Have you ever wondered what owls eat? Since owls eat their prey whole and then regurgitate the indigestible parts as owl pellets approximately 12 hours after eating, you can identify what the owl has eaten. The compact pellets contain bones, fur, etc. Using a mounting sheet and the bones, you can reconstruct the skeletons of the consumed animals. A dichotomous key helps you make a definite identification of the consumed organism's skull. This activity may be used to suggest a local food web.
In terms of survival, how does an owl's ability to form owl pellets increase its chances for survival?
How might a food web be created using owl pellets?
What skull characteristics would vary between herbivores, carnivores, insectivores, and omnivores?
How might a food web be constructed using information obtained from owl pellets?
After collecting local owl pellets, learners will classify the local animal species consumed by owls.
Based on a specimen's skull features and a dichotomous key, learners will identify the skull's common name.
Based on the collected data, the learner will construct a food web.
The Raptor Center! This is a good resource for background information on different owl species. The web site is by the University of Minnesota, College of Veterinary Medicine.
Key to Common Skulls - This is a very good key to use for identifying the animals consumed by owls. It has pictures and details. The key is from Pellets, Inc., "The Original Owl Pellet Source."
Skull Pictures of Mammals - This web site contains many skull pictures that may be helpful. Some pictures are quite good, while others are hard to see. The site is from the collection of DeLoy Roberts, a science faculty member at Skyline High School, Idaho Falls, Idaho.
Obtain your owl pellet (view image below). Place your pellet on a white sheet of paper. Be sure to record in the table below the location where the pellets were found.
Take a dissecting needle and gently tease apart the pellet.
Carefully remove all the bones from your sample. Work slowly so that you do not miss any bones.
Place your bones in a plastic cup and add diluted bleach. Soak for only three minutes to clean and whiten the bones.
By using the diagram below, arrange all the bones from each pellet on the provided mount sheet and glue into place. Glue the skull upside down so that you will still be able to identify your specimen using the dichotomous key in step seven.
Label the mount sheet with the following information.
Use the dichotomous key (skull key) below to identify your specimen's common name. This key is specific to central United States.
When you are finished, clean your work area and then wash your hands.
Long incisors - eats roots, grain etc. (herbivore)
Long canine - eats meat (carnivore)
Teeth the same length but sharp - eats insects (insectivore)
Use the checklist Compiled Owl Pellet Data to compile your class's results.
As indicated in the Compiled Owl Pellet Data checklist, calculate the percentage for each kind of organism in the owl's diet.
If you have the equipment (scanner or digital camera), obtain an image of the skeleton.
Enter your results for each organism into the Owl Pellets: "What's in Your Mystery Foil?" data form.
Answer the "Engaging Questions" found in the Teacher's Guide of this lesson.
To collect your owl pellets, you will have to look in roosting and feeding areas, old barns or farm buildings, woodlands and parks.
After you have collected your pellets, dry them and fumigate them in plastic bags with naphthalene (moth balls) to destroy insect eggs.
To make dissection easier and safer, you may wish to soak the pellets in dilute chlorox water for about two hours before the lab.
Egg cartons or petri dishes may be helpful storage containers when students are separating the bones.
To speed up identification, you may want to compare the results of this lessons with specimens that have already been identified.
When separating the bones, first separate by shape, then by size. Remember, some of the animals may have been babies, so the size may be deceiving. Be careful to wash your hands after handling the pellets. Keep in mind where they came from.
Please enter a Registration Key to continue.