What Are the Main Stages in the Sea Turtle Life Cycle?
The sea turtles have been here for over 250 million years, the archaeologists have found so many clues supporting this. Turtles are cold-blooded, they have had a shell that protects them. The lower portion of the shell is called the Plastron. These sea turtles are found all over the world and inhabit almost every type of climate. The average lifespan of a sea turtle can vary from 30 to over 100 years depending upon the species. There is a lot to know about the life cycle of a sea turtle. There are over 7 species of sea turtles, which are as below
Hawksbill
Olive Ridley
Kemp’s Ridley
Flatback
Leatherback
Loggerhead
Green Sea Turtle
Each of these sea turtles has its own life cycle. Let us now focus on the family as a whole instead of the individuals.
[Image will be Uploaded Soon]
Stage 1(the Eggs)
Every 2 to 4 years pregnant mothers crawl on the beach, bury a pit in the sand and lay their eggs. They come anywhere between dust and dawn laying anywhere between 100 to 200 eggs per nest. They will lay several nests for the course of the season. They cover up the pit and head back to sea and after 6 to 12 weeks we will see baby turtles cracking the shell wailing out of the sand and flapping their flippers across the beach. The sea turtles eggs incubate in the sand for 45 to 50 days depending upon the species of the turtle. During this time the temperatures of the nest determine whether the hatchlings will be male or female. Although this seems to be nice, 99% of these turtles don’t make it to adulthood. Most of them will perish in this tough journey ahead.
[Image will be Uploaded Soon]
Stage 2(Hatchling)
Hatching is an exhausting process for baby turtles. After breaking out of their shell they must dig their way out of the nest then cross the sea into the ocean. All of this requires frequent breaks, so these baby turtles typically weigh until night when there are fewer predators(you can say when the predators are least likely to attack) and the sand is cool enough to crawl across. Once they are through the sand they look for one signal, i.e. the faint reflection of the moon of the ocean. This behavior is innate, there is no thinking but an instinct. It’s the hatchlings' urge to head towards the light, as that leads them towards the ocean. The artificial lights can confuse the hatchlings, the lucky ones who don’t get fooled crawl as quickly as they can towards the sea hoping predators don’t get the best of them. Even when the hatchlings are in the ocean you may think everything is good, but the ocean is not that safe either. The moment the hatchlings touch the water it begins the friendsy period. There is nothing but 24 hr straight swimming. You can imagine a living creature being the size of the palm of your hand being dropped into the ocean 10 minutes after birth and now you have to swim and not stop. If you stop here you're dead, if you don’t stop you are dead as well. The shallow water is filled with creatures that love to eat a tender hatchling.
Stage 3(Small Juvenile State)
This is the stage where the research is scarce. As if you imagine trying to put a tracking device on a baby sea turtle that would transmit signals, which would never run out of a battery and doesn’t fall off. Doing all of this while not affecting the turtle’s bouncy or the ability to swim might be very difficult. As a result, these years are called the lost years. With our growing technology, these years are becoming more known to us now. It is clear that the turtles use currents to their advantage. It was first thought to be passive migration, which is unintentionally following the currents. But the evidence shows that sea turtles actively orient themself and swim. The best of the research shows sea turtles deduct earth’s magnetic field and they use it as a compass, an accurate one to navigate the oceans. The complexity of this goes beyond the scope, it is important to understand that the sea turtles have a sense we don’t have called Magnetoreception. This sense becomes very important for turtles later in their life.
[Image will be Uploaded Soon]
Stage 4(Large Juvenile State and Sub Adult State)
Once the turtles reach this stage they head to the feeding grounds in coastal waters. These feeding grounds may be over 10,000 km from their home beach. It takes from over 10 to 20 years for the turtles to reach maturity depending upon the species. It is estimated that less to 10% of the turtles that hatch reach maturity. In the feeding grounds, these large juvenile adults turn into sub-adults. The sea current will help the turtles reach their feeding habitat. Each of the turtles carries a york that can supply them with nutrients for a little while, but when it is gone they will have to find their own food. Once these turtles reach a suitable feeding habitat, sea turtles will reside there until they grow to become an adult. Sea turtles have varying diets depending upon what age they are and what species it is.
Stage 5(Mature Adult State)
Juvenile and adult sea turtles will often eat seaweeds, seagrass, and algae. They also eat small animals like jellyfish, shrimp, sea sponges, snails, molluscs, and crabs. The feeding habitat and breeding habitat are usually far away. The distance usually depends on the population of the turtles. An adult sea turtle can mature between 30 to 40 years. So in these terms, we can say it takes a period of 30 years for a sea turtle to return back to their home which they remember it all this time.
Stage 6(Mating Season)
In the feeding grounds, once these sub-adult turtles are ready to mate with their mature adults, this will be the time to start migrating back to their nesting site. These migrations can be over 1000 km. During this migration period, the male turtle will meet as many females to pass-on as much as his DNA as he can, While a female turtle will store as much sperm as she can. This is because more fertilized eggs mean more offspring, which in turn means more survivors. When in water the sea turtles slow their heart rate in order to preserve their oxygen underwater. The heartbeat is said to be slower like 9 min per beat. After mating males turtles go back to the feeding grounds whereas the female’s turtles continue to the beach. At the beach, the females lay the eggs and the cycle continues. The soon to be mothers travel back to the feeding grounds until the next mating season. The interesting fact is the mothers lay their eggs in the exact same beach where they were born. This phenomenon is called natal homing and how it works has not been fully understood. The best explanations which they have come up with would be Geomagnetic Imprinting. When they are born the hatchlings imprint on the magnetic field of the earth and use this unique signature to guide them back home decades later. But the question remains why to go back to the exact same beach, as to travel 10000 km just to reproduce doesn’t seem ideal. During this journey, they are risking death, expending tons of energy. Even though there are perfectly good nesting sites close by. It may be due to natal homing must have some kind of benefits or outway the risks for the turtle to adopt this kind of behaviour. The process of natural selection tells us that the mother doesn’t go back to her home beach and is less likely to have her offspring survive. The mothers that stuck with what they knew worked and this tendency was passed to their young. All of it has been hardwired in its DNA to go to its home beach and the offspring have a better chance of surviving.
FAQs on Sea Turtle Life Cycle: A Complete Guide for Students
1. What are the main stages in the life cycle of a sea turtle?
The sea turtle life cycle consists of four primary stages. It begins with the egg stage, where females lay their eggs in nests on sandy beaches. After hatching, they enter the hatchling stage, making a perilous journey to the sea. The next phase is the juvenile stage, often called the “lost years,” where they drift in the open ocean. Finally, they reach the adult stage, where they migrate between feeding grounds and nesting beaches to reproduce.
2. What is the difference between a sea turtle and a tortoise?
The primary differences between sea turtles and tortoises relate to their habitat and anatomy. Here are the key distinctions:
- Habitat: Sea turtles are aquatic and spend most of their lives in the ocean, while tortoises are terrestrial and live exclusively on land.
- Anatomy: Sea turtles have lightweight, streamlined shells and long, paddle-like flippers for swimming. Tortoises have heavy, dome-shaped shells for protection and short, sturdy legs for walking.
- Diet: Most sea turtles are omnivores, eating jellyfish, seaweed, and crabs. Tortoises are typically herbivores, feeding on grasses, shrubs, and fruits.
3. What determines if a sea turtle hatchling will be male or female?
The sex of a sea turtle is determined by the nest's temperature during incubation, a process known as Temperature-Dependent Sex Determination (TSD). Nests with warmer temperatures, typically above 31°C (88°F), produce mostly females. Cooler nest temperatures, usually below 28°C (82°F), result in mostly males. Temperatures in between will produce a mix of both sexes.
4. What are the scientific names for the parts of a sea turtle's shell?
A sea turtle's shell has two main parts. The upper, dorsal part of the shell is called the carapace. The lower, ventral part is known as the plastron. These bony structures are fused to the turtle's ribs and spine, making the shell an integral part of its skeleton.
5. What are the biggest threats to sea turtle survival today?
Sea turtles face numerous threats, most of which are caused by human activities. The most significant dangers include habitat loss from coastal development on nesting beaches, pollution such as plastic ingestion and oil spills, accidental entanglement in fishing gear (known as bycatch), and illegal poaching for their eggs, meat, and shells.
6. Which is the largest sea turtle species, and what makes it unique?
The Leatherback sea turtle is the largest of all sea turtle species, capable of growing over 6 feet long and weighing up to 2,000 pounds. Unlike other turtles, its carapace is not a hard, bony shell. Instead, it is a flexible, rubbery layer of skin strengthened by thousands of tiny bone plates, allowing it to dive to great depths.
7. Can a sea turtle live without its shell?
No, a sea turtle cannot survive without its shell. Unlike a hermit crab that changes shells, a sea turtle's shell is a vital and integrated part of its body. Its backbone and rib cage are fused directly to the inner surface of the carapace. Therefore, removing the shell would be fatal as it is inseparable from its skeletal structure.
8. Why do sea turtles undertake such long migrations?
Sea turtles migrate vast distances to separate their feeding and nesting areas. This behaviour is crucial for their life cycle. They travel to specific feeding grounds that are rich in food resources and then migrate to often distant nesting beaches to lay their eggs. Many females exhibit incredible navigational ability by returning to the very same beach where they were born.
9. What are the “lost years” in a sea turtle's life?
The “lost years” refer to the early stage of a sea turtle's life, from when a hatchling enters the ocean until it returns to coastal waters as a larger juvenile. During this period, which can last for over a decade, the young turtles are believed to drift with major ocean currents in the open sea. This phase is called “lost” because the turtles are rarely seen, making it the least understood part of their life cycle.
10. How are sea turtles adapted for life in the ocean?
Sea turtles possess several key adaptations for their aquatic existence. Their front limbs are modified into powerful flippers for efficient swimming, while their hind limbs act as rudders for steering. Their bodies and shells are streamlined to reduce drag in the water. Additionally, they have specialised salt glands located near their eyes to excrete excess salt, allowing them to drink seawater.
11. Why are sea turtles sometimes called “ecosystem engineers”?
Sea turtles are considered ecosystem engineers because they play a critical role in maintaining the health of their habitats. For example, Green sea turtles graze on seagrass beds, which increases the productivity of these areas. Hawksbill turtles feed on sponges, preventing them from dominating and damaging coral reefs. Their nesting activities also transport essential nutrients from the ocean to coastal dunes, enriching the beach ecosystem.
