By Dean Murray via SWNS
A colony of sneaky seals has been caught using deep-sea research sonar noise as a dinner bell.
The clever marine mammals are believed to have learned to associate the sonar with a good feeding spot where fish may have been disturbed by camera lights.
Researchers became so familiar with the repeat visitors that they named them after members of The Beach Boys.
The Northern elephant seals were repeatedly captured on camera in the deep Pacific Ocean using sonar from an Ocean Networks Canada (ONC) observatory as a signal to forage for their next fish feast, according to a new study led by University of Victoria (UVic) researchers.
The findings came almost by chance, as UVic, Instituto de Ciencias del Mar (ICM-CSIC), a Barcelona-based research institute, and ONC researchers were studying the effects of light and bait on fish and invertebrate behavior at Barkley Canyon, off the coast of southern Vancouver Island.
For the research, they used a high-definition camera, acoustic imaging sonar, hydrophone, a pair of LED lights, and automatic bait release. But a review of the camera, acoustic images and sound data revealed the surprise visitors.
Héloïse Frouin-Mouy, lead author of the publication, said: “We suspect the seals have learned to associate sonar noise from the research instrument with the presence of food—a phenomenon known as the “dinner bell” effect.
“The seals appeared to use this sound to locate an area with prey and may take advantage of fish disturbed by the camera lights, particularly targeting sablefish, their preferred meal as seen in the video footage.”
Researchers say the study, published in the peer-reviewed PLOS ONE journal, provides a unique, first-ever visual glimpse into the elusive mammal’s deep-sea behaviors, with a focus on their sophisticated feeding strategies, prey preferences as well as resting habits.
Altogether, at least eight male elephant seals, ages four to seven, were observed on camera and detected by hydrophones. They made multiple visits to the 645-metre-deep research site at Barkley Canyon along ONC’s subsea cabled observatory NEPTUNE off the British Columbia west coast between 2022 and 2023.
In one instance, the repeated visits over ten days by four of the identified seals to the research site also demonstrated that they quickly learned to use the infrastructure to forage for food more efficiently.
“We became familiar with the mammals and ended up naming them in the paper after members of The Beach Boys to differentiate between the frequency of visits and observed habits,” said Frouin-Mouy.
The adolescent males visiting the site predominantly targeted actively swimming sablefish, ignoring the over dozen other stationary or drifting prey options. Several individuals were interestingly recorded on camera and hydrophone bobbing their heads and producing low-frequency sounds while chasing prey.
Sonar videos also revealed seals power-napping on the seafloor at Barkley Canyon, another new and never-seen behavior from the adolescent male northern elephant seal.
NEPTUNE’s real-time monitoring capacity allowed the researchers to adapt the use of ONC’s subsea instruments deployed at the research site for the fish study to pick up on the presence of the seals and observe them for nearly a year.
Although northern elephant seal colonies are found as far north as Alaska and southern towards the Baja Peninsula, they are typically studied using biotags to track movement, or found primarily on land.
Results from the also completed fish acoustics experiment study will be published in the near future.
