Across much of the planet, an aquatic mystery leaves scientists in the dark.
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“For most of the ocean, we don’t know what the bottom looks like,” said Nathan Angelakis, a PhD student at the South Australian Research and Development Institute (Aquatic Sciences) and the University of Adelaide.
So Angelakis and his colleagues strapped video cameras to sea lions, which routinely dive 300 feet (90 meters) below the surface while hunting, to study parts of the ocean floor around Kangaroo Island and Olive Island off Australia’s southern coast that scientists had never seen before. Their images show meadows of lush seaweed and rugged rocks covered in coral.
Researchers hope the dives will help scientists better understand how sea lions use these habitats and how humans can manage ecosystems visited by endangered Australian sea lions.
Scientists typically map the seafloor with remotely operated vehicles and cameras towed by underwater vessels, which can be challenging and expensive.
With approval from conservation authorities, the researchers approached eight sea lions on land and administered a sedative. While the sealions were stunned, they taped patches of wetsuit material to the animals’ backs and heads, then attached small cameras and devices to track speed and location.
When the sea lions woke up, they headed into the water. After a few days, they returned to their pups on the shore and the researchers removed the devices and reviewed the images.
Angelakis said perhaps the most exciting scene was captured by a sea lion named Daphne. “She was carrying her pup out to sea, and that’s the first direct evidence we’ve collected of Australian sea lion mothers teaching or passing on their foraging skills to their pups,” he said.
The scientists trained a machine learning model on 89 hours of video, along with GPS data and environmental information, including surface temperature and the amount of plant matter in the water. The model can predict the likely habitats of unexplored parts of the surrounding ocean.
“The more we learn about them, the better chance we have of protecting them,” said Dan Costa, a professor of ecology and biology at the University of California, Santa Cruz, who was not involved in the study. “It’s a really interesting animal, so it deserves a place in the world.”
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