Introduction: 3D Printed Owl Pellet Discovery Kit

The Owl Pellet Discovery Kit is a realistic, durable, reusable and multi-use owl pellet model for student dissection. It acts as a base for a larger project where students design additional bones and pieces. The 3-D models in this kit include a mouse skull, rib bone and a femur. Typical owl pellets can also contain beaks, talons and many different bones that are held together by undigested fur which is simulated by a dryer-lint formula in this project.

This project was originally a Thing I created a few years ago. I updated the instructions from the Thing for this contest.


What's needed:

  • 3D Printer
  • Collected Dryer Lint
  • Glue
  • CAD software - Tinkercad for lower grades, Fusion 360 for middle school and up

Step 1: 3D Printing

Print the 3D models in this Instructable on the 3D printer that you have access to.

Here are the settings I used:

Rafts: Use if the prints fail without them

Supports: No

Resolution: 0.05mm to 0.2mm

Infill: 20%

Step 2: Create the Synthetic Pellet

Owl Pellet Recipe

You will Need:

  • Dryer lint - at least 1 tennis ball sized handful per pellet
  • Water
  • White School Glue (liquid, not glue stick)
  • Small bowl
  • Cookie Tray or Drying Rack
  1. In small bowl dissolve 1 tsp. glue into 4 TBSP water (mixing with finger tips dissolves glue rapidly)
  2. Hand shred dryer lint into the bowl
  3. Drop 3D printed replica bones/pieces into the mixture - it should be lumpy, consistency of stew. Additional water or glue can be added if lint quantity is larger or mixture is too dry.

  4. Gently take the pulp mixture out of the bowl, folding and scooping into your hand. Resting the pulp in the bend of your fingers, gently squeeze until no liquid runs out. It should be generally pellet shaped from being squeezed, you can squish the ends inward to make pellet shape wider if it is too long or thin.

  5. Allow 24-60 hours for pellet to dry.

Step 3: Project and Lesson Plan

Project Name

Owl Pellet Discovery Kit

Overview & Background

Students will learn to dissect owl pellets and identify bones; advanced students or higher grade levels will also design a new replica piece, modeled upon a picture of a small rodent bone or bird skeleton, for inclusion in the dissection pellet.


Students in 4th-8th grade will be expected to 3-D print the bones included here as well as creating one new bone/piece of their own (this can be done individually or in small groups). Students can use a photo of a bone to design a replica. They are expected to print their newly designed bone for inclusion in the pellet, thus the collection of bones available for future pellet dissections continues to increase and becomes varied. Students will then create an owl pellet (recipe provided) including the 3-D printed items and then through dissection identify the pieces they discover. If students are given random assortments of 3-D printed items each group or individual will have a unique set of pellet contents.

Students in 2nd-4th grade can also complete this project with focus being on the dissection and identification process; teachers can prepare pellets ahead of time for this lesson.


Grades 4-8 are able to complete this entire project. For younger audiences it can be simplified and design of a new piece may be excluded or completed as a class. In more advanced Design, Biology or Anatomy classes the quantity or skill level of bone selection for design can be increased.

Grades 4-8 are able to complete this entire project. For younger audiences it can be simplified and design of a new piece may be excluded or completed as a class. In more advanced Design, Biology or Anatomy classes the quantity or skill level of bone selection for design can be increased.


  • Science
  • Animal Studies
  • Biology
  • Design/CAD

Skills Learned (Standards)

  • Dissection/Fine Motor Coordination
  • Identifying/Scientific Reasoning
  • Following Instructions
  • Deductive Reasoning/Making an Educated Guess
  • 3-D Design - 123D Design, TinkerCAD or similar
  • Creative Thinking
  • Using a 3-D printer


Materials:Dissection probe, tweezers, magnifying glass, 3-D printer, CAD software, replica pellet bones, replica pellet ingredients (see References), skeleton charts or pictures for reference (see pdf Thing file).

Step-by-Step Overview:

  1. 3-D Print the 3 bone models provided in this project. Each student pellet or pellet dissection group should have a full set of these 3 models.
  2. Creation of a new or unique bone or non-digestible part of the student's choosing (grades 4-8) This can be done individually or in small groups depending on design skill level of students and accessibility of computers.
  3. 3-D Print student's newly designed bones, talons or beaks.
  4. Prepare Owl Pellet "recipe" (found under References).
  5. Assemble replica Owl Pellets using printed pieces and pellet recipe. Teacher could hand out random sets of 3-D printed bones (approx 4 per pellet) for each pellet or students could assemble pellets with the 3 provided here plus their own new creation.
  6. Allow for drying time of at least 48 hours, possibly 60-72 for pellets to be ready for dissection.
  7. Dissection of Pellet including Identification of contents. It is suggested that students be given pellets randomly so they do not know what bones they will discover and can then identify them from the charts provided.

Digital bone creation tips

Based on dissection of an owl pellet with real bones, I designed these models using 123D Design and 123D Catch. I recommend putting a base under any bones that are lopsided or unbalanced. If you have some portion that overhangs, add a support which you can later snip off after printing. Flipping a bone upside down for printing can also eliminate overhangs. If you use 123D Catch you need to take a sufficient number of photographs to create your model - Catch will prompt you if more photos are required to generate the mesh. 123D Design's capabilities allow you to add intricate parts to your design and manipulate them, but you can also work with basic shapes.

For the skull model included here, after completion of the design I inverted the piece to ensure printing would have a steady base. A raft was added for printing of the very thin, small rib bone and femur - the rafts easily snapped off after printing but gave a solid foundation during printing and until cool.


This project could take 5 hours of classroom time and should be incorporated and interwoven with lecture and discussion within the Animal Studies or Biology curriculum:

  • 1 hour Printing (for 3 bone models provided here)
  • 2 hours Design (new pellet creations)
  • 20-25 minutes to print new creation (per item)
  • 30-45 minutes (preparation of multiple pellets)
  • up to 1 hour Dissection

There is also a drying time for pellet mixture of 48-60 hours - leaving pellets to dry over a weekend would be ideal. Printing time need not be classroom time - the printer could be running throughout the day or after-school hours.


Students should be introduced to a unit on Animal Studies or Biology and the concept of food chains. They should also be familiar with AutoDesk 123D Design or TinkerCAD and the operation of their 3-D printer.

Collection of sufficient quantities of dryer lint should also be assigned prior to a class beginning this project.

Skeleton pictures should be available - there are several samples here, but in textbooks or online, teachers may find something most appropriate for their level or learners. Owl pellets can contain a variety of small rodent bones (mouse, vole, mole, chipmunk) as well as small bird parts or frog bones, even small lizards/salamanders. The kind of skeleton charts and number of different kinds of prey to be studied should be determined by the time frame allotted for Animal Studies and the grade level of participants.

Rubric & Assessment

Student designs can be completed individually or in small groups. Grading of 3-D design models could be based on ACCURACY of details, COMPLEXITY of bone/piece and preparation for SUCCESSFUL PRINTING or other criteria a teacher deems relevant to the lesson and level of design experience of students.

Student Dissection could be evaluated by correct IDENTIFICATION of bones/pieces (compare/contrast with skeleton graphics), DISCOVERY of all models located within the pellet (how thoroughly did student dissect pellet).

Assessment could also be made of student knowledge of concepts taught within the Animal Studies unit. An understanding of food chains or owl diet and digestion would be likely and the higher grade levels would have a great introduction to skeletal anatomy of small rodents and birds.

Handouts & Assets

There are a multitude of skeletal images available online for use in the identification process during dissection of a pellet and for inspiration when choosing what item to design and 3-D print. The following samples are to show the range of simple to complex skeletons which can be used for varying grade levels, all were found by simple image search online. Teachers may use these or something similar to supplement any textbook diagrams or other handouts they have as part of their Animal Studies or other Science unit.

Included here are a few samples (see photos above and the attached PDF document).

Classroom Science Contest

Participated in the
Classroom Science Contest