OWL PELLET DISSECTION
NAME_________________________
Problem:
What does the owl's diet tell us about its habitat? owl
screech site
Background Information: Owl
Pellets: When you see an owl pellet, you will think that it
is feces, but remember owl pellets are ejected from the mouth.
Owls typically swallow their prey whole or in large pieces. Owl pellets
are masses of bone, teeth, hair, feathers and exoskeletons of various animals
eaten by birds of prey (raptors). Owls feed early in the evening and
regurgitate a single pellet approximately 20 hours after eating. Unlike snakes,
the protein enzymes and strong acids which occur in the digestive tract of
raptors do not digest the entire meal. The relatively weak stomach muscles of
the bird form the undigested fur, bones, feather etc. into wet slimy pellets. In
this process even the most fragile bones are usually preserved unbroken. A
bird's stomach includes an anterior pouch called the proventriculus and a
muscular posterior portion called the gizzard. In owls, the gizzard compresses
indigestible parts of their prey (hair, bones, teeth, and feathers) into matted
pellets. These pellets pass into the proventriculus where they remain until
something stimulates the owl to spit them out. Hawks and other birds
of prey, some gulls and herons also regurgitate undigested remains. The
barn owls produces 1 to 2 pellets per day.
Scientists study pellets to discover differences in habitat and prey.
Pellets also reveal information about the relative number of small animals found
in an owl's feeding area. Pellets are important for scientific study because
they give us a picture of what the owl eats. Other ways to discover what
an organism eats is to
1. Dissect the stomachs of dead animals to see what is found
in there.
2. Examine animal feces to see what plant or animal parts
made it all the way through without being digested. (SCATOLOGY)
Owl pellets themselves are ecosystems, providing food and shelter for
communities which may include clothes moths, carpet beetles and fungi. Clothes
moth larvae are frequently abundant in pellets, feeding on fur and feathers. The
black spheres about the size of periods (.) that are found in the pellets are
the droppings of the caterpillars. The larvae metamorphose near the surface of a
pellet in cocoons made of fur.
The pellets WE USE were collected and fumigated to kill all bacteria and
parasites. They are perfectly safe to touch.
Materials: owl pellets, probe, used film containers or
pill bottles, forceps, old yogurt cups, glue for mounting, paper towel,
identification keys, bone sorting sheet
(Bone
Chart (http://www.carolina.com/owls/guide/Owl_Pellet_Bone_Chart_grid.pdf)
1.Measure the length and
width of your owl pellets.
Length of your owl pellet_______
Width of your owl pellet_______
2. Carefully examine the
exterior of the pellet. Do you see any signs of fur? __________
Do you see any signs of
feathers? ____________
3. What color was your pellet? _____________
Put your pellet
on a piece of paper towel. Carefully use a probe to break apart the
owl pellet and observe what is in it. Use a probe to expose all bones for
identification. Because some of the bones are so tiny and fragile,
if you are not careful, you could either lose or crush a bone. Use forceps
(tweezers) and a probe to do this. Put the fur aside for disposal.
Organize the
bones into groups (skulls, ribs, vertebrae, leg bones)
and label them. Use the bone diagram to help you identify your bones and assemble
the bones on construction paper as shown by the bone sorting chart.
Decide how many prey animals you have and record this information on the
chart. You may only have one. If more than one, try
to sort the bones to go with the skulls. Glue them to the construction
paper.
Next identify your prey animal using the identification guide
hung up around the room. Look at the:
Shape and size of the skull
Shape of eye sockets
Length of the snout compared to the rest of the skull
Grade will be based on
neatness, labeling and organization.
Analysis:
Answer the following questions on the back
page or on another sheet of paper
5. What do we know about the digestive system
of an owl based upon the pellets?
6. Owl pellets not only can give
us information about the diet of the owl, owl pellets also provide a habitat for
other animals, in fact an owl pellet is a little ecosystem all on its own. What
kind of animals are found in the owl pellet ecosystem. (Hint: read the background
at the beginning)
7. Other types of birds form
pellets. What would you expect to find in the pellet of a seagull?
8. Owls, hawks, and eagles are
types of raptors, animals which have hooked beaks and sharp claws, and are
therefore adapted for seizing prey animals. Hawks and eagles differ from owls in
that they eat their prey animals by tearing them into small pieces, picking out
the flesh and avoiding most of the fur and bones. They also have strong stomachs
which can digest most of the bone material which they might eat. The relatively
small amount of indigestible bone and fur that remain will be compacted by their
stomach muscles into a pellet similar to the owl's. Do you think an eagle pellet
would be as useful for dissecting as an owls? Why or why not?
9. Construct a diagram of a food
web (of at least 5 animals) with an owl at the uppermost trophic level. Use an
arrow to show which organism is the consumer or predator.
10. How might learning more about the barred owl's diet (what
it eats) help us preserve the animal?
11. Based on the data, how would you describe the diet of the
owl?
12. What does the data tell us about the habitat of the owl?
13. Based on the information and data in this lab, do you think
that we could have owls here in Brandon?________ Explain
your answer.
bonus question
14.If you were a zoologist doing a study of what deer eat, how would you
collect your data?
CONCLUSION: Be sure to summarize what you
did
10. Skeleton of LAC Grey mouse.
BONE SHORTING CHART
LINKS:Life
History of the Barred Owl - Ohio DNR
Owl
Pellets Assembling
a Skeleton - Virtual Assembly
Owl
Digestion Owl
Pages - Barred Owl Natural History
Barred
Owl Natural History USGS
Barred Owl Site - w/ Song Owling.com - World's Largest Owl
Website Owl Images You Can Use
What
Owls Eat -- The Bones of a Mouse
Science Content Standards
National Science Content Standards
3. Life Science Standards
Science subject matter focuses on the science facts,
concepts, principles, theories, and models that are important
for all students to know, understand, and use.
K-4 Characteristics of organisms, life cycles of
organisms, organisms and environments
5-8 Structure and function in living systems,
reproduction and heredity, regulation and behavior, populations
and ecosystems, diversity and adaptations of organisms.
Here is an example of citing this page:
Amsel, Sheri. “Movie Worksheets.” What Owls Eat -- The Bones of a
Mouse. Exploring Nature Educational Resource. © 2005 - 2012. March
2, 2012. <http://exploringnature.org/db/detail.php?dbID=27&detID=2317>
