Sea Turtles

• Major groups of reptiles

  • snakes
  • lizards
  • turtles + crocodiles
• Challenge with breathing for land -> marine

  • easier to extract oxygen from air than water
  • aquatic mammals have a metabolic advantage
• Challenge with locomotion for land -> marine

  • more energy efficient to move in water than land
• Challenge with reproduction for land -> marine

  • large offspring
  • advantageous terrestrial juvenile habitats with low predation e.g turtles
• Challenge with osmotic sea balance for land -> marine

  • require mechanisms to deal with salt ingestion despite watertight skin
• Challenge with decompression

  offset by advantages of air breathing
• Species of turtles

  • 6 hardshelled cheloniidae
  • soft shelled leatherback Demochelys corinea
• Species of hard shelled cheloniidae

  • hawksbill Eretmochelys imbricata
  • loggerhead Caretta caretta
  • Green Chelonia mydas
  • flatback Chelonia depressa
  • Kemp's Ridley Lepidochelys kempii
  • Olive Ridley Lepidochelyc olivacea
• When did the extinct group of pleurosternidae appear

  late jurassic
• What are the 4 marine turtle families and when were they established

  • toxochelydiae
  • protostegidae
  • cheloniidae
  • dermochelyidae

  Cretaceous
• Reproduction in turtles

  • adults migrate to breeding areas
  • females reach internesting beaches and return every 2 weeks -> use hind limbs to dig nest
  • eggs hatch and enter ocean -> temperature-dependant sex determination
• Embryonic development and thermal tolerance

  • incubation period decreases as temperature increases -> non-linear
  • temp decreases with depth
  • thermal uniformity produces a uniform rate of development
  • tidal inundation reduces temp and O2 levels in sand column
• Thermal tolerange range

  25 - 27 -> 33 - 35
• Other factors influencing sex determination (not temperature-dependent)

  • chance e.g marine worm
  • maximising offspring number e.g in a nutrient dense environment predominantly female
  • social e.g coral reef fish can be sequentially hermaphroditic triggered by social change like disappearance of other sex
• Temperature dependent sex determination in turtles

  • low temp = males
  • temp > 30 = females
• how is migration of sea turtles explored

  • electronic tagging
  • satellite-based tracking
• Observations of migratory patterns in turtles

  • resting depth is 15 - 20m
• Threats to a nesting beach

  • poaching
  • encroachment of predators
  • anthropogenic light pollution
  • degradation
• Turtle exclusion device in nets


  • acts as an escape hatch
  • conserving adult turtles and decreasing pressure on catching turtles