Whose tracks are those in the mud by the sidewalk? What animal drank at that puddle? Who visited the pond last night? What walked through that wet sand? Did you know you can take your kids on a real-life adventure in your own back yard, playground, creek or beach and gather the evidence to figure it out? This is a wonderful lead-in activity for studying such things as natural history, animal behavior and identification, and scientific procedures. It also improves problem-solving skills.
Tracks are everywhere, made by all living creatures -- mice, cats, sparrows, deer, beetles -- and people, too. Probably nothing holds more fascination for children of all ages, than to hold in their hands the plaster track casting of a wild animal which not so long ago actually STOOD RIGHT THERE.
Remember, since plaster is poured into the track, the resulting cast will be convex, the actual shape of the animal's foot.
Making plaster casts of animal tracks might be a daunting prospect, but it's actually simple and fun to do with kids. Try to locate some tracks before you go out with the children on your first track-making safari. If you can't find any wild ones, recruit your dog or cat to make prints in a pan of mud. A child's handprints in a muddy spot also makes great "animal tracks," and will be a fine substitute if necessary. But the best, most rewarding, tracks are those of the wildlings.
MAKING A CASTING KIT
First, put together your casting kit. Plaster of Paris is available at hardware stores. Small milk cartons provide molds (remove the ends, flatten it, then cut off several 1 1/2-inch sections. Pulled out square, they become molds.) A squirt bottle full of water, a yogurt-container for a mixing bowl, and a stick for stirring complete your kit. Tuck them all into a fishing tackle box or a plastic grocery bag, (or distribute them amongst the kids) and you're ready to go. A field guide to animal tracks is optional -- it's easy to look up the tracks after you get home.
MAKING A CAST
So. You've put your kit together, practiced mixing up a batch in the kitchen, and the kids are rarin' to go. Head for a wet spot. The best tracks will be found in fine, clean mud or sand. Indistinct tracks in dry dirt or sand will make ill-defined castings. Tracks in dust look great but may get pressed flat by the weight of the plaster (if you still want to try, mix in more water for a thinner plaster and pour very carefully).
To make a casting, press a milk carton "collar" about 1/4" into the earth around the track to confine the plaster. Pour dry plaster into the yogurt container, add water, and stir until it is the consistency of pancake batter (make enough plaster to fill the mold about 3/4" deep). Don't dawdle; it can harden up fast!
Gently pour the plaster into the track. Leave it alone for about twenty minutes to give it time to cure (longer in cold weather). The plaster will heat up as it cures -- when it cools, it will be ready. Carefully lift the collar containing the plaster track, turn it over, and examine your trophy. You may need to squirt it with water from the bottle to clean it off. Rub it gently with a finger to clean, but remember that the plaster will be a bit soft for several hours, so don't rub too hard. Remove the cardboard collar. If you want, you can leave sand or bits of dirt attached to the track for authenticity. It's good scientific procedure to write the date, location, collector and identification of the casting right on the plaster.
This is a particularly engaging activity for children who like to "collect." They'll enjoy creating plaster collections of animal, insect, and bird tracks as well as other natural items (try leaf or sea shell impressions, too). You might find yourself getting hooked on it, as well.
