How to Do An Owl Pellet Dissection


How to Do an Owl Pellet Dissection




Have you been thinking of dissecting an owl pellet? Doing an owl pellet dissection is a fantastic experience for the following reasons:
  • owl pellets often yield complete, identifiable bones which is incredibly cool
  • students learn about anatomy, especially the skeletal systems of barn owl prey and the digestive system of a barn owl
  • it's possible to arrange the bones into a fairly complete skeleton of the prey animal
  • owl pellets clearly reveal predator-prey relationships and food chains
  • students understand an owl's role in an ecosystem
  • Students use scientific inquiry skills—observation, classification, and data analysis—to identify and compare prey species, fostering critical thinking and scientific investigation skills
  • students love to do dissections
  • students who are uncomfortable with dissections will often be OK with an owl pellet dissection because the animals in the pellet were killed by an owl, rather than by a human
Cover of an owl pellet dissection lab with information about what is included in the downloadable resource
Click here to get the lab experiment, worksheets, and all activities shown in this post.


Where Do You Get Owl Pellets to do an Owl Pellet Dissection?

Owls regurgitate pellets near where they roost. It might seem like a good idea to collect pellets in the wild for free but I don't recommend this. Owls and their pellets can spread diseases so it's risky to your health—and the health of your students—to collect and dissect pellets. I recommend purchasing pellets from a reputable source (for example, Carolina Biological Supply) because they will have been heat treated/sterilized to prevent disease transmission. Purchase the largest pellets you can afford because larger pellets tend to have more bones and are more likely to contain multiple animals. However, if you can only get small pellets they are still interesting to dissect.

top image: round object wrapped in silver foil, bottom image: same object but foil is open to reveal a grayish round object with dried fur and bits of bone
Sterilized pellets usually come wrapped in foil.


How to Start an Owl Pellet Dissection

The first decision you want to make is whether to do a dry owl pellet dissection or a wet owl pellet dissection. The difference is whether or not you soak the pellet in water for 10 minutes before dissecting. A dry dissection saves the 10-minute soak period and is slightly less fragrant. However, I recommend soaking the pellet in a bowl of water first because it makes it much easier to open the pellet up without breaking the bones. Another advantage is that wet fur is less likely to become airborne. If you do decide to dissect a dry owl pellet, have a face mask on hand in case the bits of flying fur are irritating.

Materials Needed for an Owl Pellet Dissection

Here are the materials you'll need to dissect an owl pellet:
  • owl pellet—I recommend pellets from a barn owl. Barn owls swallow their prey whole, rather than tearing it up first, so barn owl pellets are more likely than other owl species' pellets to contain whole bones. Whole bones are easier to identify than broken bones.
  • dissecting needle or skewer
  • tweezers
  • magnifying glass
  • dissecting tray or plate
  • bone sorting chart — to sort and identify the type of bones you extract from the pellet
  • ruler
  • optional: bowl of water to soak the pellet
  • optional: towel — this is nice for wiping your hands and any spills
  • optional: gloves — not necessary if using sterilized pellets (which you should use!). I don't use gloves but you may prefer to use them
  • optional: face mask — this is nice to have if doing a dry owl pellet dissection because sometimes bits of fur get in the air. Also, if you sneeze a face mask helps prevent the tiny bones and other bits from flying away (:
  • optional: dichotomous key for a barn owl pellet — this is super helpful to identify the type of prey animal the owl ate
Top to bottom: skewer, ruler, blue tweezers, magnifying glass and on the right is a foil wrapped pellet
Materials for dissecting, top to bottom: skewer, ruler, tweezers, magnifying glass. The silver item is a wrapped barn owl pellet.

Bone sorting chart containing 60 photographs of bones from a mouse, vole, rat, shrew, mole and bird. The bones are labeled by bone type on the vertical axis: skull, mandible, etc..
Have a bone sorting or identification chart on hand to visually identify the bones as you find them. This makes it easier to know if you've found, for example, a scapula (shoulder blade) or a humerus (upper arm bone). This chart is included in Teacher Toy Shop's Owl Pellet Dissection resource.

Page with 11 circles, each labeled with bone types: skulls, lower jaws, scapulas, humerus, radius & ulna, hips/pelvis, femur, tibia & fibula, ribs, vertebrae, and insect parts/other stuff
Sort the bones into types (examples: skulls, lower jaws, etc.). A labeled sheet like this can help. Make your own or find this one here.

Dichotomous Key worksheet to help with how to do an owl pellet dissection. The page asks a series of yes/no questions to determine if the skull belongs to a bird, shrew, mole, rabbit, vole, mouse, or rat.
Dichotomous key for an owl pellet dissection This key identifies a bird, shrew, mole, rabbit, vole, mouse or rat.



Step-by-Step Procedure: How To Do An Owl Pellet Dissection

Step 1: Carefully remove the owl pellet from the foil wrapper.

Partially unwrapped foil showing an owl pellet inside. The pellet looks like a gray oval ball of dried fur with bits of bones exposed.



Step 2: Observe the pellet. What does it appear to be made of? Can you identify any bones? Measure your pellet: length, width, and height

Owl pellet with a ruler below it, showing the pellet is about 6 cm long. The pellet looks like a gray oval ball of dried fur with bits of bones exposed.



Step 3: Gently poke your dissecting needle or skewer into the pellet and separate it into pieces. If you hear bones breaking, stop and either work more slowly or work on another spot. Slowly tease away the fur to reveal the bones.
Owl pellet with a wooden skewer digging into it during an owl pellet dissection



Step 4: As you work, put the bones and any non-fur items into a pile. Put the fur in another pile to be discarded. Be careful not to sneeze...or the fur and bones may go flying!
Pile of fur on the left and a much smaller pile of bones on the right from an owl pellet dissection



Step 5: Once you have most of the fur cleared away from the pellet, discard the fur and then begin sorting the bones into different bone types, such as skulls, ribs, etc.  Use your bone sorting chart to help with this.
Bone sorting chart containing 60 photographs of bones from a mouse, vole, rat, shrew, mole and bird. The bones are labeled by bone type on the vertical axis: skull, mandible, etc..
This is called a bone sorting chart or bone identification chart.

Page with 11 circles, each containing bones from an owl pellet dissection and labeled with bone types: skulls, lower jaws, scapulas, humerus, radius & ulna, hips/pelvis, femur, tibia & fibula, ribs, vertebrae, and insect parts/other stuff
The bones from the owl pellet dissection have been sorted into their bone types, such as skulls and scapulas.



Step 6: Next you'll want to figure out what kinds of prey animals these skeletons are from. The animals most often found in barn owl pellets are: mice, voles, rats, shrews, moles and birds. In the next section, we'll discuss how to tell which of these prey animal skeletons you found in your owl pellet.

Identifying Animal Skeletons after Dissecting Your Owl Pellet

If you have an owl pellet dichotomous key, like the one shown here, that will definitely help with identifying the types of skeletons you find in your pellet.

Dichotomous Key worksheet to help with how to do an owl pellet dissection. The page asks a series of yes/no questions to determine if the skull belongs to a bird, shrew, mole, rabbit, vole, mouse, or rat.
This is a dichotomous key for identifying skulls found during a barn owl pellet dissection.


Start by selecting one of your skulls and inspecting the teeth. Note: it is very likely that the lower jaw has separated from the skull. The lower jaw may also have broken into two halves. If you have only one skull, then you know the jawbone belongs to it. If you have multiple skulls, it can be tricky to figure out which jawbone goes with which skull. Size may be helpful in making this determination. If you can't figure it out, that's OK. You may be able to match them up later once you know a little more about skull characteristics.

Let's start by determining if your skull belongs to a rodent. Take a look at the teeth. 

(What if it doesn't have any teeth, or holes where teeth once were? Then it's probably a bird skull.)

You can look at the teeth on either the skull (upper jaw) or on the lower jawbone. Is there a gap between with the front incisors and the back teeth? If yes, this is likely a rodent. 

Photo of a rodent skull with an arrow and bracket indicating the gap between the incisors and the back teeth
The gap between the front incisors and back teeth indicates that this is a rodent skull.



It might be a rabbit instead of a rodent; rabbits are closely related to rodents. You can decide if it's a rabbit by looking at the top front teeth. If there's a small, second pair of peg teeth behind the front teeth, then it's a rabbit.

Photo of the bottom of a rabbit skull with an arrow showing the two peg teeth right behind the top incisors
This is a rabbit skull. You can see a small pair of peg teeth behind the top front teeth.



If you have a rodent, then it's likely a vole, mouse, or rat. To determine if it's a vole, use your tweezers to pull out one of the back teeth. Vole teeth look like rows of columns, like this:
Photo of a vole tooth that looks like 5 columns glued together



Mice and rat teeth look more like a human tooth with two roots, like this:
Photo of a mouse or rat tooth with two roots. The tooth itself is somewhat broken.



If you have a mouse or a rat, you can determine which it is by measuring the skull. If it's 23mm or longer, it's probably a rat.
Photo of a rat skull with a ruler showing it's 43 mm long.





What if your skull has teeth but no gap between the front and back teeth? Then it's not a rodent. It may be a shrew or a mole. Does it have a zygomatic arch (cheekbone)? If yes, it's likely a mole. 

Check your other bones for the humerus bone(s). If it looks like what is shown here, then you have a mole.
Photo of a mole skull with an arrow and bracket showing the zygomatic arch. Below is a photo showing the characteristic flattened mole humerus.



If it's not mole, there's a good chance it's a shrew. Shrew skulls are tiny—2cm long or less. Some shrews have red-tipped teeth due to iron in their enamel.

Photo of the two halves of a shrew's lower jawbone. There's an arrow pointing to the top of the teeth and indicating that the tips of the teeth are red.



When you've finished identifying your animal skeleton(s), try re-creating a skeleton using the bones you have, like this:
Photo of a mouse skeleton laid out, bone by bone, on a worksheet with labeled rectangles for where each bone should be placed.



If you are interested in having the worksheets and activities shown in this post, plus a complete lab and additional activities and information, please click on the image below:

Cover Page for How to Do an Owl Pellet Dissection Lab Experiment





Click here to watch me dissect an owl pellet.

It's likely this lesson will create interest in learning about skeletons. Check out this blog post about teaching about the human skeletal system and creating a giant paper human skeleton model.
Cover page for a Make a Skeleton resource to learn about the human skeleton


Credits: I would like to thank the Natural History Museum of L.A. County (NHMLAC) for the use of the bones in their research collection. The photographs of the bones in this post (with the exception of the vole and mice teeth) are photos of the bones from the NHMLAC research collection and are used here with their permission.


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