Contents

• Animal Census
• Plaster Casts
• Making a Plaster Cast
• Mammal Gaits and Patterns

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Walk around in any field or forest and you are unlikely to see many of its animal inhabitants. We need sampling methods that help us census animal species. Some techniques are:

• Insects: sweep net samples, pit traps, light traps
• Reptiles and Amphibians: visual searches, pit traps, cover boards
• Birds: audio censuses, mist netting, visual samples
• Mammals: trapping, tracking

Mammals are particularly difficult to census. Fortunately, in an area with long snowy winters, we have many months when the ground is a virtual blackboard, registering the passage of larger animals. In addition, tracking is a real people-pleaser. Finding and identifying a set of tracks can be a bigger thrill than procuring an autograph of a famous person.

Tracking can involve all the senses of the scientist. Scientifically designed surveys and careful measurements of tracks can stand up in court. There is a science of tracking.

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Plaster casts are a wonderful way to study the detail of a mammal track. They are considered good scientific evidence. Tracks can be measured in great detail, for example: widths and lengths of all toes, pads, inter digit distances. Their measurements can be analyzed and used to separate species with particularly similar tracks. For example, the track made by a mountain lion is very similar to a track made by a dog. We have included a graph of the Distribution of measurements for the angle of the long axis of the outer toes of these two animals. This graph will help you understand why casting a track is an important tool for scientific study.

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• 1. Judge how much plaster is to be used.
• 2. Make sure the amount is enough to overflow the margins of the track or tracks.
• 3. Mix plaster and water to the consistency of a milkshake.

• If it is too thick add a little water .
• If too thin, more plaster.
• The mix should flow but not be runny.
• If it is too thick it will not enter all the cracks and crevices and poor detail will result.

• 4. Pour the mix gently from as close as possible.
• 5. Sometimes a mild wiggle or vibration with a stick will help the mix flow to all parts of the track.
• 6. A little experience is the best teacher so don't be afraid to practice.
• 7. Let the cast sit at least 15-20 minutes.
• 8. Cut or slide a shovel into the dirt or snow under the track and carefully lift.
• 9. Wash the casting after it has thoroughly hardened.

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After you have studied a set of tracks you will need to study the pattern of footfalls made by the animal. Be sure to include measurements of both the stride and straddle of the animal that you are studying. Here are some sample patterns.

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