Overview On Sea Turtles


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Overview On Sea Turtles

  1. 1. Overview on Sea Turtles By Matthew Davis MAR 490
  2. 2. Purpose • Genealogy of the modern sea turtles • Descriptions of different species • Breeding habits • Conservation methods
  3. 3. Ancestry • 1st turtles appeared about 220 million years ago • 1st sea turtles appeared in the fossil record around 90 million years ago o Archelon  shell length up to 2 meters long
  4. 4. Archelon fossil
  5. 5. Modern Sea Turtles • The 7 species are found in two families o Dermochelyidae : Leatherback o Chelonidae: 6 hard shelled sea turtles
  6. 6. Leatherback Sea Turtle • Dermochelys coriacea o Largest of the living sea turtles o 500 lbs to 1000 lbs o No bony shell instead shell is leathery o Feed mainly on invertebrates (e.g. jellyfish) in deep ocean waters o Only turtle to migrate to cold waters of the North Atlantic
  7. 7. Dermochelys coriacea
  8. 8. Hawksbill Sea Turtle • Eretmochelys imbricata o Named for the its hawk-like beak o Typical size is 130 lbs o Feeds on invertebrates found mostly on coral reefs o Famous for its shell
  9. 9. Eretmochelys imbricata
  10. 10. Loggerhead Sea Turtle • Caretta caretta o Named for typically large head o 300 lbs to 900 lbs o Most common seen sea turtle around Gulf Coast
  11. 11. Caretta caretta
  12. 12. Kemp’s Ridley Sea Turtle • Lepidochelys kempi o 70 to 100 lbs o Only sea turtle that nests during the day  All the Kemp’s Ridley turtles nest at one beach in one night  Known as an “arribadas”  Famous film from 1947 known as the Herrera film shows this mass nesting at Rancho Nuevo, Mexico  Up to 40,000 turtles will nest on one beach
  13. 13. Lepidochelys kempi
  14. 14. Green Sea Turtle • Chelonia mydas o Named for the green soup that was made from their meat o 350 to 550 lbs but can reach 800 lbs o Heavily poached for its meat and fat o Feed mainly on algae and sargassum
  15. 15. Chelonia mydas
  16. 16. Olive Ridley Sea Turtle • Lepidochelys olivacea o Normally 70 to 90 lbs o Found in tropical and subtropical waters o Nest in arribadas but during the night  Some arribadas will consist of 10,000 or more turtles
  17. 17. Lepidochelys olivacea
  18. 18. Flatback Sea Turtle • Natator depressus o Typically weigh about 160 lbs o Grayish to greenish in coloration o Found only the waters surrounding Australia
  19. 19. Natator depressus
  20. 20. Breeding Habitats • Typically nesting is done at night • Can lay up to a 100 eggs in a clutch o Eggs roughly the size of a ping-pong ball • Young have temperature-dependent sex determination o Incubation temperature determines sex of young • Typically 60 days to hatch
  21. 21. Conservation • Most species are on the verge of extinction • Main factors in population decline are: o Direct harvesting for meat and byproducts o Incidental capture by fishermen o Loss or alteration of nesting beaches o Increased pollution and disease  Fibropapilloma virus
  22. 22. What’s being done? • The use of TEDs as law for shrimping industry • Modified fishing gear • Proactive measures done by local communities