How to sample a footprint, maybe

 

Some months ago, I devised a way to sample volatile organic compounds (VOCs; volatile chemicals) from a footprint. I coated magnetic beads with a type of polymer, or plastic, that adsorbs VOCs from the surrounding environment. "Adsorbing" means that the chemicals bond to the surface of the plastic. The idea would be to sprinkle these beads on a footprint, then use a magnet to pick them up. Then I could desorb them in my instrument, and analyze the results to see if I could predict things like individual identity, age, and gender for an individual human, dog, or wolf. "Desorbing" means that the chemicals are released from the surface of the plastic using heat, and they then travel into the instrument for an analysis of how abundant those chemicals are in the sample. The relative abundance of VOCs between samples creates a unique (hopefully) pattern or profile.

I haven't tested it yet, but I hope to sometime this summer, first using humans, and then dogs. The next step would be to use captive wolves in their pens. My assistant and I will go out into the desert and make footprints, sample them using the beads, and then see if we can predict our individual identities when the samples are treated as unknowns in the lab. If successful, this would open up an entirely new way to non-invasively get samples from gray wolves in the wild. Footprints are more abundant in the wild than the scats I have been using so far.

Humans and animals release volatile chemicals into the environment because we are constantly defoliating dead skin cells. It is thought that bacteria then decompose the tissue of the dead skin cells and release VOCs as a byproduct. Skin tissue type is determined by the major histocompatibility complex (MHC) which is part of the DNA strand. All tissue in the body has a code from the MHC which, for example, keeps our immune system from attacking our own tissue. The immune system recognizes the code as belonging to us.