Who Passed this Way?
- Grade Level:
- Upper Elementary: Third Grade through Fifth Grade
On this field trip, students will be able to identify common animal tracks and learn how to make plaster casts of them.
Looking for evidence is one method of determining what types of animals are around, especially since many are nocturnal. Signs such as burrows, nests, droppings, or food litter can be identified-but the easiest signs to interpret are often animal tracks.
Animal tracks can be the basis for several types of investigations:
- Identifying the tracks can simply help you identify which animal passed by.
- Studying the cadence or gaiting of tracks can help decipher what the animal was doing.
- Wildlife biologists can estimate population size by the counting of tracks during a specific length of time.
- Habitat requirements of individual animals may be learned about by finding their tracks in certain areas and not finding them in others.
Track hunting is best in the early morning since many animals are nocturnal. First thing in the morning, you can usually find tracks in the sand that haven't been disturbed by people. Tracking is especially good after a fresh snowfall. Walk along the edge of the water or on the damp sand along the creek. Larger animals will use wide open spaces, while small areas around bushes may hold the tracks of mice, shrews, and reptiles. (To tell the difference between shrew and mouse prints, measure the width of individual prints. Mouse prints are more than one inch and shrew prints are less than one inch.) You may also see prints at the base of the dunes by the water that look like bobcat prints. If the prints have claw marks on them they probably belong to a coyote or dog because the claws of a bobcat are retracted when it walks. If you look closely, you may also find tiny insect traces or traces left in the sand by blowing grasses.
Explore Great Sand Dunes' web pages on animals to learn more about the creatures who may leave tracks in the sand.
Plaster of Paris, coffee cans for mixing, petroleum jelly, large coffee cans with both ends cut off, knives, sandpaper, spray bottle with water, Mammal Tracks of Great Sand Dunes (PDF)
Either as a whole group or in smaller adult-guided groups, take a hike on a trail or on the dunes. Once a track is found, clean it gently of loose particles of soil, twigs, leaves, or other litter. Take one of the coffee cans and press it firmly into the ground to give support, but allow at least one inch from the edge of the track to the edge of the can. Mix one to two cups of Plaster of Paris in a tin can or plastic cup, adding water slowly until it is a thick, pourable consistency similar to pancake batter. (Remember to take out any trash you bring in.) Pour the plaster into the mold until it is several inches deep above the track. Allow at least 15 minutes for it to harden. If soil is damp, it may take longer. When ready, lift off the can and the plaster from the track. Clean off any excess grass, dirt, etc. At this point you have a reverse track.
You can either stop here or make a cast of the imprint. If you want to make an imprint, apply a thin coating of petroleum jelly to the surface of the cast. Place it on a flat surface and put another coffee can around it. Mix up another one to two cups of plaster and pour over the track. Allow two hours to harden. Carefully remove the mold when plaster is dry. Separate the two layers and wipe the excess petroleum jelly off of the cast. Use fine sandpaper to smooth the surface. Wash the completed cast under running water.