Crayfish Behavior: Observing Arthropods to Learn about Science & Scientific Inquiry
Rop, Charles J., The American Biology Teacher
As biology teachers, we understand how important it is for students to become engaged first-hand with nature. Although bringing students to fields, woodlands, and wetlands to observe, explore, and wonder may be the preferable way to stimulate curiosity and practice scientific inquiry, field excursions are not always practical or possible
As an alternative, I have found it useful to study creatures that can easily be maintained in a laboratory setting. Organisms in the local ecosystem that can be captured readily, such as mice, snakes, fish, and various arthropods, make some of the best study subjects because their behavior is easily observable and relatively simple to understand (please see safety note below). Crayfish are exceptionally good study organisms. They are somewhat familiar to most students, and their size makes observation easy. Their active, territorial, and aggressive behavior provides an abundance of observation opportunities, and their claws add drama that students appreciate. Crayfish are very common in nearly every area of the United States, but if it is impossible to collect specimens, they can be ordered from biological supply houses or even local fishing bait stores.
The crayfish behavior investigations described here are adaptations of those I have frequently used in middle school and high school biology classes. They require very little equipment and can be used in any school setting from grades 5 through 12.
Although this study takes no sophisticated equipment, it does require imagination, ingenuity, and creative scheduling. In the beginning you will need several class sessions to set up the original investigations and model the kinds of inquiry that students will later do more independently. After the introductory class sessions, each week of the study will require several observation sessions of 10-15 minutes and at least one class session for debriefing and discussion. Continue this for as long as you feel that new lessons are being learned about crayfish, about environmental issues, and about scientific principles and processes.
Safety note: There are always safety and ethical issues associated with any laboratory investigation that uses living organisms in the classroom. Start by reading the NABT's position statement on the use of animals in biology classes and follow the link given for the "Principles and Guidelines for the Use of Animals in Precollege Education" provided by the National Research Council (http://www.nabt.org/websites/institution/ index.php?p=97). In addition, your state or government will likely have rules and laws about using animals in classrooms. For example, in Ohio, the DNR Division of Wildlife has a very useful "Guide to Using Animals in the Classroom and for Collection," available at http://www.dnr.state. oh.us/Portals/9/pdf/pub009.pdf, that gives necessary information about the ethical treatment of animals and the collection permit process, and useful information on laboratory procedures.
Crayfish (Astacidea), like other arthropods, have many reasons for moving about, including foraging for food, competing for space, searching for a mate, avoiding parasites, and escaping predators. However, movement is always risky and often costly. Optimal foraging theory is a conceptual framework that scientists use to think about the behavior of prey species (McCleery, 1978; Sephans & Krebs, 1986; Lima & Dill, 1990; Abrahams & Cartar, 2000). According to this theory, animal decisions about the risks of predation are assumed to represent a balance between the costs and benefits of behaviors. Recent studies have suggested that risk of exposure and predation can influence an animal's behavior when foraging for food or engaging in reproduction (Wellborn, 2000). Crayfish survival behaviors that are related to shelter, nutrition, the need for protection during a molt, and reproduction compete with each other and with the need for cover and safety. …