Ocean Guardians: How elephant seals are acting as 'smart sensors' for scientists to unlock ocean secrets

Elephant Seals Help Scientists Track Ocean Health Using Smart Sensors. (Image: D. Costa)

Elephant seals are now key players in ocean research. Fitted with smart sensors, these massive marine mammals are helping scientists unlock the ocean’s secrets. Researchers at the University of California, Santa Cruz, have been tracking their movements to study marine ecosystems, particularly the ocean's mysterious "twilight zone."

Seals Dive Deep to Collect Crucial Data
Marine biologists have attached smart sensors to thousands of northern elephant seals. These devices gather vital data, such as water temperature, salinity, depth, and location. They also include video and audio, giving scientists a glimpse into the seals' underwater world.

Lead researcher Roxanne Beltran explained that the seals' natural migratory patterns make them ideal data collectors. "They travel vast distances and dive deep," she said. The sensors track their dives into the twilight zone, a deep ocean layer teeming with life, located 656 to 3,280 feet below the surface.

This zone holds massive fish populations, drawing interest from potential commercial fisheries. However, it remains largely unexplored, raising concerns about its future.

Seals offer deep-sea data as concerns rise over twilight zone fishing. (Image: D. Costa)

A Natural Fit for Ocean Research
Elephant seals are perfect for this kind of research. Twice a year, thousands gather at Año Nuevo Natural Reserve in California to breed and molt. This gives scientists easy access to tag them before they embark on their long migrations.

"It’s a chaotic scene during breeding season," Beltran said. Females fight to protect pups, while males battle for mates and space. After breeding, seals take a 2.5-month foraging trip, then return to molt before a longer, 7-month migration.

On these trips, they travel halfway to Japan and back, diving deep in search of fish and squid. Each seal makes up to 75,000 foraging attempts, tracked by sensors that detect head lunges and feeding motions.

The data reveals how deep the seals dive, their hunting success, and how ocean conditions affect them. This information helps scientists better understand the twilight zone and the wider marine ecosystem.

Protecting a Fragile Ocean Ecosystem
The twilight zone is rich in marine life but remains largely untouched by commercial fishing. As interest in its fish stocks grows, scientists warn of potential risks. "We don’t yet have cost-effective ways to fish there," Beltran noted, but future efforts could disrupt the food chain, impacting species like the elephant seals.

Northern elephant seals themselves have a remarkable history. Once thought extinct due to 19th-century commercial sealing, a small group survived in Mexico. Today, their population has rebounded to about 350,000 along the U.S., Mexico, and Canadian coasts.

UC Santa Cruz has studied elephant seals since the 1970s, gathering over 350,000 observations from about 50,000 seals. The long-term research offers rare insight into how the ocean has changed over decades.

"There’s never been a more crucial time for continuous monitoring," Beltran said. "The more we learn, the better we can protect these ecosystems."

This study is published in a paper Science.