Illinois Natural History Survey - University of Illinois

Dissect an  Owl Pellet

Carolyn Nixon

 

Dissect an Owl Pellet

 

Owls do not chew their food like mammals or pull the meat from bones like hawks.  Instead, they swallow their prey whole.  After the meat is digested, the owl must regurgitate the undigested fur and bones.  These are compacted into tight oval masses and expelled from the mouth.  These regurgitated masses are called owl pellets.  Since owls routinely roost in the same place during the day, owl pellets can sometimes be found in large numbers under a roost tree.  Biologists collect these pellets and sort through them, removing the bones to determine what the owl has been eating.  Most of the bones will be intact, but no longer connected to each other.

 If you are lucky enough to find an owl pellet, you too can explore what the owl has eaten.  You will need a low, flat-bottomed pan, a teasing needle from a dissection kit, and a pair of fine-tipped forceps.  A magnifying glass or a dissection microscope would be helpful, but not necessary. 

 

To dissect an owl pellet and expose the bones inside, set the owl pellet in front of you on the pan (Photo 1).  This will help keep all of the parts together.  With your teasing needle and forceps, gently loosen the pellet.  Be very careful not to break any of the bones. Try to tease pieces loose from the main pellet (Photo 2). Once you have loosened up the pellet and pulled it apart into smaller pieces, carefully pull apart each section (Photo 3).  You should be able to pull pieces of bone away from the fur.  Some of the bones will be very tiny.  Pile the bones up in one corner of the pan.  When you have sifted through the fur and are sure you have found all of the bones, remove the fur from the pan.  You can put it in a small plastic bag or jar to save it, or you may discard it.

 

Now spread the bones out on the pan and begin sorting them into pieces that look similar (Photo 4).  You should be able to recognize skulls and lower jaw bones.  The feet may be intact or may be separated into the individual tiny pieces.  You should be able to find vertebrae, ribs, leg bones, and pelvic bones.  Sort out the pieces and determine how many animals were eaten to create the one pellet (Photo 5). (Hint: each animal will only have one skull and two lower jaw bones).

 

Use a book on mammals that includes drawings or photos of bones and see if you can determine what kind of animal bones you have found.  Bones found in owl pellets commonly include those of rodents and shrews.  You may also find bones of birds and insect exoskeleton pieces.

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