A couple of times now my kids have been involved in making casts from animal tracks. It's a great activity! Kids will learn about identifying animal tracks by doing this activity. My kids have learned a lot about animal tracks since doing this project.
What you need to do this is a package of plaster of Paris, which you can get from Walmart, a hardware store, craft store, or a place like Lowes. You will also need some cups, sticks to stir with, and water to mix in with the plaster of Paris.
Once you have your supplies you can take the kids out in a nature area (e.g., park, trail, their backyard, etc.) and locate and identify animal tracks. Once you find one you want to make a cast of you will need to mix the plaster of Paris with the water. It should be the consistency of a thick milkshake. Pour the batter into the center of the track and allow it to flow all around to create a circle around the animal track area.
This next part is the most difficult for kids... they need patience as it dries. It needs to sit for about 20 minutes to get hard enough that it won't break when you go to pick it up. Check it before picking it up. If it's tacky let it sit longer. When it feels dry, gentely pry it up. You will need to also gently brush the dirt off of the track.
Now you have a beautiful animal track that will last a long time and that they can show to others! Fun and educational project to do out in nature!
Here are some pictures from animal track cast activities my kids have done. They have gotten tracks from black bears, bobcats, turkey, deer, and other animals. They have a nice collection of tracks!