I try and be as diverse as possible on this blog, writing about as many varied and wonderful animals as I can. Unfortunately, sometimes animals fall through the cracks, either because of personal feelings (I don’t like primates, and I’m terrified of spiders), or simply by accident. One of those accidental oversights is sea turtles, of which I’ve only written about one – the hawksbill sea turtle. Today I’ll add another lovely aquatic reptile to the list, the green sea turtle.
Green seas turtles are found around the world, in the Pacific, Atlantic, and Indian Oceans. They prefer warmer waters, living in tropical and subtropical areas. Populations in the Pacific Ocean are genetically distinct from those in the Atlantic, with each group having separate feeding and nesting grounds. Adult sea turtles tend to stay near coastal areas, while young turtles are found in the deep waters of the open ocean.
As far as sea turtles go, green sea turtles look pretty normal. They aren’t even green — they’re named that because of the green colour of fat deposits under their shell. Their shells start off black, and then lighten with age. They grow to be quite large, reaching shell lengths of 100 to 120 cm, which makes green sea turtles the second largest sea turtles in the world, behind leatherback sea turtles. The largest green sea turtle ever measured had a shell length of 153 cm, and weighed 395 kg. That is one big turtle!
Adult green sea turtles are gentle, herbivorous creatures. They feed on sea grass, algae, and mosses. Hatchlings are bit of a different story: they are carnivorous, feeding on marine invertebrates and other small creatures. As they grow, green sea turtles move to a more plant-based diet, and move closer to the coast.
In terms of predators, adult green sea turtles are pretty safe; they’re a bit too large for most ocean-dwellers to bother with. There are some sharks, particularly tiger sharks, that enjoy a green sea turtle meal. Other than sharks, the most significant predator of adult sea turtles is humans. The same can’t be said for younger turtles, which fall victim to a myriad of predators, including crabs, marine mammals, and shorebirds, to name a few.
Green sea turtles come to shore to lay their eggs, after mating near the coast. Copulation in green sea turtles can last quite a while, the longest recorded copulation being 119 hours long. Poor turtles! Females are quite selective about what beach they lay their eggs on, usually returning to the beach they themselves were born on, or finding a beach with similar sand texture and colour. Females dig a hole at the high tide line of the beach, depositing 75-200 eggs in a single clutch. Though females only breed every two to four years, they lay between one and nine clutches each season that they choose to breed in.
Hatchling sea turtles get a very rough start to life. They are left on their own after the eggs are laid, and hatch after about 30 to 90 days. The young turtles are about 5 cm in length upon hatching, and have to make a treacherous walk to the ocean. Numerous predators await the hatching of the turtles with glee, and glut themselves on the poor young turtles. Many baby turtles do not make it to the ocean; only 1% of hatchlings reach full sexual maturity, which is estimated to take 20 to 50 years. Green sea turtles are a long lived species, with wild turtles living up to 80 years.
These sea turtles migrate long distances from their feeding grounds to their nesting sites. The key to migration is that you have to be able to find your way from one place to the other, and green sea turtles have a number of super cool ways of doing this. They use wave direction, sunlight, and temperature to find their way around. As well, they have magnetic crystals in their brains that allow them to navigate using Earth’s magnetic field. Animals that can navigate with magnetism always amaze me — we had to invent compasses, but some species are born with them in their brains. Nature really is the coolest.
Unfortunately green sea turtles have not fared well recently, mainly thanks to human activities. They are actively hunted for their meat, skin and eggs. Turtles also get caught in fishing nets and drown, are prone to pollution and habitat destruction. They are currently listed as endangered and are protected both worldwide and by individual countries, but serious threats to these magnificent turtles remain.
Cover image source: Brocken Inaglory via Wikipedia