Aliases: Green Turtle, Black Sea Turtle, Pacific Green Turtle
Scientific Name: Chelonia mydas
Size: Adults can reach up to 5 feet long (1.5 meters).
Weight: Adults can weigh up to 150 - 419 pounds (68 - 190 kilograms).
Carapace Length (Shell): Adults on average have a shell length between 31 - 44 inches (78 - 112 centimeters).
Gender Differences: Males have a slightly longer tail and are overall larger than females in size. Males also have longer claws on their front flippers. However, both do have paddle-like flippers which aid in their swimming.
Lifespan (Wild): Green Sea Turtles that reach maturity can live for roughly 80 years.
Diet: Juvenile Green Sea Turtles are initially carnivorous (diet consists mainly or exclusively of meat) eating things like mollusks (snails and clams), sponges, algae, and even fish eggs. As they’re maturing, they’ll incorporate plants into their diet and are considered omnivorous (diet consists of both meats and plants). Once they’re fully-grown adults, most of them are herbivores and have cut out meat in their diets due to their serrated jaw (saw-like) which helps them chew plant life like various sea grasses and algae.
Group: A group of Sea Turtles is called a bale.
-Habitat and Lifestyle-
Life Cycle: Almost everyone knows that Sea Turtles hatch from eggs that are laid on beaches in Southeast Asia, India, western Pacific islands, and Central America. One of the most dangerous events in a Sea Turtle’s life happens as soon as they hatch. As they attempt to flee into the ocean they may be attacked by predators like birds and crabs; a big percentage of hatchlings won’t make it to the water. Juveniles who did make it to the water spend anywhere from 3 - 5 years in the deep ocean. After their years of exploration, the juveniles will find shallow watered areas to call home for the rest of their days. Sadly, estimations say that only about 1% of Sea turtle hatchlings will make it to sexual maturity which occurs after about 20 - 50 years. Finally, once mating occurs the female will breach the ocean’s surface past the high tide line of the beach to lay her eggs. She then returns back to the sea.
Breeding: Mating occurs every 2 - 4 years.
Gender Deciding Factors: Nests in areas above 30 degrees Celsius tend to favor female hatchlings whereas areas below 30 degrees Celsius tend to favor male hatchlings. Egg positioning also plays a role in whether a hatchling may be male or female. If the egg is more towards the center of the nest then it has a higher chance of resulting in a female hatchling due to the center being warmer.
Number of Eggs per Nest: Each nest will contain about 110 eggs.
Number of Nests per Season: On average, a female Sea Turtle can create 2 - 8 nests in a single season.
Habitats: Generally, Green Sea Turtles stay near island and continental coastlines. Depending on their stage in life, Green Sea Turtles can be found in many different types of environments. Younger juveniles can be found in the open ocean as they spend years swimming around before they settle down. Older juveniles and mature adults will find permanent residence in areas that are more shallow like coral reefs, seagrass beds near shore, and salt marshes. These areas are generally good spots for protecting the turtles. Globally, you can find Sea Turtles in warm tropical waters to subtropical waters.
-Role in the Ecosystem and Endangerment-
Ecosystem Roles: In the varying areas Sea Turtles can be found, they have a strikingly powerful role to play in each. For instance, on the beaches where their eggs lay cracked and empty, key nutrients are given to the ecosystem through the eggshells. For the turtles located in the seagrass beds, they feed on the seagrass and in doing so they improve the health and development of the seagrass; this in turn results in a suitable habitat and place for feeding for various species of fish and crustaceans (crabs, shrimp, barnacles, crayfish, etc).
Conservation Status: Green Sea Turtles are listed as Endangered whereas some subpopulations in the Mediterranean are listed as Critically Endangered. Some human-caused threats include being hunted, poached, and having their eggs collected. Whereas accidental threats like boats, pollution, habitat destruction, and fishing nets are reducing the population as well.
Here’s a seriously cute photo for your Wednesday: A monk seal watches a baby turtle crawl on the beach at Papahānaumokuākea Marine National Monument. A UNESCO World Heritage Site, Papahānaumokuākea encompasses 139,797 square miles of the Pacific Ocean – including the Hawaiian Islands National Wildlife Refuge and Midway Atoll National Wildlife Refuge (usfwspacific). Many of the islands and shallow water environments are important habitats for rare species such as the threatened green sea turtle and the endangered Hawaiian monk seal.
Photo: Comber the green sea
turtle being released into the Pacific Ocean off southern California, October
23, 2016, Photo credit: SeaWorld San Diego
I’ve been asked, “What
difference does one turtle make?”
It is absolutely true that
one turtle, in comparison to the entire world’s population, represents a small contribution
to that population. However, rehabilitating
that one individual from an endangered or threatened population can ensure
decades of offspring over a lifespan of up to 80 years.
Every turtle that strands
and is treated, successfully or not, teaches us something. The first lesson they teach us is how to
successfully respond, which is vital to know if we ever have a spill or
catastrophe that causes mass turtle strandings.
And erratic ocean conditions like algal blooms, El Niño, oxygen
depletion, and warming sea surface temperatures are resulting in greater
numbers of stranded turtles.
Photo: Track of Comber, a rehabilitated male green sea turtle
released back to sea on October 20, 2016. Data
courtesy of Hubbs-SeaWorld Research Institute (Dr. Brent Stewart)
Additionally, many of the
turtles we have treated are juveniles or very young adults. This age group is crucial as the future
breeding population, and very little is known about them. The period between hatching and return to the
nesting area is known as the “lost years” because when the turtles leave their
nests, they are too tiny to track with conventional satellite equipment, and they
are seldom encountered until the females return to nest 20 or more years later
– unless we find them stranded. And
males are even more mysterious since they spend their lives at sea.
And each stranded turtle we
successfully release has a story with important lessons. A green sea turtle named Comber, stranded in
Canada in 2015 and released in November 2016, was the first ever successful sea
turtle rescue from Canada. With a
satellite tag attached, Comber was released to the sea southwest of San Diego.
He shocked us by heading straight back to Canada! When his transmitter finally failed on March
30, 2017, he was in British Columbia a few miles north of where he stranded,
showing signs of normal turtle activity.
He was able to swim over 1,500 miles in frigid waters in the dead of
winter, and based on another turtle released in 2011, it may be more common
than we know. Two turtles can tell a story, but we need more information to
develop a pattern.
Photo: Tucker in the
hyperbaric oxygen chamber at the Virginia Mason Center for Hyperbaric Medicine
with a team of experts that included Seattle Aquarium veterinarian Lesanna
Lahner and Jim Holm, MD, medical director of hyperbaric medicine. Photo credit:
Hopefully, the pattern will
fill in a bit more brightly this fall. Three sea turtles, stranded in December
2014 and 2015, are returning to the Pacific Ocean on September 11! All three will be equipped with satellite
transmitters to map their travels. And
all three have already provided us with valuable information, teaching us lessons
in treatment of cold-stranding and buoyancy.