For the first time ever, scientists have had help from sea lions in mapping the ocean floor. And the marine mammals have done their job well, capturing six different marine habitats, including algal meadows and reefs, that make up South Australia’s seabed, researchers report in a recently published study.
For much of the planet’s ocean, what the seafloor looks like is still a mystery. Conventional surveys using specialized underwater equipment and vessels require large crews as well as good weather, which makes mapping wide areas challenging and expensive, Nathan Angelakis, lead author of the study and a doctoral student at the University of Adelaide, Australia, told Mongabay in an email.
As an alternative, the researchers fit small, lightweight video cameras and movement trackers on eight adult female Australian sea lions (Neophoca cinerea). The team had two goals: to understand the habitats and food that are critical for the endangered species, and to map the little-known seafloor off southern Australia’s coast.
The sea lion videographers ended up capturing more than 89 hours of data and footage, recording around 560 kilometers (350 miles) of the continental shelf, at depths of 5-110 meters (16-360 feet). On reviewing this data, the scientists saw that the sea lions eat a wide variety of fish, small sharks, stingrays and octopuses, either by flipping rocks over, digging up sand, or ambushing schools of fish. “We were also lucky enough to capture footage of a mother taking her pup on a trip to sea, providing the first direct evidence we have that Australian sea lion mothers pass on their foraging skills to pups,” Angelakis said.
The team also identified six kinds of seabed habitats from the videos. They combined this habitat data at different locations, with long-term oceanographic and environmental data for those locations, to then predict habitats for areas that the sea lions didn’t visit. “This allowed us to map and predict habitats on the seabed for more than 5,000 square km [1,930 square miles] of previously unexplored seabed across the continental shelf in southern Australia,” Angelakis said.
Sea lion swimming through invertebrate reef, sponge garden, macroalgae reef, bare sand, and invertebrate boulder habitats. Video: Angelakis et al. 2024.
Katie Dunkley, a marine researcher at the University of Cambridge, U.K., who wasn’t involved in the study, told The Washington Post that while the number of sea lions used in the study was small, the study was a “proof of concept” showing that sea lions can help us map the ocean floor.
Angelakis added that such baseline knowledge of seabed habitats and the conditions that influence their distribution is crucial “for understanding how they may be impacted by human activity.” Furthermore, the study improves our understanding of the marine habitats that are crucial for the rapidly declining Australian sea lions, he said.
“This information is fundamental for better conserving and managing their populations in the future,” Angelakis added.
Banner image of Australian sea lion by John Turnbull via Flickr (CC BY-NC-SA 2.0).
Credits
