Investigating Keystone Species with Owl Pellets
Your students will enjoy assuming the role of ecologists to make predictions about whether the barn owl is a keystone species in a community. Students dissect barn owl pellets for insight into the diet of an owl. Working in groups, they dissect 2 owl pellets and use bone charts to identify prey species through investigation of remains found within the pellets. They then explore the food web of the barn owl and examine how the decline of a barn owl population could affect the ecological community. This activity requires approximately 50 minutes.
You can find comprehensive safety information about owl pellets in the Resources section of Carolina’s Web site. Owl pellets from Carolina Biological Supply Company are heat sterilized at 200° F for 2 hours. We recommend placing disposable plates, trays, or large sheets of paper under the pellets during dissection so students do not work directly on tables and desks. Be sure your students thoroughly wash their hands and sanitize their work area after handling the owl pellets. As an added measure, you may choose to have students wear disposable safety gloves during the dissection. Students may dispose of the owl pellets’ contents in the trash after completing the exercises.
- 2 Owl Pellets (heat-sterilized)
- 2 Wooden Probes
- 2 Plastic Forceps
- 2 Paper Plates or Trays (or large sheets of paper)
- Cleaning Supplies (such as surface wipes and cleaner)
- Clear Tape (optional)
- Hand Lens and/or Stereomicroscope (optional)
- Disposable Gloves (optional)
Teacher preparation and procedure
Distribute the Student Guide to the groups, including the bone charts. Alternatively, download the Carolina Owl Pellet Activities App, which includes bone charts, a bone identification key, video, and background information. Go to the iTunes® store and search for “Owl Pellet Activities” to download this Carolina app for your iPhone®, iPod® touch, or iPad®.
Review background information and the dissection instructions with students. Stress safety, proper dissection techniques, and the need to keep bones organized as students are working with the pellets.
Encourage students to take their time and remove all the bones they can find. Some bones may be small and hard to see.
Be available during the lab activity to help students identify the bones found in the owl pellets. Students might have difficulty identifying the prey organisms if a skull is not included in the pellet. Help students use the bone charts, and help students reason that if more than 2 femurs are found, more than a single prey was consumed.
- Organisms other than those listed on the bone chart, such as grasshoppers, may be found. Have students record these organisms as “Other” prey.
- If available, have students use hand lenses or stereomicroscopes to assist in the identification of the bones.
- Students may use clear tape to attach the bones directly to the bone charts. This will also help with identification.
When your students have completed the owl pellet dissection, they can use our barn owl online database to see how the contents of their pellets compare with barn owl pellets from all over the United States. You can follow up the keystone species activity with a study of species interactions. Carolina EcoKits™: Species Interactions provides students the opportunity to work with living organisms exhibiting examples of predation, competition, symbiosis, and parasitism.