Leatherback Sea Turtle:Dermochelys coriacea
The leatherback sea turtle is the most unique of all sea turtle species. They have the largest thermal and geographic ranges out of any reptile in the entire world. The leatherback is also the largest reptile in the entire world. There is fossil evidence to suggest that this species has remained majorly unchanged for over 110 million years! They have survived 5 mass extinctions and are only now facing extirpation from different ocean basins due to extreme and long-term pressures caused by the human race.
The global range of the leatherback sea turtle.
The leatherback sea turtle is the only sea turtle species that does not have a hard, bony carapace made of keratin. The carapace of leatherback sea turtles is made of cartilage. The leatherback carapace has seven ridges, and the standard protocol for measuring the size of a leatherback is to measure the length of the carapace along the right side of the center ridge and the width at the widest point of the carapace.As there is much that we need to learn about leatherback growth and developmental rates, we can use these measurements as a proxy for age of the turtle. It is thought that leatherbacks reach sexual maturity anywhere between nine and twenty-two years of age, when they come back to the beach on which they were born to lay their first clutch of eggs. They may reach 60-80 years of age but this still needs to be studied.There are no claws on leatherbacks but there are on all other species. The design of their body makes them very hydrodynamic in the water. They often travel as fast as 35 km a day as part of their cyclic oceanic migrations. The deepest dive ever recorded was to 4,000 feet and lasted around 85 minutes!
Papillae inside a leatherback’s throat.
Leatherbacks feed only on jellyfish species like gelatinous zooplankton, moon jellies, and sea nettles. They have special papillae in their throat to assist with swallowing their slippery prey. They are a keystone species because they regulate jellyfish populations, which also helps to promote the health of fish stocks, as jellyfish are an opportunistic predator and consume juvenile fish species and fish larvae.
Leatherback sea turtles are a keystone species and important for healthy oceans, as they regulate jellyfish population and help foster healthy fish stocks globally.
Leatherbacks have been referred to as a polar reptile. They have an incredible layer of insulating fat.And they are not warm or cold blooded but exhibit something that has been termed Gigantothermy. Gigantothermy is thought to be a body life history characteristic exhibited by polar bears, panda bears, and even dinosaurs.One of the mechanisms observed in their physiology is something called counter-current heat exchange, which occurs when veins carrying oxygen-poor, cooler blood heading back to the heart, and arteries carrying oxygen rich warmer blood coming from the heart, are located close to each other. This arrangement allows heat to be conserved in the extremities. When leatherbacks dive they can withstand temperature differences that other sea turtles cannot…they are therefore found at latitudes that none of the other more tropical sea turtles will be found at. Other sea turtle species are ectotherms, meaning they use the environment to regulate their body temperature…much like the basking green turtles found in Hawaii that are using the sun to warm up!In leatherback sea turtles, when they are overheated, their skin turns a pinkish color as they flush blood to the outside of their body in an effort to cool down.The body temperature of individuals measured off the coast of California is typically six to seven degrees higher than the temperature of the ambient environment, providing further evidence that this species is able to regulate the temperature of its body to utilize foraging habitats at latitudes where jellyfish can be found and where no other marine turtle species can reach.
There are a couple constraints of being a turtle: 1. you must breathe air, 2. lay your eggs on land, and 3. spend the majority of your life in the ocean. This use of both oceanic and terrestrial habitat presents unique and expansive conservation challenges for sea turtles in general but specifically for leatherbacks. Leatherbacks do not occupy nearshore foraging habitats during their developmental period like other sea turtles but spend all of their developmental life stages as a pelagic species out in the open ocean. This makes protecting them from fishing efforts even more of challenge because already protected reefs and sea grass beds do not provide protection for this species. There are seven subpopulations of leatherback sea turtles in the world, and each subpopulation is evaluated separately and then the entire species is evaluated as a whole based on the likely number of individuals left in the population, their total available habitat, current threats, and the amount that the population is increasing, decreasing or stable. Four of the subpopulations are critically endangered (West and East Pacific, Southwest Atlantic, and Southwest Indian), two are data deficient (Southeast Atlantic and Northeast Indian), and one is least concern (Northwest Atlantic). Because the Northwest subpopulation’s population is actually slowly increasing, this species overall is considered vulnerable.
A juvenile leatherback sea turtle caught in artisanal fishing gear off the coast of Manta, Ecuador in January 2019.
The East Pacific subpopulation of the leatherback sea turtle is arguably the most endangered subpopulation of any sea turtle species around the world. At the mass nesting site, where 50-100 individuals used to nest each night, in 2018/2019 only 13 turtles nested for the entire 5-month nesting season. The most recent official estimate from 2013 indicates that there were only 633 individuals in the entire East Pacific and this number is likely as low as 200 individuals at present.
The East Pacific subpopulation expected to be functionally extinct by the year 2040, if the current rate of decline continues. We cannot let that happen.
To be clear on exactly what it means to be a “Critically Endangered Species”, I have outlined below this status’ criteria from the International Union for the Conservation of Nature. A taxon is Critically Endangered when the best available evidence indicates that:
1. An observed, estimated, inferred or suspected population size reduction of ≥90% over the last 10 years or three generations, whichever is the longer, where the causes of the reduction are clearly reversible AND understood AND have ceased.
2. An observed, estimated, inferred or suspected population size reduction of ≥80% over the last 10 years or three generations, whichever is the longer, where the reduction or its causes may not have ceased OR may not be understood OR may not be reversible.
3. A population size reduction of ≥80%, projected or suspected to be met within the next 10 years or three generations, whichever is the longer (up to a maximum of 100 years).
4. An observed, estimated, inferred, projected or suspected population size reduction of ≥80% over any 10 year or three generation period, whichever is longer (up to a maximum of 100 years in the future), where the time period must include both the past and the future, and where the reduction or its causes may not have ceased OR may not be understood OR reversible.