Get Regular Updates!
Search

Earth

image|

Alex Kydd

Why do sharks dive?

Why do sharks dive?

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

Why do sharks dive?

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 PhD research.

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

Video|Sammy Andrzejaczek
Sammy and her colleagues tagged tiger sharks to find out why they dive

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.

Video|Sammy Andrzejaczek
See what tiger sharks do when they dive

“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.”

SPAM AND NAILS

Sammy says tiger sharks feed on just about everything.

“Stomach content analysis has found their normal prey items, such as turtles and rays and fish,” she says.

“But they’ve also found some really interesting things, such as licence plates, cans of spam and nails.”

“So they’ve got a very broad diet.”

Tiger sharks may search for food as they move up and down through the water column, Sammy says.

A tag on a tiger shark at Ningaloo Reef…
. Credit: David Palfrey
View Larger
Image |

David Palfrey

A tag on a tiger shark at Ningaloo Reef…
…helps to reveal shark activity below the surface
. Credit: Alex Kydd
View Larger
Image |

Alex Kydd

…helps to reveal shark activity below the surface

“On the way down, they’re scanning the seabed for prey,” she says.

“And then on the way, up they’re searching for silhouettes of prey at the surface.”

NINGALOO’S TOP PREDATORS

Sammy says studying top predators like sharks can help us understand the ecosystem as a whole.

How tiger sharks move through Ningaloo Reef and feed can help us figure out how they might be impacting the animals beneath them in the food chain, she says.

But hours of watching tiger sharks hunt hasn’t put Sammy off the animals at all.

Time spent tagging and monitoring sharks
. View Larger
Time spent tagging and monitoring sharks
These were the highlights of Sammy’s PhD
. View Larger
These were the highlights of Sammy’s PhD

She says her time tagging sharks at Ningaloo was the best month of her PhD, if not her life.

“At first, I was a bit apprehensive about it … getting that close to some very big animals,” Sammy says.

“But they were very chilled once you had them restrained alongside the boat.”

“They’d just sit there, you’d attach the tag, you’d take the line off and they’d just swim off really calmly, it was pretty amazing to see. They’re just absolutely beautiful animals.”

We love science puns VIDEO

Republish

Creative Commons Logo

Republishing our content

We want our stories to be shared and seen by as many people as possible.

Therefore, unless it says otherwise, copyright on the stories on Particle belongs to Scitech and they are published under a Creative Commons Attribution-NoDerivatives 4.0 International License.

This allows you to republish our articles online or in print for free. You just need to credit us and link to us, and you can’t edit our material or sell it separately.

Using the ‘republish’ button on our website is the easiest way to meet our guidelines.

Guidelines

You cannot edit the article.

When republishing, you have to credit our authors, ideally in the byline. You have to credit Particle with a link back to the original publication on Particle.

If you’re republishing online, you must use our pageview counter, link to us and include links from our story. Our page view counter is a small pixel-ping (invisible to the eye) that allows us to know when our content is republished. It’s a condition of our guidelines that you include our counter. If you use the ‘republish’ then you’ll capture our page counter.

If you’re republishing in print, please email us to let us so we know about it (we get very proud to see our work republished) and you must include the Particle logo next to the credits. Download logo here.

If you wish to republish all our stories, please contact us directly to discuss this opportunity.

Images

Most of the images used on Particle are copyright of the photographer who made them.

It is your responsibility to confirm that you’re licensed to republish images in our articles.

Video

All Particle videos can be accessed through YouTube under the Standard YouTube Licence.

The Standard YouTube licence

  1. This licence is ‘All Rights Reserved’, granting provisions for YouTube to display the content, and YouTube’s visitors to stream the content. This means that the content may be streamed from YouTube but specifically forbids downloading, adaptation, and redistribution, except where otherwise licensed. When uploading your content to YouTube it will automatically use the Standard YouTube licence. You can check this by clicking on Advanced Settings and looking at the dropdown box ‘License and rights ownership’.
  2. When a user is uploading a video he has license options that he can choose from. The first option is “standard YouTube License” which means that you grant the broadcasting rights to YouTube. This essentially means that your video can only be accessed from YouTube for watching purpose and cannot be reproduced or distributed in any other form without your consent.

Contact

For more information about using our content, email us: particle@scitech.org.au

Copy this HTML into your CMS
Press Ctrl+C to copy

We've got chemistry. Want something physical?