Grade Range: Adaptable for Grades 3 – 8.
Overview: Learn about food webs by dissecting owl pellets.
What You Need: Owl Pellet Dissection Kit
Activity Objective: Draw and understand a food web based on what is observed in an owl pellet.
Safety Precautions: Owl pellets have been heat-sterilized, yet it is still a good idea to protect your hands and surfaces! Cover students’ workspace with newspaper, foil or use a disposable tray. Wear disposable gloves and wash hands thoroughly after handling owl pellets.
How does a predator-prey ecosystem, where one member is routinely eaten for food, continue to exist?
Download: Owl Pellet Dissection Lab
Introduction
A food chain is a hierarchy of organisms that rely on each lower member of the chain for food. Often drawn as a simple diagram with arrows from one organism to the next, food chains highlight the transfer of energy from one trophic level to the next. A trophic level refers to the position an organism occupies in a food chain. Food chains start with plants (primary producers) which obtain 100% of their energy from the sun. Plants and subsequent members of the food chain are then eaten for food by consumers. However, as little as 10% of the energy in each level of the food chain can be transferred to the next. This means that the size (which impacts the amount of available energy) of a lower trophic level dictates the size of the next trophic level.
- Primary Producers (Autotrophs) – use energy from the sun
- Consumers (Heterotrophs) – feed on other organisms for energy and nutrients
- Primary consumers – eat primary producers
- Secondary consumers – eat herbivores
- Tertiary consumers – eat other carnivores
- Quaternary consumers – eat other carnivores
A predator-prey ecosystem can be thought of as a subset of a larger food chain in which one consumer (predator) feeds off a lower consumer (prey). These types of relationships are very common in nature and provide an interesting way to study ecosystem population dynamics, or how the number of predator and prey are related.
What do you know about food chains and how the size of each trophic level or position in the chain is determined?
What To Do Part 1
1. Use the owl pellet kit’s supporting materials to first dissect the owl pellet.
2. Can you identify different bones? Use the bone sorting chart and identification key.
3. Try to fit the bones together. Can you determine what the owl ate?
What To Do Part 2
1. Based on your observation, record the number of each of the animals that your owl ate:
Rodent =
Shrew =
Mole =
Bird =
Other =
2. What other types of bone did you find?
3. What other undigested material, if any, did you find?
4. Assume for every day the owl eats it regurgitates 1 pellet per day, on average.
How many animals would an owl then eat:
In a week:
In a month:
In a year:
5. Draw a food chain, with an owl at the top. Label the chain (primary producer, etc.). Add in other organisms that would make this a food web rather than a food chain.
6. Assuming 10% of energy is transferred from one trophic level to the next, what percentage of the initial (plant) energy does the owl receive?
7. What would happen if an animal in this food web did not exist?
8. Now that you’ve finished the activity, complete the below table to answer the guiding question.
i. Add the relevant data you collected and calculations to the Evidence section
ii. Interpret and analyze the data to determine what it means
iii. Add your justification and assumptions to the Justification section
iv. Based on analysis and interpretation of the evidence, develop your Claim
v. Present and discuss your claim
