Why do sharks dive?

January 7, 2019 by ​michelle Wheeler, Particle

Is it to regulate their body temperature? Conserve energy? Find food?

Tiger sharks at Ningaloo Reef are thought to search the seafloor for prey as they dive down and scan for silhouettes as they swim up to the surface.

But could there be other reasons why the sharks continuously move up and down through the water column?

That's what UWA student Sammy Andrzejaczek is hoping to find out for her Ph.D. research.

Sammy captured 24 tiger sharks at Ningaloo Reef and attached tracking devices to them for up to 48 hours.

Best described as Fitbits for sharks, the devices recorded activity rates and other data 20 times a second.

"I can even look at each individual tail beat," Sammy says.

"It helps us understand why they move the way they do, how environmental change might impact their movements and how removal of prey species from the water column may affect their movement."

Caught On Camera

The tags also contained video cameras, so Sammy could see the habitats the sharks moved through and the animals they encountered.

She watched how the sharks reacted to prey and how the prey reacted to the sharks.

Spoiler alert: Tiger sharks can be pretty lazy—Sammy says something as simple as a turtle noticing a shark and turning away could cause the shark not to bother hunting the turtle down.

"It's all the interactions that are happening on a daily basis that we don't actually usually see," Sammy says.

"Because if you put a human in the water, it's not a natural system any more."

"We get the daily life of a tiger shark without having to distract it from its normal routine."

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