A diet of jellyfish

If you mention jellyfish to a sea turtle biologist, the first thing he will think of is a leatherback turtle as the diet of a leatherback consists exclusively of jellyfish. The digestive track of a leatherback is uniquely designed to efficiently process jellyfish prey. The green turtle, on the other hand, has a diet that consists mainly of algae and seagrasses. The anatomy of the green turtle is perfect for this diet: its finely serrated beak is ideal for scraping algae off rocks and chomping on seagrasses. However, scientist might have been wrong about this ‘vegetarian turtle’: there are more and more reports of green turtles feeding on jellyfish.

Video courtesy of Sundive Byron Bay

How is it possible that it is only discovered is recent years that green turtles eat jellyfish? Could it be that green turtles only recently developped a taste for jellyfish? More likely is the explanation that green turtles have always opportunistically eaten jellyfish but that is was underreported in the past. With more and more people using cameras to film nature, rare or unusual animal behaviours are sometimes uncovered!

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Turtle-cams

A turtle’s underwater life has long been a mystery for science. Modern equipment such as GPS loggers give a lot of interesting insight into the turtle’s life, but there are things that GPS loggers simply cannot register. To learn more about the behaviour of turtles on a fine spatio-temporal scale, scientists resort to different technologies.

In 2005 Dr Richard Reina from Monash University collaborated with National Geographic to study the behaviour of female leatherbacks during their nesting season. The researchers attached video cameras to the carapace of female leatherbacks using suction caps. The cameras were automatically released from the turtle after several hours and the researchers then relocated the devices using a VHF transmitter. The footage presented an interesting view of underwater life from a turtle’s perspective and provided new insight into the private life of leatherbacks:

  • The video showed that the females turtles did not feed during the nesting season (which can span several months!).
  • The footage also exposed the aggressive and harassing behaviour of males wanting to pair with the females. Some males would repeatedly strike and bite the females. Others would even try to prevent the females from returning to the surface.
  • The video also revealed that some females seemed to actively avoid the males.

The results of this study were published in the Journal of Experimental Marine Biology and Ecology.

Using the turtle-borne camera has therefore given the researchers a great perspective on what the turtles do in their natural environment. New research published last month in Frontiers in Ecology and Evolution studied the feeding behaviour of leatherbacks off the coast of Nova Scotia. In the following video you can see a leatherback looking for its favourite meal!

Video courtesy of the Canadian Sea Turtle Network