Radio Telemetry

Read part one HERE

Radio telemetry seems like a simple concept: point the antenna in the direction of the transmitter and the signal will get louder.  By following the loudest signal, you will eventually find the transmitter and the animal to which it is attached.  However, a plan in practice is much more challenging than one on paper.  

I snapped the black headphones over my ears.  The sounds of the forest went quiet, replaced by a faint, periodic beeping in my left ear.  As I lifted the metal antenna above my waist, the beeping grew louder.  All around me was forest.  No obvious paths were discernible to the naked eye; the turtles seemed equally likely to be traveling in any direction.  Between the leaf litter and the undergrowth, we could easily overlook a box turtle, even if we walked right past one.  If we couldn't find the turtles with radio telemetry, we stood no chance of seeing them again.  

I scanned the antenna to the right; the beeping grew into a sharp chirp.  I continued scanning until the chirp dropped back to a dull blip.  I moved the antenna to the left and the chirp returned.  We now had a direction in which to head: straight into the brambles.  The vines and thorny tangles of greenbriar worked their way around my legs and intertwined themselves with my snake stick and the telemetry antenna.  “Just free acupuncture,” Marcel and I joked, trying to stay positive as our arms and legs collected dozens of scratches.  Where the beeping pointed us, we went, regardless of thorns, swamp, slippery earth, or even rattlesnake flagging (colored ribbons showing where timber rattlesnakes had recently been found).  

Eventually the beeping became indiscernible from every angle.  I reached down to lower the sensitivity, or RF, and started searching again.  Our radius of possible locations grew smaller and smaller, until we had narrowed the signal down to a patch of forest floor about the size of a square meter.  I pointed the antenna towards the patch of earth; something not unlike a small gunshot rang in my ear.  I flipped the antenna back behind me, away from where the turtle should be.  The beep was muffled and dull.  I continued this test all around the patch of leaf litter with similar results.  

Marcel and I both strained our eyes, hoping that a turtle would materialize.  “They certainly are cryptic,” Marcel said.  “It must be right in front of us,” I responded, uncertain of my telemetry skills. After several minutes of staring, we finally spotted her.  The white epoxy caught my attention and revealed the leading edge of a partially buried carapace.  My eyes formed the outline of a turtle where I had previously seen just sticks and leaf litter.  “My goodness, here she is,” I said.  

Spotting our camouflaged reptiles wasn't the only issue.  The hilly terrain that the turtles called home was notorious for causing “bounce.”  As we hiked, the signal would get louder or softer regardless of how close to the turtle we were.  The slopes caused the signal to ricochet and be picked up by the receiver at odd angles.  This would send us hiking in circles, often up and down the ravines to no avail.  But luckily for us, we had Vince.

A student from Hocking College, Vince was volunteering with us for the summer.  He had taken two semesters of radio telemetry and his experience showed.  Turtles that would have taken Marcel and I half an hour to find, Vince found in fewer than ten minutes.  He worked quickly and efficiently; sometimes following the signal directly to the turtle without ever pausing to listen.

Even with Vince’s skills, tracking the turtles took hours.  From day to day, the turtles rarely stayed in the same place.  After a week of searching, we found one female preparing a nest almost a mile from the field where she had been first caught.  The other turtles didn't move quite as far, but distances of a quarter mile or more in two days came to be expected.  We tracked several turtles as they trekked from the woods to sunny hillsides along the bypass (possibly moving there to mate).  Some turtles mysteriously crossed fences designed to keep reptiles in.  Others stayed in the same field for weeks (our obvious favorites).  As we observed their movements, few patterns emerged.  We could only ponder what secrets were held in the data we had collected.  

Tracking the turtles soon became systematic and ritualized.  Marcel, Vince, and I divided the workload between us.  One person tracked, while the other two collected data.  When a turtle was found we formed a circle around it, pulling equipment and clipboards from our bags and belts.  We took GPS coordinates, measured the moisture levels of the soil, the temperature and the humidity, the canopy cover, and observed percentages of ground cover.  Once this was all written down, we took a second random point fifty meters away from the turtle and repeated the process all over again.  “We are recording more data than we probably need,” Marcel told me.  “But it will make our study more robust.”

It was difficult and tiring work, but it was easy to do because we all wanted to find these turtles.  Some were like old friends that we were eager to see again; others were challengers, taunting us if we didn't find them.  It was a bizarre and adventurous game of hide and seek that never quite seemed to end. We eventually made a competition out of it—a point for laying eyes on the turtle we were tracking, two points for finding a new unmarked turtle. Loser bought lunch. 

I realized we were beginning to know these turtles as individuals. We couldn't yet predict their behaviors or movements, but their distinct personalities were starting to take shape. Some turtles were loners while others were gregarious (we found one turtle named Poopzilla copulating on at least two occasions). Some were shy when we found them, others were out plodding along or feeding. A turtle society was beginning to come to light right before my eyes. It was delightful, surprising, and even dramatic. I was an honored witness of a world few had ever seen. 

One turtle, Doris, left the safety of the woods and ventured to within ten feet of the Nelsonville Bypass. She was risking her life for reasons we did not understand. Perhaps her home range was so ingrained that she was unable to adapt to a new and deadly obstacle. She was an old turtle, far older than the road, and probably several times older than myself (box turtles live to well over a hundred). Garrett Sisson, a grad student studying rattlesnakes, had told me that of the road-killed herps he saw along the bypass, box turtles were by far the most plentiful. Of the turtles we were tracking, Doris was the closest turtle to the bypass, but not the only one at risk. There was a good chance of losing at least one of our animals to the road; all we could hope was that our research would improve the chances of survival for future turtles.