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Adult green sea turtles love snacking on jellyfish and small invertebrates

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Posted May 27, 2018

Humans eat everything. We love meat, but we also like eating our vegetables. We cannot eat plain grass, but some herbs make our dishes delicious. Meanwhile a lot of animals are pure herbivores or pure carnivores. For the longest time we considered turtles to be just herbivores, but now scientists from the University of Queensland revealed that green turtles don‘t say no to carnivore snacks.

Green sea turtles love grazing on sea grass, but sometimes turn to carnivorous snacks. Image credit: P.Lindgren via Wikimedia (CC BY-SA 3.0)

Green sea turtle lives in tropical and subtropical regions of the world. Two distinct populations live in Atlantic and Pacific oceans, but they can also be found in the Indian Ocean as well. Green turtles, surprisingly, are not really green. Usually their shells are black, but sometimes they can be a bit of an olive colour. Their name comes from the usually green fat found beneath its carapace. Fat becomes green because of consumed vegetation – green turtles love grazing on sea grass and algae, but younger ones eat fish eggs, molluscs, jellyfish, small invertebrates and worms as well. Up until now it was thought that only juvenile green turtles are omnivorous, but this new study may change this belief.

Sea grass and algae have poor nutritional value, which limits the growth rate of the turtle. That is probably why younger turtles are omnivorous. But now scientists say that adult green turtles also snack on jellyfish and small invertebrates. It actually makes sense, because their long-term diet reflects the availability of food. This discovery will have implications on conservation efforts, because now we know that the diet of green sea turtles is more complex than previously believed. Their diet also reflects their lifestyle. Young turtles spend 6-10 years at sea, where food is more diverse. But then they come to near-shore foraging regions, where they spend the rest of their lives, leaving only to mate.

Scientists studied diets of foraging green turtles at three sites at Port Curtis in Central Queensland. These areas are the long-term habitats of green sea turtles, characterized by sandy sea grass meadows. Scientists analysed the gullet contents of the animals before safely releasing them and found various kinds of plant material, such as mangrove, sea grass and various kinds of algae. However, they also found some animal material as well. Owen Coffee, one of the authors of the study, said: “A large proportion of the turtles sampled had supplemented plant material with animal material, likely jellyfish and ctenophores, when they were available”.

Green sea turtles are suffering from human activity, such as poaching, hunting, fishing nets and boat strikes. Their behaviour is still poorly understood and so conservation efforts are limited. Understanding what they eat could help us understand their movement and improve our ability to protect them.

 

Source: University of Queensland

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