Grade Levels

K - 10

Objectives

    Students will investigate changes in beaver habitat areas caused by beavers and interrelationships between beavers and their environment by:

• observing   clues to beavers' life history;
• modeling    beaver-predator behavior;
• inferring    protective importance of hearing and smelling.

Standards of Learning

Science:

• Kindergarten: K.1, K.2, K.6
• Grade One: 1.1, 1.2, 1.5, 1.7
• Grade Two: 2.1, 2.5, 2.7
• Grade Three: 3.1, 3.4, 3.5, 3.6, 3.10
• Grade Four: 4.1, 4.5
• Grade Six: 6.1, 6.2, 6.8, 6.9, 6.11
• Life Science: LS.1, LS.4, LS.7, LS.8, LS.9, LS.11, LS.12
• Biology: BIO.1, BIO.9

English:

• Kindergarten: K.13
• Grade One: 1.3
• Grade Two: 2.11
• Grade Three: 3.7, 3.9
• Grade Four: 4.7, 4.8
• Grade Five: 5.7
• Grade Six: 6.1, 6.3, 6.7, 6.8
• Grade Seven: 7.1, 7.8, 7.9
• Grade Eight: 8.1, 8.5
• Grade Nine: 9.4
• Grade Ten: 10.7, 10.8, 10.9

Background

    The beaver could easily have been the product of a "create-a-wetlands-animal" activity in which students build an imaginary animal with every part being adapted for some aspect of its environment. For protection against the chilling effect of life in water, the beaver has a dense pelt, a layer of subcutaneous (under the skin) fat, and specialized heat exchanging circulation to its extremities. Organs in its groin, called castor glands, secrete an oil which the beaver uses to mark its territory. Sebaceous glands produce oil which waterproofs the beaver's fur. On each hind foot, the second claw is split and used like a comb to keep the fur groomed for maximum water repellency. The hind feet are webbed to provide propulsion through the water. The outermost digits on the forepaws are modified for grasping, much like a human thumb, and the front claws are long and adapted for digging.

    This animal's characteristic large front teeth grow continuously, keeping pace with the constant wear from gnawing on wood. To seal out water during dives, the beaver's ears and nose have special flaps and the back of its mouth closes. Its front teeth project through the lips to permit gnawing, chewing and swallowing underwater without forcing excessive amounts of water into the digestive tract and lungs. A beaver's eyes have nictitating membranes which serve as under water goggles.

    The beaver's astounding array of specialized behaviors have led many to credit the animal with high intelligence, but most of these behaviors are probably instinctive. This animal has a powerful compulsion to stop running water, hence it builds dams. Small trees, branches and twigs are stored on the bottom of the pond to consume when the water freezes. Tail-slapping may be a warning signal of danger. Beavers build elaborate lodges complete with underwater entrances and emergency exits, overhead ventilation, and separate grooming and sleeping areas. Their tendency to girdle (gnaw the bark off completely around the trunk) trees too large to actually cut down kills the trees and opens the forest canopy, permitting new sapling growth and thus ensuring a food source for future generations.

    Since beavers significantly alter lowland habitats, a wide variety of plant and animal species rely on beavers for their own habitat requirements. Beaver ponds become home for many slow-water fishes such as bluegill and pickerel. Aquatic and wetland plants take root in and around beaver ponds, benefiting from the continuous water supply and open canopy. Wading birds and waterfowl are attracted to the abundant fishes and plant foods. Other parts of the ecosystem also benefit from beavers: their ponds serve as firebreaks, thus protecting nearby forests, and as sediment traps, keeping waterways cleaner downstream.

    Throughout North America's past, beavers have been cherished and pursued by man. Its meat has been eaten by many and the tail is considered a delicacy. Beavers' castor glands have been used to manufacture perfumes and medicines (but not castor oil, which comes from plants). The beaver has been most sought for its fine fur. Beaver pelts were among the earliest trade items between the first settlers and Native Americans, and for a time, were very fashionable as coats and top hats. Trappers, in pursuit of the beaver, led the way for the settlers' westward advance.

    As a result of relentless trapping pressure, beaver populations were virtually eliminated from Virginia. However, beavers today represent a great success story in wildlife management. In the 1930s, about 12 pairs of beavers from other states were released in a few Virginia Piedmont and mountain counties. For many years thereafter, beavers enjoyed unofficial endangered species status protection (the Endangered Species Act was initiated int he 960s). Today, scarcely any headwater in Virginia or the Chesapeake watershed is without resident populations of beavers and they once again contribute to the fur trade through a carefully managed trapping program.

    Unfortunately for would-be observers, beavers tend to be most active at twilight and night. thus they cannot predictably be seen by groups visiting the parks. However, beavers leave many signs which can be examined, including gnaw marks on trees and stumps, dams, lodges, canals radiating from pond edges, foot prints and tail drag marks in the mud, and small piles of slightly odoriferous mud and leaves which mark the beaver's territory. THese signs, plus an abundance of beaver literature ranging from fables to scientific papers, make the beaver an ideal subject for interdisciplinary studies.

Materials

• dark bandana or similar material for a good blindfold
• odor source such as bottle of cologne
• guided imagery reading selection (optional)
• paper, pencil and clipboards for poems or drawings (optional, one set per student)

  To wear:

• "wettable" footwear

Resources

Brady, I. 1876.

Beaver Year. Houghton Mifflin Co., Boston.

Council for Wildlife Conservation and Education, Ind. 1986.

The Unendangered Species: The Success of Wildlife Management in North America    (FREE Filmstrip)> P.O. Box 1075, Riverside, CT 06878.

George, W.T. and L.B. 1988.

Beaver At Long Pond.   Greenwillow Books, NY.

Johnson, P. 1984.

"The Dam Builder is at it Again!" National Wildlife Magazine   June-July.

Johnson, S.P.(ed). 1962

Everyman's Ark.   Harper & Bros. NY.

Kalas, S. and K. 1987.

The Beaver Family Book.   Picture Book Studio.

Kipling, R. Reprinted 1987.

Just So Stories.   Grossman.

Sattler, H.R. 1982.

Noses Are Special   Abingdon Books, Nashville.

Schroeder, H. 1983

The Beaver - Wildlife Habits and Habitat Series.   Crestwood House, MN.

Von Frisch, K. 1974.

Animal Architecture.   Van Nostrand Reinhold Co., NY.

Wood, M. 1981.

Spirits, Heroes, & Hunters from North American Indian Mythology.   Schocken Books, NY.

Procedure

Before the Trip:

1. Visit the park to locate the areas with the most beaver activity. Consult with park staff.

2. Review the entire activity procedure with the class, but do not provide information about beavers yet. Assign several students to find pictures or drawings of beavers to bring to class (or find some yourself).

3. Divide the class into teams of three or four students.

4. Assign each team one or more of the following questions. Brainstorm at least three plausible answers to each:
   
   • Since the beaver spends much of its life in the water, even in winter, how might the beaver be adapted to stay warm?
   • Beavers have special organs, called castor glands, that secrete an odorous oil. How might the beaver use this oil?
   • Some of the claws on a beaver's hind paws are split. What could be the function of these split claws? (Hint: It has to do with staying dry.)
   • The beaver's "little fingers" are offset slightly to oppose the other digits for grasping, somewhat like the human thumb. How can this be important for the beaver's lifestyle?
   • Why are a beaver's hind feet webbed?
   • How might the beaver use its flat tail?
   • Beavers have clear, eyelid-like structures (called nictitating membranes) over their eyes. What functions(s) might these serve? Why do a beaver's front teeth grow continuously?\
   • What could be the purpose of special flaps inside the beaver's ears, nose and mouth?
   • Why might beavers store small trees, branches and twigs on the bottom of their pond?
   • How can it be to the beaver's advantage to gnaw the bark off in a complete circle around the trunk of trees which are too large for the beaver to completely cut down? (Hint: Think about how the forest might change.)
   • What are some plants and animals that might be attracted to an area after beavers have moved in?
   • How might a forest benefit from having beaver ponds in its watersheds?
   • How might the aquatic animals and plants living downstream benefit from beaver ponds upstream?
5. At the end of the brainstorming session, a representative from each team presents their answers to the rest of the class.

6. If available resources permit, the teams can then research their questions in the library and make quick follow-up presentations. If not, provide students with the accompanying background information.

7. Show the accompanying pictures of beaver signs so students will recognize these in the field.

At the Park:

1. Lead the students into an active beaver area.

2. Give each team a different beaver sign to look for. After a few minutes, re-assemble the group and ask each team to point out their sign if they found it. Discuss any other signs that are found as well as the effects of the beavers on the environment.

3. Find a comfortable spot within the beaver area for the class to sit quietly: Explain that the beaver has relatively poor vision but has good senses of smell and hearing. Ask students to close their eyes and to sense the beavers' world for two to five minutes using only their senses of smell and hearing What does it smell like and sound like?

4. When time is up, ask students to share things they sensed by using a "memory circle." THe first student begins by saying, "In the beaver habitat, I heard ...,"   or "I smelled ..."   and add an observation. The next student repeats the first student's observation and adds a new one. To avoid reciting a chain of 25 observations, the fourth student can start repeating only the three most recent observations (i.e. adds one to the end and drops one from the front.)

5. Next play a beaver simulation game. This can be played in the beaver area or another part of the park, preferably covered with leaf litter to make the hearing part of the game easier. Try a sample run with the "beaver" not blindfolded. THe procedure is as follows:
   
   • Students form a large circle.
   • One student designated the beaver stands in the middle of the circle.
   • Another student, designated the predator, is given an odor source such as a bottle of cologne. (In places where they coexist, beaver predators include bobcats, bears and coyotes. In most of Virginia now, the main predators are man and stray dogs.)
   • All the other students are non-predators.
   • The leader points to one of the students, either the predator or a non-predator.
   • The selected student walks slowly toward the beaver, pausing between steps. If the selected student is the predator, he (she) must wave the odor source in front of him/her with each step.
   • If the beaver detects an approaching predator, it claps its hands (simulating the tail slap), and points to the predator. If the beaver has correctly located the predator, the predator must return to the circle edge.
   • If the predator gets close enough to tag the beaver before it claps, it becomes the next beaver.
   • If a non-predator is selected, it also slowly walks toward the beaver, but passes by without tagging it. If the beaver claps its hands as a false alarm, the non-predator becomes the next beaver. (In nature, it would be to the beaver's disadvantage to frequently signal danger and flee if there is no danger, since it might not get enough to eat or be able to perform other important tasks on land.)
6. After playing the game for several rounds (teacher's discretion), ask the students to discuss the game. Some Questions to ask include:
   • What were the best strategies for the beavers and the predators?
   • In nature, why would the beaver lose if it frequently made the danger noise and fled from non-predators?
   • Why would it be important for a beaver to use its senses of smell and hearing rather than just sight?
   • Would a beaver be more cautious to sounds and smells on land or in the water and why?

Follow Up

Variations

1. Design a field study to answer a question about beaver behavior and describe the method of implementation. Sample questions:
   • When are beavers most active?
   • Is lodge or dam building behavior learned or innate?
   • What are their food preferences?
   • Are they evenly distributed throughout Virginia?

2. Students research the following: Thousands of years ago some beavers of North America were 7-1/2 feet long. Why and when did they die out?

Where in the Park

When

Time Required at the Park:

1 to 2 hours, daylight hours. Small quiet groups may glimpse a beaver in evening or early morning (special arrangements may be necessary).

Time of Year:

Any time is suitable, but in fall there will be more fresh sings, since beavers are most active then.