SEA CHANGE: GULF ISLANDS NATIONAL SEASHORE. Sea Turtles Hurdles. Objectives: Grade Level: 4th-8th grade Activity Time: Two, 45-minute lessons

Transcription

1 Grade Level: 4th-8th grade Activity Time: Two, 45-minute lessons Subject Area: Biology Life Sciences Day 1 Discuss sea turtles found in the Gulf of Mexico, to include natural versus human dangers. Day 2 Re-enforce content from Day 1 with students participating in the activity described below, followed by reflection of what the students learned. materials: (class to be divided into two groups) One plastic or paper bag per student Cards/paper to identify predators or limiting factors (students may draw the cards) 40 to 60 feet of string or rope Poker chips (five chips per student in Turtle Group) Dried beans (100 beans per student in Turtle Group) Clothes pins/paper clips/yarn (to attach identity cards to students in Limiting Factor Group) Post-It sticky pads (to identify when a turtle is tagged by a limiting factor ) Objectives: Students will: Identify characteristics of sea turtles. Name five species of sea turtles living within the Gulf of Mexico. Describe the life cycle of sea turtles. Distinguish between natural and human dangers to sea turtles. Develop suggestions to help increase the survival and successful reproduction of sea turtles. 1

2 vocabulary: Arthropod an invertebrate with jointed limbs and a segmented body. Carapace the outer shell of the turtle. Carnivorous animals that eat only meat. Clutch a batch or group of eggs. Crustacean an arthropod with a body covered with a hard shell. Endangered having the possibility of becoming extinct. Extinct no longer exists. It has died-out. Herbivorous animals that eat only plants. Incubation a time period in which it takes eggs to develop and hatch. Invertebrate an animal without a backbone. Limiting factor a condition or creature that reduces the population of various species. Mollusk an invertebrate with an unsegmented body, often having one or two shells. Omnivorous animals that eat both plants and meat. Predator an animal that hunts/preys upon other animals. Prey an animal that gets hunted. Solitary alone; living without companions. Streamlined having a body designed to offer the least possible resistance through water or air to maximize swimming or flying efficiency. background: Sea turtles are air-breathing reptiles that inhabit tropical and subtropical seas. They cannot retract their flippers or necks like land turtles. Their bodies are streamlined and they have large flippers which make them a perfect fit for life at sea. There is no distinction between the size of an adult male or female turtle; they are equal in size. Like most reptiles, sea turtles lay eggs. Sea turtles also do not have visible ear flaps but they do have eardrums. They do not have teeth but they have powerful jaws that are like modified beaks. Each sea turtle species is adapted to its diet. Unlike other species, sea turtles are not social creatures. They generally live a solitary life. They usually only interact with one another during mating season. Threatened the likelihood of becoming endangered. 2

3 There are seven species of sea turtles throughout the world. All are listed as endangered (threatened with the possibility of becoming extinct) or threatened (has the likelihood of becoming endangered). Five of these reside in the Gulf of Mexico. They are the Hawksbill, the Loggerhead, the Leatherback, the Kemp s Ridley, and the Green Sea Turtles. Of the five species of sea turtles that reside in the Gulf of Mexico, the Loggerhead is the only species on the threatened list. The remaining four species are listed as endangered. nesting periods. Most species will nest during the warmest months. The females will crawl above the tide line (usually at night) to bury their eggs. They use their rear flippers to dig an average nest of about 16 inches in depth. Each species has a different nesting cycle and quantity of eggs deposited. The Hawksbill nests an average of every two to three years laying two to four clutches (160 eggs per clutch) approximately 15 days apart. The incubation period is between days. The Kemp s Ridley is listed as the smallest of all sea turtles. It measures between 22 to 30 inches in carapace (the upper shell) length and weighs between 66 to 100 pounds. At the opposite end of the spectrum is the Leatherback. It is the largest of all sea turtles, measuring in length from four to eight feet and weighing anywhere from 650 to 1300 pounds. The diet of sea turtles varies among species. Some species may be carnivorous (meat-eating), or herbivorous (plant-eating), while others are omnivorous (both meat- and plant-eating). Hawksbills survive on a diet of mollusks such as, bivalves (oysters, clams, or scallops), univalves (whelks and similar snails), squid, and octopuses and crustaceans including sponges, shrimps, and squid. The Loggerhead also feeds on mollusks and crabs as well as sponges, jellies, and aquatic plants. As the largest of all sea turtles, the Leatherback has a diet of exclusively jellies and other soft-bodied creatures. Although Kemp s Ridleys are primarily carnivorous, feeding mostly on crabs, they do eat jellies, snails, clams, and fish. Green Sea Turtles are primarily herbivorous. They feed on sea grasses and seaweed. Occasionally they feed on crustaceans and jellies. Sea turtles usually only leave the water during The Loggerhead will nest every other year and lays three or four clutches ( eggs per clutch) a season. The incubation period is also between days. The Leatherback usually nests every two to three years laying six to nine clutches (80 90 yoked eggs per clutch) with an average of 10 days between nesting periods. The incubation period for these eggs is between days. 3

4 temperature. If the eggs survive natural predators, such as raccoons, ghost crabs, dogs, humans, or other similar organisms, they will hatch and dig their way to the surface and journey toward the sea. During this stage, they will incur the same predators as when they were eggs, but sea gulls and other shore birds become predators as well. Once sea turtles enter the water, they also become prey to other sea creatures. As a result, only about one to five percent of the hatchlings survive the first year. Sea turtles must mature for approximately 10 years before they return to nesting sites and begin the life cycle again. The Green Sea Turtle nests every two to three years like the others. They will lay several clutches (each clutch containing between eggs) in day intervals. The incubation period for these eggs is two to three months. Lastly, the Kemp s Ridley is the only species of sea turtles that nests annually. They often come ashore during the daytime to nest. Unlike other sea turtles, the Kemp s Ridley nests only in a particular beach near Rancho Nuevo, Mexico. Large groups come ashore to nest at the same time in what is called an arribada, which is Spanish for arrival. They lay approximately two clutches ( eggs per clutch) 25 days apart. The incubation period for these eggs is approximately 55 days. In addition to natural predators, sea turtles have human enemies. Not only do humans destroy sea turtles for their eggs, shells, leather, oil, and related products, they also contribute to their declining numbers in other ways. For example, dune buggies may break the eggs buried in the sand. The construction of commercial and private buildings along coastal sites may create a barrier that prevents the turtles from reaching their nesting sites. Equally as hazardous are fisherpersons. Their discarded fishing gear and plastic waste, as well as their fishing nets, can cause the sea turtles to become entangled and drown. Since many turtles feed on jellies, they can mistake floating trash, particularly plastic bags, as food and it becomes lodged in their throats or digestive system and they die. Once the eggs are buried, the females return to sea. The eggs are buried for three purposes: to protect them from surface predators, to help keep them soft and moist, and to help maintain the proper 4

5 introduction: Turtle Hurdles The purpose of this activity is to introduce students to the life cycle and hurdles of a sea turtles survival. The students will learn to identify which limiting factors (human interaction) and predators play a major role in the survival of sea turtles. The students will be divided into two groups, one as sea turtles and the other as limiting factors/predators. They will then take their places on land and on sea and begin traveling while trying to avoid obstacles that will endanger their lives. procedure: 1. Set-up the playing field as shown in Diagram B. 2. Divide the class into two groups. Group 1: Limiting Factors This group is then divided into two smaller groups. One will be the In-Sea group and the other will be the On-Land group. Each group will have limiting factors from predators and human intervention. Everyone in this group is given a plastic bag to store the beans from sea turtles he or she tags. In-Sea: Predators (sharks, fish, killer whales, and/ or sea birds) Limiting Factors i.e., human intervention (fishing gear entanglement, chemical pollution, plastic liter, boating accidents, and/or shrimpers not using Turtle Exclusion Devices [TEDs]). On-Land: Predators (sea gulls, ghost crabs, raccoons, and/or dogs) Limiting Factors i.e., human intervention (shoreline development, dune buggies, and/or humans collecting eggs). Each student shall be provided a bag, to hold beans from tagged sea turtles and a card identifying which type of limiting factor he or she represents. Attach these cards using the clothes pins to the students clothing or use string or yarn for the cards to be worn around each student s neck to identify the limiting factor. Group 2: Turtles Attach a card identifying each student as a sea turtle to his/her clothing. Have each student count 100 beans and place them in his or her bag. Each bean represents a sea turtle. Each bag of beans represents the sea turtle that have hatched from a single nest. 5

6 3. Before beginning the game, explain the following rules and then walk the students through the activity. A. All sea turtles will be starting on the beach in nesting areas. Sea turtles will then hatch and must cross the beach and enter the water. They will have to spend 10 years in the open water. The year zones simulate time spent in the ocean. Each sea turtle must move between year zones and pick-up one poker chip when it reaches each year zone. Each poker chip represents two years of ocean survival. Upon collecting five poker chips, the sea turtles must return to the nesting area to lay eggs and begin the life cycle again. B. While moving in the ocean, each sea turtle should try to avoid limiting factors and predators. If a sea turtle is tagged by a limiting factor or predator, the sea turtle must stop, count 10 beans and place them in the limiting factor s/ predator s bag. C. The areas labeled ocean s sea grass represent sea turtle safety zones. While in these safety zones, sea turtles may not be tagged by a limiting factor/predator. Sea turtles may only rest here for short periods at a time. OPTIONAL: To simulate the sea turtles growing too large to effectively using the sea grass for cover, the teacher may wish to eliminate the Sea Grass safety zones. D. The following rules must be obeyed by the limiting factors/predators: Any sea turtle counting beans to another limiting factor/predator cannot be tagged. All other limiting factors/predators, other than the one who just tagged the sea turtle and receiving the beans, must stay a distance of at least four steps away from sea turtle depositing the beans to the limiting factor/ predator bag. They may not tag the same sea turtle consecutively. E. Should a sea turtle lose all 100 beans, it is dead. The student/ sea turtle must then return to the beach and become a beach front development, i.e. a condominium. When additional developments are added, the student/ sea turtle must sit next to an existing development. Once the coastal area is filled with beach front developments and the sea turtles are no longer able to access their nesting area, the sea turtles are forced to remain at sea, vulnerable to limiting factors/predators until they are dead. F. When all sea turtles have died or returned to the nesting area, the activity is finished. 4. The teacher must review the rules at least twice to ensure the students understand the procedures and their roles. The students may now assume their roles as endangered sea turtles and limiting factors (either predator or human activity) and the activity may start. 5. Upon completing the activity, have the students discuss the results. Some students may be disturbed by the high mortality rate and benefit from the realization that there are groups trying to minimize sea turtle deaths due to human contribution. Make sure to emphasize that natural limiting factors (predators) are important in order to keep nature in balance. Otherwise, we might have over-population. 6

7 The production of more young than will survive also plays a vital part in the cycle of life. Sea turtles can become food for other species, ensuring the survival of that species. Have the students explain the life cycle of sea turtles. 6. Discuss with the students factors that limit the survival of sea turtles. Ask students to make a list of specific ideas that may help ensure the successful survival of the sea turtles nesting areas. Students may also suggest specific recommendations to help increase the successful reproduction and survival of Ocean Literacy Essential Principals and Fundamental Concepts (OLEP&FC): National Science Education Standards (NSES): Life Science: Life cycles of organisms Organisms and Environments Reproduction and Heredity Populations and Ecosystems Diversity and Adaptations of Organisms Personal and Social Perspectives: Populations, Resources, and Environments 5. The ocean supports a great diversity of life and ecosystems. d. Ocean biology provides many unique examples of life cycles, adaptations and important relationships among organisms (symbiosis, predator-prey dynamics and energy transfer) that do not occur on land. i. Estuaries provide important and productive nursery areas from many marine and aquatic species. 6. The ocean and humans are inextricably interconnected. d. Much of the world s population lives in coastal areas. e. Humans affect the ocean in a variety of ways. 7

8 Extension Activities: 1. Students may log onto the imms.org website to track released Kemp s Ridley Sea Turtles, having Global Positioning Systems (GPS) adhered to their carapaces. Students can identify where the sea turtles travel, follow their migration process, and make inferences if feeding habits are based on where they swim. 2. Students may also incorporate math by locating the longitude and latitudes of these sea turtles. (Possibly using a GPS). 3. Establish a sea turtle information center in their classrooms, using the website. 4. Replay the Turtle Hurdle activity without any human factors. 5. Where possible, visit sea turtle rehabilitation/ restoration facilities and identify what actions may be taken to enhance the stability of sea turtle populations. 6. Change the ratio of predators and limiting factors to sea turtles and replay the activity. Perhaps use 1/3 predators and 2/3 turtles. 7. Nest Zone: Where female sea turtles lay eggs and hatch. (This is the beginning of the baby sea turtles journey toward the sea.) Beach Zone: The baby sea turtles must survive this zone in order to get to the sea. (One of the most dangerous zones the baby sea turtles will encounter due to high predation and other limiting factors. Sea Zone (Open Ocean): The sea turtles survive in this zone for at least 10 years before the females can return to nest. Year Zones: Sea turtles must visit each of these zones in order to acquire sufficient poker chips necessary to reach the 10- year maturity age before returning to nest. (The sea turtle must alternate between the Year Zones getting one chip per trip between zones. These are areas where sea turtles cannot be tagged by limiting factors/ predators.) Sea Grass Zones: These are also areas where the sea turtles are safe from being tagged. They may visit these zones for short periods of time until they are four-years old. Once they are four-years old, they are too big to be able to hide in the grass.! 8

9 resources: National Research Council (NRC), 1996: National Science Education Standards. National Academy Press, Washington, D. C. Ocean Literacy-Essential Principals and Fundamental Concepts National Geographic Education & Children s Programs. nationalgeographic.com. NOAA Office of Education , National Marine Fisheries Service. noaa.gov/pr/species/turtles/. Project Wild, Aquatic Turtle Hurdles. Pages sea-turtle/hatching-&-care.htm sea-turtle/reproduction.htm sea-turtle/physical-characteristics.htm sea-turtle/pdf/ib-sea-turtle.pdf WIDECAST Wider Caribbean Sea Turtle Conservation Network html. Revisions by: Joseph (Skipper) Talley and Denise Reinke, Animal Care Specialist/Educator and Marine Education Specialist, Institute for Marine Mammal Studies-Center for Marine Education and Research, Gulfport, MS. The National Park Foundation is the national charitable partner of the National Park Service. 9