Conservation & Science

New insights to help young white sharks survive

What can scientists studying white sharks learn from an expert on mountain lions? As it turns out, quite a lot.

Monterey Bay Aquarium and its research colleagues have been tagging juvenile white sharks in southern California since 2002. Now they’ve gained new insights into white shark survival from those data tags. Photo courtesy Steve McNicholas

Such a collaboration is on display in new research published in the Journal of Applied Ecology. Models that estimate survival rates for top predators on land, according to the study, can also work in the ocean. The research also revealed important safeguards that can help protect white sharks while they’re young and vulnerable.

At the heart of the effort was the work of lead author John Benson. Before taking his current role as a professor at the University of Nebraska, John was a post-doctoral researcher at the Monterey Bay Aquarium, working with senior research scientist Sal Jorgensen.

Young white shark on exhibit at Monterey Bay Aquarium.

“We always learn things from adjacent fields,” says Sal, who specializes in white sharks, and who coauthored the paper along with six others. “John made his name studying mountain lions in Southern California.”

John’s past work also involved black bears in Louisiana, panthers in Florida, wolves and coyotes in Canada, and moose and their various predators in Alaska. After so much experience on land, John saw working with Sal at the aquarium as a chance to—as the saying goes—get his feet wet. Read more…

In the belly of the beast: a shark tag’s travels

“If you were to put a Fitbit on a white shark, where would you put it?” asks Monterey Bay Aquarium research scientist Salvador Jorgensen. “The answer is in its stomach.”

Jorgensen and his colleagues are trying to learn where and when white sharks feed by using an electronic tracking device called a “Daily Diary” that works like the activity-logging Fitbit. Where a Fitbit tracks steps, the Daily Diary tracks tail beats. It also monitors changes in temperature and pressure.

Sharks are apex predators that occupy the top of the food web—but their might does not always keep them safe from human activity. And without sharks to keep prey animal populations in check, the food web could crumble. Knowing when and where sharks feed will help researchers identify places that need protection so that white sharks can have plenty of food to eat in peace.

A challenging project

Devices like the Daily Diary are a popular way to study wild animals, Jorgensen says. But attaching them to an ocean animal is challenging. It’s relatively easy to place an accelerometer on the leg of a sedated cheetah, but a shark is a whole other kettle of fish. So instead, Jorgensen and his team have the shark do what it does best: eat.

The internal tag was wrapped in whale blubber so the shark would swallow it. Photo courtesy Sal Jorgensen.
The internal tag was wrapped in whale blubber so the shark would swallow it. Data were later calibrated to align with the orientation of the shark’s body. Photo and illustration courtesy Sal Jorgensen.

In their latest study, published in the Journal of Animal Biotelemetry, the team – which includes researchers from the Aquarium, Stanford University and Montana State University – used the internal Daily Diary attached to a pop-up archival transmitter (PAT) tag to record feeding behavior in wild and captive sharks. In the wild, researchers lured white sharks to a skiff using a seal-shaped decoy. They wrapped the two internal tags in whale blubber—like putting medicine in a dog treat—and fed it to the shark.

Getting the tag back is easier than you’d think. Like owls, sharks eat their food and later regurgitate solid and indigestible materials. When the tag is regurgitated, it floats to the surface and pings its location to the research team.

What the data reveal

The stored data tell the story of shark feeding behavior. Sudden bursts of acceleration indicate that a shark is swimming fast to ambush its prey. If the shark is successful, the acceleration is followed by a measurable increase in stomach temperature.

White shark swallows a feeding tag. Photo courtesy Sal Jorgensen.
White shark swallows a feeding tag. Photo courtesy Sal Jorgensen.

Of course, that knowledge has to come from data stored on the physical tag, which isn’t always easy to retrieve from the ocean – especially if someone beats you to it.

One time, researcher Paul Kanive got a favorite shark, nicknamed “Scar Girl”, to swallow the tag. But right after he returned from his sampling trip, Kanive got a call from Jorgensen saying that Scar Girl’s tag had surfaced north of San Francisco, in Tomales Bay, and the signal was heading toward the boat ramp at Nick’s Cove. Kanive raced over and asked everyone on the dock if they had, by chance, retrieved any bright orange devices in the water.

‘Find something orange?’

Kanive noticed a man putting a kayak on his truck and asked him if he had found anything orange. “And he kind of stopped and smiled,” Kanive said. “He was like, ‘Ah, I knew that thing would get me in trouble!’”

Kanive said the kayaker was happy that he was able to help the team out but, “He was blown away that I was there asking him if he found something that nobody saw him find.” After he retrieved the tag, Kanive was able to get Scar Girl to swallow it once more.

– Cynthia McKelvey

Citation: Jorgensen SJ, Gleiss AC, Kanive PE, Chapple TK, Anderson SD, Ezcurra JM, Brandt WT, Block BA. (2015). “In the belly of the beast: resolving stomach tag data link to temperature, acceleration and feeding in white sharks (Carcharodon carcharias).” Journal of Animal Biotelemetry, December 2015, 3:52.

Unlikely landing for white shark tag

For the first time since we started tagging juvenile white sharks in southern California more than a decade ago, we’ve retrieved one of the tags in Monterey Bay.

Data tag washed up on a Monterey Bay area beach 10 months after it was fitted on a juvenile white shark off the southern California coast.
This data tag washed up on a Monterey Bay area beach 10 months after it was fitted on a juvenile white shark off the southern California coast.

The tag spent 10 months on a young shark before it popped free over Labor Day weekend and washed ashore just north of the Pajaro River, in Santa Cruz County. Several aquarium staff members went beachcombing and found the data-rich tag on Sunday, near the high tide line.

The tag showed up in an area where a number of young white sharks have been spotted in recent weeks. Several were featured on Big Blue Live when they were caught on camera by airborne film crews. Our white shark research scientist Sal Jorgensen photographed the sharks this week as well.

An aquarium team scoured the beach north of the Pajaro River. They found the shark tag near the high tide line.
An aquarium team scoured the beach north of the Pajaro River. They found the shark tag near the high tide line.

Our research team speculates that unseasonably warm sea temperatures drew the young sharks far north of their usual haunts off southern California and the Baja Peninsula.

The shark was collected and tagged on November 6, 2014 in Santa Monica Bay by our research partners with the Southern California Marine Institute and the California State University Long Beach Shark Lab. At the time, it was about 6.5 feet in length and weighed 146 pounds. Based on its size, they estimated it to be just over a year old.

Juvenile white shark spotted in Monterey Bay the week of September 7.
Juvenile white shark spotted in Monterey Bay the week of September 7.

No other juvenile white shark has carried a data tag this long, so our white shark team is eager to download the information stored on the tag. They’ll learn where the shark journeyed over the past 10 months, and the water temperatures it favored.

We and our colleagues have tagged 93 sharks since we began tagging juveniles in 2002. Data from the tagged animals show a seasonal migration pattern between southern California and Mexico, with the sharks appearing to seek out warmer waters.

This is the first time young white sharks have been seen in such numbers in Monterey Bay since the last El Niño event in 1997.

Here’s a video showing some of the young white sharks in the bay’s warmer waters this summer.

Learn more about our shark research program.

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