How do we identify individuals, or predict age and gender from chromatograms?

 

This is a chromatogram from the scat of a captive gray wolf at Wild Spirit Wolf Sanctuary near Ramah, New Mexico. Notice the red and light blue streaks; these are chemical compounds contained in the volatiles over the scat - all the chemicals that make up the scat's smell.

How do we tell which ones may, for example, identify this wolfs individuality (like a fingerprint)? First, we use a statistical analysis called ANOVA (analysis of variance) to ID which chemicals, or streaks, in the chromatogram, are important for individual identity. ANOVA compares all of the individuals in our study, and finds those chemicals that are important for individual identity, age classification, or gender identity. Next, we used a pattern recognition technique with error estimation to estimate how well we could classify an unknown scat sample.

We had to be able to reproduce the study; that is, be able to take an entirely unknown scat sample, and predict how well we could classify that unknown into individual identity, for example. Could we tell that an unknown scat sample belonged to, say, Brutus?

Our results from captive wolves look quite good so far, but we aren't yet finished with the analysis. Our aim is to publish the results in a peer-reviewed scientific journal.

[Eric Burnham is a Senior Research Associate at NMSU. His research takes principles from trace explosive detections to detect rare and elusive Mexican Gray Wolves non-invasively. He's currently running a crowdfunding campaign to extend his work from captive wolves to those in the wild. Consider checking out his project page --->]