To Track Bull Sharks, First Hit Their Snooze Button

Posted November 6, 2023
Last Updated November 7, 2023 @ 5:41am

Shark

For these researchers in Southern Africa, tagging the apex predators starts with putting them in trancelike tonic immobility.

Daly and colleagues catch the famously ferocious fish off the coast of southern Mozambique and fit them with transmitters as part of a long-distance tracking project to reveal more about the animals’ habits. The team uses strong lines and circle hooks—harmless to the sharks—baited with striped bonito fish, thick rubber mats to protect the inflatable boat from sharp teeth, and something called tonic immobility: essentially, a shark’s Achilles’ heel.

“Once you can get a shark upside down, they pretty much just fall asleep,” says Daly. “It’s pretty incredible.”

Knowing a shark’s immobility trigger is one thing, but for Daly’s team, turning the creature upside down while aboard an inflatable craft out on the ocean is another.

File:Bull shark (Carcharhinus leucas) (23096642576).jpg - Wikimedia Commons

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To Track Bull Sharks, First Hit Their Snooze Button

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