Lesson Plan

Beavers on the Trace

North American Beaver (Castor canadensis) at Rock Springs, milepost 330.2

North American Beaver (Castor canadensis) at Rock Springs, milepost 330.2

NPS Photo

Overall Rating

Add your review
Grade Level:
Ninth Grade-Twelfth Grade
Subject:
Biology: Animals
Duration:
2 hours in field and 1 class period
Group Size:
Up to 36
Setting:
outdoors
National/State Standards:
Biology I: 3b
Keywords:
keystone species, biology, Beaver, animals, animal population

Overview

On a National Scenic Trail students will observe how a keystone species can create an ecosystem used by a variety of different species, leading to an overall increase in biodiversity.
The students will be visiting a National Scenic Trail and observing an ecosystem created by a keystone species (beavers).

Objective(s)

Enduring Understanding: Keystone species are those that modify the environment in such a way that the overall ecosystem builds upon the change.

Essential Question: Why are beavers considered a keystone species?

The students will:

1.) Learn about the interrelationships among organisms.

2.) Understand what a keystone species is and its role in the environment

3.) Learn the benefits and problems with beavers

Background

A keystone species is one that modifies the natural environment in such a way that the overall ecosystem builds upon the change. The primary keystone species is the beaver (Castor canadensis). The ponds, wetlands, and meadows formed by beaver dams increases biodiversity and improves overall environmental quality. The beaver is classified as a mammal and is the largest aquatic rodent in North America weighing 25 to 75 pounds. The beaver's most distinctive feature is their large flat tail, which serves as a rudder when swimming, a prop when sitting or standing upright, and stores fats for the winter. Beavers will also slap their tail on the surface of the water as a danger warning signal to other beavers. Beaver are also known for their large front incisor teeth that never stop growing so they do not become too worn despite years of chewing on hardwoods. Beaver fur consists of short fine hairs for warmth and long hairs for waterproofing. They have castor glands on the underside of their abdomen from which they can excrete an oily substance (castor) that they use in the grooming process to waterproof their fur and to mark their territory. Beavers are pure vegetarians. They eat fresh leaves, twigs, stems, bark, and cambium (soft tissue under the bark), along with many aquatic plants. Beavers are monogamous and mate for life. Mating usually takes place in January and February and the young called kits are born in March to April. The young usually live with the family unit (colony) until 2 years of age. Then they move or are driven off by parents to establish their own home colony. These offspring travel an average distance of 4 miles from their natal colony.

Beavers build and maintain houses called lodges. There are two main types, the conical lodge and the bank lodge. The most recognized is the conical lodge that is surrounded by water and is made from sticks, rocks, and mud. The second type of lodge is the bank lodge. It is made from excavating into the bank of a stream, river, or pond. Once the lodge is made beavers build dams to flood areas so they can get food and protection from predators. The dams, channels, and lodges beavers build have gained them the reputation as "Nature's Engineers". No other animal with the exception of man can significantly alter its habitat to suit its own needs and desires. Native Americans revered the beaver and referred to them as "Little People" for this reason.

Benefits of Beavers:

Reduces channel scouring and stream bank erosion

Development of new wetlands

Increases fish and waterfowl habitat

Wetlands serve as water filters that capture silt and pollutants

Helps buffer against flash floods

Recharges underground aquifers

Problems Caused by Beavers:

Build dams that can cause flooding that may damage timber, agricultural crops, homes, roadways, and garden plants.

Damage water retention structures

Gnaw bark around the base of a tree causing it to die

Stopping the water flow in culverts

Causes damage to pond dams by burrowing into them

United States Department of Agriculture estimates that beavers annually cause about $100 million in damage to public and private property in the Southeast

Materials

1.) Notebook and pen/pencil

Procedure

Assessment

Students will be graded using a rubric in answering the questions about the field trip.

Park Connections

Beavers are a keystone species along the Natchez Trace Parkway.

Extensions

Refer to the beaver when teaching topics such as principles of ecology, interactions in ecosystems and the biosphere.

Additional Resources

Natchez Trace Parkway

 Jamie L. Whitten Bridge located @ mp 290

Rock Spring located @ mp 330

Cypress Swamp located @ mp 122

River Bend located @mp 122.6

Vocabulary

Keystone species