The Australian sea lions glide and dart through underwater tunnels, over seagrass beds and rocky reefs, searching for a meal and dancing with dolphins around a giant bait ball of fish – all the action captured by a camera stuck on their back.
“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 trouble. They were hunted until the early 20th century. Commercial fishing nets and pots have proved to be a more modern threat.
Numbers have crashed by 60% in the past 40 years, leaving only about 10,000 of them mostly spread thinly across 80 breeding sites along Australia’s south and west coastline.
Goldsworthy’s “slow TV” is the result of new efforts to employ the sea lions to map the ocean floor – and their own habitats – by sticking cameras with satellite tracking to their backs.
So far, eight females from two seal colonies have filmed almost 90 hours of footage across more than 500km, helping scientists to map 5,000 sq km of habitat. The sea lions have mapped rocky reefs and seagrass meadows along the continental shelf, and shown humans the places that are important to them.
With that information, conservationists will have much clearer ideas on how to protect the country’s only endemic seal.
Goldsworthy, of the South Australian Research and Development Institute (SARDI), has been studying the fast-disappearing marine mammal for 25 years. But he says the cameras are a gamechanger.
“Information has been so elusive, because they’re feeding at the bottom of the sea,” he said. “Now we get this amazing, exquisite detail. They’re giving us a window into their world that we haven’t had before.
“Just like humans know our streets, the sea lions know the sea bed in intimate detail for hundreds of kilometres and they build up this knowledge over time. They have a mental map of their environment and they are leading you to places of profound significance for them.”
Mapping and understanding the seabed habitat is an expensive and laborious business, often done by towing cameras behind boats, or by leaving baited cameras underwater. The sea lions are faster, cover more ground, are untroubled by the weather and do the work for free.
So far, sea lions from colonies at Olive Island and Seal Bay in South Australia have been doing the work.
Nathan Angelakis, a PhD student at the University of Adelaide and SADI, said the video was mapping critical habitats as well as previously unexplored areas of the seabed.
He said: “We deployed the instruments on adult females so we could recover the equipment a few days later when they returned to land to nurse their pups.”
To trial the cameras, scientists first had to attach them. After darting the sea lion with a sedative, researchers gave them a short-acting anaesthetic through a breathing mask while they stuck the camera on to a piece of fabric, which was then stuck with resin on to the sea lion’s fur. The fabric is left on the fur, to fall off at the next moult.
One revelation from the footage, Goldsworthy said, came when one mum took her pup out to hunt while she had a camera attached. The female was showing the pup where to go and how to hunt.
The team has also discovered that individual animals have different tastes – some like to eat lots of cod, others go for octopus, sting rays or cuttlefish, while others dig out prey by rolling over rocks with their noses and flippers.
A study outlining the sea lions’ camera work, funded by the Australian government’s National Environmental Science Program and the Ecological Society of Australia, was published in the journal Frontiers in Marine Science.
