Sea turtles are renowned for being one of the oldest animals living today, having been around for 110 million years. Known as marine reptiles, sea turtles are one of only four reptiles that have adapted to life in the sea – the others being crocodiles, marine iguanas, and sea snakes. Many sea turtles don’t even mature until they are around 20 years old, so it’s no surprise that some of them can live for a long time. But just how old is the world’s oldest sea turtle? We’ll discover the oldest sea turtle and see how they compare against other turtles.
Background on Sea Turtles
Sea turtles can easily be distinguished from other turtles by their limbs which are actually flippers, and by the shape of their shell which is long and tapered at each end, meaning that they can’t retract their head under it for protection. There are seven species of sea turtle alive today – leatherback, hawksbill, olive ridley, Kemp’s ridley, green, loggerhead, and flatback. Sea turtles are found in almost every ocean around the world, except for the polar regions, and some have been known to migrate extremely long distances.
Most sea turtles are omnivores and eat a range of seaweed, jellyfish, squid, and barnacles, although the green sea turtle is a herbivore, and they use their front flippers to seize and hold their food. Sea turtles are excellent swimmers and can spend up to 40 minutes at a time underwater while foraging for food.
Sea turtles spend the majority of their lives at sea and in fact only the females come onto land, and even then only to lay their eggs. Females come onto the beach under the cover of darkness and digs a hole in the sand using her flippers and then lays a clutch of eggs (usually between 60 and 180) and then covers them over. Incredibly, female sea turtles even make several decoy nests to try and protect their eggs from predators before she returns to the sea without a backward glance.
Tiny hatchlings around 1 inch long are born after 60 days and head for the sea upon leaving the nest. Once they’ve reached the sea they then swim out into the open water where they will remain for many years until they have reached maturity. Only once they are mature do they then return to the waters around the shoreline to begin breeding.
Sea Turtle Lifespan
The lifespan of turtles ranges from 30 to 80 years depending on the species. However, a lot of guesswork is involved when trying to age sea turtles as they spend much of their time at sea and there is no truly reliable method of ageing them.
Kemp’s ridleys are the smallest sea turtles and although not a lot is known about their lifespan, it is estimated to be at least 30 years. The lifespan of olive ridley sea turtles is around 50 years, while the hawksbill is 50 to 60 years. Green turtles have an average lifespan of 70 years, while the flatback and loggerheads can also live for 70 to 80 years. Leatherback sea turtles are the largest sea turtles and it is estimated that their lifespan is more than 50 years, but little is truly known about their longevity. Leatherbacks are also able to dive deeper and travel further than any of the others. Leatherbacks have been recorded as travelling 10,000 miles to their nesting sites and diving to depths of 4,000 feet.
The World’s Oldest Sea Turtle
The oldest sea turtle in the world was likely around 100 years old and washed ashore in the United Kingdom. However, there are some reports of older sea turtles worth inspecting.
Several websites will list the oldest sea turtle as being more than 400 years old. This supposedly very old turtle lives in an aquarium in the Chinese city of Guangzhou. We searched far and wide to find the original source for this report and were unable to find anything. The oldest living animal on land is a tortoise named Jonathan that was born less than 200 years ago (less than half the age of this reported sea turtle). Some marine animals can reach very old ages, such as the Greenland shark which can reach perhaps 500 years of age.
However, the Greenland shark has several adaptations to reach this extremely old age, and its unlikely sea turtles could reach such an advanced age. A better candidate for the oldest sea turtle ever washed ashore more than 30 years ago.
A leatherback sea turtle that washed up on a beach in Wales in the UK in 1988 was the largest sea turtle ever recorded at a massive 2,019 pounds and was estimated to be around 100 years old. Scientists were fairly certain of the age of this sea turtle due to its massive size and it is possibly the most reliable record as one of the oldest sea turtles in the world. This huge sea turtle was preserved and has been on display in the National Museum of Wales since 1990.
Animals that take a long time to reach maturity generally have longer lifespans. With turtles taking 20 years to reach maturity, they could be a species that reaches lifespans longer than 100 years. Sea turtles have a heart rate of about 25 beats per minute near the surface but while diving can slow their heart rate to just 1 beat per minute. Like other long-lived animals, having a slower heart rate can lead to longer life expectancy.
How do Sea Turtles Compare with other Turtles and Tortoises?
On the whole, sea turtles have a similar lifespan to other turtles as freshwater turtles also have long lifespans. A Blanding’s turtle was believed to have been 83 years old when it was captured in a forest reserve by the University of Michigan in 2016. The female turtle has been caught several times since 1954 as part of an ongoing study. Alligator snapping turtles are also estimated to have a lifespan of around 100 years.
However, as noted earlier, tortoises have a much longer lifespan than sea turtles, with a Seychelles giant tortoise currently being the oldest living land animal at 189 years old. Jonathan hatched in approximately 1832 and there is even a photo of him as a mature adult in 1886.
Conservation: Are Sea Turtles Under Threat?
Sadly, all seven species of sea turtles are considered to be under threat – loggerheads and green sea turtles are classed as endangered, while hawksbill and Kemp’s ridleys are critically endangered. Leatherback sea turtles and olive ridleys are classed as vulnerable. Although there is no data on the IUCN red list for flatback turtles, they are classed as an endangered species in their native Australia.
Although the only natural predators of adult sea turtles are large sharks and crocodiles, predators do still play a part in their declining numbers as the eggs and hatchlings are at risk from them. Birds, crabs, fish, and raccoons frequently prey on young sea turtles and only 1 in 1,000 make it to adulthood.
Unfortunately, natural predators aren’t the only things that sea turtles have to worry about as us humans are a large threat to them as well. Sea turtles are often caught up in fishing nets as bycatch and plastic waste and pollution is a problem too. Sea turtles often don’t realise that plastic is not food and they eat it which causes illness and even death. Even climate change is affecting these majestic animals as their nesting sites are quickly disappearing.