Leatherback Turtle Found in Denmark – Normal or Anomaly?

Hot on the heels of our recent SWOT Q&A featuring Bibi Santidrián and Rotney Piedra’s views on the “InvestEGGator,” we found another curious news story worthy of attention about a leatherback turtle that washed ashore in … Denmark!?. Tanja Rahbek of Naturcenter Tønnisgård told us that the leatherback probably came ashore alive, but was found dead with a severe head wound on November 3, 2020 after a period of strong winds. The turtle has since been frozen and is currently awaiting a necropsy in the Fiskeri og Søfartsmuseum — Museum for Fishing and Shipping in Esbjerg.

Long-time SWOT-teamer, Dr. Bryan Wallace, graciously accepted our offer to answer a few questions about this unique piece of turtle news.

The Northwest Atlantic Leatherback Regional Management Unit (RMU) in orange (Wallace, et al., 2010), to which this turtle is thought to belong, and the site where the turtle stranded in Denmark (black pin).

SWOT: This seems very far north to find a sea turtle. Aren’t they normally more tropical? Is this a record of some sort? or have turtles been reported before in these temperate latitudes?

Bryan: Very far north! But not the farthest north that leatherbacks have been documented. Reliable sightings of leatherbacks extend from ~71 degrees N to 47 degrees S! There are many records of turtles stranding on coasts across high latitudes in The Atlantic Ocean, including Iceland, the Baltic Sea and the UK. The northernmost record was an adult female caught in northern Norway in 1997. These turtles most likely are born and breed in the Wider Caribbean! Imagine that maybe just last year, this turtle was floating through tropical seas, looking at palm trees and people in swimsuits!

SWOT: The water must be quite cold up there. as reptiles how do they handle it?

Bryan: It is! But they can! Leatherbacks, in particular, are especially suited for life in cold waters. By swimming nearly continuously, they generate body heat, and their large size and other adaptations—like a layer of insulating fat, changes in blood flow, and a type of vascular cross-current heat exchange —help them retain heat. They may be reptiles, but they have evolved to thrive not just in these really cold waters where there is lots of their favorite food (jellyfish!), but they can also enjoy the warm temperatures of the tropics when they’re ready to reproduce. There aren’t many animal species on the planet that migrate over such vast areas and through such different temperatures, and certainly no other ‘cold-blooded’ species.

SWOT: Do you know why it died? What are the main causes of mortality for a leatherback?

Bryan: Not sure in this particular case; perhaps the folks who found it are collecting more information about how and why it died. The body looks to be in pretty good condition in the pictures, which suggests that it might have been healthy and relatively close to shore when it died, so that its body didn’t have far to drift before washing up on shore. A possibility is that it became entangled in a fishing net or line and drowned, but it’s not possible to conclude anything from the pictures themselves.

Main causes of mortality for leatherbacks around the world are accidental capture in fishing gear and harvest of turtles and eggs for human consumption.

SWOT: Overall, how are leatherbacks doing worldwide? The IUCN Red list used to show the species as "Critically Endangered" globally, but now they are "Vulnerable," so does that mean they no longer need conservation attention?

Bryan: The global Red List status isn’t the most useful gauge of how they’re doing, because it doesn’t tell us the status of the seven different populations, which vary from “Critically Endangered” all the way to “Least Concern,” but overall leatherbacks populations in different parts of the world are generally declining, with few exceptions. For example, the North Atlantic leatherback population, including this animal found in Denmark, is currently listed as “Endangered” on the Red List because the average number of females that nest each year on Caribbean beaches has declined by >60% in recent decades.

Dr. Bryan Wallace (right), seen here with Charles Darwin (left), is the Director of Ecolibrium, Inc., an environmental consultancy based in Boulder, Colorado, USA, and is currently the IUCN Red List Coordinator for the Marine Turtle Specialist Group. Bryan is a wildlife ecologist specializing in applied conservation biology, protected resources biology, and marine ecology and conservation, and has been working in sea turtle biology and conservation for 20 years, mainly in Latin America and the USA.

Relevant SWOT Report articles:

Northwest Atlantic Leatherback Working Group. 2019. Status Update: Modern Threats Taking a Toll on Northwest Atlantic Leatherbacks. In SWOT Report—The State of the World’s Sea Turtles, vol. 14: 34-35.
Rodriguez Baron, J.M., Williard, A., Abrego, M.E., Tobon, A., Bermudez, D., and Arriatti, Y. 2018. Building Bycatch Solutions from the Ground Up for the East Pacific Leatherback. In SWOT Report—The State of the World’s Sea Turtles, vol. 13: 36-37.
Wallace, B., and Hutchinson, B. 2016. The Conservation Status of Leatherback populations Worldwide. In SWOT Report—The State of the World’s Sea Turtles, vol. 11: 28-31.
Benson, S.R. 2012. Seeing the Big Picture: Leatherback Migrations in the Pacific. In SWOT Report—The State of the World’s Sea Turtles, vol. 7: 7.
Piedra, R. 2010. Las Baulas Marine Park - An Enduring Hope. In SWOT Report—The State of the World’s Sea Turtles, vol. 5: 24-25.
Saba, V., and Wallace, B. 2009. Location, Location, Location - Why Leatherback Populations Vary Globally. In SWOT Report—The State of the World’s Sea Turtles, vol. 4: 8-11.
Dutton, P., Benson, S., and Hitipeuw, C. 2008. Pacific Leatherback Sets Long-Distance Record. In SWOT Report—The State of the World’s Sea Turtles, vol. 3: 17.
Mast, R., and Hutchinson, B. 2006. The World’s First Global Glimpse of Leatherback Nesting. In SWOT Report—The State of the World’s Sea Turtles, vol. 1: 14-15.
Dutton, P. 2006. Building our Knowledge of the Leatherback Stock Structure. In SWOT Report—The State of the World’s Sea Turtles, vol. 1: 10-11.
Tagging of Pacific Pelagics (TOPP). 2006. Leatherbacks Help to Map the Pacific. In SWOT Report—The State of the World’s Sea Turtles, vol. 1: 21.

Online Exclusive ArticlesAshleigh BandimereNovember 19, 2020Leatherback