Sea lions are mapping the ocean floor with cameras attached to their backs

The sea lions captured dozens of hours of footage — including of parts of the seabed that have never been mapped before. Researchers hope the information will inform conservation efforts for the sea lions, who are endangered, and shed some light on the seabeds, which remain a mystery.

The footage the sea lions captured revealed some “awe-inspiring” scenes, said lead author Nathan Angelakis — like sea lions flipping over rocks on the seabed to catch octopuses, or taking their pups to sea to teach them to forage. “It’s amazing the number of things we see,” he said in an interview.

Angelakis set out to use sea lions to map unfamiliar ocean habitats about four years ago as part of his PhD research. Seabeds are diverse and sensitive ecosystems, and we know little about how they operate. Typically, exploring them is done with remotely operated underwater vehicles, but deploying and operating those devices is expensive and can only be done in certain weather and terrain.

Australian sea lions, however, can be deployed at a lower cost, are able to record footage quickly across large areas that are difficult to access, and are less disturbed by bad weather. Recording benthic habitats — meaning habitats that occur at the bottom of the ocean — from the sea lions’ vantage point is also useful, the study says, because it “provides a novel way to understand the ecological value” of those habitats “from a predator’s perspective.”

Some habitats may be more valuable to certain sea lions than others based on different metrics than those valued by humans, like biodiversity, Angelakis said. By trying to use “anthropocentric human metrics to quantify [the value of a habitat], you may be missing important things,” he said.

Other scientists have used animals to study marine environments, including in South Africa, where white sharks were equipped with cameras to record kelp forest habitats. But the Australian researchers say they may be the first to use sea lions to map previously unmapped habitats of the continental shelf in southern Australia.

Between December 2022 and August 2023, the researchers traveled to Kangaroo Island and the western Eyre Peninsula, home to two colonies of Australian sea lions. There, they identified which sea lions to use in their research, focusing on healthy, female sea lions who were on their own, to minimize the disturbance caused in the colonies.

They sedated the chosen sea lions, while monitoring their vital signs, to install the cameras, which were stuck to small neoprene patches and glued to the sea lions’ fur. The process was approved by the University of Adelaide’s Animal Ethics Committee, as well as government bodies responsible for animal welfare and the environment, the study said.

The researchers then tracked the sea lions’ movements using GPS. When the sea lions returned to land between two and 10 days later to nurse their pups, the researchers got their cameras back — with 89 usable hours of daytime footage, captured at a depth of between 5 and 110 meters. The sea lions recorded a total of about 560 kilometers of seabed habitats.

Using female sea lions had two advantages, said Angelakis: They were sure to return to land eventually to nurse their pups, and they are especially important to the survival of the species because they take care of their offspring.

One of the limitations of the study is that the sea lions may have selectively chosen to travel to some areas or to forage in some habitats and ignore others, so there is a chance the researchers missed some other habitats, said Angelakis.

Katie Dunkley, a postdoctoral researcher in marine behavior at Cambridge University who was not involved in the Australian study, said the small number of sea lions used was not “an optimal way to quantify and fully capture habitat variations and consistencies.”

However, she said the experiment was a “proof of concept” for the novel use of sea lions to map ocean floor habitats. “This approach lets us see how animals and their behaviours directly interact with their habitat which is exciting,” Dunkley said in an email.

After analyzing the footage, the researchers were able to map unexplored parts of the ocean and identify the habitats that are particularly important to sea lions. Once they had some areas mapped using GPS and dive data, they used long-term oceanographic data and machine-learning models to predict the habitats present in other parts of the continental shelf, even in areas where the sea lions didn’t go.

The researchers hope this knowledge will contribute to efforts to conserve the Australian sea lion population — which has been listed as endangered by the International Union for Conservation of Nature. The study was financed by the Australian government and the Ecological Society of Australia.

Knowing which habitats sea lions favor and where those habitats are is “really fundamental information,” said Angelakis, because it can help inform decisions about which areas should be protected to help conserve the species.

The information is “completely key to having more meaningful conservation efforts in the future,” he said.