obtained through outside reference material and added to the case study handout.


  1. Boinski, Sue. 1999. The social organization of squirrel monkeys: Implications for ecological models of social evolution. Evolutionary Anthropology 8(3):101-112.
  2. Boinski, Sue, and Susan Cropp. 1999. Disparate data sets resolve squirrel monkey (Saimiri) taxonomy: Implications for behavioral ecology and biomedical usage. Int. J. Primatol. 20:237-256.
  3. Boinski, Sue, Katharine Jack, Craig Lamarsh and Jessica A. Coltrane. 1998. Squirrel monkeys in Costa Rica: drifting to extinction. Oryx 32:45-58.
  4. Boinski, Sue, and Laura Sirot. 1997. Uncertain conservation status of squirrel monkeys in Costa Rica, Saimiri oerstedii oerstedii and Saimiri oerstedii citrinellus. Folia Primatol 68:181-193.
  5. Cropp, Susan, and Sue Boinski. 2000. The Central American Squirrel Monkey (Saimiri oerstedii): Introduced hybrid or endemic species? Molecular Phylogenetics and Evolution. 16(3):350-365.
  6. Janzen, D.H. 1983. Costa Rican Natural History. Chicago, Illinois: University of Chicago Press. pp 12-65.
  7. Stiles, F. Gary, and Alexander Skutch. 1989. A Guide to the Birds of Costa Rica. Ithaca, New York: Comstock Publishing. pp. 4-19.

If you would like to locate more Central American squirrel monkey references, consult the library database BINABITROP at the OTS web site http://www.ots.ac.cr.

You might also enjoy viewing this Quicktime movie (2.5 MB) of a squirrel monkey (Saimiri oerstedii) catching and eating insects at his home in the Drake Bay Wilderness Camp near Corcovado National Park. This movie, provided with permission by Dr. Hays Cummins, is one of several used in connection with his Tropical Ecosystems of Costa Rica course. See his extensive multimedia collection at http://jrscience.wcp.muohio.edu/html/TropEcoCostaRicaImage.html.

Go back to the case

Acknowledgements:  This case was developed with support from The Pew Charitable Trusts and the National Science Foundation as part of the Case Studies in Science Workshop held at the University at Buffalo on June 12-16, 2000. The author would like to thank Grace Wong (Universidad Nacional Autonoma de Costa Rica) and Sue Boinski (University of Florida, Gainsville) for providing information about differences between subspecies of the Central American squirrel monkey. The anonymous reviewers who read this case prior to posting it on the web provided very useful suggestions for improvement. Finally, special thanks to the students of the Fall 2001 OTS Undergraduate Semester Abroad Program for their enthusiastic participation and helpful feedback regarding this case study.

Image Credit:  Photograph of Saimiri oerstedii is provided courtesy of Lawrence Williams and the Squirrel Monkey Breeding and Research Resource, University of South Alabama. Used with permission and partially funded by NIH grant P40-RR01254.

Date Posted:  4/03/02 nas

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