Lesson Plan

Hoofin' It! - Field Sampling

numerous sheep bedded down on tundra
Dall sheep often group together in remote areas
NPS Photo


The lesson plans in our 'Hoofin' It!' unit help students learn the basics of animal classification and what characteristics are common to mammals, mainly through studying Dall sheep.

Lesson fourteen teaches students how scientists count wildlife populations.


Students will be able to categorize wildlife into populations and count wildlife populations


The "Hoofin' It!" unit explores the natural resource management of Dall sheep in the national parks of northwest Alaska. Students will learn about Dall sheep, where they live, how they have adapted to their environment, and how wildlife biologists study them to understand how to protect their populations within national parklands. Links to other lessons in the unit can be found at page bottom.

Dall sheep are a wild sheep that lives on steep mountain slopes across the Alaska. The sheep are an integral part of the natural ecosystem, and they are prized by subsistence and recreational hunters. In the early 1990s, the Dall sheep population in the Baird Mountains of Noatak National Preserve declined dramatically, losing half its population in two years. Wildlife managers closed the sheep hunting season for seven years to allow the population to grow again.

Why did the population drop so suddenly? What are the natural and human factors that affect the Dall sheep population? In the spring of 2000, Brad Shults, a wildlife biologist for the National Park Service, began a research project to learn more about Dall sheep population dynamics. Shults hopes to better understand sheep by studying the number of lambs that are born, how long sheep live, what are the most common causes of death, where do they go from season to season, and just how many sheep are there?


Before You Begin

Review about research techniques in the reading Dall Sheep and People: Wildlife Management of Dall Sheep.


  1. Work with the class to phrase a question about population size that can be answered through scientific investigation. The question should be along the lines of "How many objects of a certain type are there in an area of known size?" 

    Discuss with the class types of questions can be answered through scientific investigation and what types of questions are more difficult to answer. 

  2. Take the students outside to a big area or field. Look around and decide on an object whose population you will measure. It may be rocks, plants (all plants or a specific type), sticks, etc. Sample areas won’t be large, so don’t select full-sized trees. 

  3. Discuss with the students how they might design and conduct an investigation answering their population size question. If an area is too large to count every object, how might they estimate the population anyway? Scientists use a method known as field sampling. They carefully count all the objects in a small, manageable area or a series of areas and then make an estimate from those sampling areas to the entire area. 

  4. As a class decide the extent that you would like your population estimate to cover. For instance, a soccer field, a playground, the parking lot, etc. 

  5. Sometimes science requires only simple tools and instruments. In this investigation, use a tape measure to mark off at least five different sampling areas that are a meter square. Select sampling areas that represent the variety within your larger area. 

  6. You may split your class into five groups and have each group count all of the specified objects in that sampling square. If the object is numerous or difficult to see, you can have each member of the group count separately, and see if they arrive at the same number, and use the mean as the number of individuals. 

  7. Record the number of individual objects within each of the one-meter squares. Determine the average (mean) number of individuals per square meter by using the information collected from each of the sample areas. Use the following as an example for the calculations. 

     Area  Number of Individuals
     Area 1 1
     Area 2 14
     Area 3 0
     Area 4
     Area 5
     Total Number of Individuals 41

    Average number = (total number of individuals / 5 square meters)
     = 41 / 5 square meters
     = 8.2 per square meter
  8. The class now has a measure of the average number of individuals per square meter. This number is known as a population density. 

  9. To determine the total population, calculate the area of your complete population extent, e.g., the field or playground. (For younger students, remind them how to calculate area by measuring the long side and short side of a rectangle and multiplying.) 

  10. Multiply the density per square meter times the total area in square meters to determine the total population estimate.

    Scientists review each others' work by asking questions about how they did their research, and what conclusions they draw from their research. Have the students brainstorm a list of questions to ask each other about their techniques and conclusions. You can do this as a class, and have the students answer them together as a class, or students can brainstorm in their small groups and then ask them of another group which must answer the questions. 

    Scientists make their results public. Have the students make a presentation of their research methodology and results for the public. They can do this as individuals or in their small groups. Create a small poster that describes the question to be answered, the methodology used, the data, the results, and the conclusions they can draw from those results. These can be presented to the class or put on display in the hall. 

Discussion Questions 

  • Is the total population estimate the true number of individuals in the area? 
  • If you sampled another square meter area, would you get the same population density? 
  • If the objects you were counting were very much larger (trees) or smaller (grains of sands) how would you need to adapt your research design? 
  • Was it difficult to know which objects to count? Were some objects similar but not to be included? (For instance, if you are counting pebbles, when is an object a pebble and when is it sand or rock? If you are counting leaves how small can a leaf fragment be before it is no longer considered a leaf?) 
  • How might wildlife researchers counting populations in a large habitat area decide where and when to sample? 

Students can discuss the various habitat needs for each population and then draw their needs on the mural. For example, squirrels need trees for food and shelter so the students would draw or cut out pictures of trees for their squirrel population.

Students could collect various materials from the local area and glue them to the mural (i.e. tundra, grass, rocks, needles).

Suggested Assessment

Ask the students if a population can include two or more different kinds of animals (Answer: no).

Give the students a worksheet with pictures or drawings of animals. Ask them to state the size of each population.

Additional Resources

The "Hoofin' It!" unit explores the natural resource management of Dall sheep in the national parks of northwest Alaska. Students will learn about Dall sheep, where they live, how they have adapted to their environment, and how wildlife biologists study them to understand how to protect their populations within national parklands.

This unit is designed for grades K-12. Many of the lesson plans are appropriate for younger grades, although the later part of the unit are geared towards middle and high school. A class needn't do every lesson in the unit to gain insights into wildlife management - each can be approached as a stand-alone lesson on a particular biology-related topic.

Lesson 1
Hoofin' It! - What Do You Know?

(Understanding taxonomy; k - 12th grade)
Lesson 2
Hoofin' It! - Vertebrate Grab Game

(Exploring types of vertebrates; 3rd - 6th grade) 
Lesson 3
Hoofin' It! Vertebrate Mysteries

(A vertebrate matching game; 8th - 12th grade)
Lesson 4
Hoofin' It! Special Parts

(Animal adaptations; k - 12th grade)
Lesson 5
Hoofin' It! Hard to See?

(Camoflague; k - 8th grade)
Lesson 6
Hoofin' It! - Sheep Maneuvers

(A predator-prey game; k - 12th grade)
Lesson 7
Hoofin' It - Year of the Sheep

(Life cycle of a Dall sheep; 3rd - 12th grade)
Lesson 8
Hoofin' It! - Who's Got My Habitat?

(Habitat and wildlife populations; 3rd - 12th grade)
Lesson 9
Hoofin' It! - Habitat Grid

(Exploring wildlife habitat; k - 3rd grade)
Lesson 10
Hoofin' It! - Through the Seasons

(A game looking at seasonal impacts on wildlife; 2nd - 11th grade)
Lesson 11
Hoofin' It! - Population Art

(Intro to counting wildlife populations; k - 2nd grade
Lesson 12
Hoofin' It! - Population Calculation

(Graphing and analyzing sheep population data; 6th - 10th grade)
Lesson 13
Hoofin' It! - Scavenger Hunt

(A game connecting students to wildlife; k - 6th grade)
Lesson 14
Hoofin' It! - Field Sampling

(How scientists count wildlife populations; k - 12th grade)
Lesson 15
Hoofin' It! The Bean Counters: Mark-Recapture

(Learning to use the mark-recapture method for population surveys; 5th - 12th grade)