Get Regular Updates!
Search

Tech

image|

TJ Ostendorf

What do sharks do all day?

What do sharks do all day?

A shark tracking device reveals the day-to-day activities of lemon sharks.

What do sharks do all day?

Do you know what most people do all day? Where do they go, what do they eat, who do they talk to? Well, if you think it’d be hard to track a person’s every move, imagine tracking the behaviour of a wild animal, in the ocean.

The life of most marine animals is a bit of a mystery—it’s pretty hard to track any animal cruising through the ocean. But now, Murdoch University fish biologist Lauran Brewster and her team have found a neat way to get an up-close view of the day-to-day activities of a wild marine species.

“It can be very hard to study wild animals in their natural environment, particularly when they travel long distances or live in an environment that makes them hard to observe,” says Lauran.

View Larger
Image|TJ Ostendorf
Lauran Brewster has found a neat way to get an up-close view of the day-to-day activities of wild lemon sharks

In the new study, Lauran attached a Fitbit like device, known as an accelerometer, to the fin of several lemon sharks to learn about their daily habits.

Tracking a lemon shark

Lemon sharks are found in the Americas and West Africa, spending most of their time in shallow ocean waters. While juveniles are fairly well studied in enclosed conditions, it is not so easy to study them in the wild. They spend most of their day in hard-to-reach places, so it’s hard to know what they are up to throughout the day.

“This has prevented scientists from determining what these animals do on a daily basis and how long they spend performing different activities,” Lauran says.

“Accelerometers (like those used in wearable Fitbits) can help us overcome this hurdle. They collect body movement data from these animals, which can then be used to calculate energy expenditure and be classified into different behaviours,” she adds.

Lauran started by tagging semi-captive sharks and watching their behaviour. The data obtained from these gizmos was analysed through a complex statistical approach known as machine learning.

A shark tracking device reveals the day-to-day activities of lemon sharks. The data revealed some interesting detail about sharks' daily activities.
Image|Bimini Biological Field Station Foundation
Lauran attaching an accelerometer
“Machine learning is a model that learns patterns in data and can be used to identify similar patterns in new data and make predictions from it.”

“Very basically, machine learning is a model that learns patterns in data and can be used to identify similar patterns in new data and make predictions from it,” says Lauran.

You might not know it, but we are all exposed to the workings of machine learning every day.

“For example, when Facebook recognises people to tag in a new photo or gives you a recommendation for your next Netflix series based on your previous viewing history, that is the product of machine learning,” she adds.

After developing this approach on the captive sharks, Lauran was able to classify five basic behaviours.

“The model identified five different behaviours for lemon sharks, like swimming and resting. Also, successful prey capture (represented by the shark shaking its head from side to side), burst swimming and chafing behaviours, where the shark performs a barrel roll movement to scratch its back,” says Lauran.

A day in the life … of sharks

In her study, which took place in the Bimini Islands, Bahamas, Lauran tagged a total of 24 wild sharks.

Tagging the sharks was the easy part, as juvenile lemon sharks are commonly found around the area the researchers were studying. The tricky part was getting the data.

“The hardest part is finding the shark again to retrieve the tag so we can download the data,” says Lauran.

Twenty were recaptured, which provided the data for the study.

View Larger
Image|Sarah Bridenbaugh
Two accelerometer-tagged sharks resting together

After analysing the data from these wild sharks, Lauran found that these sharks hardly get any rest, especially in summer.

“The time spent on different activities varied dramatically. For example, they spent, on average, 1% of their day resting during the warmer months and 10% during the colder months,” says Lauran.

The data also revealed some details about their daily activities. For instance, these sharks prefer to capture prey in the early evening and don’t seem to like eating during high tide. The data also showed that they eat more when the water is warm.

This information will improve our understanding of the ecology of this species and may also help us understand how human activity is affecting the behaviour of these elusive species. However, so far, the data collected for these sharks is limited to pristine environments, but a great deal of the ocean is far from pristine.

Now, Lauran plans to study the behaviour of sharks living in areas affected by human development.

“We have been able to determine the fine-scale activity budget of a wild shark species here in pristine conditions. We can compare it with the activity of other lemon sharks inhabiting waters degraded by human development as a means to assess the risks associated with coastal development and establish how to manage the impact development has on coastal species,” says Lauran.

With this information, Lauran hopes to understand how this species responds not only to human disturbance but also to changing environmental conditions such as temperature change.

Vital science 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?