overview: ages: time: 40 - 60 minutes - get to...

Dissecting Owl Pellets

GRAB N’ GO ACTIVITY:

OVERVIEW:This is a hands-on activity that will give your students wonderful insights and tactile experience with owls and what they eat. Your students will handle actual owl pellets, dissecting them to determine what foods owls have eaten.

As a precaution, owl pellets are sterilized before shipping to schools, so they are generally safe to handle without gloves.

However, if any of your students are allergic to animal hair, they may have a reaction to owl pellets, and may be required to use a dust mask. You can also provide a plant sprayer to mist the pellets occasionally, which is effective at keeping dust confined to the tabletop.

The owl pellets your students will dissect will likely have the bones of several mice in them, and possibly the remains of other organisms. Most commercially supplied owl pellets contain mouse bones, and we will assume that in this activity. The best indication of how many mice might have been incorporated into the pellet will be the number of skulls that can be found in a single pellet.

OBJECTIVES:• Gain insights into the diet and biology of owls

through an analysis of the contents of an owl pellet.• Develop a better understanding of mammalian

skeletal anatomy based on remains recovered from owl pellets.

PRIOR KNOWLEDGE:The more your students know about owls before doing this activity, the more they will enjoy and benefit from it. We recommend building up your students’ knowledge and appreciation of owls through any of the following activities:

• Divide your class into groups and give each group a one-day assignment, to find an image and basic information about a species of owl found in Canada. Have them locate this information on the Internet, and make a one-page report that includes:

• A photo of the owl. • Where the owl lives. • What the owl eats. • Details about the size, markings, and

physical features of the owl.

Here is a list of owls found in Canada:-Boreal owl -Screech Owl -Snowy Owl-Barred Owl -Hawk Owl -Great Grey Owl-Great Horned Owl -Barn Owl -Spotted Owl-Northern Pygmy Owl -Short-eared Owl -Burrowing Owl-Long-eared Owl -Flammulated Owl -Northern Saw-whet Owl

Have your students compile these reports into a booklet they can copy for each member of your class.

Ages: 6+Time: 40 - 60 minutes

Get to Know Program • 201-2040 Springfield Road. • Kelowna, British Columbia • T: 250-980-3969 • E: [email protected] • gettoknow.ca



WHAT ARE OWL PELLETS?Owl pellets are neat little packages of fur, bones, and other indigestible stuff that are regurgitated (spit up) sometime after an owl has finished digesting several meals. You can find owl pellets on the ground under trees where owls like to roost or nest.All owls cough up pellets as a part of how they digest their food. Most of the time, they swallow their prey whole without chewing or tearing the flesh apart. This means that owls naturally have a lot more bones, feathers, and fur in their diet. After several meals of whole animals, an owl collects a lot of indigestible material in its gut. All this stuff is gathered in the gizzard, a muscular pouch in the owl’s digestive system. The gizzard operates like a trash compactor, pressing all the bones, fur, feathers, or other indigestible stuff into a firm, ovalshaped ball. When the pellet gets big enough, the owl spits it up and lets it drop to the ground below.

Owls in the wild eat whatever is on the local menu. In other words, owls living where there are lots of mice will eat (you guessed it!) mice. They also eat other things depending on what’s available, including insects, frogs, mice, weasels, small birds, even larger prey like porcupines. As you might expect, larger owls like larger prey, and smaller owl species eat smaller prey. The smallest owls, such as Canada’s Pygmy Owl and Boreal Owl, depend on insects, small birds, frogs, and mice. The Great Horned Owl, Canada’s most common owl, eats a great variety of things including ducks, porcupines, squirrels, grouse, along with its staple food of mice.

The stuff in an owl pellet can tell you a lot about what the owl has been eating. It can also tell you something about the prey animal itself, because its remains are nicely preserved in the pellet.


Biologists who study owls depend on this kind of information, and frequently analyze owl pellets as part of their work in protecting wild owls.

The owl pellets you’ll be working with are totally sanitary. They have been sterilized to kill any bacteria or parasites that might have been present in the pellets when they were fresh. Owls have powerful stomach acids that usually kill all the bacteria in the pellets. Sterilizing the pellets before packaging them is an added precaution. The only problem you might have is if you are allergic to dust. Owl pellets are dusty, but you can get around this by spraying them with a plant sprayer as you work on them, or by wearing a dust mask.



PREPARATION:Owl pellets: you can buy owl pellet dissection kits from any of several science supply companies. See the section “Sources and Resources” at the end of this activity plan for places to get owl pellets. If this activity is new for you, we recommend you dissect an owl pellet of your own as part of your preparation.

For ideas on how to prepare your students so they get the most out of this experience, see the section on “prior knowledge” above.

SAFETY:If any of your students have allergies to mice, animals, or dust, you should provide them with dust masks to wear, or use a plant sprayer to moisten their pellets as they work to control airborne dust particles.

PROCEDURE:The student worksheet contains complete instructions on how to do this activity. Go over these steps with them before allowing them to proceed.

TIPS AND ENRICHMENT:• If you only have one pellet and / or would like to

do a dissection that the whole class can see, use an overhead projector and screen. Your entire class can watch while you demonstrate how to break up the pellet and what can be found inside. You can arrange the bones and other remains on a piece of plastic transparency film.

• Create a mouse “fossil” by arranging recovered mouse bones on the surface of some wet plaster of Paris. Allow the plaster to set, spray the surface with cooking spray, and pour more plaster over the bones. The spray allows the two halves of the plaster imprint to be separated. This will give you an artificial fossil that mimics the challenges faced by palaeontologists who extract delicate fossils from sedimentary rocks.


• Dissecting microscopes can be used to help find and identify smaller bones. If you have dissecting microscopes, be sure your students know how to use them.

SOURCES AND RESOURCES:1. Boreal Northwest (the recent merger of Boreal

Laboratories and Northwest Scientific) has a comprehensive list of owl pellet education resources including supplies of owl pellets, dissecting kits, posters, and much more. Go to http://boreal.com

2. Skulls Unlimited, Oklahoma City, OK. Class kits available. Go to http://www.skullsunlimited.com/owl-pellet-sets.htm

3. Workman Publishing, New York: “Owl Puke” kit includes an owl pellet, dissecting tools, sorting tray, and a wonderfully written and illustrated book on the topic of owls and owl pellets. See http://www.workman.com

4. Jim Cornish of Gander, Newfoundland has developed an excellent student activity on owl pellets. You can download a pdf copy from http://www.cdli.ca/CITE/pellet_activity.pdf



MATERIALS:To complete this activity, you will need:

• One owl pellet • Sheet of newspaper• Sorting tray (egg carton, plastic ice cube tray or

other container with small compartments)• Fine tweezers or forceps• Glue (regular white glue or hot melt glue gun)• Sheet of stiff paper or thin cardboard• An old toothbrush (marked so that no one uses

it by mistake to brush their teeth!)• Magnifying glass (optional)

PROCEDURE1. Find a clean place to work and lay out all the

materials as described in the list above. Be sure you have good lighting.

3. Unwrap the owl pellet over the newspaper.

4. Break the pellet in half, then into smaller and smaller pieces. You can do this with your fingers, or you can pick it apart with a tool like a nail or needle.

5. As you break the pellet into smaller and smaller pieces, you will notice small bones. Use the tweezers (forceps in science-speak) to place them in the sorting tray.

7. The bones may have fur tightly packed in and around them. You’ll need the small brush to remove it.

8. Work through every bit of material from the owl pellet removing any tiny bones you find. If you find seeds, spruce needles, or other identifiable plant material, put this into it’s own pile.

9. When you are done taking apart the pellet, you should have three piles, the biggest with bits

MOUSE BONE IDENTIFICATION CHART:The bones and other material you got from the pellet can tell you something about the owl’s eating habits. Based on the “evidence”, answer the following questions:

1. What animals did the owl eat (hint: don’t assume the owl ate only mice)?

2. Is there evidence of more than one animal in the pellet? How many animals may have been eaten by the owl to make this pellet?

3. Is there plant material in the pellet? How do you think it got there?

4. Select some bones from your sorting tray and use them to build a partial skeleton of one of the owl’s prey.

5. Glue the bones onto the cardboard in the same way they are arranged in the Mouse Bone Identification Chart, and label them.

S u b m i t y o u r w o r k t o t h e G e t t o K n o w C o n t e s t f o r a c h a n c e t o w i n w i l d p r i ze s & g o t o

t o f i n d m o r e f r e e r e s o u r c e s a n d a c t i v i t i e s

gettoknow.ca


of fir and dirt, a smaller one with small bones, and a third with identifiable plant bits such as seeds.

10. Your next task is to identify and sort the bones. Use the chart below to help you identify them. Place each kind of bone in its own compartment in your sorting tray. Use the bone identification chart to help you.

Additional Resources:Find more Educational Resources at: www.gettoknow.org/education/



SOURCED AND ADAPTED FROM: http://www.vrml.k12.la.us/Upload/bonesortingchart.jpg

Skulls

Jaws

Shoulder Blades

Front Legs

Hips

Hind Legs

Assorted Ribs

Assorted Vertebrae




MOUSE BONE CHART

overview: ages: time: 40 - 60 minutes - get to...

Documents