Hide Like A Cephalopod: Make An Octopus Den

One of the world’s most famous cephalopods, octopuses are well known for their soft, round heads, bulging eyes, and eight sucker-covered arms. Though they live in all the world’s oceans, octopuses display incredible variety across over 300 species—from the giant Pacific octopus, which measures up to 13 feet across, to the star-sucker pygmy octopus at barely an inch. Some, like the argonaut, spend their lives floating across the open ocean. However, most octopuses make their homes on the ocean floor in a den, just like the one author Randi Sonenshine describes in her book, The Den That Octopus Built.

Look at the picture above. What do you see? If you look closely, you may notice the red eyes of the common octopus (Octopus vulgaris). It’s hiding in an octopus den! Nestled in a hole among the rocks, it’s made its home. What do you notice about the den?

“Just as people need lodging for the night, octopuses need shelter… These dens are wonderful hiding places.” –Marine biologist David Scheel

Octopuses are usually solitary creatures. They return to the same home each day. Without hard outer shells to protect them from predators, they need somewhere safe to rest when they aren’t hunting. Octopus dens are also where females tend to their eggs, securing them to the roof of her den in clusters or strands.

Octopus dens are often found along the edges of ocean waters, tucked into crevices in coral reefs, or dotted along rocky shores. Sometimes they make their homes in naturally occurring holes or caves, but octopuses have strong, muscular arms that they can use to dig burrows. Some even build elaborate barricades made of shells, rocks, and found items like cans and bottles, while others simply have a pile of gravel marking the entrance.

Outside an octopus den, you may find evidence of the resident’s dinner. They often leave discarded shells from their meals—midden—near the entrance, but may also collect trinkets and treasures, such as sea glass. These areas are called octopus gardens.

You may only have two arms instead of eight, but your challenge is to build an octopus den of your own. Here’s what you’ll need:

• An octopus plushie or figure to live in your den
• Various rocks, shells, sand, or clay
• Upcycled items like cardboard, take-out containers or plastic bottles
• Camouflage items such as plants, seaweed, moss, sponge, or algae
• Items for your octopus garden, like glass beads

As you collect materials, think about whether they’d work underwater, where octopuses live. To create your den, start by piling rocks to form a cave-like structure that will fit your octopus. Try using different materials to fill gaps, hide the den, and create a barrier to protect the entrance.

You’ll notice the materials don’t include glue or tape. Under the ocean, octopuses don’t have such materials, so try to build your den without them. Are you as good an engineer as an octopus?

To be successful, your den must meet the following criteria:

• Your chosen octopus must fit entirely into the den. An octopus needs to be able to retreat into the den for safety.
• You must protect the entrance from unwanted visitors.
• The den must be hidden or camouflaged in some way.

What building strategies were most successful for creating a sturdy den that doesn’t collapse? What materials were best for disguising your den? What challenges did you face when building your den, and how do you overcome them?

For a bigger challenge, try these extensions.

• Make your own octopus figure using scientific evidence.
• Test your den underwater. Fill a sink, bucket, or basin with water and see how well your structure survives a wet environment.
• Be the octopus. Build a den big enough for you!

This activity needs examples of model octopus dens. A model is a representation of an idea, object, event, process, or system that isn’t easy to observe directly. If you create a model of an octopus den using this activity, we’d like to share it right here on this page. So take a picture of your model and send it to us using the form below or by sending it to educate@sciencefriday.com.

• Want to learn more about octopuses and other cephalopods? Dive into our Cephalopod Week Spotlight for stories, videos, and activities.
• Octopuses have more than one way to hide from predators. They are masters of disguise. Discover more about their color-changing abilities and camouflage.
• In his book, Many Things Under a Rock, marine biologist David Scheel writes about looking for octopuses in the wild. Watch his Q&A with the SciFri Book Club. Or read the Young Readers Edition of the book and spark conversation with interesting discussion questions.

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K-12 Education     Beyond The Classroom

Credits:
Lesson by Sandy Roberts
Digital production by Sandy Roberts
Contributors: Sara Bolduc, Sandi Cedruly, Diane Morse Daly, and Tiffany Lucey