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Green sea turtle (Chelonia mydas) with a plastic bag, Moore Reef, Great Barrier Reef, Australia © Troy Mayne / WWF

Green sea turtle (Chelonia mydas) with a plastic bag, Moore Reef, Great Barrier Reef, Australia © Troy Mayne / WWF

What do sea turtles eat? Unfortunately, plastic bags

11 Oct 2018

Keywords
  • plastic
  • marine pollution
  • hawksbill turtles
  • marine species
  • marine turtles

Would you rather pick a fight with a jellyfish or a plastic bag?


For sea turtles this question should be simple. Their scales protect them from the worst of a jellyfish's venom, and the resulting meal is both tasty and nutritious, but a single piece of plastic can be deadly.


The problem is that sea turtles don’t know what plastic is, and they don’t get to choose.


What do sea turtles eat?

There are seven species of sea turtles found in the world’s oceans today, and they each have different dietary preferences.


  1. Loggerhead: Hatchlings are omnivores (meaning they eat both animals and plants) but adults are carnivores, with favoured prey including crabs, whelks and conchs.
  2. Green: Fully grown sea turtles are herbivores and like to hang around coral reefs to scrape off seagrass and algae. Hatchlings, however, are omnivorous.
  3. Hawksbill: The bird-like beak that gives them their name allows hawksbills to access cracks on coral reefs to reach sea sponges, which is pretty much all these fussy eaters want.
  4. Leatherback: Leatherback turtles are often known as gelatinivores as they only eat invertebrates such as jellyfish and sea squirts.
  5. Flatback: This species will eat everything from seaweed to shrimp and crabs.
  6. Kemp’s ridley: Meat is the only thing on the menu for the Kemp’s ridley - though they have a strong preference for crab.
  7. Olive ridley: Another omnivorous species that eats jellies, sea cucumbers, fish and a wide variety of other things.

The earliest ancestors of these seven species appeared on Earth around 220 million years ago, and today’s sea turtles have evolved to be perfectly suited to hunting beneath the waves.


That was until plastic came along.


Why do sea turtles eat plastic?

Plastic has only been mass produced since the 1940s, but it’s having a devastating impact on sea turtles.


Research suggests that 52% of the world’s turtles have eaten plastic waste, and the east coast of Australia is named as one of the most dangerous places for these ancient animals.


The reasons are simple: a floating plastic bag can look like a lot of jellyfish, algae, or other species that make up a large component of the sea turtles’ diets.


Which turtle species are most at risk from plastic?

Baby turtle hatchling climbing over plastic bottle, Juani Island, Tanzania © Brent Stirton / Getty Images / WWF-UK

 

Whatever they prefer to eat, no sea turtles are safe.


The carnivorous loggerhead and mainly plant eating green turtle are commonly found on Australia’s Great Barrier Reef, and both were shown to be consuming plastic in alarming quantities according to a study from the University of Tokyo.


In fact, loggerheads ate plastic 17% of the time they encountered it, likely mistaking it for jellyfish. This figure rocketed to 62% for green turtles probably on the hunt for algae.


However, it’s not just ingesting plastic that causes problems for turtles. Entanglement in marine debris can easily kill through drowning or preventing individuals from hunting or escaping predators.


Tragically, the accumulation of plastics at key nesting beaches means that baby turtles are among the most at risk from plastic entanglement.

 

What happens to sea turtles that eat plastics?

The outlook for turtles that eat plastic is bleak: for 22% ingesting just one plastic item can be a death sentence.


Sharp plastics can rupture internal organs and bags can cause intestinal blockages leaving turtles unable to feed, resulting in starvation.


Even if they survive, consuming plastic can make turtles unnaturally buoyant, which can stunt their growth and lead to slow reproduction rates.


What can I do?

With the odds stacked so heavily against sea turtles it can be difficult to know how you can help.


The answer is simple, we need to reduce the amount of plastic entering the ocean. Australia alone contributes 130,000 tonnes to the world’s seas every year, and this is killing turtles.


This starts at an individual level so pledge to #ReduceYourUse today, sea turtles everywhere are depending on it.


Make the pledge today

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