GENTLE JAWS?
Grades K - 2

Mother crocodiles have a special pouch in their lower jaw which allows them to carry eggs and hatchlings without harm. The powerful jaws of the crocodile allow it to bring down a wildebeest or gently crack open an egg.

The jaws of a crocodile resemble many modern day tools. Students will explore and discover the delicate pressure that must be exerted to keep an egg intact.

A mother crocodile can carry about a fourth of the hatchlings in her mouth at a time. Students will estimate the number of various size eggs that will fit into their mittened hand.

"National Geographic: Crocodiles: Here Be Dragons"

Students will be able to:

• Experience the similarities between the action of a crocodile's jaws and that of modern tools. These similarities include: comparing the motion, size and flexibility of the material of each object.
• Understand how the combination of their strength and the composition of the materials of each tool act upon an object.
• Estimate the number of eggs that will fit into their hand.
• Learn to modify estimates based on experience with one egg size and compare the relationship to a new egg size.
• Recognize that materials tools are made of and the design of the tools allow for more or less precision.
• Recognize the difference between a guess and an estimate.

For Activity 1

• a variety of plastic eggs (These eggs are usually purchased with 30 per bag in most craft stores. There should be one bag of each size egg.) at least one mitten for each group of four

For Activity 2

• a variety of tools, including tweezers, pliers, tongs, vice grip, variable wrench, strawberry huller, clothes pin (Have one tool available for each group of four.)
• table covered with plastic paper towels, etc. to clean up broken eggs
• several dozen fresh, raw eggs (A minimum of one egg per child.)
• timer (egg timer or sand timer)
• two small baskets (or bowls) per group

Ask students: What are some things you know about crocodiles. (Responses might include big, scary, lots of teeth, like an alligator.) List student ideas.

Ask students: Do you know of any famous crocodiles? (Cornelius, Peter Pan; Lyle, Lyle Crocodile)

Ask students: Do you know of a crocodile that has sharp teeth? The teacher should make up additional questions stemming from the list of student ideas.

Show students a plastic egg, or perhaps the slide book Who's Hatching by Charles Reasoner. Ask students: What are some things that come out of an egg? Show that crocodiles come from eggs.

To give students a specific responsibility while viewing ask them to notice whether the information they see verifies their original list, or adds any new insight. When students discover information from the video, they should raise their hands in order for the teacher to pause the tape and discuss any additions (or verifications) to the original list.

Focus will be on the nesting section of the video.

PLAY tape when narrator says "Downstream the dragons are nesting."

PAUSE when students raise their hands. Record responses.

RESUME segment until the section on hatchlings begins. (This section begins with a view of a waterfall.) STOP.

Activity 1

After viewing the video, ask students: Do you remember how the mother crocodile carried her eggs? (In her mouth.)

Next ask: Do you remember how many hatchlings she could carry at one time? (20 hatchlings.)

Show students the largest size plastic eggs. Ask them to place a mitten on their hand to represent the mouth of a crocodile.

Have students guess how many eggs they could hold in their hand. Record answers on the board.

Pass around a bin containing several large plastic eggs of the same size. Have each child take a handful. After everyone has done this, ask students to look around to see different ways of holding the eggs in their hands. Ask them which method do they think holds the greatest number of eggs. Have students count the eggs to check their original guess, and to see if any method seemed to work best.

Next, show students the next smaller plastic eggs. This time explain to students that you want them to estimate the number of eggs they can hold in their hand. They should not be guessing this time. They should, through prior knowledge, be more accurate and purposeful in choosing a quantity.

Repeat process above with the next size eggs. Ask students to count the eggs to see if the actual number of eggs is closer to their estimated count.

Repeat process with even smaller plastic eggs, beginning with student estimates.

Discuss with students the difference between an estimate and a guess. Elicit from the students that: an estimate is based on some information, a guess is based on lack of prior knowledge.

Activity 2

Ask students to list adjectives that would describe the ways in which a mother crocodile uses its jaws when it is taking care of the eggs. Ask students if they think it would be difficult for a crocodile to be gentle with its jaws. Why?

Look for words in the original list that are opposites to these adjectives. List them on a chart.

Tell students that all of these words are true when describing a crocodile's jaws for the reasons they mentioned earlier.

Assessment in the primary grades should be very informal. While observing students in the science center (or elsewhere in the room) you might ask individual students questions such as: Where does a crocodile lay her eggs? or Name a tool that reminds you of a crocodile's mouth, or Where do crocodiles live?

To further explore this concept, show students an array of tools that resemble the motion of a crocodile's jaws. Tell students that these tools are one example of how people have looked at nature and adapted it to fit their own needs.

Divide students into groups of four. In front of each group place a basket filled with 6 eggs along with an empty basket and a tool.

Set the timer for 30 seconds. Two students out of each group will observe, while the other students try to move the 6 eggs (using their tool only) without breaking any to the other basket. Discuss results informally while activity continues.

Allow other half of students to perform the same experiment.

Provide a center area or table using the plastic eggs for students to experiment with various tools to determine which designs work best for the purpose of moving eggs.

1
If you live near a zoo and if you are permitted to take field trips, find out if it has a reptile collection. If it does, ask if the zoo is incubating reptile eggs or if one of the reptiles has recently laid eggs. If so, arrange a trip.

2
Crocodile Egg Hunt. Before beginning this activity, hide 20-30 plastic eggs in a small area outside. (If you prefer, eggs may be hidden inside the classroom.) When class begins, talk about eggs and remind them of the video about crocodiles and their eggs. Talk about how the crocodile "hides" the eggs in the sand to help protect them from predators, and so the eggs which they are about to find are also hidden. Take the children outside and let the hunt begin!

3
If you haven't already done so, read the story of Peter Pan or show the video. Talk about how crocodiles can be dangerous and gentle at the same time. What happened when Captain Hook got to close? Generate a list of qualities that a real crocodile possesses as well as a fictitious one.

4
Make a crocodile hand puppet (pattern at the end of this lesson). Children glue the upper and lower jaw to a paper bag. Or they can fold a paper plate in half and add teeth. They can then pretend to be Mama crocs and pick up plastic eggs from a bowl and carry them to another.

5
Have children work on an "at home" project by making a collage of egg laying animals out of magazine and catalog pictures.

6
Encourage children to visit the school or local library to borrow books on crocodiles, alligators or other reptiles.

7
Involve students in making a list of other animals and attributes that humans have somewhat copied to make life easier. (Woodpecker and the chisel, webbed feet and swimming flippers, birds' wings and the wings of an airplane.)

8
Discuss endangered animals and ways to help eliminate the problem. Students can design a plan to save an animal of their choice.

9
Have students develop a personal oral hygiene chart to report daily care.

1 Social Studies: Study the climate and region of the Grumeti where crocodiles live.

2 Language Arts: Have students write a story or poem about a crocodile. One might be about a real crocodile and the other about a fictitious one.

Children can take a well-known story like The Three Bears or Three Billy Goats Gruff and change the main characters to crocodiles. Ask: How would the story change? Would it still make sense? Would it make a good story?

3 Math: Size comparison: Have children lie on the floor, head to toe, to equal 23-24 feet. (The length of a large, present-day crocodile.)

Children can use a recipe to create a Crocodile Salad. 1 egg 1 small pickle, whole 1 tablespoon mayonnaise

Hard boil egg, remove the shell and mash. Add mayonnaise and mix. Slice the pickle in half, lengthwise. Chop one half of the pickle and add to the egg mixture. Mound the egg salad on a plate and lay the other half of the pickle, skin side up, on top of the salad to represent a crocodile. Serves 1.

4 Health: Have a dentist and a veterinarian visit to talk about tooth care.

MASTER TEACHER:Grace Bickert

Click here to the worksheet associated with this lesson.