Biology
Owl Pellet Dissection
Key Ideas/Takeaways:
1. Predator-prey relationship and food chains
2. Skeletal structures and bone identification
3. Hunting habits and digestive system of owls
Duration of Lesson: 60-80 minutes
Supplies:
-Chinette plates with sections
-Owl pellets (enough for each student to dissect two-three small ones)
-Tweezers
-Toothpicks
-Disposable nitrile gloves
-Ziploc bags
-One or two magnifying glasses for each table
-Notecards for students to take bones to
-Handout of owl pellet bone identification for each student
Introduction: (15 minutes)
Owl Hunting Habits and the Food Chain
Begin by asking students what they know about owls – what they look like, when are they awake,
what do they eat, etc. Some students may know what owls eat, but a lot of them probably don’t. So to
begin, introduce the idea of a food chain. Up on the board, or on worksheets, offer students three
animals/plants that are in a chain and have them correctly identify the order. For example, a mouse eats
grass and a snake eats mice. Do this a few times with different animals and plant combinations. Then,
have students hypothesize what they think owls eat on their worksheet (see attached). Do they think that
owls are predators or prey? A predator is an animal that eats other animals while prey is an animal that
is eaten by other animals. Often, animals can be both predators and prey. The students should be able to
correctly guess that owls are predators, although they may need some help guessing what they eat.
Now is a good time to introduce some of the owl hunting habits. Owls are nocturnal creatures,
meaning that they hunt at night while other animals are sleeping. Owls use their eyes to spot their prey,
however, they are so big that they cannot move in their sockets. As a result, they have to move their entire
heads to look somewhere else. Because owls hunt at night, their eyes have adapted to become very large.
This increases the surface area with which their eyes can collect light, similar to when human pupils get
larger in the dark to allow more light in. Additionally, owls have a smaller vision of field than people do.
For people, the vision of field makes an arc 180° across whereas owls have a vision of field that has an
angle of 110°. Another interesting fact about owl hunting is that they bob their heads up and down to
gauge distance.
Owl Digestion
Now that students have a general idea of what owls eat (rodents such as mice, moles, shrews,
etc.), it’s time to discuss digestion of food. Like most birds, owls cannot chew their food. So, they
swallow their meals whole. Unlike other birds that have a crop, a sack-like structure that collects food to
be digested later, owls pass their foods straight to their gizzards. Gizzards are organs that use digestive
fluids mixed with small amounts of sand or gravel to grind up and dissolve usable tissue from the prey.
Materials that cannot be digested, such as bones and feathers, are compacted into a pellet in the gizzard
and are then regurgitated.
Owl Pellet Dissection: (40 minutes)
Now, it’s time to start the owl pellet dissection. Each student should have:
-Chinette plate
-One owl pellet (medium sized, otherwise, two small ones)
-Pair of gloves
-Pair of tweezers
-A few toothpicks
-Rodent bone identification sheet
-Index card
-Ziploc bag
Although most students will not want to handle the pellets, remind them that the pellets are
completely sterile – so they very clean. If they don’t feel comfortable touching the pellet with their hands,
they can wear gloves.
Once students have their materials, have them softly break the pellet in half using their fingers.
Remind them that there are very small, fragile bones in the pellet so they need to be gentle as they dissect
them. Then, students can use their fingers, tweezers, or toothpicks to collect bones from the pellet and
place them into the section on their plates. Some students work much faster than others, so having extra
pellets on hand for those who finish quickly will help. Additionally, some students have pellets that are
extremely hard and difficult to pick apart, so giving them a new pellet to work on can help.
After the dissection has been completed, have students sort through their bones and match them
up to the ones on the diagram. The students can then answer questions about what kinds of rodents they
found on their worksheet. Finally, have student tape their bones to an index card to save, or if time is
short, have them place all of their materials, including unfinished owl pellets, into Ziploc bags. They can
take these home and finish later.
Conclusion: (5-10 minutes)
Bring the class back together and have them share what animal bones they found. Ask them how
many animals they think they found based on the number of skulls. Then, go over the owl food chain
once more and have students discuss why studying owl pellets and dissection are important in science.
They should get the general idea that dissecting owl pellets, like many different dissections, help
biologists understand animal behavior we might not be able to observe otherwise – like the anatomy of
the owl digestive system or what they eat.
Owl Pellet Activity Questions
1.) What do you predict you will find inside the owl pellet?
2.) How many animals were in the pellet?
3.) Why do owls make pellets? What kinds of materials are in them?
4.) Why are owls nocturnal? How do they hunt so well at night?