Following fishers, a member of the weasel family, is full of pitfalls. Conservation biologists generally tell how many fishers are in an area by using tracking boxes, a non-invasive device that will record a fisher's tracks. Unfortunately, if there were several fisher tracks in the same area, it was always impossible to tell whether one or many fishers actually left them. That was until Dr. Justina Ray, the director of the Wildlife Conservation Society, Canada, and colleagues, were sitting around a campfire and noticed that fisher fingerprints seemed to be every bit as unique as human fingerprints. They wondered, if you could use computer software to identify individual human fingerprints, could you do with the same with fisher fingerprints? The answer turned out to be yes.