Identifying Bones in Owl Pellets: A Complete Bone Chart
Posted by PelletPal Team on Oct 16th 2026
Once the fur is cleared away, an owl pellet leaves you with a small pile of bones that can look bewildering at first. The good news: a barn owl's prey is mostly small mammals, and their skeletons follow the same basic plan as ours. Learn a handful of shapes and you can name almost everything on the tray.
Start with the skull and jaws
The skull and lower jaw (mandible) are the most important bones for telling which animal you have. Each animal has one skull and two lower-jaw halves, so they are also how you count individuals.
Look closely at the teeth — a magnifying glass helps.
Prey identification chart
| Prey | Skull size (approx.) | Key features |
|---|---|---|
| Vole | Medium, about 2–3 cm long | Large orange-tinted incisors at the front; a gap (diastema); cheek teeth with flat grinding surfaces and a zigzag enamel pattern. Skull looks blocky and sturdy. |
| Mouse / deer mouse | Small to medium, about 2–2.5 cm | Long curved incisors and a gap, like a vole, but cheek teeth have rounded cusps (bumps) rather than a flat zigzag. Skull more slender with a longer snout. |
| Rat | Larger, often 4 cm+ | Same rodent pattern as a mouse but much bigger and heavier. |
| Shrew | Small, about 1.5–2 cm, very delicate | No gap: a continuous row of many small pointed teeth. In many North American shrews the tooth tips are reddish-brown. Long narrow snout. |
| Mole | Medium, elongated | Continuous row of pointed teeth (like a shrew) but larger; very broad, shovel-like front-limb bones. |
| Small bird | Varies | No teeth; a beak (sometimes separate); very large eye sockets; thin, rounded braincase. Bird bones are often hollow. |
Rodents (voles, mice, rats) are gnawers: two big front incisors, a gap, then grinding cheek teeth. Insect-eaters (shrews, moles) have many sharp teeth with no gap. That single difference sorts most skulls in seconds.
Bone chart: the rest of the skeleton
| Bone | Where it is | What it looks like | Human equivalent |
|---|---|---|---|
| Mandible | Lower jaw | L-shaped half-jaw with teeth; found in pairs | Jawbone |
| Scapula | Shoulder | Thin, flat, roughly triangular blade with a ridge | Shoulder blade |
| Humerus | Upper front leg | Short, stout long bone with a broad head at one end | Upper arm |
| Radius & ulna | Lower front leg | Two thin bones; the ulna has a hook at the elbow end | Forearm |
| Pelvis | Hips | Paired, irregular bones with a round socket and an opening (often found as halves) | Hip bones |
| Femur | Upper hind leg | The largest long bone; ball-shaped head angled at the top | Thigh bone |
| Tibia & fibula | Lower hind leg | Long bone; in rodents the fibula is fused to the tibia for part of its length | Shin bones |
| Vertebrae | Backbone | Small, irregular bones with a hole for the spinal cord and projecting spines; tail vertebrae are tiny cylinders | Spine |
| Ribs | Chest | Thin, curved, needle-like bones | Ribs |
| Phalanges / claws | Feet | Very small bones, often grain-sized | Finger and toe bones |
Front leg or back leg?
Students often confuse the humerus and femur. The femur is usually longer and has a rounded head set off at an angle from the shaft, designed to fit the hip socket. The humerus is shorter and stockier. The tibia is the longest bone in a rodent's hind leg and the fibula joins it partway down, which makes it easy to spot.
Counting individuals
To find the minimum number of animals in a pellet, choose a bone that occurs only once per animal on each side. The most reliable is the lower jaw: count all the left mandibles and all the right mandibles, and take the higher number. If you have three left vole jaws and two right ones, the pellet held at least three voles. This "minimum number of individuals" method is the same idea archaeologists and ecologists use with bone assemblages.
Common identification mistakes
- Calling every skull a mouse. Check the cheek teeth: zigzag and flat means vole.
- Missing shrews. Their skulls are tiny and fragile; work slowly and use a lens.
- Mistaking a pelvis half for a skull fragment. Look for the round hip socket.
- Counting both jaw halves as two animals. Separate left from right first.
Turn identification into data
Once each student has named their prey, combine results in a class table: number of voles, mice, shrews and birds. Convert to percentages and draw a bar chart. Discuss what the owl's diet says about the habitat it hunted in — a high proportion of voles suggests grassland and meadow. Our article on barn owl ecology and food webs takes that discussion further.
Get the chart in your kit
Every PelletPal pack includes a bone ID chart showing skulls and key bones of common prey, so students can match finds at the table. For a full class, the Pack of 20 provides plenty of data; for more bones per dig, try the large Pack of 10. New to the process? Start with how to dissect an owl pellet.