Owl Pellet Dissection - Triton Science

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Name ___________________________________________ Date ___________ Period ______
Owl Pellet Dissection
Background:
Owl pellets are masses of bone, teeth, fur, and feathers. Owls swallow their prey
whole. The soft parts of the prey are dissolved by proteolytic enzymes (protein
digesters) and strong acids, which occur in high concentrations in the stomachs of owls
and other raptors. The relatively weak stomach muscles of the owl form the undigested
material into pellets. Each whole owl pellet usually contains virtually complete skeletons
of the animals that the owl ate the night before the pellet was formed.
You will be dissecting the pellets from the barn owl, Tyto alba. These owls feed early in
the evening and regurgitate the pellet 18 to 20 hours after the feeding. The kinds of
prey species in each pellet varies, the averages are: 2.5 voles (Microtus), 0.7 shrews
(Sorex), and 0.1 other species. Major factors that determine the kind of ratios of
species found in owl pellets are where the owl lives and what prey are seasonally most
abundant.
Materials:
Owl pellet
Sheet to glue skeleton on
Toothpicks
Procedure:
1. Place a pellet on a sheet of white paper and gently pull the pellet apart using the
toothpicks provided.
2. Clean the bones of debris and sort them according to type (skull, vertebrae, leg,
etc.) Use the keys provided to help you sort the bones properly. Clean the skulls
thoroughly as possible since these are the best bones for identifying the prey.
3. Use the “Key to Skulls of Common Barn Owl Prey” to identify the prey species.
4. Record your species on the class data sheet on the white board.
5. Examine the bones that have been separated out and grouped according to type.
Lay these bones out corresponding to their position in the natural skeleton (use
the example to help you out). Glue these bones on the card stock provided and
label the mammal.
6. Create a data table that will include all of the class data, this should include name
of prey and number of prey recorded. Graph the class results of species eaten
using a bar graph.
Continued on other side ……

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