Why do sea turtles live so long? That’s probably a question you can’t even begin to answer. Before we attempt to answer it, let’s have a look at the life of a sea turtle is and some of the things you probably didn’t know.
There are 7 known species of sea turtle today, and these turtles have a lifespan of between 30 – 5o years. There have been some documented records of sea turtles as old as 150 years but the upper limits of the sea turtle lifespan remains undocumented. It is the green turtle which is known to have the longest lifespan with some living well beyond 80 years. For a large sea creature that lives so long, it must have had to develop a pretty thick skin (excuse the pun) and some successful physical and behavioural adaptations.
Female sea turtles will nest between 2 to 8 times in a season, resulting in clutch of 100 eggs laid each time. These eggs are very vulnerable to predators and once the little turtles hatch, the make the treacherous trek to the sea to start life on their own in the ‘open ocean phase’. Not much is known about this phase of a sea turtles life expect that it lasts between 2 and 10 years depending on a number of factors. Once mature, an adult female will go ashore to nest every 2 to 5 years and will nest well into old age.
We cannot tell how old the oldest sea turtle lived to be because scientists haven’t found a fool-proof way to determine this. The first hurdle is that tracking devices rarely stay attached longer than 2 years, and secondly analyzing the bone structure to determine age isn’t a surefire method either and the jury is still out on the accuracy of this. Myrtle, the turtle, who has lived at the Cape Cod Aquarium is estimated to be 90 years old, but a life lived in captivity doesn’t prove that sea turtles will live that long in the wild.
In order to preserve the life of the individual and therefore the survival of the population, these amazing creatures are able to slow their metabolism down and then go without food for months on end. Considering these are large creatures, this is an amazing survival adaptation. The key facets to the sea turtle’s success are the fact that it grows very slowly and has a very slow metabolism. The metabolic rate plays a key role in longevity as they “control the fitness of the individual” which ultimately will determine the size and structure of the population. In the animal kingdom, the slower the metabolism, the longer the lifespan. Just think about slow moving large creatures like elephants- they too have been recorded to reach very old age. Sea turtles are even more amazing because they can slow their heart rate down to as little as 9 beats per minute. By comparison, a healthy adult humans heart rate will sit at about 50 beats per minute while at rest. Slowing the heart rate down has allowed the sea turtle to be able dive for feeding for up to 5 hours. Male turtles also take a key role in the survival of the species, and during times when the turtle population is waning will mate with multitudes of females.