In search of food, the Australian sea lions glide and dart through underwater tunnels, over seagrass meadows and rocky reefs and dance with dolphins around a giant bait ball of fish – all the while capturing the action with a camera they carry on their backs.
“I can watch this stuff for hours,” says Prof. Simon Goldsworthy. “It’s like the best slow TV ever. You just don’t know what you’re going to see next.”
The Australian sea lion is in danger. They were hunted until the early 20th century. Commercial fishing nets and traps now pose a greater threat.
Their numbers have plummeted by 60% over the last 40 years, leaving only about 10,000 individuals left, mostly scattered across 80 breeding grounds along the south and west coasts of Australia.
Goldsworthy’s “Slow TV” is the result of a new effort to use sea lions to map the sea floor – and their own habitat – by sticking satellite-tracking cameras on their backs.
So far, eight female seals from two seal colonies have shot nearly 90 hours of footage covering more than 500 km, helping scientists map 5,000 square kilometers of habitat. The sea lions have mapped rocky reefs and seagrass beds along the continental shelf, showing people the places that matter to them.
With this information, conservationists can have a much clearer idea of ​​how to protect the country’s only endemic seal.
Goldsworthy of the South Australian Research and Development Institute (SARDI) has been studying the rapidly disappearing marine mammal for 25 years, but he says the cameras will fundamentally change things.
“Information has been so hard to come by because they feed on the sea floor,” he said. “Now we’re getting these amazing, exquisite details. They’re giving us a glimpse into their world that we didn’t have before.”
“Just as humans know our roads, sea lions know the sea floor in great detail for hundreds of kilometers and build up this knowledge over time. They have a mental map of their surroundings and will guide you to places that are of great importance to them.”
Mapping and studying the seafloor habitat is an expensive and laborious process, often involving towing cameras behind boats or placing baited cameras underwater. Sea lions are faster, cover larger areas, are unaffected by the weather and do the work for free.
Until now, sea lions from colonies on Olive Island and Seal Bay in South Australia have done this work.
Nathan Angelakis, a PhD student at the University of Adelaide and SADI, said the video maps critical habitats as well as previously unexplored areas of the seafloor.
He said: “We used the instruments on adult females so that we could collect the equipment a few days later when they returned to land to nurse their young.”
To test the cameras, the scientists first had to attach them. After giving the sea lion a tranquilizer, the researchers administered a short-acting anesthetic through a breathing mask while they taped the camera to a piece of cloth, which was then glued to the sea lion’s fur with resin. The cloth stays on the fur and falls off during the next molt.
One of the revelations from the footage, Goldsworthy said, came when a mother and her pup went hunting with a camera attached. The female showed the pup where to go and how to hunt.
The team also found that individual animals have different tastes – some prefer to eat cod in large quantities, others target octopuses, stingrays or squid, and still others dig up their prey by rolling their noses and fins over rocks.
A study funded by the Australian Government’s National Environmental Science Program and the Ecological Society of Australia describing sea lions’ camerawork was published in the journal Frontiers in Marine Science.
