Set up the activity areas as shown in the diagram at the end of this page. Give each student a paper or plastic bag.
2. Divide the class into two groups.
Each student counts out 50 beans to place in his or her bag. Beans represent turtles. Each bag of beans represents the turtles that hatch from a single nest.
Group 2 — Limiting Factors
Divide this group into two smaller groups, on land and in-sea.
On-land: predators (e.g., raccoons, dogs, ghost crabs, foxes and gulls) and limiting factors from human activities (e.g., dune buggies, human egg collectors, shoreline development)
In-sea: predators (e.g., sharks, killer whales) and limiting factors from human activities (e.g., entanglement in fishing gear, eating plastic litter, illegal killings by humans)
Give each student a sign that indicates what kind of limiting factor each one represents. Attach these identity signs to students' clothing with clothespins.
3. Walk the class through the activity and explain these rules:
A. Turtles must hatch, cross the beach and spend 10 years in the open sea. The turtles running between the year zones simulate the time in the ocean. They pick up one poker chip at a year zone and then run to the other year zone to pick up another poker ship. Each chip represents two years of successful ocean survival. After collecting five poker chips, turtles return to the nesting area to reproduce.
B. Turtles try to avoid limiting factors and predators. If tagged by a limiting factor, a turtle stops, counts out 10 beans and places those 10 beans in the limiting factor's bag.
C. The ocean's sea grass areas are turtle safety zones where limiting factors cannot tag them. The teacher may set a time limit for how long a turtle may rest in a sea grass zone. OPTIONAL: The educator may eliminate the safety zones after the turtles have been in the ocean for a while. This simulates the turtles growing too big to hide in the sea grass.
D. Limiting factors must obey the following rules:
- They cannot tag the same turtle twice in a row.
- They cannot tag turtles that are counting out beans to another limiting factor.
- They must stay at least four steps away from any turtle that is transferring beans to another limiting factor.
E. Any turtle that loses all 50 beans is dead. It must go to the beach and become a condominium. If the condominiums (sitting side by side) eventually block the access to the nesting beach, the remaining turtles die without reproducing and starting the next cycle.
F. The activity ends when all turtles are either dead or have returned to the nest area.
4. Review the rules two times to make sure the students understand their roles and the procedures. Students then become endangered sea turtles and limiting factors and conduct the activity.
5. After completing the activity, encourage the students to discuss the results. It is likely that some students will be disturbed by the high mortality of the turtles and will benefit from the realization that there are groups actively trying to diminish human contributions to such high mortality. However, it is also important to emphasize that natural limiting factors are built into the scheme of things. If all sea turtle eggs survived, there might well be an overabundance of these creatures. Many animals produce more young than will survive, serving as food for other species as a part of nature's dynamic balance. Ask the students to briefly describe the life cycle of sea turtles.
6. Summarize the importance of the high numbers of turtles that result from the reproduction. Ask the students to identify and discuss the factors that limit the turtles' survival. Since sea turtles are threatened with extinction, the limiting factors affecting their survival seem to be out of balance. What specific recommendations would the students suggest to increase the successful reproduction and survival of sea turtles?