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Turtle Hurdles Background Info | Objectives | Materials | Evaluation Background
Information As with
most reptiles, turtles lay eggs. The eggs look somewhat like
wet, pliable table tennis balls. Female sea turtles dig deep
holes on beaches with their rear flippers. They lay and bury
their eggs in these holes. Sometimes the females make repeated
nesting visits in one season. Mature female sea turtles may
deposit several hundred eggs in one season. Once the eggs are
buried, the female returns to the sea or seeks new nest sites.
The eggs are on their own for nearly two months. If the eggs
survive predation by raccoons, ghost crabs, foxes, dogs, and humans,
the sea turtles hatch, dig their way upward through the sand, and
promptly head toward the sea. The hatchlings' journey across the beach is typically accompanied by predatory crabs, raccoons, and dogs, with gulls and frigate birds joining in. Once hatched, only about one to five percent of the turtles survives the first year. In the sea, the turtles must mature for nearly a decade before returning to nesting sites as a natural part of their life cycle. Biologists are uncertain how long sea turtles reproduce and live. They are preyed upon by fish, sharks, killer whales, and humans. The motives for human predation are based predominantly on products that are outlawed in many countries. Jewelry, leather, oil, and food are the primary uses. Turtle eggs are seen by some as a boost to longevity and vigor; tens of thousands of eggs are illegally harvested for vanity sales. Evidence suggests that a serious human threat to the turtles is the poaching of their eggs in their nesting sites. There are other, human-caused factors, Dune buggies may break the eggs buried in the sand. More damaging, give the scope of the impact, is commercial and private construction (condominiums, private homes, hotels, etc.) on coastal sites. This may create a barricade that prevents the turtles from reaching their traditional nesting sites and eliminates many nest sites. Entanglement in discarded fishing gear and plastic waste cast into the oceans is a serious hazard, killing many sea turtles each year. Many turtles fall accidental victim to the nets of large fishing crawlers. Once caught in the nets, they drown. Efforts are being made to popularize special crawling devices that will prevent turtles from getting into the nets. One of the turtles' favorite foods is jellyfish. Many turtles mistake the human-produced litter of floating plastic bags for this food. The result is that their digestive tracts become blocked with the plastic and they perish. Six of the seven known sea turtle species are officially designated either endangered or threatened. The leathery of Leatherback, Olive Ridley, Kemp's Ridley, Hawksbill, Green, and Loggerhead are all either officially endangered or threatened. Only the Austrailian Flatback is not so designated. If laws are obeyed, protecting the turtles from use for commercial and personal products, they are more likely to survive. The major purpose of this activity is for students to become familiar with some of the limited factors affecting the survival of sea turtles, as well as the role of human beings in contributing tot he endangerment of other species. Objective Level Materials Procedure 3. TURTLES Give each student who represents a population of sea turtles a packet of 100 baby turtle markers. 4. LIMITING FACTORS Give each student who represents a predator or other limiting factor a tag that designates what threat he or she represents to the turtle. About half this group (or 1/4 of the class) should be on-land predators and limiting factors. The other half (1/4 of the class) should be in-sea predators and limiting factors. On-land wild predators (for eggs and hatchlings): raccoons, dogs, foxes, ghost crabs, gulls Other on-land limiting factors (for eggs and hatchlings): dune buggies, human egg collectors, shoreline development. In-sea
wild predators: sharks, killer whales. 5.
Explain the playing field as follows: Sea Grass Zones places where the turtles are safe until they reach four years of age. At that age they are too large to hide from predators. Mortality Zone the place where the mortality container is kept. It prevents the turtle markers from being scattered. 6.
Explain the rules as follows: They
cannot tag the same turtle twice in a row. D. any turtle that loses all 100 turtle markers is dead and must go to the beach zone and become a condominium. If the condominiums (sitting side-by-side) eventually block access to the nesting site, the remaining turtles die without reproducing and starting the next cycle. E. The game is over when all the turtles have returned to the nest area or are dead. 7. Review the rules two times to make sure the students understand their roles and the procedures. Become endangered sea turtles and limiting factors and conduct the activity. 8. 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. 9. Summarize the importance of the high numbers of turtles that result from the reproduction. 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? Extension Evaluation Write a law that would help protect sea turtles. What would the law include? Who would enforce it?
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