Researchers design new camera tag for white sharks
Scientists know that white sharks are important ocean predators, but many aspects of their lives are still a mystery. For example, each winter, large white sharks leave the California coast and swim halfway to Hawaii, congregating in an area known as the "White Shark Café." The males then repeatedly dive hundreds of feet below the surface. Researchers speculate that the sharks might be chasing prey or mating.
By attaching a miniature video camera tag to a white shark's fin, researchers at the Monterey Bay Aquarium and the Monterey Bay Aquarium Research Institute (MBARI) hope to collect video footage that shows–for the first time ever–exactly what the sharks are doing down there.
The project is the brainchild of white-shark expert Sal Jorgensen, a research scientist at the Monterey Bay Aquarium, who has studied these amazing animals since 2005. During this time, Jorgensen has used several types of electronic tags to document previously unknown aspects of the sharks' lives. Some recorded information about their geographic location and the depth of their dives. Other tags emitted high-frequency clicks that allowed sharks to be tracked when they approached listening stations close to shore. A third type was a three-dimensional motion-sensing tag designed to be swallowed by a shark to record its feeding activity before being naturally regurgitated and delivering its stored data.
Many researchers have attached video cameras to sharks in the past–including our colleagues at Stanford University, with whom we're collaborating on studies of adult white sharks off California's Central Coast. But these tags only needed to stay on for a few days to document feeding and other behavior in the California Current.
The new camera tag would need to stay on for several months. Faced with multiple design challenges, Jorgensen decided to partner with engineer Thom Maughan at MBARI, the aquarium's sister institution.
"It's easy for a biologist like myself to dream up questions we'd like answered with technology," Jorgensen says, "but somebody has to actually push the envelope and make that happen. And that's where the top-notch ocean engineers at MBARI come in."
Jorgensen and Maughan came up with a long list of engineering requirements for the camera tag. It had to be small and easy to attach to a shark's dorsal fin. It had to stay on the shark for up to nine months, until the shark returned to the California coast from its offshore location. It had to survive dives as deep as 1,000 meters (3,300 feet), and bursts of acceleration to speeds up to 25 miles an hour. It needed a battery that could power 10 hours of video recording, as well as internal data processing and storage systems. And it had to be programmable, so it would only collect video when a shark made repeated dives at the "White Shark Café"–the behavior Jorgensen is trying to understand.
Reflecting on the technical challenges involved in making all of this work, Jorgensen described developing the Café Cam as very much "like a mission to Mars."
For his part, Maughan loves engineering challenges like this. "Some of our engineers heard about Sal's proposal and thought it was nuts," Maughan said. "But I thought I could see a way to do it using off-the-shelf parts."
Working with other engineering partners, including Desert Star and Custom Animal Tracking Solutions, Jorgensen and Maughan have developed a prototype whose camera, processor, and battery can capture video footage of great white sharks in the remote Pacific Ocean. The team has conducted one- to five-day tests of the Café Cam on sharks in coastal waters, making improvements to the camera design each time. They are still trying to work out the best way to attach this tag to a shark's fin.
This summer, Maughan hopes to attach a tag to one of MBARI's underwater robots (an autonomous underwater vehicle, or AUV), which will make repeated deep dives to simulate the behavior of white sharks in the wild. This will allow the researchers to test their software that turns on the camera only at key moments during the shark's dive.
In December or January, when most white sharks are leaving the California coast, the researchers will travel to one of the white shark hotspots such as the Farallon Islands, offshore of San Francisco. There they will try to get the sharks to swim close to their small boat and quickly clip the camera tag onto the shark's dorsal fin.
Ideally the tag will stay on the fin and remain in sleep mode until the shark reaches the White Shark Café a month or so later. At the café, male sharks make repeated dives down to 250 meters (800 feet), up to 150 times a day. The camera would be programmed to start recording during these dives when sudden changes in swimming patterns are detected, and pause when routine swimming resumes.
When the shark heads toward the surface again, the camera would go back into sleep mode, remaining that way until the shark returned to the California coast in August or September. At that point it would automatically release itself from the shark's fin and send a signal by satellite to researchers on shore, who would take a boat out to recover it. Only then could researchers watch the recorded video–and see what the shark saw.
Once they have demonstrated that the camera tags work, the researchers plan to make their design open source, sharing what they've learned with anyone who wants to build similar tags.
In the meantime, they are looking forward to seeing a white shark's perspective of a rendezvous at the White Shark Café.