Grade K–3Ocean Ecosystems & Food Webs

The Den That Octopus Built

Written by Randi Sonenshine

Illustrated by Anne Hunter

This is the den that Octopus built. And this is the crab that crept past the den that Octopus built. And this is the fish that followed the crab... In the tradition of the classic cumulative tale, Randi Sonenshine and illustrator Anne Hunter take readers on a lyrical journey through a living ocean ecosystem — from the octopus's carefully constructed den to the wide-open sea beyond. Each page adds a new creature to the chain, building a vivid, interconnected picture of ocean life. Gorgeous pencil-and-watercolor illustrations bring the underwater world to life with warmth and scientific accuracy, making this a perfect read-aloud for science and literacy alike.

View Teacher Guide

From the Library Director

The Den That Octopus Built is a quiet masterpiece. Randi Sonenshine has taken the cumulative tale — one of the oldest and most satisfying structures in children's literature — and used it to do something genuinely brilliant: teach the concept of a food web without ever once using the words 'food web.' Anne Hunter's illustrations are extraordinary: soft, detailed, luminous pencil-and-watercolor work that makes the ocean floor feel like a place you could actually visit. Each creature is rendered with scientific care and genuine affection. The cumulative structure does exactly what it should — it builds anticipation, reinforces memory, and creates a satisfying sense of connection and consequence. By the end, children have internalized the idea that every creature in this ecosystem depends on every other one, and they've done it through the pleasure of a story rather than the labor of a lesson. This is a perfect book for ocean science units, food web discussions, and any classroom conversation about how ecosystems work. It's also simply a beautiful book — the kind that makes children want to look at every page twice. Highly recommended for K–3.

Big Idea

Every creature in an ecosystem is connected — what one animal does ripples outward to affect every other living thing around it.

Discussion Questions

1
The story is told like a chain — each animal connects to the one before it. Why do you think the author chose to tell it that way? What does the chain structure teach us about how the ocean works?
2
The octopus builds a den at the beginning of the story. Why do animals build dens, nests, or shelters? What does the den give the octopus? What other animals in the story have a 'home' of some kind?
3
Each animal in the story either eats or is eaten by another animal. What would happen if one of the animals in the chain disappeared? Which animal do you think the ecosystem could least afford to lose? Why?
4
The ocean in this book is full of creatures that depend on each other. Can you think of an ecosystem on land that works the same way? What animals are connected to each other in a forest, a meadow, or a pond?
5
Octopuses are known for being very intelligent and creative. What does the octopus do in this story that shows those qualities? What else do you know about octopuses that surprises or impresses you?
6
The illustrations in this book are very detailed and scientifically accurate. What did you notice in the pictures that you might not have noticed just from the words? What did the illustrations teach you that the text didn't?
7
The story ends back where it began — with the den that Octopus built. Why do you think the author chose to end that way? What does it feel like when a story comes full circle? What does it say about ecosystems?
8
If you could add one more animal to the chain in this story, what would it be? Where would it fit? What would it eat, and what would eat it?

Activity: Build the Chain: Our Ocean Food Web

Students recreate and extend the food web from the story, then investigate what happens when one link in the chain is removed — building a concrete understanding of ecosystem interdependence through hands-on modeling.

1
Before reading, ask students: Has anyone ever played the game where one person starts a story and each person adds a sentence? Introduce the idea of a cumulative tale — a story where each new part adds to everything that came before. Then ask: Can you think of any other stories that work that way? (This Is the House That Jack Built, There Was an Old Lady Who Swallowed a Fly.) Tell students: today's book uses that same structure — but it's also teaching us something real about how the ocean works.
2
Read The Den That Octopus Built aloud, pausing after each new animal is introduced to ask: What does this animal eat? What eats this animal? After reading, create a class chain on the board: draw each animal from the story in order and connect them with arrows showing who eats whom. Ask: What do we call this kind of diagram? Introduce the term 'food chain.' Then ask: What if there were MORE connections — what if the crab also ate something else, and something else also ate the fish? Introduce the term 'food web.'
3
Introduce the 'Build the Chain' activity. Each student (or pair) receives a set of ocean animal cards (pre-made or student-drawn): octopus, crab, fish, seal, shark, plankton, sea urchin, kelp, and two animals of their choice from a reference list. Students arrange the cards and draw arrows to create their own ocean food web — each arrow points FROM the food TO the animal that eats it. Students must include at least 6 animals and at least 8 connections.
4
The 'What If?' challenge: once food webs are complete, each student removes one card from their web and traces the consequences. What happens to the animals that ate that creature? What happens to the animals that creature ate? Students write or dictate 2–3 sentences explaining the ripple effect: 'If the [animal] disappeared, then [animal] would have less food, and [animal] would have more of [food source]...' Encourage students to think about whether the whole web would collapse or just change.
5
Share and connect: students share their 'What If?' scenarios with a partner or the class. Close with a discussion: What did you learn about ecosystems that surprised you? What does it mean for an ecosystem to be 'healthy'? What are some real threats to ocean food webs today — and what can we do about them? If time allows, have students write one sentence they want to remember about ocean ecosystems and post it on a class 'Ocean Wall.'

Standards Connections

CCSS.ELA-LITERACY.RL.K-3.5 — Explain major differences between books that tell stories and books that give information, drawing on a wide reading of a range of text types; identify the cumulative tale structure
CCSS.ELA-LITERACY.RI.K-3.3 — Describe the connection between a series of historical events, scientific ideas or concepts, or steps in technical procedures in a text
CCSS.ELA-LITERACY.W.K-3.2 — Write informative/explanatory texts in which they introduce a topic, supply facts and definitions, and provide a concluding statement
NGSS 2-LS4-1 — Make observations of plants and animals to compare the diversity of life in different habitats
NGSS 5-LS2-1 — Develop a model to describe the movement of matter among plants, animals, decomposers, and the environment; food web modeling
SEL — Systems Thinking: Understand that actions have consequences beyond the immediate; recognize interdependence in communities, ecosystems, and relationships