They really are. I read this morning about a company that uses PIT-tags in curb-side recycling containers to track recycling rates, and distributes rewards based on a households recycling rate. Pretty bright. If I had thought of that I might be rich right now. But instead I put them into rocks. So I am not rich.
I've spent the past few days starting to analyze data on cobble movements on the Elwha shoreline that we collected using PIT_tagged rocks. All told, we tagged 224 rocks by drilling a 1/4" hole in the rock and epoxying (is that a verb? Like facebooking?) the tag in place. The tagged rocks were placed at three different locations (shown on the groovy map as small, barely discernible black dots) and then we mapped and surveyed the movements of the tags using a reader and GPS unit over periods of days, weeks and months.
The re-find process involved walking the beach with a reader unit (looks just like the crazy old guys you see early on Monday morning down at Main Beach in Santa Cruz, looking for quarters and lost rings in the sand). When the reader antennae and a PIT tag come into proximity (usually about 1 meter) the reader squeals and records the tags ID. We can then GPS the location of the rock using its ID as a Waypoint in the GPS.
The movements surprised me. In some cases, I found that relatively large material, that I hadn't expected to move at all during the summer, was moving 15 to 20 m per day. Our next step is to try to survey movements around a storm event.