The Pad Patterns are Unique 
What About Imperfect Prints? Tracks gathered from wild fishers using track plates are generally similar to the above image although never quite this clear. Often portions will be smudged, covered with forest debris, or obscured in some other manner. It is not necessary, however, for a print to be as complete and clear as this one for it to be useful. The size, shape and spacing of the individual dots varies so much between individuals that only a small portion of the print is needed for it to contain enough information to be reasonably sure it came from a particular fisher. If two tracks are sufficiently clear and detailed in the same region of the print then it will be possible to make an effective comparison to determine if they were made by the same individual. How Much of the Print Needs to be Clear? If the portion of the prints being compared is very small then there is always a possibility that they any similarities noted are merely due to chance and that the prints were made by different individuals. How much of the print must correspond to be reasonably certain that you have the same fisher? Surprisingly little - as few as 10 individual dots in common between two prints conveys pretty convincing evidence that they were made by the same animal (for more details see the advanced study section). Information Content of the Pattern The main portion of the metacarpal pad, roughly trapezoidal in shape, contains the bulk of the useful information. About a thousand dots might be visible in a very clear track. With high quality tracks it is easy to see, therefore, how one might be able to match many more than 10 dots. The more dots in correspondence between two tracks the less likely that they were made by two individuals. Advanced Uniqueness 
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