By Mary Pringle for The Island Eye News
Photos by Barb Bergwerf
- Hot chicks and cool dudes. The sex of sea turtles is determined by the temperature in the middle third of the incubation time under the sand. The pivotal temperature for loggerheads is about 84 degrees Fahrenheit – above this for females and below it for males. Since sea turtles don’t have sex chromosomes as humans do, their sex is not determined at conception.
- Mothers cry when giving birth. Female sea turtles have tears streaming down their faces when they are onshore laying eggs. This is not because of emotions but rather because of salt regulation. They have salt glands in their heads that can rid them of the excess salt they take in from drinking ocean water. Some ocean dwelling birds have the same glands for this.
- Magnetic crystals in their heads. Sea turtles use the earth’s magnetic fields as one of the cues for navigation during migration. Scientists have located a substance called magnetite in their brains. They also use vision (LIGHTS OUT), the downhill slope of the beach and the direction of the wave action to orient themselves when starting their journey.
- Can lay up to 800 eggs in a summer. Loggerheads can only hold up to about 200 eggs at a time. But about every two weeks, they can produce about 120 eggs and come ashore to lay them. Clutches can vary greatly in size, but each turtle can lay up to six times during a season. Most will nest every other year, taking time off between nesting seasons.
- Love to eat jellyfish and have a one way esophagus. They have sharp pointed structures called papillae in their throat and esophagus. These spines point backward making it a one way trip for slippery food such as jellyfish. Leatherback turtles can weigh as much as 2,000 lbs. and can eat 450 lbs. of jellyfish every day – the weight of an African lion!
- Cannot retract head and flippers like land turtles. Sea turtles cannot protect themselves from sharks and other predators by pulling in their head and flippers. Instead they have to be quick and turn their bodies so that these vulnerable parts are away from the attacker. If they can get their hard shell exposed, then the chances of being killed and eaten are not very great.
- Have mouths suited to their diets. Loggerheads have strong jaws and large heads for crushing hard shells of horseshoe crabs, conchs, whelks and blue crabs. Leatherbacks have a sharp pointed hook for piercing and grabbing jellyfish. Green sea turtles have a serrated lower jaw for shearing and scraping sea grass vegetation. And Hawksbills have a birdlike beak for cutting and biting chunks of sponges in coral reef crevices.
- Can hold their breath for hours. They are champions in holding their breath. This can last up to five hours underwater and slow their heartbeat to about once every nine minutes. This can help them enter a hibernation type state in the winter.
- Have been around for a very long time. Sea turtles have been on earth for over 100 million years, some say 175 million. Each one can live to 100 years or more even though most die within a few hours of hatching. That’s why it’s good to lay so many eggs. It’s hard to believe they once shared the planet with the Tyrannosaurus Rex.
Mary Pringle has been the Project Leader for the Isle of Palms/Sullivan’s Island Turtle Team since 2000. It is one of about thirty nest protection projects under the South Carolina Department of Natural Resources. She is also on the Sea Turtle Stranding and Salvage Network.