Who?
Family: Chelonidae
Species: Chelonia mydas
Species ID: C.CM
Description: A hard-shelled sea turtle with a brown, green, or black oval shell (1) possessing two large curved flippers at the front of the body and two short rounded flippers at the rear (2). The head is small with a blunt snout (3) and two elongated rectangular scales (4) just above each eye distinguish this from other sea turtles. Males have a tail that extends past the two rear flippers, while females have a shorter tail (5)
Maximum size: 1.4m (the largest hard-shelled marine turtle)
Longevity: Up to 75 years
Status: Endangered according to the IUCN endangered species list
Green Turtles & People: Green turtles have long been sought after by fishermen for their eggs, meat, and shell, while coastal development has disrupted nesting activity. These and other human activities have caused a population decline of roughly 50% in the green sea turtle in the last decade, a trend that will be difficult to reverse in this slow-growing species.
Where?
Geographical Range: This turtle is found throughout the world’s tropical seas, and is widespread throughout the Caribbean
Coral Reef Zone: Shore zone, back reef, fore reef and drop-off zones
Favourite Habitats: These large vegetarians frequent seagrass beds but can also be found in algae-covered reef areas where they tend to sleep at night
Depth Range: 0–35 m (0–115 ft)
A Day in The Life:
Dawn: Turtles begin roaming the reef looking for food
Day: Turtles usually feed and in season may also migrate or mate
Dusk: Feeding declines and turtles seek shelter for the night
Night: Turtles settle under reef ledges to sleep. In season, nesting occurs on beaches
Who Eats Who
The adult green turtle is herbivorous, feeding on seagrass and algae. Young green turtles are omnivorous, and become strictly herbivorous when they reach adulthood. The large size and hard shell of adult green turtles make them vulnerable to only the largest predators, such as the tiger shark, while virtually all reef predators can eat the small juveniles.
Scuba Diver & Snorkeler Best Practices
Carefully select entry and exit points. Carefully select points of entry and exit from the water to avoid damaging the coral reef.
What?
Approach
Reactions to snorkelers and divers vary depending on a turtle’s previous experience with humans. In areas where turtles are hunted, they may be wary, while in areas where divers are common, they are usually unafraid.
Feeding Behaviour Adult green turtles are strict herbivores. During the day they can be found roaming the reef, feeding on algae, or grazing on seagrass in the back reef zone. Juveniles are found more frequently on seagrass beds, which are more sheltered than the outer coral reef. In addition to eating seagrass, juveniles may also consume jellyfish, snails, crabs, and other invertebrates.
Observe, record & share:
O C.CM-101 – Grazing: Both adults and juveniles frequently graze on algae and seagrass, and in fact one type of seagrass called “turtle grass” has earned its name by being one of the green turtle’s favourite snacks
O C.CM-102 – Omnivorous juvenile: Young green turtles also eat invertebrates, such as small jellyfish, snails and crabs, but will become vegetarians as they grow into adults
Attack & Defense Behaviour Green turtles are not territorial, and mainly concern themselves with defence from aggression during breeding activity, and from predators like sharks and humans. The main defence against attack is its hard shell, also called the carapace. The shell accumulates scars that can be ‘read’ by snorkelers and divers to learn a little about the history of the turtle. Green turtles are very agile and will dive while employing zig-zag evasive manoeuvres to escape from fast predators such as sharks. In serious situations, they can inflict a nasty bite with their powerful jaws. At night, turtles wedge themselves under ledges in the reef and nap for a few hours at a time. Sea turtles do not possess gills, so they must periodically return to the surface for a gulp of air.
Observe, record & share:
O C.CM-201 – Carapace defense: Scars on the carapace or body of a turtle can tell a story about its history (see the highlight illustration for more detail)
O C.CM-202 – Sleeping in crevices: At night, turtles sleep under protective reef ledges
O C.CM-203 – Evasive manoeuvring: Turtles dive and swim in fast zig-zag patterns
O C.CM-204 – Aggressive biting: Turtles may inflict nasty bite wounds during serious fights
Reproductive Behaviour Turtles come together during the breeding season to mate in shallow water near nesting beaches. Courting males gently bite the female’s flippers or neck to initiate mating. If the female is receptive, the male mounts from behind, using the large claws on his flippers and his tail to hold on. Males compete for females and may butt shells and bite to win a mate. Unreceptive females avoid mating by facing the males, tilting their bodies to float vertically in the water so that they cannot be mounted, or sometimes by crawling up onto the beach where males refuse to follow. When ready to nest, females crawl onto the beach at night, dig a pit in the sand and lay just over 100 eggs. The eggs hatch at night, usually about a month and a half later. The young turtles dig themselves out of their nest and rush immediately towards the water. In the Caribbean, the green turtle’s breeding season spans April to October.
Observe, record & share:
O C.CM-301 – Nests and nesting: Crescent-shaped marks in the sand indicate recent nesting activity, and observers may even see females digging the nest and laying eggs
O C.CM-302 – Hatching: Deep, circular depressions in the sand mark recently hatched nests that have collapsed. Observers may even see young turtles running for the water
O C.CM-303 – Courtship biting: Courting males are known to gently bite the female’s flippers or the soft skin of her neck
O C.CM-304 – Copulation: Males mount females from behind, curling the two front flippers and the long tail around the female for a good grip
O C.CM-305 – Male-male competition: Males often compete for females and may fight by butting shells and biting
O C.CM-306 – Female rejection: Females may avoid mating by facing males, tilting their body to float vertically in the water, or crawling up onto the beach
Highlight Behaviors
Reading scars: A turtle’s shell and body accumulate various scars during its lifetime that can be read by divers and snorkelers to learn about its history.
1 - Deep, parallel slice-marks usually indicate an encounter with a boat propeller
2 - Crescent-shaped gouges and scrape-marks usually indicate a shark attack
3 - Small circular gouges are usually caused by barnacles that have been knocked off
4 - Scars around the limbs are often caused by tangling in fishing line
5 - Cracks in the carpace are often the result of a boat collision
6 - It isn’t all bad! Small metal or plastic tags on the flippers indicate that this turtle is being monitored for scientific research in order to learn more about the species
7 - Two parallel crease lines on the belly of a male turtle indicates mating activity since these creases develop when mounting females
Did You Know?
• The name “green” turtle stems from the green colour of its fat.
• The green turtle is a world-class traveler, and may migrate up to 4800 km (3000 mi), at a speed of up to 24 km/h (15 mph), in order to reach traditional nesting beaches.
• Hatchling sea turtles instinctively orient towards the brightness of the ocean (which is brighter than the shore due to reflections of light from the sky). Artificial lights visible from the beach often confuse young turtles and cause hatchlings to head towards the land instead of the sea.
What to do ?
Share your observations today! Discover your species of interest, observe its behaviour, and share your pictures and videos with friends and coral reef enthusiasts around the world! Upload media to the web, tagged with species common name (ex.: trumpetfish) and species ID code (ex.: A.AM) or species behaviour code (ex.: A.AM-101)
Observation Key:
O Easy
O Not so easy
O Tough
