The document provides an overview of sea turtles including their ancestry, the seven modern species, and conservation efforts. It describes how the first turtles appeared over 220 million years ago and the first sea turtles 90 million years ago. Today there are two families, one containing the leatherback turtle and the other containing six hard-shelled species like the loggerhead and green sea turtle. Most species are threatened by overharvesting, accidental fishing captures, and habitat loss. Conservation efforts include using turtle excluder devices and modifying fishing gear.

1. Overview on Sea Turtles
By Matthew Davis
MAR 490

2. Purpose
• Genealogy of the modern sea turtles
• Descriptions of different species
• Breeding habits
• Conservation methods

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. Archelon fossil

5. Modern Sea Turtles
• The 7 species are found in two families
o Dermochelyidae : Leatherback
o Chelonidae: 6 hard shelled sea turtles

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. Dermochelys coriacea

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. Eretmochelys imbricata

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. Caretta caretta

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. Lepidochelys kempi

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. Chelonia mydas

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. Lepidochelys olivacea

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. Natator depressus

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

23. 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

24. What’s being done?
• The use of TEDs as law for shrimping
industry
• Modified fishing gear
• Proactive measures done by local
communities