Owls’ Who-Who
Owl Pellet Dissection
Developed by: Lisa McCready
Concepts Addressed: Owl Pellet Dissection, Owl Adaptations - Biology
Lab Goals: Students will begin to understand how to classify the skeletal parts of owl prey and begin to
intellectualize the importance of owl pellet studies and owl adaptations.
Lab Objectives:
 Students will conduct measurements
 Students will demonstrate the capability to manipulate tools to dissect an owl pellet
 Students will differentiate and categorize bones belonging to different animals
 Students will record data on owl pellet contents
 Students will hypothesize about the owls prey and habitat
 Students will calculate the amount of prey eaten over weeks, months, and years based on owl
pellet contents
 Students will summarize data via graphs and charts
 Students will demonstrate the capability to articulate skeletons
 Students will discover the importance of owl pellet studies
Oregon Benchmark(s) Addressed: Lesson can be adapted for many grade levels. Below are
benchmarks that can be met for 1st through 5th grade.
First Grade
1.1
Structure and Function: Living and non-living things have characteristics and
properties.
1.1P.1 Compare and contrast physical properties and composition of objects.
1.1L.1 Compare and contrast characteristics among individuals within one plant or animal
group.
1.2
Interaction and Change: Living and non-living things interact.
1.2L.1 Describe the basic needs of living things.
1.3
Scientific Inquiry: Science explores the natural world using evidence from
observations.
1.3S.1 Identify and use tools to make careful observations and answer questions about the
natural world.
1.3S.2 Record observations with pictures, numbers, or written statements.
1.3S.3 Describe why recording accurate observations is important in science.
Second Grade
2.1
Structure and Function: Living and non-living things vary throughout the natural
world.
2.1L.1 Compare and contrast characteristics and behaviors of plants and animals and the
environments where they live.
2.3
Scientific Inquiry: Scientific inquiry is a process used to explore the natural world
using evidence from observations.
2.3S.1 Observe, measure, and record properties of objects and substances using simple tools to
gather data and extend the senses.
2.3S.2 Make predictions about living and non-living things and events in the environment based
on observed patterns.
2.3S.3 Make, describe, and compare observations, and organize recorded data.
Third Grade
3.3
Scientific Inquiry: Scientific inquiry is a process used to explore the natural world
using evidence from observations and investigations.
3.3S.1 Plan a simple investigation based on a testable question, match measuring tools to their
uses, and collect and record data from a scientific investigation.
3.3S.2 Use the data collected from a scientific investigation to explain the results and draw
conclusions.
Fourth Grade
4.1
Structure and Function: Living and non-living things can be classified by their
characteristics and properties.
4.1L.1 Compare and contrast characteristics of fossils and living organisms.
4.2
Interaction and Change: Living and non-living things undergo changes that involve
force and energy.
4.2L.1 Describe the interactions of organisms and the environment where they live.
4.3
Scientific Inquiry: Scientific inquiry is a process of investigation through questioning,
collecting, describing, and examining evidence to explain natural phenomena and
artifacts.
4.3S.1 Based on observations identify testable questions, design a scientific investigation, and
collect and record data consistent with a planned scientific investigation.
4.3S.2 Summarize the results from a scientific investigation and use the results to respond to the
question being tested.
4.3S.3 Explain that scientific claims about the natural world use evidence that can be confirmed
and support a logical argument.
Fifth Grade
5.2
Interaction and Change: Force, energy, matter, and organisms interact within living
and non-living systems.
5.2L.1 Explain the interdependence of plants, animals, and environment, and how adaptation
influences survival.
5.3
Scientific Inquiry: Scientific inquiry is a process of investigation based on science
principles and questioning, collecting, describing, and examining evidence to explain
natural phenomena and artifacts.
5.3S.1 Based on observations and science principles, identify questions that can be tested, design
an experiment or investigation, and identify appropriate tools. Collect and record multiple
observations while conducting investigations or experiments to test a scientific question
or hypothesis.
5.3S.2 Identify patterns in data that support a reasonable explanation for the results of an
investigation or experiment and communicate findings using graphs, charts, maps,
models, and oral and written reports.
5.3S.3 Explain the reasons why similar investigations may have different results.
Materials and Costs:
List the equipment and non-consumable material and estimated cost of each
Magnifying Glasses, $2.70 each x 30 (http://wardsci.com/) ...............................$81.00
Tweezers (Plastic Forceps) $4.95 per package of 6 x 5 (http://wardsci.com/) ....$24.75
Rulers (Clear works best) $0.75 x 30 (http://wardsci.com/) ................................$22.50
Scale (1 is sufficient) (http://wardsci.com/) .........................................................$19.50
Microscope (Optional) (http://pellet.com/) ..........................................................$66.00
Estimated total, one-time, start-up cost: ..................................................................$213.75
List the consumable supplies and estimated cost for presenting to a class of 30 students
Owl Pellets, $1.85 x 30 (http://pellet.com/) .........................................................$55.50
Black Construction Paper, $1.75 for a package of 50............................................$1.75
Toothpicks, $1.00 for package of 250 ...................................................................$1.00
Pencils, $.08 x 30 ...................................................................................................$2.40
Dixie Cups, $5.99 for package of 100 ...................................................................$5.99
Glue Sticks, $8.29 for package of 18, $8.29 x 2 ..................................................$16.58
Wax Paper, $2.00 a roll..........................................................................................$2.00
Ziploc Bags (Students can take their bones home in them) $5.00 for 50 ..............$5.00
Estimated total, one-time, start-up cost: ....................................................................$90.22
Copies and Handouts (one per student)
Owl Pellet Dissection Data Sheet
Bone Charts
Rat Skeleton/Articulation Guide (Optional)
Mouse Skeleton/Articulation Guide (Optional)
Skull Identification Visual Dichotomous Key (Optional)
Skull Identification Written Dichotomous Key (Optional)
Owl Coloring/Informational Pages (Optional)
Each year thereafter, cost will only be $90.22 unless you have to replace your non-consumable
materials.
Time:
Initial Preparation time: 60 minutes (buying supplies)
Preparation time:
15 minutes (getting supplies together before lesson)
Instruction time:
10 – 15 minutes for lecture
45 – 60 minutes for activity
10 – 15 minutes for wrap up/conclusion
Clean-up time:
5 minutes
Background Information:
Sources
http://en.wikipedia.org/wiki/Main_Page
http://www.kidwings.com/owlpellets/flash/v4/index.htm
http://www.kidwings.com/teacher/owlpellets/index.htm
http://www.eagle-bluff.org/Owl%20Pellets.pdf (this link provides another lesson plan for owl dissection, helpful forms,
and background information on owls and their adaptations – it is an excellent source).
Rodentia is an order of mammals also known as rodents, characterized by two continuously growing
incisors in the upper and lower jaws that must be kept short by gnawing.
Forty percent of mammal species are rodents, and they are found in vast numbers on all continents other
than Antarctica. Common rodents include mice, rats, squirrels, chipmunks, gophers, porcupines,
beavers, hamsters, gerbils, guinea pigs, degus, chinchillas, prairie dogs, and groundhogs. Rodents have
sharp incisors that they use to gnaw wood, break into food, and bite predators. Most eat seeds or plants,
though some have more varied diets. Some species have historically been pests, eating seeds stored by
people and spreading disease.
In terms of number of species—although not necessarily in terms of number of organisms (population)
or biomass—rodents make up the largest order of mammals. There are about 2,277 species of rodents
(Wilson and Reeder, 2005), with over 40 percent of mammalian species belonging to the order. Their
success is probably due to their small size, short breeding cycle, and ability to gnaw and eat a wide
variety of foods. (Lambert, 2000)
Rodents are found in vast numbers on all continents except Antarctica, most islands, and in all habitats
except oceans. They are the only placental order, other than bats (Chiroptera) and Pinnipeds, to reach
Australia without human introduction
Shrews are small, mouse-like mammals of the family Soricidae. Although their external appearance is
generally that of a long-nosed mouse, the shrews are not rodents and not closely related: the shrew
family is part of the order Soricomorpha. Shrews have feet with five clawed toes, unlike rodents, which
have four. Shrews are also not to be confused with either tree shrews or elephant shrews, which belong
to different orders.
Shrews are distributed almost worldwide: of the major temperate land masses, only New Guinea,
Australia, and New Zealand do not have native shrews at all; South America has shrews only in the farnorthern tropics, including Colombia. In terms of species diversity, the shrew family is the fourth most
successful of the mammal families, being rivaled only by the muroid families Muridae and Cricetidae
and the bat family Vespertilionidae.
All shrews are comparatively small, most no more than mouse size. The largest species is the House
Shrew (Suncus murinus) of tropical Asia which is about 15 cm long and weighs around 100 grams;
several are very small, notably the Etruscan Shrew (Suncus etruscus) which at about 3.5 cm and 2 grams
is the smallest living terrestrial mammal.
In general, shrews are terrestrial creatures that forage for seeds, insects, nuts, worms and a variety of
other foods in leaf litter and dense vegetation, but some specialize in climbing trees, living underground,
in the subniveal layer or even hunting in water. They have small eyes, and generally poor vision, but
have excellent senses of hearing and smell. They are very active animals, with voracious appetites and
unusually high metabolic rates. Shrews must eat 80-90 % of their own body weight in food daily.
They do not hibernate, but are capable of entering torpor. In winter, many species undergo
morphological changes that drastically reduce the animal's body weight. Shrews can lose between 30%
and 50% of their body weight, shrinking the size of bones, skull and internal organs.
Whereas rodents have gnawing incisors that grow throughout life, the teeth of shrews wear down
throughout life, a problem made more extreme by the fact that they lose their milk teeth before birth, and
therefore have only one set of teeth throughout their lifetime. Apart from the first pair of incisors, which
are long and sharp, and the chewing molars at the back of the mouth, the teeth of shrews are small and
peg-like, and may be reduced in number.
Moles are the majority of the members of the mammal family Talpidae in the order Soricomorpha.
Although most moles burrow, some species are aquatic or semi-aquatic. Moles have cylindrical bodies
covered in fur, with small or covered eyes; the ears are generally not visible. They eat small
invertebrates living underground. Moles can be found almost anywhere in North America, Asia, and
Europe, although there are no moles in Ireland.
A mole's diet primarily consists of earthworms and other small invertebrates found in the soil. The mole
may also occasionally catch small mice at the entrance to its burrow. Because their saliva contains a
toxin that can paralyze earthworms, moles are able to store their still living prey for later consumption.
They construct special underground "larders" for just this purpose; researchers have discovered such
larders with over a thousand earthworms in them. Before eating earthworms, moles pull them between
their squeezed paws to force the collected earth and dirt out of the worm's gut.
Birds (class Aves) are winged, bipedal, endothermic (warm-blooded), vertebrate animals that lay eggs.
There are around 10,000 living species, making them the most numerous tetrapod vertebrates. They
inhabit ecosystems across the globe, from the Arctic to the Antarctic. Birds range in size from the 5 cm
(2 in) Bee Hummingbird to the 3 m (10 ft) Ostrich. The fossil record indicates that birds evolved from
theropod dinosaurs during the Jurassic period, around 150–200 Ma (million years ago), and the earliest
known bird is the Late Jurassic Archaeopteryx, c 155–150 Ma. Most paleontologists regard birds as the
only clade of dinosaurs that survived the Cretaceous–Tertiary extinction event approximately 65.5 Ma.
Modern birds are characterized by feathers, a beak with no teeth, the laying of hard-shelled eggs, a high
metabolic rate, a four-chambered heart, and a lightweight but strong skeleton. All birds have forelimbs
modified as wings and most can fly, with some exceptions including ratites, penguins, and a number of
diverse endemic island species. Birds also have unique digestive and respiratory systems that are highly
adapted for flight. Some birds, especially corvids and parrots, are among the most intelligent animal
species; a number of bird species have been observed manufacturing and using tools, and many social
species exhibit cultural transmission of knowledge across generations.
Many species undertake long distance annual migrations, and many more perform shorter irregular
movements. Birds are social; they communicate using visual signals and through calls and songs, and
participate in social behaviors including cooperative breeding and hunting, flocking, and mobbing of
predators. The vast majority of bird species are socially monogamous, usually for one breeding season at
a time, sometimes for years, but rarely for life. Other species have breeding systems that are polygynous
("many females") or, rarely, polyandrous ("many males"). Eggs are usually laid in a nest and incubated
by the parents. Most birds have an extended period of parental care after hatching.
Many species are of economic importance, mostly as sources of food acquired through hunting or
farming. Some species, particularly songbirds and parrots, are popular as pets. Other uses include the
harvesting of guano (droppings) for use as a fertilizer. Birds figure prominently in all aspects of human
culture from religion to poetry to popular music. About 120–130 species have become extinct as a result
of human activity since the 17th century, and hundreds more before then. Currently about 1,200 species
of birds are threatened with extinction by human activities, though efforts are underway to protect them.
A crop (or croup) is a thin-walled expanded portion of the alimentary tract used for the storage of food
prior to digestion that is found in many animals, including gastropods, earthworms, leeches, insects, and
birds.
In a bird's digestive system, the crop is an expanded, muscular pouch near the gullet or throat. It is a part
of the digestive tract, essentially an enlarged part of the esophagus. As with most other organisms that
have a crop, the crop is used to temporarily store food. Not all birds have a crop. In adult doves and
pigeons, the crop can produce crop milk to feed newly hatched birds.
Scavenging birds, such as vultures, will gorge themselves when prey is abundant, causing their crop to
bulge. They subsequently sit, sleepy or half torpid, to digest their food.
Procedure
1. LECTURE: Introduce information via the game.
For my lecture I use a game with questions that are multiple choice, true or false, or wild. The wild
questions are open ended questions. As you work through the questions with the students you can
use the material as a stepping stone for lecture and furthering the students understanding surrounding
owls. I created a board with letters that spelled out, “Owl Pellets Rock!” A student would choose a
letter and behind that letter was either “M/C, T/F, or WILD.” While the student choosing the
question is the one who gets to give the answer, all students should have a piece of paper and write
their guesses down as you progress through the game. This gives all students a sense of involvement
and gets them excited about getting the questions right. You can customize your game and content to
fit your students and goals.
The following are 15 questions (the majority of which were taken from the lesson plan found at
http://www.eagle-bluff.org/Owl%20Pellets.pdf)
1. T/F Owls can turn their heads all the way around?
a. FALSE – All owls have eyes that are fixed in the sockets, so they must be
able to turn their heads to see. However, they can only turn their heads about
270 degrees.
2. T/F All owls hunt at night?
a. FALSE – Northern Hawk Owls and Great Gray Owls hunt primarily during
the day.
3. M/C
If owls were the same size as humans, their eyes would be the size of
oranges, grapefruits, or watermelons?
a. Grapefruits – The eyes of an owl are about the same size as human eyes, but
compared to their head and body size, their eyes are extremely large.
4. WILD
Which owl is generally stronger, male or female?
a. FEMALE – They are usually larger and therefore, stronger than the males.
5. M/C
There are roughly how many species of owls worldwide, 75, 150, or 300?
a. 150.
6. M/C
The Elf Owl is the smallest owl, standing only 6 inches tall and it weighs
as much as, 22 pennies, 66 pennies, or 100 pennies?
a. 22 PENNIES – 2 ounces.
7. M/C
Some Great Horned Owls in the wild have lived up to 9, 27 ½, or 75 years
old?
a. 27 ½ YEARS OLD
8. WILD
Using this keen sense, a Barn Owl can locate its prey in total darkness?
a. HEARING.
9. M/C
A Barn Owl can hear a mouse’s footsteps from how many yards away, 30,
60, or 90?
a. 30 YARDS.
10. T/F Owls do not have teeth?
a. TRUE – They use their strong beaks to tear apart prey and swallow large
chunks whole.
11. WILD
Owls eat a wide variety of animals, making them what type of eater?
a. CARNIVORES.
12. WILD
It is in the body part that the owl’s meal is separated into two parts,
digestible and non digestible?
a. GIZZARD – If it is digestible, it passes through the digestive tract and if it is
not, it forms into a pellet (Gizzard is a specialized stomach with muscles that
form the pellets).
13. WILD
This branch of Zoology is the study of birds?
a. ORNITHOLOGY.
14. WILD
This is another name for birds of prey like owls, hawks, eagles, and
falcons?
a. RAPTOR.
15. WILD
Owls do not have this particular organ that other birds, like eagles and
hawks have, which allows for storage of food until the stomach is ready to receive it.
Because of the lack of this organ, owls must regurgitate their pellets more often?
a. CROP – an expanded, muscular pouch near the throat.
2. Transition into activity with an explanation of the tools/supplies and their purpose:
a. Owl Dissection Data Sheet – make sure to record data as you go along.
b. Owl Pellets – make sure to take measurements before getting wet to dissect.
c. Gloves – only required if the pellets are not safe for direct handling, or if the students prefer
to wear them.
d. Rulers – use to get length and width – decide as a class to either use cm or inches.
e. Scale – use to get the weight/mass in grams.
f. Wax Paper – work with your owl pellet over the paper.
g. Dixie Cups – fill with small amount of warm water and use to dip the pellet in. This will
make the pellet easier to pull apart.
h. Toothpicks – use as a tool, along with the tweezers, to gently pry apart the pellet and its
contents.
i. Tweezers (plastic) – the students are less likely to crush the bones with plastic tweezers, but
they still need to be careful.
j. Black Construction Paper – the bones can be laid on this paper.
k. Magnifying Glasses – use to get a better look at the pellet contents.
l. Bone Charts/Dichotomous Keys – use to identify contents.
m. Glue Sticks – use to articulate the skeleton.
n. Articulation Paper – use this paper to glue the bones onto.
o. Ziploc bags – for the students to take their bones home in.
3. Owl Pellet Dissection Directions:
a. Remove pellet from foil.
b. Record length, width, and weight.
c. Dip pellet in Dixie Cup as needed.
d. Set pellet on wax paper and begin to carefully pull apart with toothpicks and tweezers.
e. Place bones on black construction paper.
f. Compare bones to charts and record data.
g. Answer all questions on data sheet.
h. Using articulation diagram/paper, glue the bones in place.
i. Clean up.
4. ACTIVITY TIME: As the students are working through the experiment move around the classroom
and observe. Ask questions and provide encouraging feedback, however, do not provide answers to
the students immediately if they have questions. Try to have them figure it out on their own.
5. CLEAN UP.
6. FOLLOW UP/CONCLUSION: There are many things you can do at this point. It all depends on
your goals for your class. The following are suggestions based on this particular lesson:
a. Compile the data from questions 1 through 4 into graphs or charts as a class and discuss.
Following are suggestions for different approaches:
i. Graph the mass of the pellet vs. the number of skulls found within the pellet.
ii. Graph the length vs. the width.
iii. Develop a histogram of the skull lengths.
iv. Graph the total number of bones vs. the total number of skulls.
v. Let the students decide what data would be best to graph.
b. Discuss all, or some, of questions 5 through 10. Close with a discussion about the importance
of these studies.
7. QUIZ: Use the quiz included, or provide your students with your own assessment based on the
specifics of your lesson. Choose an appropriate quiz time, but it should not be given directly after the
lesson.
Assessment:
QUIZ – 30 copies printed before lesson
1. Using the provided skulls and bone chart, please list what type of animal the skulls belong to:
a. Skull #1
b. Skull #2
2. Provide as many reasons as possible why it can be important to study the contents of owl pellets
(1 point per reason). You can use the back of the paper if you run out of room:
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
3. Why do owls regurgitate material in the form of pellets?
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
4. What was the most interesting thing you learned participating in this lesson?
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
Additional Information:
Origional sourses and information:

Owl Pellet Dissection Data Sheet, pg 15
of the following PDF file – I modified
the Owl Pellet Dissection Data Sheet to
include weight and question number 8.
http://www.eaglebluff.org/Owl%20Pellets.pdf

Bone Chart http://www.edb.utexas.edu/faculty/jacks
on/pdf/Bone_Chart.pdf

Rat Skeleton http://www.edb.utexas.edu/faculty/jacks
on/pdf/Rat_Skeleton.pdf

Additional Skull Identification
Dichotomus Key (Visual), pg. 14 of the
following PDF file - http://www.eaglebluff.org/Owl%20Pellets.pdf

Additional Skull Identification
Dichotomus Key (Written) http://www.kidwings.com/teacher/owlp
ellets/dichotomouskey.htm

Owl Coloring Pages http://www.kidwings.com/teacher/colori
ngpages/main.htm
Crop
Modified from: http://www.eagle-bluff.org/Owl%20Pellets.pdf
Owl Pellet Dissection Data Sheet
NAME: ______________________________________________
1. What is the size of your pellet?
Length ________ Width ________ Weight __________
2. How many skulls were in your pellet? ________
3. Record the number of each of the animals that your owl ate to form your pellet.
Rodent ______
Shrew ______ Mole ______ Bird ______ Other ______
4. How many other kinds of bones did you find?
Ribs ______ Jaws ______ Pelvis ______ Scapula ______ Humerus ______
Vertebrae ______ Other ______
5. Did you find a complete skeleton? List some reasons why you may not find a whole skeleton.
_________________________________________________________________________________
_________________________________________________________________________________
_________________________________________________________________________________
6. What was the diet of the animals whose skulls you found in the pellet? Did you find any evidence of
this?
_________________________________________________________________________________
_________________________________________________________________________________
7. Where does the owl’s prey live? Describe its habitat.
_________________________________________________________________________________
_________________________________________________________________________________
8. Assume that an owl forms one pellet each day, which contains 3 skulls. How many animals would
an owl eat? In a week __________
In a month __________
In a year __________
9. What can you say about the mammal population in the area where your pellet was found? Is your
answer a good guess, or would you need more pellets to be sure? Why?
_________________________________________________________________________________
_________________________________________________________________________________
_________________________________________________________________________________
10. Why do you think farmers might want owls in their barns?
_________________________________________________________________________________
_________________________________________________________________________________
________________________________________________________________________________
Answers
(do not print for the students):
5. Reasons for incomplete skeletons:
a. Some bones can fall off the carcass as the bird tears and lifts the prey to their mouth.
b. Some smaller bones may actually get digested.
c. Some bones may remain in the gizzard and be regurgitated later.
6. Possible animals found in pellet:
a. Rodents – Most eat seeds and plants, diet can vary though.
b. Shrews – Seeds, nuts, insects, worms, vegetation.
c. Moles – Earthworms, small invertebrates.
d. Birds – Seeds, exoskeletons of insects, plant stalks, fish bones – basically anything a bird
eats that is not digestible.
8. Calculations:
a. In a week – 3 skulls per pellet, 1 pellet per day = 21
b. In a month – 4 weeks in a month (average 4.3) = 84 (90.3)
c. In a year – 12 months in a year = 1,008
9. The data acquired can tell us an average for one owl, or all owls combined for the class, but we also
need to know how many owls are in the area to get a better idea of the mammal population.
10. To stop rodent infestations.
From: http://www.edb.utexas.edu/faculty/jackson/pdf/Bone_Chart.pdf
From: http://www.edb.utexas.edu/faculty/jackson/pdf/Rat_Skeleton.pdf
Original Source: ©1996 Carolina Biological Supply Company
From: http://www.eagle-bluff.org/Owl%20Pellets.pdf
From: http://www.kidwings.com/teacher/owlpellets/dichotomouskey.htm
If your animal has...
1. a) 3 or fewer teeth on each side of its upper jaw?
b) At least 9 teeth on each side of its upper jaw?
Then...
go to 2.
go to 3.
2. a) 2 biting teeth on its upper jaw?
b) 4 biting teeth on its upper jaw?
go to 4.
the skull is from a rabbit.
3. a) A skull length of 23 mm or less and brown teeth?
b) A skull length of more than 23 mm and 44 teeth?
the skull is from a shrew.
the skull is from a mole.
4. a) The roof of its mouth extending past the last molar?
b) The roof of its mouth not extending past the last molar?
go to 5.
go to 6.
5. a) A skull length of 22 mm or less?
b) A skull length of more than 22 mm?
the skull is from a mouse.
the skull is from a rat.
6. a) Flat molars (back teeth)?
the skull is from a meadow vole.
b)
Rounded molars (back teeth)?
the skull is from a deer mouse.
From: http://www.kidwings.com/teacher/coloringpages/main.htm