Species
Madagascar
Madagascar, with its vast coastal areas and diverse marine ecosystems, is a haven for several species of marine turtle. These include:
- The green turtle (Chelonia mydas).
- The hawksbill turtle (Eretmochelys imbricata).
- Leatherback turtle (Dermochelys coriacea).
- Loggerhead turtle (Caretta caretta).
Nosy Be
Sea turtles can be seen throughout the Nosy Be archipelago. They choose the coasts of the surrounding islands for the richness of their marine biodiversity and the warmth of their waters. Coral reefs, sea grass beds and mangroves provide an ideal habitat for sea turtles.
Nosy Tanikely is renowned for snorkelling and diving with hawksbill turtles. Nosy Sakatia attracts green turtles with its beautiful sea grass beds. At Nosy Komba, you can snorkel with both species. Nosy Iranja, Nosy Radama and Nosy Mitsio are places where sea turtles come to lay their eggs in large numbers every season. It is very rare to see the leatherback turtle in this area of the Indian Ocean.
Nosy Iranja
There are two main species of marine turtle on Nosy Iranja and in the Nosy Be archipelago, which are present all year round:
- The green turtle (Chelonia mydas).
- The hawksbill turtle (Eretmochelys imbricata).
Nosy Iranja is a veritable sanctuary for marine turtles. The island is sparsely populated and there are very few hotels. Some of the island’s beaches are uninhabited. The island is fairly green, and the tops of the beaches are planted with vegetation, providing natural protection to hold back the sand and protect the turtles. There are not many artificial lights to illuminate the beaches and disturb the sea turtles.
Green turtles
Green turtles are easily recognised by their large size and smooth shell. They can measure up to 1.5 metres in length and weigh more than 200 kilograms. They can swim very fast. Their shells are generally green, with shades of brown. The name ‘green turtle’ comes from the colour of their fat, due to their mainly herbivorous diet. Males can be distinguished from females by the size of their tails, which are longer and thicker. It is this long tail that allows the male’s penis to penetrate the female.
Habitat and distribution
Green turtles prefer shallow lagoons, coral reefs and sea grass beds. In Madagascar, they frequent protected waters where they can find an abundance of seaweed and seagrass.
Diet
Green turtles are carnivorous in the juvenile stage and then mainly herbivorous in adulthood. This diet plays an essential role in preserving seagrass beds by preventing the overgrowth of certain plants.
Hawksbill turtles
Habitat and distribution
Hawksbill turtles are found mainly on coral reefs in tropical regions. In Nosy Be, they are often seen in lagoon
Diet
Unlike green turtles, hawksbill turtles are carnivores. They feed mainly on sponges, but also on sea anemones, jellyfish and other marine invertebrates, thus contributing to the health of coral reefs.
Physical and behavioural differenc
Here are the main differences between green and hawksbill turtles:
- Scales on the head: Green turtles have one pair of pre-frontal scales on the head, while hawksbill turtles have two pairs.
- Number of claws: Green turtles have one claw per flipper, while hawksbill turtles have two per flipper.
- Carapace: Green turtles have a smooth carapace, while hawksbill turtles have overlapping, serrated scales.
- Size: Green turtles are generally larger, reaching up to 1.5 metres, while hawksbill turtles measure between 60 and 90 centimetres.
- Diet: Green turtles are herbivores, feeding on sea grass, while hawksbill turtles are carnivores, eating mainly sponges.
Other species
Leatherback turtle (Dermochelys coriacea)
This is the largest of the seven existing species of marine turtle. It eats only jellyfish. Although very rare, the leatherback turtle is sometimes seen on the coasts of Madagascar, sometimes from November to March, during the nesting season.
Loggerhead turtle (Caretta caretta)
The loggerhead turtle is present in Madagascar, although in smaller numbers than the green and hawksbill turtles. It prefers deep waters but sometimes comes to lay its eggs on Madagascan beaches.
Let's help preserve these remarkable creatures for future generations.
Marine turtle nesting in the Indian Oce
Nesting habits of green turtles and hawksbill turtles in Madagascar
Sea turtles choose to lay their eggs at high tide, which can be during the day or at night, although they usually prefer to lay at night when it is cooler and there is less activity on the beaches. Green turtles lay their eggs in open, sunny areas during the day. Hawksbill turtles tend to lay their eggs in less open areas. Using their rear flippers, they dig holes around 50 centimetres deep. They lay between 100 and 150 eggs in these holes before covering them with sand to protect their offspring from predators and the elements.
Laying periods
Green and hawksbill turtles
Green and hawksbill turtles lay their eggs every 2 to 6 years, several times a season on the same beach where they were born. Green turtles lay their eggs between June and October. Hawksbill turtles lay their eggs from October to February.
The 7 phases of egg-laying
Sea turtles perform a fascinating ritual when they come to lay their eggs on beaches. Every movement seems meticulously calculated.
- Getting out of the water.
- Preparing the site.
- Nest foundation.
- Egg-laying.
- Closing the nest.
- Camouflage.
- Back to the sea.
1. Getting out of the water.
The female turtle emerges from the water and climbs to the top of the beach.
2. Preparing the site.
Once at the ideal location, the turtle begins to clean the sand, which prepares the area for the construction of the nest.
3. Nest foundation.
Next, she starts digging a deep hole, up to 50 to 60 cm deep. She uses her hind legs for this task. The hole must be deep enough to protect the eggs from predators, heavy swells or other external elements.
4. Egg-laying.
The egg-laying itself is an intense phase. The tortoise deposits its eggs in several series.
5. Closing the nest.
After having laid, the tortoise starts to cover the eggs with sand. Its back legs bring back sand on eggs, and it uses its flippers to pack the whol
6. Camouflage
To hide the traces of its passage and protect its nest from predators, the turtle rotates on itself, thus blurring the clues to its activity.
7. Back to the sea.
Finally, the turtle returns to the sea. Hesitant or not, it sometimes takes detours before submerging back into the ocean. Each turtle seems to have its own way of saying goodbye to the beach and its young.
Incubation and hatching: a race against tim
Emergence
After hatching, the little turtles begin their journey up the slope from the nest, which can take up to 48 hours. In Nosy Iranja, humans often accompany this phase manually. This is questionable.
Once they have left the nest, they instinctively head for the sea, often guided by the light on the horizon. Generally, they take advantage of a high or rising tide to ease their descent towards the ocean, a critical period when their survival is severely tested.
The saga of the first few days at sea
Once in the water, they swim non-stop for 24 hours or more to reach the open sea, where they float and cannot yet dive, making them easy prey for seabirds.
The critical newborn phase
After several days, when they abandon this frenetic swimming behaviour, turtles are no longer considered to be hatchlings. At this stage, they begin to concentrate on feeding, often allowing themselves to be carried along by the ocean currents as they search for food.
Can you see a sea turtle laying eggs or emerging?
The rules for observing
a clutch:
- t night, do not use a flashlight. Red light is best for the situation.
- Don’t make any noise.
- Do not touch the turtle
- Stay behind the turtle and don’t get too close.
emergence:
- Under no circumstances should you use lights or flashes, otherwise they will become disorientated.
- Stand several metres away from the emergence.
- Do not touch the small turtles.
- Let them return to the sea without intervening.
Threats and conservation
Marine turtles are under serious threat from habitat destruction, pollution, accidental fishing and poaching. Protecting nesting sites is crucial to their survival. In Madagascar, conservation efforts are being put in place to protect these species. Programmes to monitor nesting beaches, reduce plastic pollution and raise awareness among local communities are essential to their survival.
By better understanding their differences and needs, we can help to preserve these fascinating species. Madagascar, with its exceptional marine biodiversity, plays a crucial role in the conservation of marine turtles. Together, we must continue to protect these creatures for future generations.
FAQ
What species of marine turtle are found on Nosy Be?
There are two main species of turtle on Nosy Be and Nosy Iranja, which are present all year round: the green turtle (Chelonia mydas) and the hawksbill turtle (Eretmochelys imbricata).
Where can you see sea turtles in Nosy Be?
Nosy Tanikely is renowned for snorkelling and diving with hawksbill turtles. Nosy Sakatia attracts green turtles with its beautiful sea grass beds. At Nosy Komba, you can often come across them while snorkelling. Nosy Iranja, Nosy Radama and Nosy Mitsio are places where sea turtles come to lay their eggs in large numbers every season.
When do sea turtles lay their eggs?
Green and hawksbill turtles lay their eggs every 2 to 6 years, several times a season on the same beach where they were born. Green turtles lay their eggs between June and October. Hawksbill turtles lay their eggs from October to February.
When are baby sea turtles born?
Small sea turtle eggs hatch around 2 months after being laid. They emerge at high tide or rising tide.
Is it possible to see a turtle lay eggs or emerge?
Yes, it is possible to observe a sea turtle egg-laying or an emergence. It is best not to disturb them and to follow the correct observation rules.
