Fifth-graders found tiny skulls, rib cages and jaws from voles and mice when they dissected owl pellets.
Valley’s fifth-graders do, in a hands-on project
“Look — it’s part of a jaw. It has teeth on it, too.”
“Here’s part of the rib cage.”
“I have three skulls.”
“It looks like an eyeball socket.”
“I figured out I have a vole. There’s a long tooth coming out of the bottom jaw.”
These were among the discoveries when fifth-grade students at Methow Valley Elementary School became food-web detectives last week as they dissected owl pellets. Owl pellets are compacted capsules of fur and bone that the birds can’t digest and instead regurgitate.
The owl-pellet lesson was part of a larger unit on animal adaptations in the How We Organize Ourselves unit in the school’s International Baccalaureate program, fifth-grade teacher Brooke DeVlieg said.
Before they examined the pellets, the class watched a video and went over what they’d learned about owls. The students described owls’ remarkable adaptations, including the birds’ ability to turn their head 270 degrees to find prey in the dark with their over-sized eyes. Some owls can spot a vole from half a mile away, or detect a vole 2 feet under the snow.
With their serrated wings, owls fly almost silently, which helps them sneak up on prey. The great horned owl has asymmetrical ears that it can move or turn independently for precise hearing. Some owl species have a specially adapted talon, which they can rotate to grip a branch or a meal.
But because owls don’t have any teeth, they swallow prey such as voles and mice whole, although they sometimes use their beaks to break larger animals into smaller pieces.
The owl’s gizzard breaks down the food and filters out the parts the owl can’t digest. The gizzard compacts those parts into small pellets and regurgitates them when the gizzard becomes full. A barred owl can spit up three or four pellets a day, DeVlieg said.
People sometimes find these pellets in the woods where owls live. Because the contents of the pellets contain so much information about owls’ diet, there are companies that collect and sterilize the pellets for use in classrooms. That’s how the fifth-graders got more than 60 sterilized, foil-wrapped barred owl pellets to dissect and study.
DeVlieg obtained a $290 grant to buy a pellet for each student. “It sounds gross, but it is very cool. The owl spits it up in a nice packet,” she said.
Tiny bones
Dissecting an owl pellet isn’t like cutting up a frog. Instead, the pellets are little nuggets of compacted fur and bones that can be teased apart with tweezers.
Most of the students tackled their pellets enthusiastically, although some were a little squeamish. “Mine does not look sanitized,” said one student, reaching for a pair of gloves.
As the students pried apart the pellets, they found delicate bones that they matched with an anatomical drawing of a vole, one of the most common meals for a barred owl. The pellets could also contain bones of pocket gophers, shrews or even small birds.
As part of the class, the students also got to see an owl. Fifth-grade teacher Sabrina Freedman brought in a small owl that she found dead outside her house on a frigid morning in December.
Maps and biomes
The How We Organize Ourselves unit included a study of geographical systems that organize information about different biomes and habitats, such as latitude and longitude and maps.
The classes studied the vertebrate animal-classification system, looking at birds, fish, amphibians, reptiles and mammals. They learned about ways animals adapt to survive in various conditions around the world.
Then they looked at predators and prey, carnivores and herbivores, and producers and consumers, and how animals derive nutrition and energy from food. The applied those concepts to what they found as they dissected the owl pellets, DeVlieg said.
As part of the unit, students invented and illustrated fantastic islands with habitats such as the Penguin Paradise, the Scaly Foothills, and the Forgotten Stream. They populated the islands with fanciful creatures, including the devil-claw unicorn, rainforest eel and sea tiger.
