Owl Pellets and Predator Prey Relationships

Last Thursday, January 15, I visited the Jefferson Elementary School in the Schalmont CSD. I did Owl Ecology for the 5th graders. It's a fun session to do that gets students excited about science, helps illustrate scientific methods and gives the students a chance to explore and understand owls and their relationship to their prey.

There are many resources about owl pellet dissection. I suggest checking out pelletsinc. for owl pellets and teaching resources. You can click on the link to reach this great resource. Here I would like to give some thoughts on how dissecting owl pellets can lead into a discussion of predator prey relationship.

The culmination of the class is to analyze the results of the owl pellet dissection. From our investigation we know, not only what the owls ate, but also how many of each of their prey were eaten. On this day we had the following results:
Mrs. Guzewich's class - 11 pellets dissected - 19 mice, 6 shrews, 1 moles, 0 birds
Mrs. Fitzgerald's class - 10 pellets dissected - 22 mice, 4 shrews, 0 moles, 0 birds
Mrs. Walker's class - 10 pellets dissected - 23 mice, 0 shrews, 0 moles, 0 birds
Mrs. Wood's class - 11 pellets dissected - 25 mice, 8 shrews, 1 mole, 1 bird

The total number of pellets dissected was 42 with a total of 89 mice, 18 shrew, 2 moles and 1 bird. That gives an average of 2.6 prey per owl pellet for the samples investigated at Jefferson Elementary. A barn owl produces about 4 pellets a night. So in one night they might eat at least 10 animals. In one year an owl might eat over 3600 mice (mice being the most common prey - the numbers seen above can help illustrate a discussion of what the most common food for barn owls is). This large consumption of prey illustrates the concept of a balance in nature between predator and prey. Prey species reproduce in large numbers. These prey support a population of predators. As the predators increase the number of prey decreases. This smaller number of prey can not support as large a population of predators. The number of predators begin to decline. As the number of predators decreases the number of prey that survive can increase, eventually allowing for an increase in the number of predators. This balance of increasing, then decreasing then again increasing is part of the story behind population cycles of wildlife.