In October of last year, the National Aquarium welcomed a very exciting new resident to the Animal Care and Rescue Center: a juvenile green sea turtle that we named Kai.
Kai came to us from South Carolina Aquarium, where she arrived in 2018 after suffering injuries to her shell from a boat strike. Although her shell injury healed well, the experts at South Carolina Aquarium quickly realized that she was also having buoyancy control issues and was unable to dive. A CT scan showed the cause: a buildup of gas, which was created when the boat strike damaged the part of Kai's spinal cord that affects digestion, creating blockages in her gastrointestinal tract. These blockages led to excess gas, which causes Kai to be overly buoyant and interferes with her ability to dive.
When a sea turtle is unable to control its buoyancy, it cannot dive and forage for food like it normally would, meaning it would be unlikely to survive in its natural habitat. As a result, Kai—like many sea turtles with similar buoyancy control issues—was deemed non-releasable by the National Oceanic and Atmospheric Administration.
As she started to outgrow her space at South Carolina Aquarium, her caretakers began looking for a new home for Kai. The National Aquarium was chosen because of the extensive resources available to our staff that will allow us to continue Kai's rehabilitation and provide appropriate accommodations for the rest of her life.
Ever since Kai's arrival at our Animal Care and Rescue Center last year, our experts have been hard at work not only caring for her daily needs, but also working to find a solution to her buoyancy issues. When she arrived, our team attached weights to her shell with a turtle-friendly epoxy, which were adjusted frequently based on where the gas seemed to be located in her system. This weight system provided a counterbalance to the trapped gas and allowed her to swim and dive normally, but readjusting these weights was a constantly evolving process that involved staff from our husbandry and Animal Health teams working together to determine the placement of the weights and how heavy they needed to be.
This weight system was functional but not ideal because of the repetitive application required every month or so, and the poor visual aesthetic. Never satisfied to settle for the status quo, our experts began to create a more permanent solution: a weighted shell prosthetic that would be attached to Kai's shell. This prosthetic, created by our exhibit fabrication team, is designed to be safe, functional and naturalistic.
The first step in the developing the prosthetic was creating a mold of a portion of Kai's shell. The exhibit fabrication, husbandry and Animal Health teams then worked together to determine the proper placement of the shell weights inside the attachment to allow the weight to be dispersed evenly.
Our exhibit fabrication team decided to use sheets of lead for Kai's shell attachment weight material because they're both heavy and dense but also thin and malleable, allowing our team to shape them like an armored plate to fit Kai's shell without taking up much room. These sheets of lead are completely encapsulated between a bottom prosthetic, which is attached to Kai's shell, and a top prosthetic, which is painted to realistically match Kai's natural shell.
After extensive planning and experimentation, the exhibit fabrication team created Kai's first prosthetic shell attachment, which weighed 11 ounces. The attachment was applied to Kai's shell on April 19, and although it appeared at first that the prosthetic was helping her swim to the bottom of her habitat, it didn't last long. After 35 days, it began to crack and Kai's buoyancy issues returned. The team believes that water or air may have gotten underneath the prosthetic.
The attachment was easily removed, and the team went back to the drawing board. A second prosthetic was created and attached to Kai's shell at the end of May. This version of the prosthetic is slightly thicker and heavier than the first—weighing in at 15 ounces—and was applied to Kai's shell with a two-part epoxy that our experts hope will keep air and water from getting in between Kai's shell and the attachment again.
Although this second attachment hasn't cracked like the first, Kai is still overly buoyant and is not able to rest on the bottom of her habitat like a sea turtle typically would. This could be a behavioral response since she's dealt with her buoyancy issues for almost four years and may need to learn how to rest on the bottom, but our team will continue to create new versions of the prosthetic, increasing the weight incrementally until it's just right and allows Kai to swim and dive naturally.
"It's a work in progress—and we knew it would be because there's not a lot to go off of from other institutions." Ashleigh Clews, Animal Care and Rescue Center curator, explained. "But we're committed to figuring out the process, no matter how long it takes."
While our experts continue to work to create the perfect shell attachment prosthetic, our husbandry and Animal Health teams continue to care for Kai's day-to-day needs. According to Ashleigh, Kai is doing great—she has a healthy appetite, her target training is going well, and she's always interested in visitors to her space during donor tours of the Animal Care and Rescue Center.
Stay tuned as we continue to share updates on Kai's journey and our team's progress in creating her prosthetic shell attachment!