Northern elephant seals use a deep-sea research sonar as a lunch ring.

According to a new study conducted by researchers from the University of Victoria, northern elephant seals have been repeatedly captured on camera in the deep Pacific Ocean, using the Ocean Networks Canada Observatory's (ONC) sonar as a lunch call to get food for their next fish feast.

The study, published in the journal PLOS ONE, provides a unique, first-ever visual look at the behavior of elusive deep-sea mammals with an emphasis on their complex nutrition strategies, prey preferences, as well as leisure habits.

In total, at least eight male elephant elephants between the ages of 4 and 7 were seen on camera and found with hydrophones during several visits to the 645-meter-deep research site in Barkley Canyon, located along the ONC NEPTUNE Underwater Cable Observatory off the west coast of British Columbia between 2022 and 2023.

The conclusions came almost by chance; UVic, Instituto de Ciencias del Mar (ICM-CSIC), a research institute in Barcelona, and ONC researchers studied the effect of light and bait on the behavior of fish and invertebrates in Barkley Canyon using a high-resolution camera and an acoustic imaging sonar. , hydrophone, a pair of LED lights and automatic bait release.

But viewing the camera, acoustic images and sound data revealed unexpected visitors.

"We suspect that seals have learned to associate the sound of the sonar coming from the research instrument with the presence of food - a phenomenon known as the "lunch bell" effect.

"It seems that seals use this sound to determine the location of prey, and can use fish disturbed by camera light, in particular, hunting sable, their favorite food, as seen in the video," says Eloise Fruin-Mui, the lead author of the publication.

Fruin-Mui, a visiting researcher at UVic in the Faculty of Biology and an associate professor at the University of Miami, collaborated in this study with Francis Juanes, Professor of Biology at UVic and the Department of Fisheries Research at Liber Ero, as well as Associate Professor Rodney Rowntree. The co-authors of the article are also Jacopo Aguzzi from ICM-CSIC and Fabio De Leo Cabrera from ONC.

In one case, repeated visits within 10 days by four of the identified seals of the research site also demonstrate that they quickly learned to use the infrastructure for more efficient food production, adds Fruen-Mui.

"We met mammals and ended up naming them in the newspaper after the members of The Beach Boys to distinguish between the frequency of visits and observed habits," she says.

Teenage males visiting this place mainly hunted actively swimming black fish, ignoring more than a dozen other variants of stationary or drifting prey. Several individuals were interestingly recorded on the camera and hydrophone, shaking their heads and making low-frequency sounds while chasing prey.

The sonar video also showed seals napping on the seabed in Barkley Canyon - another new and never-ever-meet behavior of the northern elephant teenage male elephant.

NEPTUNE's real-time monitoring capabilities allowed researchers to adapt the use of ONC underwater tools deployed on the research site to study fish to detect the presence of seals and observe them for almost a year.

Although colonies of northern elephant seals are found even in the north, up to Alaska, and in the south, near the Bach Peninsula, they are usually studied using biotags to track movement, or are found mainly on land.

The results of the completed experiment on fish acoustics will also be published in the near future.