Dugongs are large mammals that look like a cross between seals and walruses but are actually more closely related to elephants. They live in the coastal areas of the Indian Ocean, the Indonesian archipelago, and the southwestern Pacific around the Philippines.

Dugongs are threatened in almost all of their habitat, but they thrive in Western Australia's Shark Bay, where an estimated 10,000 dugongs eat sea grass and try to avoid tiger sharks, their primary predator.

In this lesson, students will focus on the relationship between dugongs and elephants. They will look at pictures of these animals and describe the similarities and differences in their appearances. They'll read about and discuss the dugong's special adaptations to ocean life and they'll draw evolutionary trees showing dugongs and elephants. They will finish by adding text to their trees describing dugong adaptations.

Geography, life sciences

Standard 8: "The characteristics and spatial distribution of ecosystems on Earth's surface"

Two hours

• Computer with Internet access

Students will

• guess which large land animal the dugong is related to;
• compare and contrast photographs of a dugong and an elephant, and list and discuss their findings;
• read and answer questions about dugongs;
• discuss how dugongs are well suited to life in the ocean;
• draw evolutionary trees that include dugongs; and
• list dugong adaptations on their trees.

Have students look at the picture of a dugong in National Geographic's Sulu-Sulawesi Seas interactive map. (Click "Begin" and then scroll over the map to find the link to the dugong picture.)

Ask the students if they have ever seen an animal that looks like this. They might have seen pictures of manatees, which are relatives of the dugong that live in the Caribbean and off the coast of the southeastern United States.

Have students go to this dugong fact sheet and scroll down to see the map of the dugong's geographic range. Ask them to name the continents where they could travel to see dugongs.

Tell the class that dugongs are related to a land animal that they're familiar with. Can they guess which animal this is? Give them hints, such as "This is the largest land animal in the world" or "It lives in Africa and Asia." Students will probably be able to guess the elephant with the help of these hints.

Explain that, as amazing as it might seem, about 25 million years ago dugongs and elephants had the same ancestor. It probably looked like a strange elephant—perhaps like the palaeomastodon pictured on this evolutionary tree.

Over a very long time, some members of this ancient elephant species went into the water and evolved characteristics that allow them to live their entire lives at sea, as dugongs.

It's essential for students to realize that elephants did not magically transform into dugongs, nor did they give birth to dugong babies. Rather, this was an incredibly slow process in which animals were born with slightly different traits than their parents had. If these traits allowed them to live more easily in the ocean, they'd survive and pass the traits on to their offspring. Eventually, more and more animals had these traits.

Have students look at the pictures of dugongs and elephants at these Web sites. Ask them to list the similarities and differences they notice just from observing these photographs.

National Geographic: Creature Feature—African Elephants
National Geographic: Sights & Sounds—Sulu-Sulawesi Seas (Click "Begin" and then scroll over the interactive map to find the dugong.)

Discuss students' lists as a class. What are the main differences between these two species? Did students notice any similarities?

Have students go to the United Nations Environment Programme's Kids Only: Manatees and Dugongs site, which has sketches and text about these two related species. Have them click on "Manatees and Dugongs" and "Dugongs." Ask them to focus on dugongs as they answer these questions about dugongs' adaptation to ocean life:

• How does a dugong's tail help it in the water?
• How do its forelimbs ("arms") help it in the water?
• How long can it hold its breath? Why does this matter?
• Do dugongs have tusks? How do their teeth or tusks help them?

Discuss students' answers as a class.

Provide students with this additional information about the dugong's special adaptations to ocean life. You might want to write these facts on the board so they can read it along with you:

• They are shaped somewhat like dolphins.
• Their nostrils are covered with a valve that helps keep the nostrils closed while they're underwater.
• Their mouths are positioned on the bottom of their big heads.

Ask students how each of the dugong features they've learned about helps make the ocean an ideal habitat for this animal. Also ask them whether elephants have any of these features. Could elephants survive in their land habitat with these traits? Could dugongs survive without them?

Students should realize that dugongs had to evolve these features in order to live in the ocean, and elephants had to keep their own special characteristics in order to live on land.

Have students use colored pencils and poster board to draw evolutionary trees showing an ancient elephant, a modern elephant, and a dugong. The ancient elephant should be at the top of the tree, and the elephant and the dugong should be branches farther down.

Ask the students to write information on their trees that describes the special characteristics that make dugongs different from elephants and able to live in the ocean. They should list these characteristics as close as possible to the dugong's picture and make it clear that they refer to the dugong.

Have students return to the map of the dugong's range. Explain that dugongs are threatened in most of their range, but are thriving in a place called Shark Bay, Western Australia, where about 10,000 dugongs live. Have them look at a map of Shark Bay.

Have students read this text about manatees and dugongs and then use the arrow at the bottom of the page to continue on to the next two pages.

Ask students to write captions to describe what's happening in each of the pictures on these pages. Then have them write sentences or paragraphs answering the question "What can be done to protect dugongs?"

This material is based on work supported by the National Science Foundation under Grant No. 0229817.

Any opinions, findings and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation.

Dugong dugon
Elephant Evolution
National Geographic: Creature Feature—African Elephants
National Geographic: Crittercam Chronicles
National Geographic: Sights & Sounds—Sulu-Sulawesi Seas
United National Environment Programme: Kids Only—Manatees and Dugongs