Pin the Tail on the Dolphin

How to attach a prosthetic flipper.

Download the MP3 audio version of this story here, or sign up for The Explainer’s free daily podcast on iTunes.

A baby dolphin with a stump for a tail may get a prosthesis, according to her caretakers at Florida’s Clearwater Marine Aquarium. Experts will meet soon to talk about how a prosthesis for “Winter” might be held in place. How do you pin a tail on a dolphin?

With straps or a tight-fitting sleeve. There’s only one dolphin in the world with a rubber tail, and she got hers a couple of years ago. “Fuji” wears a $100,000 device made from rubber, reinforced plastic, and metal screws. The first design for the prosthesis used belts to attach it to Fuji’s backside, but the material scratched her skin and had to be abandoned. The second version—designed by the sculptor Kazuhiko Yakushiji—is held in place by a plastic covering that fits over the tail stump. (Fuji wasn’t crazy about either version. Trainers had to prepare her by first attaching a rubber band or a piece of fabric to her stump.)

The rubber-tail designers had an easier time with Fuji than they will with Winter. Fuji needed a prosthesis because a wasting disease had eaten away about three-quarters of her tail flipper. She still had a nubbin on the end of her tail that could be used to secure the device, though. No such luck with Winter—she lost her entire tail to a crab trap.

The designers might try to strap on the tail with nylon. The U.S. Navy already uses this technique with the minesweeping dolphins in its Marine Mammal Program. These animals wear radio beacons attached to their pectoral fins in case they get lost on a mission. The beacon sits on a nylon belt with a plastic clip that’s fitted for each dolphin. The belt comes with a special link that slowly dissolves in seawater. If the dolphin gets so far from the Navy ship that it’ll never be recovered, the belt (and beacon) eventually fall off and leave the animal unencumbered in the wild.

Military dolphins also carry special equipment with their noses and mouths. In the 1980s, the Marine Mammal Program developed a cup system that could be placed over the animal’s nose. The device tows a long, thin “banana float.” When the dolphin finds an underwater mine, it’s trained to jerk its nose out of the cup, which triggers the banana float to break open. One part attaches to the mine while the other sends a marker up to the surface.

Starting with the Gulf War, dolphins have been using radio transmitters instead of banana floats. These attach to hard rubber biteplates that each animal carries in its mouth. By pushing the front of the biteplate against a mine, the dolphin can deposit the tracking device.

Dolphins and sea lions are also trained to use biteplate systems to mark or capture waterborne intruders. When they spot an enemy diver underwater, they can poke him with a biteplate to release a strobe-light beacon. They might also carry C-shaped clamps that snap shut on a diver’s leg. Once a dolphin cuffs the diver, it swims back to its handler with a tether line.

Got a question about today’s news? Ask the Explainer.

Explainer thanks Tom LaPuzza of the Space and Naval Warfare Systems Center.