From the massive wingspan of the American White Pelican to the incredible size of the Eastern Hellbender, recently the focus has been on very large specimens from the Tetrapod Collection. So for this month’s post, I’d like to write about one more giant specimen we have and end the trilogy of the colossal species.
With an average length of seven feet and an average weight of 2,000 pounds, the Leatherback Sea Turtle (Dermochelys coriacea) is the largest species of turtle on the planet. Leatherbacks are believed to have the widest global distribution of any vertebrate, meaning they can be found in any of the world’s temperate oceans. Like most other sea turtles, leatherbacks feast on soft bodied organisms such as jellyfish, squid, blue-green algae, etc… One unique trait of the Leatherback Sea Turtle is that it has the ability to maintain warm body temperatures in cold water. Reptiles are famously “cold-blooded” and can only heat up their bodies using their surroundings. However, Leatherback Sea Turtles seem to be able to generate and maintain their own body heat through adaptations such as their large body size, changes in blood flow and a thick layer of fat. The leatherback is the only sea turtle species that doesn’t have a hard bony shell. A leatherback’s top shell (carapace) consists of leathery, oil-saturated connective tissue that is almost rubbery to the touch. Even after decades of storage at the museum, oils are still leaking from the carapace of our specimen. For more general facts about the Leatherback Sea Turtle, visit the National Geographic’s website .
All seven species of sea turtles (leatherbacks included) are endangered, with some species even being classified as critically endangered (meaning they are facing an extremely high risk of extinction in the wild). There are a number of reasons for the turtles being in danger of extinction such as poaching, habitat loss, pollution, collisions with boats, people stealing turtle eggs, etc…
However, a paper by Lewison, Freeman and Crowder (2004) discusses another reason for the turtle’s decline. When fishermen throw out their nets in hopes of catching fish such as sardines or mackerel, they often end up catching many other animals such as dolphins, sharks, and sea turtles by mistake. This is known as bycatch, and many times these other non-target species will see drastic reductions in population because of it. I know it may be hard to picture an animal as massive as the Leatherback Sea Turtle getting caught in these nets, but these are very large nets that are often used for large groups of fish. When a turtle becomes entangled in the net, they can drown or suffer external injuries while struggling to get out. This study aimed to determine what effect bycatch has on leatherback numbers and what they found was shocking. According to their research, 50,000 leatherback sea turtles were caught as bycatch in the year 2000. This research and other investigations like it, have led to some new policies regarding the use of drift nets. According to the American Bird Conservancy, Russia has banned the use of drift nets due to the harm they cause to seabirds, marine mammals and other aquatic species such as sea turtles.
As I had mentioned earlier, all sea turtle species are endangered and the Leatherback is no exception. This phenomenon of bycatch illustrates how much damage commercial fishing can do to the oceans’ ecosystems and how we should think of ways to alleviate this problem. There has already been much success in reducing bycatch by using specially designed nets that help free any turtles that become ensnared, and many fishermen have begun to employ these nets in their everyday work. These animals are unique due to their immense size and awe-inspiring presence, to lose them would be a major defeat for conservationists worldwide.
“Leatherback Sea Turtles, Leatherback Sea Turtle Pictures, Leatherback Sea Turtle Facts – National Geographic.” National Geographic. http://animals.nationalgeographic.com/animals/reptiles/leatherback-sea-turtle/
Lewison R. L., Freeman S. A., Crowder L. B. 2004 Quantifying the Effects of Fisheries on Threatened Species: The Impact of Pelagic Longlines on Loggerhead and Leatherback Sea Turtles. Ecology Letters 7, 221-231.
Nevins, Hannah. “Russian Ban on Drift Net Fishing Bodes Well for Seabirds American Bird Conservancy.” American Bird Conservancy. N.p., 31 July 2015