Life Cycle - Natural Environment (2B)
Lab 

   
OBJECTIVES:
  • Exploring owl pellets.
  • Determining the eating habits of a great horned owl. 
VOCABULARY:
  • owl pellet
  • prey
MATERIALS:

SLIDESHOW:

Students dissect an owl pellet.  

Owl pellet and its contents

BACKGROUND:

Owls swallow their prey nearly whole, however, the fur and bones of their prey cannot be digested.  The food goes into the proventriculus which is found just before the gizzard. (Owls do not have crops like many other birds.)  As food starts to digest in the gizzard, the muscles separate the fur from the bones.  The fur and bones are then pushed forward to the proventriculus.  About 12 hours after eating their prey owls spit out a "pellet," an ellipsoidal to spherical glob.  Owl pellets are clean of all flesh and odorless.

The pellets that your students have in the kit are from a wild Great Horned owl.  This owl hunts rabbits, rodents, and birds.  The owl is about 18-25 inches in height.  The ear tufts are set wide apart, and the owl has yellow eyes.  The body feathers are a mottled gray brown in the upper body and a fine dark gray horizontal barring below.  The Great Horned has a deep resonant hooting, "hoo, hoo-hoo, hoo."  The materials for this kit are from the San Francisco Bay area, but Great Horned owls range in all of North America up to the northern tree limit.  They build nests in trees, crevices or cliffs with 2 or 3 white eggs.

  PROCEDURE:

  1. Each pair of students should get an owl pellet, a microscope or hand lens, a toothpick or  tweezers  or any other instrument that can separate the bones from the pellets.  Students may use their hands, but caution them that the bones are little and not to break them. 
      
  2. Instruct students to separate the fur from the bones and then have them look carefully at their contents.  Instruct students to  record the information on their lab sheet.  Point out to students that on their lab sheet there are some clues to the type of mammal that they will find in their sample.   Use the enclosed sheet so students can find what part of the animal the bone is from. 
      
  3. Have the students put the remains back in the bag, so they can be reused.  If you want them to look like when they were coughed up, put a little water on the material and stick it back together.  Make sure that you dry them up before you seal the bags, otherwise it will get moldy.  You should leave one pellet together, so students can see what a complete pellet looks like.
      
    If you have access to a local supply of owl pellets every year, you can have the students paste the bones down and make a display.  Label the different bones. Owls are found just about everywhere, so look under trees that you might hear a "hoot"  during the night. 

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