In 2021, the New England Aquarium in the U.S. state of Massachusetts began surgically implanting acoustic tags in rescued loggerhead sea turtles before returning them to the ocean. Four years on, these tags are providing a rare peek into where rehabilitated turtles travel.

“Surgically implanted acoustic transmitters have been used for many years in many other species, especially fish. But to our knowledge, we are the first to surgically implant them in turtles,” Dr. Charles Innis, a veterinarian and senior scientist at the New England Aquarium, told Mongabay by email.

The Aquarium’s Sea Turtle Hospital has been rescuing injured sea turtles that wash ashore in New England for more than 30 years.

Some sea turtles get injured in boats collisions or entanglements with fishing gear, Innis said. Many individuals also suffer from “cold stunning, a hypothermia-like condition that causes turtles to become very weak,” he added, which results in them not being able to swim and washing up on the beach. “Many are already dead when they are found. The ones that are still alive often have pneumonia or other serious infections,” Innis said.

Conservationists have been rescuing and releasing sea turtles for decades. Yet “there remain outstanding questions on the outcomes of rehabilitated turtles, including immediate and long-term post-release survivorship and integration into wild populations,” Kara Dodge, research scientist at the New England Aquarium, told Mongabay by email. “To objectively evaluate the contribution of rehabilitation programs, we require post-release monitoring data to answer these questions.”

Dodge said loggerhead sea turtles (Caretta caretta) can live up to 80 years. While external tags fall off or get damaged more easily, capturing only a few years of data, surgically implanted acoustic transmitters “can provide data for up to a decade,” Dodge added.

After receiving a federal permit in 2021, the researchers implanted acoustic transmitters inside 14 rehabilitated loggerheads at the Sea Turtle Hospital.

The transmitters give off unique ultrasonic pings in water. “The turtles need to swim within range of a receiver to be detected, and then the receiver owner must be willing to share that detection data,” Innis told Mongabay. “But we are involved with a large network of collaborators that collectively have many receivers, so we are aware of thousands of detections of our turtles so far.”

The team has received nearly 6,000 turtle detections along the U.S. East Coast, from Massachusetts to Florida, most of them in continental shelf waters.

The data show that all the turtles have survived beyond the first year since their release. Some are even returning to New England waters in the summer and fall. This “was surprising and tells us this area may be more important for loggerheads than we previously thought,” Dodge said.

The team expects to continue receiving data from most tags through 2025, and a few through 2032.

Banner image of a loggerhead sea turtle released in 2021, courtesy of Vanessa Kahn/New England Aquarium.