Formal Lab Report

Owl Pellet Lab IName ______

Purpose: To see what information about an owl’s diet and niche can be learned from an owl pellet.

Background: On the floor of abandoned buildings, beneath a grove of tall trees, or under the structures that

offer shelter from inclement weather, you may find signs left by some birds that most people see infrequently. These objects are uniformly dark gray and measure from 1 ½ to 3 inches long and ¾ to 1 inch in diameter. They contain a wealth of information about wildlife. They are owl pellets.

Owls are not picky eaters like certain other raptors (animals with hooked beaks and sharp talons [claws] adapted for seizing prey). The owl, like many other birds, swallows its prey whole. Many parts of an animal are not digestible, such as hair, feathers, bones, teeth, and the hard outer shells of insects. The owl’s digestive system allows it to store these indigestible parts

while letting the digestible parts pass to the intestines. The owl then regurgitates the unwanted parts

in the form of a pellet. An owl pellet is a roundish mass that is covered with fur and sometimes

feathers from its prey. Fresh specimens are shiny and coated with mucus. Bones and other hard

remains are located within the interior of the pellet. About 12 hours after consuming a meal, an owl

casts, or regurgitates a pellet. Owl pellets are clean of all flesh and virtually odorless.

Owl pellets can provide evidence of the owl’s dietary habits and role in its environment, or niche.

Owl pellets have been used for scientific study of small mammals and their distribution. With owls

doing the collecting, the scientists must locate the owl roost to obtain the pellets and then study the

skulls and bones of small prey living in an area. From these bones the prey species can be counted

and identified.

The owl plays a role in limiting the population size of its prey. Of the animal species common to an

owl’s diet, the prey species that is most abundant in the area will be the species most likely to be

captured and consumed by the owl. This limits the population size of that herbivore, which in turn

protects the supply of plants upon which the owl’s prey feeds. Farmers especially appreciate barn

owls, which keep populations of crop-eating rodents under control.

Materials: barn owl pellet, metric ruler, metric caliper, glass baby food jar with lid, water, dishwashing

detergent, cheesecloth, rubber band, blue plastic weighing “boat”, triple beam balance forceps, probe, gloves (optional—provided by student), peroxide solution, 100 ml beaker, white glue,

5 x 8 index card, egg carton.

Procedure:Wash your hands thoroughly at the end of each period while doing this lab!

1. Keeping the foil on the pellet, measure and record its length and width in cm using the metric

caliper. Record your results in Data Table #1.

2. Carefully peel the foil off of the pellet. Place the pellet in a blue weighing “boat”.

3. Examine the outside of the pellet. Use a bulleted list to describe external features.

(space provided on Data Table #1)

4. Place the pellet on the pan of a triple beam balance and find its mass. Record your data in

Data Table #1. Remember to subtract the weight of the weighing “boat”!

5. Place your “naked” pellet in a clean baby food jar and cover the pellet with water.

(or fill the jar halfway with water, whichever is greater)

6. Bring your jar and pellet up to your teacher. A single drop of dishwashing liquid will be added.

7. Close the jar and shake gently for 30 seconds. Let the jar stand for five minutes and shake again.

8. Use a wax pencil to write your name & class period on jar. Place jar and pellet in lab area under

the sign for your class period. Leave pellet to soak over night.

9. Get small rubber band and square piece of cheesecloth from teacher.

10. Open baby food jar and use a rubber band to secure cheesecloth over the opening of jar.

11. Pour the contents of the jar through the cheesecloth into a 100ml beaker.

12. Discard the liquid in the sink—be sure no solids go into the sink – that means check for

bones BEFORE you pour the water down the drain!

13. Place the contents of the jar (the now soaking wet pellet!) on a piece of paper towel.

14. Carefully, separate the pellet into two halves. Be sure not to break any bones!

15. Each partner will work with half of the pellet and separate the bones from the fur, feathers and

other debris in the pellet.

16. Dissect the pellet completely and save all the bones. Use probes, forceps or your fingers as

necessary, but proceed carefully to avoid crushing any small bones.

17. Clean the bones as thoroughly as possible and place them in an empty egg carton.

18. After checking with the teacher that you are indeed done, wrap the fur and other soft materials

up in the piece of paper towel they are on and discard it into the trashcan.

19. Use the picture chart to sort the bones. Separate the bones by type and place them in the

individual, labeled sections of your egg carton.

20. Record the bone types found in your pellet and the number of each kind on Data Table #2.

21. Using the charts and booklets, identify the type of organism you have using the cranium and

mandibles. Check with your teacher to make sure you have identified the organism(s) correctly!

22. Add your results to the class data table.

23. Choose your best skull. Using the bones for which you have the most complete skeleton and

that match your skull, reconstruct the skeleton on paper. Use the skeleton rubric and other class packets for help. NOTES: “Bone bartering” is permissible! All large bones should clearly be from the same animal!

24. Place your most complete set of bones in a jar and cover them with peroxide solution (see

teacher for solution!). Cap the jar and leave the bones in this solution for 24 hours.

25. Rinse the bones with fresh water and allow them to dry.

26. Get small rubber band and square piece of cheesecloth from teacher.

27. Open baby food jar and use a rubber band to secure cheesecloth over the opening of jar.

28. Pour the contents of the jar through the cheesecloth into a 100ml beaker.

29. Discard the liquid in the sink—be sure no solids go into the sink – that means check for

bones BEFORE you pour the water down the drain! Check cheesecloth too!

30. Please put the names of your group members and class section on the back of an index card.

Identify the type of skeleton under your names. Do not write “rodent”!

31. Using white glue, reassemble the clean bones to affix them to the front of the index card.

Please be neat and pay attention to how the bones are positioned!

32. Clean up!! Wipe tables, close glue bottles, rinse and return all equipment used, store materials in

appropriate area in lab…

Data: