1. Food Webs and the Skeletal System
What is the Relationship??

2. Maryland Science Content Standards
Students will be able to explain that the transfer and transformation of matter and energy links organisms to one another and to their physical setting
Students will cite evidence from research and observations that organisms that eat plants or animals break down what they have consumed (food) to produce the materials and energy they need to survive or store for later use.

3. Essential Questions
How do biotic factors interact with one another and how can a change in either one affect the food web?
What system do animals, including the human organism, have in order to control and coordinate movement?

4. How Do We Answer These Questions?
Owl pellets (known as “castings”) are accumulations of undigested portions of food items which are regurgitated or “coughed up” by an owl as this material is unable to be excreted as feces. Pellets contain bones and other hard materials such as bird beaks and claws; head parts, thorax or wing casting of insects, seed husks and other coarse vegetable materials.

5. How Do We Answer These Questions?
Pellets are also made up of fur and feathers. Owls swallow their food whole or in large parts. The soft parts of the prey are easily digested by enzymes or protein digesters. The relatively weak stomach muscles of the owl form this undigested mass into a wet and slimy bolus. Rarely are even the most fragile bones broken. Each whole bolus (pellet) could contain complete skeletons of the animals the owl has eaten the night before.

6. What to Do……
Place your pellet on a paper towel, observe the color and record the length and width
Squeeze the pellet gently, making cracks to insert probes.
Remove fur and debris from the bones as some bones and skulls are very fragile.
Identify and sort the skull and bones on the Specimen Identification and Sorting Chart.

7. What You May Find…. You may find: Ribs Vertebrae Toes
Dried out bodies of clothes moth larvae
Fur
Small black droppings made by clothes moth larvae
Pupae castings

8. Prey Found in Owl Pellets
Shrew: Long pointed snout; 32 insectivorous teeth for crushing and piercing the hard shell of insects
Mole: Long flexible snout; 44 teeth similar to a shrew. Five toes on each foot
Deer Mouse: Sixteen teeth; sharp bi-colored tail. It eats berries, seeds, fruit and insects

9. Prey Found in Owl Pellets
House Mouse: Grayish brown fur, sixteen teeth, but the incisors are smooth. Eats most everything
Vole: Small ears, long fur hair and short tail. Sixteen teeth rather large compared to deer mice. Upper incisors are not grooved. Most common animal in owl pellets.
Rats: Grayish brown fur. Sixteen teeth. Skulls will be much larger than the mice

10. Prey Found in Owl Pellets
Birds: beaks; back and pelvis consists of several fused bones. Breast bones have high central ridge for the attachment of the flight muscles. The long bones of the leg and feet may be intact
Other: Chitinous remains of grasshoppers and other insects may also be found in owl pellets

11. Probability Vole 70% Shrew 20% Mole 5% Deer Mouse 2% House Mouse 2%
Rat 1%
Swallow (small bird) rare

12. Questions:
Answer the following questions in your composition notebook:
Title: Owl Pellet Investigation
Date: 4/1/2017

13. Summary Questions
Which prey animal is most abundant in your owl pellet sample?
If all the pellets studied came from the same site, what conclusion could you draw about rodent population and owls in that specific area?
If an owl regurgitates an average of 2 pellets a day and the average number of prey found in a pellet is .
Create a food web using the data found in your pellet.

14. Connection
How does the skeletal system of the prey compare to the skeletal system of the human body? Include both similarities and differences. Before answering, set up a graphic organizer to help put your thoughts in order.
What type of bone was found the most in the owl pellets? What is the function of these bones? Why were so many found?

15. Connection
How was the skull of the prey similar to the skull of a human? Diagram the skull in your composition notebook (using the handouts on your tables) and label the parts of the skull.
The vertebra (backbone) of the prey were small bones with an opening in the middle. What do you suppose the opening is for? Do you think your vertebra look the same?
We looked at the ball and socket joints. What parts of your body contain this type of joint? Why is this particular joint important?