Owl Pellet Lab Name: Date: BACKGROUND Barn owls are predators that feed on small mammals, birds, and caterpillars. Because birds do not have teeth, owls use their sharp beaks and talons to tear the prey into small pieces or swallow it whole. Enzymatic juices break down the body tissue of the prey, but leave the bony material and hair undigested. Depending upon the prey eaten, the undigested portions may include beaks, claws, scales or insect exoskeletons. This undigested material is regurgitated once or twice a day in the form of a compact pellet. PURPOSE Investigation of the biomass involved in the food chains of barn owls. PROCEDURE 1.Record the region in the United States of your pellet on the top of a 3” by 5” card along with you and your partner’s name. 2.On a piece of notebook paper also put you and your partner’s name and the pellet’s region. 3.On the notebook paper record the color, texture, shape and size of the pellet. Make a sketch of the pellet and record it’s length and width. 4.Using a needle, carefully tease the pellet apart. Pick out the bones and separate them from the hair. 5.Put the bones in a beaker of warm water for about five minutes. The hair should float to the top. 6.Put the floating hair on a paper towel and discard. Pour off the water from the top. 7.If there is still a lot of hair entangled in the bones, repeat the above step. 8.Use the I.D. sheets to identify the type of bone, skull, teeth, legs, ribs, feet, etc... 9.Identify the animals from which they came and list these animals on your notebook paper. 10.Tape the bones from each type of animal on the 3” by 5” index card. Turn in the 3” by 5” card and notebook paper, one per group. For Activity 3 follow the “Observations and Data Collection” section below making sure each group turns in answers! OBSERVATIONS AND DATA COLLECTION Using the attached charts and dichotomous key, identify the different kinds of prey the owl has eaten. Record these on the handout, “Activity 3” chart, in the student handout packet. Once you have this data, record the results on the board for the purpose of determining the class totals. The total biomass for each species will then be determined by multiplying the prey weight times the class total. 1

2

ANALYSIS QUESTIONS 1.How many prey animals did you find in your owl’s pellet? (Estimate using the number of skulls) Assuming this is true, how many prey did it eat in a day? How many would it take to feed the owl for a year? What prey where highest in number in the pellet? 2.Using the mass figures for your pellet, what was the mass of the prey represented in your one pellet? How much was the mass for one day, assuming that an owl eats two pellets a day? Now calculate the approximate biomass needed to support your owl for a year. Which prey contributed the most in biomass for your owl? 3.Now estimate the biomass required to support your Owl’s prey for one year. Assume the 10% rule! 3

5

6

7

8