Prototypes for Pinnipeds: Small-Scale Manufacturing at The Marine Mammal Center

by Erin Hanson
- Dec 7 2015 - 6 min read
Two elephant seal pups interact in a pen at The Marine Mammal Center. Courtesy The Marine Mammal Center.

Working at a nonprofit often requires extra ingenuity to make up for lack of funds or resources. For the staff at The Marine Mammal Center in Sausalito, California, that means creating tools, otherwise commercially unavailable, that combine elements from both human and small-animal medicine.

And for veterinarian Dr. Greg Frankfurter, specifically, it’s channeling his inner MacGyver to launch a small-scale manufacturing run of sedative darts for animals in distress.

Dr. Greg Frankfurter performs an intubation on patient Cappy. Courtesy The Marine Mammal Center.

Those animals are mainly seals and sea lions (also called pinnipeds) entangled in trash, plastic, fishing line, nets, and other debris along the California coast. The Marine Mammal Center, a veterinary hospital and research facility that has rescued 20,000 marine mammals since 1975, responds to hundreds of calls each year regarding sick, orphaned, and injured animals along 600 miles of coastline. The Center is handling a dramatic increase in sea lion and seal strandings this year—more than 1,747 rescued by mid-November—due largely to warmer ocean waters that are affecting the distribution of fish throughout the animals’ feeding range. Many of these animals end up stranded on beaches far from their regular habitat. The Center rescues and cares for those animals with the help of world-renowned veterinarians and more than 1,000 volunteers. But recovering the animals is a challenge in itself.

The Center uses tranquilizer darts—much like those for terrestrial animals—to sedate entangled animals before recovery, a relatively new practice thanks to a sedative drug combination approved in 2013. Many entangled animals are otherwise healthy and naturally resist capture, making it difficult to recover them. Although sedation is a welcome improvement to simply capturing with nets, animals darted near water tend to then dive into the water. Pinnipeds can drown if they fall asleep in the water, so quick recovery procedures are paramount.

“It takes about five to 10 minutes for that drug combination to take effect, and we needed some means to track these animals from the point where we dart them until they’re actually asleep,” Frankfurter explains. “Normally, what people use for tracking land animals is a transmitter that uses radio waves, but radio waves don’t transmit under water. That’s where we figured out that we could attach this acoustic transmitter, instead, to the dart, and then we could use a hydrophone to track those animals.”

A self-described tinkerer, Frankfurter admits that his initial assumptions—simply building a tube to house the acoustic transmitter and affixing it to the prefabricated dart/drug-containment vessel—were naive. A fully functional dart needs to not only detach from the drug housing but also withstand the pressures of flight and impact. “I started trying to just build the piece from an existing piece of tubing, essentially,” Frankfurter says. “We had something that was working, but it took a long time to make and wasn’t very effective. We needed something that was going to be stable, easy to build, and something we could reproduce.”

Visitors get an aerial view of marine-mammal patients in the rehab pens at The Marine Mammal Center. Courtesy David Wakely/The Marine Mammal Center.

So Frankfurter made his way to TechShop in San Francisco in search of additional expertise to perfect his acoustic dart. There, he learned how to model his design in Autodesk Inventor, easily creating multiple iterations that he could then 3D print and test. “Often, I’d shoot them, and they would explode immediately, and I would be back to square one,” he says. “But the nice thing about 3D printing is, it’s easy to make little tweaks and just print it again, as opposed to if you’re just building the piece from scratch.”

Fortunately, a pro bono partnership with a design team from Autodesk and Pier 9 enabled Frankfurter to take those initial prototypes to the next level, designing and 3D printing two functional models. Each of those models comprises four main parts: the drug-containment vessel, the acoustic transmitter, the housing that connects those pieces, and a tail piece to make it fly straight. To test the darts, Frankfurter fired them at targets to validate their integrity after multiple impacts. He and a colleague also shot slow-motion video to ensure the darts were flying correctly. And he sent the prototypes to a third-party lab to confirm that the transmitter casing wasn’t damping the sound, which needs to be audible from roughly a half-mile away.

The final acoustic dart. The acoustic transmitter is housed within the 3D-printed tubing. Courtesy Benjamin Shaw.

Succeeding in those tests, the prototypes are now working darts in use at the Center. But the true test is, of course, a real rescue in the field. When the Center receives calls about entangled animals, the six-person response team includes trained veterinarians, animal handlers, boat drivers, and other professionals with marine-mammal experience. They try to get within approximately 40 yards of the animal before firing the dart with a CO2 gun that is similar to a paintball gun (but definitely not a paintball gun). The dart penetrates the animal about an inch to an inch-and-a-half to get through the thick layer of blubber and inject the drug into the muscle; it’s later removed by making a small incision to free the barb.

“The first time we darted an animal with the acoustic transmitter, we left here about 5 o’clock in the morning to drive down to where we tend to see the most entangled animals, which is in the Monterey region,” Frankfurter says. “Immediately, we went out and found an entangled animal. So we got everything all set up, darted it, and it immediately dove into the water. We were able to track it using the hydrophone and recovered the animal in about 10 to 15 minutes. That animal was successfully brought here, disentangled, and released.”

With a viable acoustic dart now in use, the question becomes how the Center moves from small-scale manufacturing to volume manufacturing. The cost to print one of the darts is about $25 (not including the cost of the drug-containment vessel or the acoustic transmitter). Although the Center needs about 15 to 20 darts per year at its current response rate, it hopes to not only expand its response ability but also make the acoustic darts available to others.

Volunteers prepare carriers to transport California sea lion pups to their release site. Courtesy Ingrid Overgard/The Marine Mammal Center.

“We hear about entangled sea lions and fur seals all over the place, so we’re really trying to get a product into people’s hands that is easy to use and something that most people can either print or build on their own,” Frankfurter says, noting those users need the veterinary expertise and training to use them. “As it is right now, we’ve consulted with people in Mexico, people in Chile, and people in Australia who are interested in using this technology to disentangle animals in their areas, as well.”

As for Frankfurter, he’s been applying his newfound design skills to other marine-mammal uses, including a 3D-printed plastic flipper tag—yet another example of that MacGyver-esque ingenuity. “I learned a lot out of the design process, being able to use the Inventor software that I’ve now used for a variety of other projects, as well as just learning a lot more about 3D printing,” Frankfurter says. “But really for me, the best part is making something that we can actually go out and use. At the end of the day, if I can disentangle one animal and get it back out there, that’s the best thing.”

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