PHOENIX -- The 7-foot-long alligator floated motionless in the water, waiting for the prey to get just a few feet closer.
But if this had been a swamp, rather than a swimming pool in north Scottsdale, Ariz., any prey would surely have noticed the bright orange water wing wrapped around the gator's tail, preventing him from sinking.
The alligator is Mr. Stubbs, who is part science project, part human endeavor, and much more. He's also half-gator, half-rubber. The 11-year-old crocodilian now sports a 3-foot-long prosthetic tail, attached firmly with nylon straps. It replaces the original, which was bitten off more than eight years ago. As far as anyone at the Phoenix Herpetological Society knows, Mr. Stubbs is the first alligator to tolerate, if not sport, a prosthesis.
It will take months, however, before Mr. Stubbs learns how to properly use the tail. For now, handlers are happy with smaller milestones.
"The fact he doesn't try to bite it (the tail) is a good sign," said Russ Johnson, president of the Phoenix Herpetological Society. "Learning how to use it is going to take a lot of training."
The months-long project was overseen by someone well-versed in anatomy. Marc Jacofsky is executive vice president of research and development at the CORE Institute in Phoenix, which specializes in orthopedic care - for humans.
While visiting the Herpetological Society, Jacofsky was asked whether it would be possible to make an artificial tail for Mr. Stubbs.
"I looked and saw there was enough there that we could probably do something that wouldn't involve surgery," Jacofsky said. "I also liked the idea because it would improve his life. Our motto at the CORE Institute is 'Keep life in motion,' and this certainly fit in with that. I was on board."
Jacofsky estimated the project has cost the CORE Institute about $6,000 in donated labor and materials.
Mr. Stubbs had been a project since shortly after arriving at the center in May 2005. The then-3-year-old gator was one of 32 confiscated from the back of a truck pulled over near Casa Grande, Ariz., Johnson said. The Arizona Game and Fish Department was called as soon as the cargo made its presence known.
Game and Fish called the herpetological center, which takes in as many as 20 alligators a year confiscated in Arizona, Johnson said.
When he saw the gator missing a tail - without it he was only about 20 inches long - Johnson needed a few minutes to come up with a name. X-rays later would reveal crushed vertebrae where Mr. Stubbs' spine came to an abrupt end, proof the tail was bitten off. It probably was done by another alligator, Johnson said.
The center tries to re-home its alligators in zoos or wildlife refuges, but it was clear Mr. Stubbs wasn't going anywhere. Johnson and other handlers spent six months teaching him to paddle with his front feet, since the gator was missing his usual source of propulsion.
But Johnson wondered whether they couldn't do something more. About 18 months ago he pitched the idea of an artificial tail to Jacofsky, and a plan was set in motion.
Using cameras and a computer, Justin Georgi, an assistant professor in the department of anatomy at Midwestern University in Glendale, Ariz., studied Mr. Stubbs for weeks. Georgi studies alligator and reptile locomotion. At times he would attach reflective dots to the gator, whose jaws were secured with electrical tape before each session. The dots would form a 3-D computer model, allowing Georgi to see exactly how Mr. Stubbs got around.
Georgi used the research to devise the tail's specifications. It had to be buoyant, and weigh just seven to nine pounds. It also had to be flexible, so when Mr. Stubbs wiggled his rear stump, the tail would swing to propel him forward.
CORE Institute research associate, Sarah Jarvis, would craft the tail from silicone rubber. She had seen the movie "Dolphin Tale," based on efforts to fit a dolphin with an artificial tail. "The fact I could do the same thing for an alligator, I thought, 'How cool is that?' " she said. "That I would be the one to build it was just amazing."
With a mold and findings in hand, Jarvis used Body Double and Dragon Skin - two types of silicone rubber - to create a tail. It included a sheath that would fit over Mr. Stubbs' stub.
Jarvis painted the prosthetic so the gator would not have to go around with a translucent tail. She tried to match nature's colors, using green, black, brown and red. It came out a little grayish for her tastes, but was close enough.
The first fitting in January did not go as well as hoped, Jarvis said. The rubber straps had too much give and tended to dig into the gator's skin.
Still, the tail had an immediate impact. Without it, Mr. Stubbs tended to pick up his hind end and walk in circles. With its added weight in back, he walked in a straight line.
The team also was pleased that Mr. Stubbs accepted a rubber limb trailing him.
"The big question when we attached it was, what would he do?" Jarvis said. "Did he think it was attacking him? Was he going to bite it? But once we had it on, he didn't react at all."
Nylon straps were substituted and other minor adjustments were made. Soon, Mr. Stubbs showed no signs of irritation.
The tail didn't do too well in water. It took on water, sinking and taking the 35-pound Mr. Stubbs with it. So the workers added filler for a better fit and cut a small drainage hole halfway down the tail.
The more complex problem was Mr. Stubbs himself. The alligator had no idea how to swim with an artificial tail, often going into a barrel roll as he attempted to balance.
Johnson, who taught the gator to dog paddle, now must train Mr. Stubbs to swim like an alligator.
"I have to erase everything I've taught him," Johnson said. "He needs to know he has a tail and what to do with it."
The tail's biggest test was Wednesday, when the team gathered at the Phoenix Herpetological Society to see how Mr. Stubbs would do in the deep, treacherous waters of a backyard swimming pool.
Before he was let loose, a $3 water wing was attached to Mr. Stubbs' tail, since an abbreviated test earlier had him struggling to stay afloat.
This time, Mr. Stubbs floated easily. That was a good sign.
"It's all about balance at this point," Johnson said. "The fact he can float with no trouble is a big step."
The crew wanted to see the gator swim, so Johnson poked him with the bristled end of a pool broom. Mr. Stubbs briefly wriggled, the tail waving behind him. It was the moment everyone had been hoping for.
Johnson said it will be three to six months of training before Mr. Stubbs relearns what it's like to swim like an alligator. But with as many as 60 or 70 years ahead for Mr. Stubbs, based on a gator's expected life span, Johnson has plenty of time. More tails will need to be crafted in the future, because alligators grow throughout their lifetimes.
"He is going to have a long and happy life here," Johnson said. "Right now I want to get him to the point where he doesn't need that floaty anymore. That way the other gators will stop making fun of him."
Scott Craven, The Arizona Republic