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From: Resilient Planet Mission 4: Paradise Found (pp: 74)

Apex Predator

In this lab, students will analyze the contents of an owl pellet. Knowing what the owl eats will help them understand something about the ecosystem in which the owl lives.

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Apex Predator

To understand energy flow within the coral reef ecosystem, Enric Sala studies the feeding behavior of sharks. One of the strategies he and his team use is to examine the most recent meals of this predator. To do so, they force warm water into the stomach of a captured shark. In response, the animal vomits its stomach contents. After this procedure, the animal is released back into its natural environment.

On land, another predator, the owl, also reveals part of its most recent meals—naturally. Owls ingest whole large chunks of their prey. Later, they cough up undigested matter in a type of “fur ball” called a pellet. Within the pellet, you will discover the skeletal remains of all sorts of animals eaten by the owl.

In this activity, you will analyze the contents of an owl pellet. You will use your anatomy skills to identify the collected bones. Knowing what the owl eats will help you understand something about the ecosystem in which the owl lives.

Materials

Lab 1 Data sheet
owl pellet
small flat dish
one 250-mL beaker
hand lens
paper towels
length of string

identification keys
laboratory balance
toothpicks
gloves
ruler
white glue
index card

Lab Prep

Cover your work area with paper towels and wear protective gloves.
Obtain an owl pellet and place it on a small, flat dish.
Record a description of the external appearance of the pellet. Measure and record the size of the pellet. Use a string to measure the circumference.
Place the pellet on the balance to determine its mass.
Compare your measurements with those made by other teams.
Make a prediction of how many skulls you will find in one pellet.

Make Observations

If it is hard and dry, soak it in water for several minutes.
Use toothpicks to carefully extract all bones from the pellet.
Do the best you can to organize the bones by individual prey. Use these bones to assemble a skeleton. Then, use white glue to secure the skeleton to an index card. Draw the missing bones on the card.
How many skulls did you find? Was your prediction close?
Using the identification keys, try to identify the species of the prey. If you cannot identify the species, use the keys to make an educated guess about the type of animal, such as "mouse," or "rodent." Be as specific as you can. Write the name on the card.
Do research to determine what your prey animal eats. Create a food chain from the information you gathered. Compare your findings with those of your classmates.

Extension

Construct a personal food web using the composition of your last six meals.

Journal Question
Based on your understanding of predators, food webs, and Dr. Sala’s new biomass model, what can you infer about the role of the apex predator and the impact it makes on the ecosystem?

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