The “REMUS SharkCam,” an autonomous underwater vehicle (AUV), navigated the waters off Mexico’s Guadalupe Island in November 2013. Outfitted with six high-definition video cameras, the AUV provided Woods Hole Oceanographic Institution engineers and scientists a panoramic view of the clear waters, which are a hotspot for great white shark activity.
Switched to the vehicle’s rear camera view, the observer can only hear the AUV’s whir and see a blue expanse. Suddenly, a great white strikes from below, taking the AUV in its mouth. The shark holds on for a few seconds, grappling with the inedible object before releasing it and swimming away.
What scientists know of great white shark predatory behavior is largely limited to surface observations. Off the coast of South Africa, near an island aptly denoted as Seal Island, scientists have captured footage of sharks launching themselves out of the water in bids to capture seals in their jaws.
However, great white shark behaviors in the deep remain a mystery.
“The sharks actually spend the bulk of their day at greater depths, and we wanted to know what they were doing,” says biologist Greg Skomal, who works with the Massachusetts Division of Marine Fisheries, to R&D Magazine. “In the case of Guadalupe Island…it’s been a little bit of a dilemma or mystery as to where the sharks have been feeding.”
Enter the REMUS 100, which in 2013 gave Skomal and colleagues an unprecedented view at great white shark predatory behaviors beneath the surface. According to Skomal, the REMUS technology has been used for years to map and survey the bottom of the ocean and assist in search and salvage operations, among other tasks. The 80 lb AUV can travel to depths of 100 m, and is outfitted with a variety of sensor data, including temperature and salinity instruments.
Results from the 2013 trip were recently published in the Journal of Fish Biology.
Over the course of six AUV missions, the team tagged and tracked four sharks, one male and three females, including the 21-ft female Deep Blue. Over 13 hrs of video data was collected. The AUV automatically navigated the ocean waters based on communications with the transponders tagged to the sharks.
“It’s really quite remarkable what these engineers have been able to achieve,” says Skomal.
However, the REMUS SharkCam also had its fair share of unanticipated interactions. Thirty interactions occurred with 10 sharks that were not being tracked. On nine occasions, the sharks aggressively bit the AUV’s rear, a behavior the researchers interpreted as predatory.
According to Skomal, the predatory behavior occurred at depths between 50 and 100 m.
The researchers believe the sharks use the clear waters to spot seals, but strike from below, where they’re shrouded by darker water.
The collected footage was subsequently used for Discovery Channel’s 2014 “Shark Week.”
Last month, Skomal and colleagues returned to Guadalupe Island for two weeks to continue their research. Keeping mum on the results from the recent trip, Skomal did say, “Anytime we go into the field with the technology, what we’re trying to do is advance it and take it to the next step.”
This time around, the researchers wanted to extend the duration and depth of their tracks, and track into the night. “We were successful on all accounts,” Skomal says.
The research team brought a new AUV, the REMUS 600, on the trip. According to Woods Hole Oceanographic institution, the REMUS 600 weighs 530 lbs and can travel to depths of 600 m.
The new video footage will be released in summer 2016 during Discovery Channel’s “Shark Week.”