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Teacher Activity Notes

What Do Owls Eat?

PLAN

Summary

Students learn basic lab dissection skills and analyze the components of an owl's diet by dissecting an owl pellet.

Objectives

Students:

\checkmark demonstrate lab skills using dissection tools.

\checkmark explain how owl pellets are formed, what they consist of, and how owls obtain energy.

Student Materials

  • Activity Guide
  • Resource 1
  • Resource 2
  • Activity Report
  • 1 owl pellet; 1 sheet of white paper; 1 set of Tweezers; 1 dissecting needle or probe; 1 ruler; 1 copy of drawings of rodent and bird bones; 1 sheet of construction paper; 2 petri dishes; 2 rubber gloves (optional)

Teacher Materials

  • Activity Report Answer Key

Advance Preparation

Prepare copies of Resources 1 and 2 and Activity Report.

You can order owl pellets from a scientific supply company. Some possible sources are

Pellets, Inc., 3004 Pinewood, Bellingham, WA. Phone number: (206) 733-3012. Fax number: (206) 738-3402.

Carolina Biological Supply Company, 2700 York Rd., Burlington, NC 27215. Phone: 1-800-227-1150.

Genesis Inc., P.O. Box 2242, Mount Vernon, WA 98273. Phone: (206) 422-6764, FAX: (206) 422-6765. For Owl Pellet Kits, call 1-800-4PELLET.

These companies have the pellets as well as charts and drawings of bones, rodents, and birds. They also have excellent illustrations of food webs. The charts and drawings help students figure out exactly which animals are represented in their pellet. This helps them be more precise in their investigation instead of simply piling up unknown bones. If you know of an owl roost (check abandoned barns), you will be able to find a pile of owl pellets below the owls' favorite resting spots.

Estimated Time

Two or three 50-minute periods

Interdisciplinary Connections

Language Arts Have students research what type of plants rodents eat to write about a more complete food chain of an owl.

Prerequisites and Background Information

An owl is a nocturnal hunter. Like other birds of prey it is a raptor and swallows its prey whole. An owl cannot break up the bones and fur by chewing. Therefore it cannot digest anything larger than the openings in its intestine. The owl regurgitates the bones, fur, and feathers of its prey in the form of a compact pellet covered with mucus. The pellets dry quickly and accumulate under the owl's roost. Typically an owl will regurgitate two pellets a day. The rodents that are most often found in these pellets are voles, shrews, and mice. However, you can also find small birds and the cocoons of large insects. Since no bones are digested, students can find almost complete skeletons inside the pellet. Sometimes even the skull and lower jawbones are intact because fur has matted around them.

IMPLEMENT

Introduce Enrichment 2-1 by giving students some background as to how owl pellets are formed and what owls usually eat. Explain to students that the pellets are safe to handle. Point out that the pellets do not have any flesh in them because the owl digested it all. Likewise, reassure students that the pellets do not have any maggots or other decomposers inside.

Steps 1-3 Divide the class into pairs, and distribute all other materials before you hand out the pellets. Warn students to be very gentle with the pellets, scraping the top of the pellet with their probe or scalpel. Otherwise, they'll break the bones inside. Ask students to read through all the steps before they begin.

As they begin the activity, tell students they'll need to keep bones and fur separate as they dissect since the activity lasts more than one day. Each group will need one petri dish in which to put the fur they are still analyzing and one petri dish in which to put the bones that they've found. As students find bones, they'll want to know which animals the bones came from. Refer them to Resources 1 and 2.

Extend Enrichment 2-1 by having students draw a food chain of an owl, as in Activity 2-1: Draw a Food Chain. In order to complete the food chain, students will have to research what plants each rodent eats.

Helpful Hints

Remains of birds and insect cocoons are rare in most batches of owl pellets. Therefore, draw attention to any such remains that are found. Encourage the students to share their findings with each other.

Step 4 On the second and third days students will be finishing their dissecting and can begin sorting, gluing, and labeling the bones on construction paper. The charts and drawings of bones are important at this point. Encourage students to be creative in their organization of the bones: they can try to reconstruct a skeleton, or group the bones by type (femur, tibia, scapula, etc.) or by the animal they came from.

You may wish to assign the Activity Report as written class work or homework.

ASSESS

Use the final product, an organized poster of all the bones found in an owl pellet, and responses to the Activity Report to assess if students can

\checkmark demonstrate careful and thorough lab skills required to complete a dissection.

\checkmark identify the contents of an owl pellet.

\checkmark explain the difference between carnivore and omnivore.

Enrichment 2-1: What Do Owls Eat? – Activity Report Answer Key

  • Sample answers to these questions will be provided upon request. Please send an email to teachers-requests@ck12.org to request sample answers.
  1. Before dissection: Length of owl pellet: Width of owl pellet: Diameter: Observations of outside of pellet:
  2. Are owls carnivores or omnivores? (Can you find evidence that owls eat plants?) Explain why you think so.
  3. Use the hand lens to examine your findings. Sketch any two items found in your owl pellet. Label your sketch.
  4. Where do you think would be the best place to find owl pellets?

Enrichment 2-1 Activity Guide: What Do Owls Eat? (Student Reproducible)

Introduction

How can ecologists find out what an animal eats without watching it eat? One way is to analyze the leftovers after an animal has eaten. To find out what owls eat we can analyze the pellets of bones and fur that they cough up after eating. Owls swallow their prey whole. They digest all of the soft tissue-the skin, muscle, and fat. But the owl can't digest the bones, fur, or feathers. These leftovers form a compact pellet that the owl regurgitates from their stomachs. The pellets include entire skeletons of whatever the owl ate. In this activity you will discover what an owl eats by dissecting one of these pellets.

Materials

  • Resource 1 - Tweezers
  • Resource 2 - Dissecting needle or probe
  • Activity Report - Construction paper
  • Owl pellet - Ruler
  • White paper - 2 petri dishes

Procedure

Step 1 Place the pellet on the white paper so you can see it better. Before you begin dissecting, make a sketch of your owl pellet, showing its actual size. Then label its length and width in centimeters. Record your observations of the outside of the pellet.

Step 2 Use the tweezers and probe to gently scrape away the fur from the outside of the pellet. Do not try to break the pellet in half or pry into the middle of it. You'll break the bones inside. Separate the bones from the fur or feathers, making sure that you thoroughly clean any debris from the bones. The drawings on Resources 1 and 2 are for comparison of the shape of the bones you will find in the owl pellet. The drawings are much larger than the actual bones.

Step 3 After you have completely extracted all of the bones from the pellet (even the tiny ones), categorize the bones. You can categorize them by putting them in piles by type such as skulls, ribs, hipbones, vertebrae, leg and arm bones. Or make up your own category. Identify the prey of the owl by matching the skulls to the drawings on Resource 1 or Resource 2.

Step 4 Once you have organized the bones, glue them onto the piece of construction paper. Make sure you label each set of bones and what animals you think are included in your owl pellet.

Enrichment 2-1 Resource 1: What Do Owls Eat? (Student Reproducible)

Enrichment 2-1 Resource 2: What Do Owls Eat? (Student Reproducible)

Enrichment 2-1 Activity Report: What Do Owls Eat? (Student Reproducible)

1. Before dissection:

Length of owl pellet: _______

Width of owl pellet: ________

Diameter: _________

Observations of outside of pellet:

2. Are owls carnivores or omnivores? (Can you find evidence that owls eat plants?) Explain why you think so.

3. Use the hand lens to examine your findings. Sketch any two items found in your owl pellet. Label your sketch.

4. Where do you think would be the best place to find owl pellets?

Image Attributions

Description

Authors:

Grades:

6 , 7 , 8

Date Created:

Feb 23, 2012

Last Modified:

Feb 23, 2012
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CK.SCI.ENG.TE.1.Human-Biology-Ecology.3.4

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