Owl Pellets

by Skip Via
skip@westvalleynaturalists.org

Do you have owls nesting near your home? If so, you may have encountered owl pellets, perhaps without realizing what they are.

Owls are raptors, and like all raptors they are carnivores. Depending on the owl species, they may eat small mammals (gophers, voles, hares, etc.), smaller birds (robins are a favorite around my house), reptiles (e.g, snakes), and insects–or typically several of these depending on what’s available to them. They either swallow their food whole or tear it into bits and swallow those. Then they hang around and digest what they’ve consumed.

Owls can’t digest many parts of the animals they consume in this manner. The bones, teeth, fur, hard exoskeletons, beaks, and feathers have to be dealt with somehow, so they are compacted and regurgitated by the owl from a perch usually high in a tree. Again depending on the species, they can be as small as the tip of a human finger or slightly larger than a golf ball. They’re dark in color and may have bones visible at the surface.

A fresh great horned owl pellet on a rock. Lots of bones and fur are visible. This will be a fun one to dissect when it dries out.

Some people mistakenly think owl pellets are owl poop. They’re not. This is owl poop, and it’s hard to miss. It’s common to find it near pellets.

‘Nuff said.

One other note–the owls around my house seem to prefer two specific trees for their little digestive rests. Virtually all of the pellets we’ve found here are under the same two trees.

What’s Inside?

Let’s find out. We’ll dissect a great horned owl pellet from my yard. Get a clean sheet of white paper and a few tools. I use an X-ACTO knife for most of my dissections, and sometimes tweezers are a big help. Needles or pins are good for delicate work. Dried pellets should be safe to handle. but using gloves is a good idea as is washing your hands thoroughly when you’re done.

Start by breaking apart the pellet and looking for bones. Use the edge of the knife blade to scrape off the hair or feather residue and see what comes up.

Getting started. X-ACTO knife for scale.
Mostly done, except for some small bones in the fur.
Just under the knife you can see a skull, and just under that three jawbones with teeth–so there are at least two fewer voles to worry about in my yard.
Larger leg and arm bones. and smaller, delicate rib bones. Some small bones which I think are vertebrae.
Skull and jawbones closeup. Note the teeth in the jawbone samples. Right under the middle jawbone is what appears to be the back of the skull, showing the vole’s rear teeth.

Given that this pellet was composed of loots of fur, and knowing a little about what to expect from past dissections, I’m sure most of these bones are from a vole. For comparison, here is a skeleton of a vole.

Compare these to the bones in the photos. The bones below are likely the vole’s shoulder bones.

And here is the skull with two jawbones. Most of the back half of the skull is missing (except for possibly some teeth, shown above)–probably crushed in the process of being consumed or regurgitated.

With a little work, it may be possible to assemble most of the vole’s skeleton. And there are always more pellets to look at.

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