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Experimental study on artificial flukes for a Bottlenose dolphin “Fuji”

2012,4,1 category:Report


In Fall 2002, a female bottlenose dolphin (Tursiops truncatus) “Fuji” lost 75% part of her flukes because of an unknown disease. Would it be possible to make the world’s first artificial flukes? Would the flukes allow her to swim and jump again as before? For scientific research, we started this experimental study on artificial flukes in cooperation with Bridgestone Co. Japan’s largest tire maker.

About “Fuji”

Fuji was caught in Kawana, Itoh, Shizuoka prefecture and transported by air to Ocean Expo Park, Okinawa in November 1976.
Her estimated age is 42, approximately 271 cm in length and weighs 211 kg as of 2011. She is a great mother of three children. Curently, her children Conny (female, born in June 9, 1989), and Chao (male, born in November 18, 1995) is living in the park with her.

The unknown disease on her flukes

Fuji has suffered from the unknown disease since October 16, 2002. She had symptoms such as loss of appetite, discoloration and necrosis in distal parts of flukes. The blood analysis and biochemical examination revealed she had a complex of infection and circular insufficiency. We excised the diseased parts by electronic surgical knife on October 25 and on November 7. With antibiotics and transfusion for 60 days, she thoroughly recovered from the disease, although she lost 75% of her flukes.

The first step of the project

This project first started when our veterinarian consulted for assistance to Bridgestone Sports Co.,Ltd. on November 27, 2002. One week after this contact, Bridgestone Co. agreed to cooperate in the project. To compensate her lost flukes, we officially started to develop artificial flukes in May 2003.

The goal of this project was to give scientific answers for the following questions:

We started this project not from the compassion for Fuji only, but for a scientific experiment. Fuji did not have any problem living in the park. It was reported that wild cetaceans without flukes appeared.

How to make artificial flukes

The first flukes cast was made of silicon on July 5, 2003. We developed the first model (40° hardness silicone rubber, 48cm wide, 30cm long, 2000g, Photo①) on September 12. But when tested on Fuji, it did not work well because of the attachment problems. The design of attaching belts caused scratches on her flukes. After reconsideration, we decided that we needed a more accurate mold of Fuji’s flukes and ordered to a famous acrylic sculptor. (Photo②)
At the beginning of March 2004, the band type second model (70° and 40° hardness silicone rubber, 70cm wide, 25cm long, 2200g, Photo③) was made. Since the band type receives greater water resistance, it was necessary to be improved into the cowling type. In mid-June of 2004, the cowling type (70° hardness silicone rubber, containing carbon cross reinforced plastics, 70cm wide, 25cm long, 2200g) was tested on Fuji. Observing the movement of the flukes same as other dolphins in the park, this model was confirmed to be functionally useful.
At this stage, artificial flukes were mechanically strong enough for swimming but not enough to sustain physical momentum of jumping. After the attempt to improve the material for the reinforced plastics and silicon rubber strength, we developed the flukes with stronger natural rubber material. In mid-Dec of 2004, the cowling type olympic model (70° hardness silicone rubber, containing cfrp, 70cm wide, 25cm long, 2500g, Photo④) was made in cooperation with Bridgestone Cycle Co., Ltd. It makes Fuji to jump 3m at the highest point. Curently we use the cowling type YBECC model (natural rubber, containing fabric reinforced plastics for conveyor, 70cm wide, 35cm long, 2500g, Photo⑤), which enable to wear for a long time by adopting a durable natural rubber materials. This model allow mass production by hot pressing method with exclusive alminium mold and receive a permanent supply.

The Institute of Cetacean Research and our aquarium collaborated to analyze the swimming speed of the dolphin and demonstrate a significant benefit of such artificial flukes.

Training of Fuji

Rehabilitation training (1st stage)

In nature, the dolphins dislike to be attached a foreign object on their body. Fuji initially rejected artificial flukes. Therefore, we phased attachment training for Fuji.
For dolphins’ health control, it is very important to accustom them to the husbandry training. They need to allow the trainers to insert a thermometer into their anus and they need to lift their flukes out of water for taking blood samples. These trainings make it easy to check dolphins’ health conditions. The rehabilitation training of Fuji was similar to the husbandry training.
1) First, we taught Fuji to show her flukes at the trainer’s sign and let the trainer touch the flukes.
2) When she was accustomed to being touched, a piece of cloth or rubber band was attached to her flukes.
3) We continued this training patiently till Fuji get used to it. Finally, attaching artificial flukes was attempted.

Training was not easy as it might sound. At the beginning of training, Fuji had strong reaction to artificial flukes. She would struggle out of the trainer’s hand and swim away.
However, the trainers took time to train her patiently. We never forced the training to her aiming she became perfectly fine with the flukes.

Rehabilitation training (2nd stage)
When she became comfortable with artificial flukes, we started the next stage of the rehabilitation training. The first step of this stage was swimming training with the flukes. Even though she got a new flukes, she did not start swimming immediately. She was used to just floating in the pool and being hand-fed by the trainers. She got tired easily as we often saw her resting.
1) Trainers threw fish into the pool to let Fuji swim after the food.
2) Two trainers called Fuji using underwater bells at the both ends of the pool. She was trained to swim back and forth between them.
3) Next step was to make Fuji swim from 4m deep tank into 50cm shallow pool. In the shallow pool it was much easier for the trainers to attach the flukes to Fuji.
This last step took a long time. The shallow pool was an unfamiliar place for Fuji so she was scared. Though she could enter to the shallow pool, she felt uncomfortable and swam back to the main tank soon.

Trainers attracted Fuji to the shallow pool with the food. Now she can not only let trainers attach artificial flukes but also receive health check in the shallow pool.
4) When she got used to wearing the flukes, we began to train her to jump and touch a target. The training was started without attaching artificial flukes. When she learned to jump without the flukes, we started training with the flukes attached.
Fuji became able to jump strongly and touch the target. Now she can also do high jumps.

You can meet Fuji wearing artificial flukes about 4 hours a day at the Dolphin Lagoon Pool.

Future Plans

So far we have made 38 artificial flukes of 8 versions. However, the newest version is not yet perfect. We still continue our research for better materials and way of attachment. We are still trying out new ideas. At the same time, the research for artificial flukes might give us an insight into the function and mechanism of the natural dolphin flukes.
In order to achieve our goals, we would like to get more people involved and ask for diverse opinions.
Please come and visit Fuji at the Dolphin Lagoon Pool. We welcome your visit and will be happy to answer your questions.
Artificial flukes were registered as a patent in December 2009. (Patent No. 4421491)

Despite the effort of the treatments, Fuji died on November 1st (Sat) 2014, 2:45 p.m.
We would like to thank you for encouraging Fuji all time.