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Nearshore Connections: Sea Otter Story

In this activity, students learn about the role of Sea Otters in their coastal habitat, through an interactive story. 

Kelp forests are undersea forests made of seaweed instead of trees. Many types of fish live in kelp forests, finding shelter and reliant on the kelp to lay their eggs on. Crabs, sea urchins, snails, clams, shrimp, sea stars, and other invertebrates are also found in kelp forest environments.

Sea otters play a very important role in keeping kelp forest ecosystems healthy.

The sea otter is an example of an important keystone species (a species that, if removed, has a great effect on other species and can cause collapse of the food web).

Sea otters find all their food and shelter in kelp forests. These large members of the weasel family love to eat sea urchins and crabs, often using a rock as a tool to crack the animals' hard shell. When not eating, they wrap the ends of the anchored kelp fronds around themselves and sleep floating on the surface, like fastening a seat belt. Baby otters "wear a seat belt" to prevent them from floating away while their mother's dive for food in the kelp forest.

Even though sea otters live their whole lives in cold Pacific waters, they don't get cold. Other marine mammals have evolved blubber to keep warm; instead of this fatty layer, sea otters have some of the thickest hair of any animal. This dense fur traps a layer of air to keep their skin dry and warm when properly clean and groomed. Sea otters may have up to a billion hairs in their coats, compared to the average person who has about 10,000 hairs on their entire head.

In the 1700s and 1800s, sea otters were hunted for this thick fur coat, until there were no more sea otters found on the BC coast. When this keystone species was removed, populations of many organisms were effected, and everything changed. Sea otters had kept kelp forests healthy by eating animals that graze on (eat) kelp. Sea urchins are voracious consumers of kelp, and with nothing to eat urchins, they feed uncontrollably and destroy kelp forests. In coastal areas where there are no sea otters, there has been a change from forests to deserts, or "urchin barrens", and many fish and other creatures are without protective homes, breedng grounds, juvenile nurseries or food sources.

Sea otters were reintroduced in the 1970s to northern Vancouver Island, and we can now find healthy kelp forests in some areas of the BC coast. Scientist have tracked the kelp forest response to the changing food webs as Sea Otters have spread from the original re-introduction sites. Sea otters have engineered the habitats where they live by facilitating the survival and growth of kelp forests.

Objectives

  • Describe the concept of a “keystone species” and explain the role that such an organism plays in its environment.

  • Explain the term “species at risk” and list examples of marine species at risk.

Materials

  • Per Class or Group:
    puppets/drawings of a sea otter, a rock and a sea urchin(s)
    diagram (or photo) of a giant kelp forest
    diagram (or photo) of sea urchin barren
    paper
    drawing materials

     

Key Questions

  • What differences can you observe?
  • Why does a plant without sunlight stop growing?

What To Do

  1. Demonstrate the story using the sea otter, rock and sea urchin puppets as props.

Alternative: Create a diorama or poster, and have each student draw and label a different living part of a kelp forest.

Extensions

  • The effect of sea urchins on kelp forests can be compared to the effect of pine beetles on pine forests.
  • Make an Ollie the Otter Sea Otter puppet out of a lunch bag

Other Resources

Monteray Bay Aquarium | Sea otter lunch bag puppet

Vancouver Aquarium | Sea Otters