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Q&A: How a Turtle With Fake Limbs Got a Leg Up

Five years ago, a group of fishers discovered Yu, a loggerhead sea turtle, off the coast of Japan.

She was severely injured, having lost both her front limbs. But an intrepid group of scientists, including  members of industry and University of Tokyo researcher Katsufumi Sato, one of National Geographic’s 2009 emerging explorers, has developed and tested a pair of prosthetic limbs for Yu to help her swim better. (National Geographic News is part of the National Geographic Society.)

Now 25, Yu was recently fitted with her 27th pair of prosthetic flippers at her home, the Suma Aqualife Park in Kobe, Japan.

The molded plastic limbs are attached to a jacket that fits over Yu’s shell. The stubs of her existing front limbs are inserted into the prosthetics so that Yu can swim using the same motions and muscles that she did before her attack. (See related pictures: “Fake Limbs, More Help Animals Heal.”)

Karin Hayashi, one of the scientists who helped test the prosthetics and who just completed her master’s degree at the University of Tokyo, sat down with National Geographic to share more about how she built the turtle’s artificial limbs and what’s next for Yu.

Q: How did the turtle get injured?

A: The turtle was probably injured by a shark attack. When it was found, there were many marks of shark bites on its carapace [back of its shell].

How did it come to your attention?

I was studying about behaviors of sea turtles, using an animal-borne recorder, which could record behaviors of animals under natural conditions at the University of Tokyo. The Sea Turtle Association of Japan, who established a project to create artificial fins for the injured turtle, asked my supervisor, Dr. Sato, to measure the swimming ability of the injured turtle using the animal-borne recorder. And Dr. Sato gave me the opportunity to join the project.

turtle picture
Yu swims after receiving her 27th pair of prosthetic flippers at the Suma Aqualife Park in Kobe, Japan, on February 11. Photograph from Suma Aqualife Park via Reuters

What made you think of creating prosthetic limbs for the turtle?

Dr. Kamezaki, the head of the Sea Turtle Association of Japan, thought of releasing the injured turtle to the ocean at first. However, one [school]boy entreated Dr. Kamezaki to help the turtle because he was worried that the turtle could not survive another shark attack with the injured limbs. Being provoked by the boy’s passion to help the injured turtle, Dr. Kamezaki started the artificial-fins project that purposes to recover [her] swimming ability by attaching artificial fins, which have been developed by Kawamura Gishi Co., Ltd [a Japanese company that designs prosthetics].

Have there been an increasing number of animals getting prosthetics recently? If so, why?

Yes, I think so. I think the reason for that could be an improvement of techniques to create prosthetics for humans so that they could also apply the techniques to injured animals. Another reason could be that because people were more interested in animal conservation. (See sea turtle pictures.)

How do the limbs work?

Sea turtles generate thrust to swim forward by moving their forelimbs up and down like wings of birds. Also, female turtles use their forelimbs to move on land for breeding. Thus, the functions of forelimbs are important for sea turtles’ locomotion.  (Also read about Digital Nomad Andrew Evans’s experience with a turtle with a fake flipper.)

What were you hoping to accomplish by giving the turtle artificial limbs?

We were hoping that the injured turtle became able to swim and move on land like healthy turtles with the artificial fins.

How does the turtle seem to like its new limbs?

When the artificial fins are applied to the injured turtle, she stays calm and seems not to care about [being] attached to the fins. However, her swim speed has not been improved, unfortunately, with the artificial fins so far.

What’s next for the turtle?

The most recent artificial fins were attached to a jacket-like suit slipped over the head of the injured turtle. However, we [were] concerned that she could not swim efficiently because of the increased drag produced from the jacket. The members of the artificial-fins project are working on a new method of attaching the artificial fins to her.

This Q&A has been edited for length and content.


  1. Harris Torner
    Boca Raton, Florida,USA
    July 13, 7:55 pm

    How can you go to great lengths to save all those sea turtles but violently kill so many Dolphins in the Cove?

  2. Harris E. Torner
    Boca Raton, FL ( Southeast Flroida coast.)
    October 11, 2013, 3:40 pm

    I am a volunteer at a local nature center that specializes in marine conservation,education,sea turtle nest monintoring& rehabilation with a university marine biology lab on premsis. How can you guys help a sea turtle using prosthetic flippers but still kill all those Dolphins, Whales& Purposes? There seems to be a total disconnect between the different animals? They both have a right to live just as do we humans.

  3. drdavidbrown
    southern afganistan
    February 22, 2013, 10:01 pm

    Turtles are so amazing. Especially the ability to outlive humans.

  4. Cathy
    February 22, 2013, 9:09 pm

    Oh how wonderful !!! And this comes from a country that sets out each year with the intent to slaughter the innocent Whales …. What gives??? There we go.. We saved an injured Turtle…. Now…. Back to killing those whales… Which is it Japan..??? Save the wildlife or Slaughter it ? Make up your minds !!!

  5. Yo Menashe
    February 22, 2013, 12:01 pm

    I grew up with a father with a “wooden leg”, WWII amputee below the knee, and remember upgrades many times. The original had a hinged knee with a leather lace-up around his thigh, and another harness that went around his waist, and a shoulder strap that he refused to wear. By the time of the last upgrade (~30 years ago) the technology had advanced so that a harness, and knee joint, were no longer necessary.

    Yu’s story really touched me (not to mention the similarity of our names).


  6. Animal lover
    February 22, 2013, 6:27 am

    Look at the delight of saving a crippled animal and bringing his life back to normalcy and these are probably the same people who eat meat for food. Strange paradox this one.

  7. Brenda Kim
    South Korea
    February 22, 2013, 3:56 am

    Poor thing.
    Will this article be continued?

    Well , at first, she thought ‘what’s this”, she must have been puzzled with prosthetic two wings~

    Nature, sometimes it looks like so harsh for all the creatures ; to get meals, you have to kill some other thing.

  8. 25
    February 21, 2013, 9:17 pm

    this reminds me of dolphin tale because she prosthetic fins

    February 20, 2013, 11:43 pm

    I have been viewing YOU FOR 49 yrs..I will always be amazed at the beautiful coloring contrast stunning photgraphy.Sensational journalism!!