Marine biologists from Canada set up a subsea observatory equipped with a bunch of fancy monitoring equipment, but also some yummy bait. The idea was to attract fish and other marine wildlife to the location and then study how they react to light and other stressors.
However, the experiment later took a surprising twist. Nearby male northern elephant seals heard the researchers’ sonar and realized the spot was brimming with food. The setup turned into a dinner bell and the seals were happy to photobomb the experiment.
The scientists from the University of Victoria didn’t mind though, as the accidental encounter made for a much more interesting study. Now it sheds new light on the foraging strategies of these elusive marine mammals, revealing behaviors previously unseen in the deep Pacific Ocean.
Smart Hunters, New Behaviors
Equipped with a high-definition camera, sonar, and other tools, the researchers set up shop at Barkley Canyon, a deep trench off Vancouver Island’s west coast. All was set to record the Pacific marine life. But as they reviewed their footage and sonar data, something unexpected was happening: an influx of northern elephant seals.
Footage from the subsea observatory operated by Ocean Networks Canada (ONC) off the coast of British Columbia shows the seals repeatedly visiting the deep-sea site to feed on fish. It appears that the seals have learned to associate sonar signals from the observatory with the presence of prey.
The seals weren’t just passing by — they were targeting sablefish, a prized meal, which was easy pickings as the fish were dazzled by the camera’s lights.
In total, eight male seals between the ages of four and seven were caught on camera, repeatedly returning to the same site. Over ten days, some seals visited multiple times, demonstrating a clear ability to use the equipment’s noise to their advantage. They quickly learned that the sonar signals meant fish were nearby.
“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, a visiting scientist at the University of Victoria in the department of biology and assistant scientist at the University of Miami.
Footage also revealed something new about these deep-diving mammals. Researchers observed the seals power-napping on the ocean floor, a behavior never documented before. As the observatory’s sonar captured images, the seals took brief rests before resuming their hunt. In addition to hunting, the seals were also producing low-frequency sounds, perhaps to help communicate or locate prey.
Resilient Hunters
Northern elephant seals, once teetering on the brink of extinction, have staged one of the most remarkable wildlife comebacks in history. Hunted for the oil in their blubber in the 19th century, they were believed to be extinct in 1892. But about 20 survived, and today, their population has grown to over 200,000.
Weighing up to 5,000 pounds, these marine mammals spend most of their lives in the open ocean. They dive thousands of feet deep to hunt for squid, fish, and other creatures. Evolved to withstand the immense pressures of the deep ocean, these seals have specialized blood chemistry. Their unique blood stores vast amounts of oxygen and their muscles can function on minimal oxygen. This allows them to plunge over 5,000 feet underwater and hold their breaths for up to two hours.
These new findings offer a rare glimpse into the underwater world of northern elephant seals. Until now, most studies on these animals focused on their movements near the surface or used biotags to track them across their migratory routes. Seeing them adapt so quickly to human-made infrastructure is yet another testament to their intelligence and ability to thrive in the deep ocean.
The results also raise new questions. Are other deep-sea creatures learning to exploit human technology in similar ways? How might our research activities be unintentionally altering the behaviors of marine animals?
But, despite this rare dinner party thrown by the researchers, life isn’t without risk for these ocean voyagers. Elephant seals face growing challenges from a warming ocean, which is altering the availability of their prey. Researchers are monitoring how these environmental shifts might affect the species in the years to come.
For now, the study opens a new chapter in our understanding of elephant seals and their remarkable survival strategies in one of the planet’s most challenging environments.
The findings appeared in the journal PLOS ONE.
