Adventures in Radiotracking

Since there are probably about 3 people reading this blog who know what radiotracking is like, I thought I should describe it. When we catch a bat, we glue a little radiotransmitter to its back. It has a tiny battery that will allow it to emit beeps every second or so at a certain frequency until the battery dies (about 2 weeks later). We use an antenna attached to a receiver to detect the beeps and thus determine the location of the bat.

The strength of the radio signal is influenced by distance and objects (such as trees) between us and the bat. Bernie foraged extensively along the highway, where we often had a clear 'line of sight' and thus a nice strong signal. Carter, on the other hand, does not forgage much along the road where we caught him and instead forages in a valley with many trees between us and him. When we have a signal for him at all, it's usually weak and difficult to hear.

Radiotracking generally goes something like this: We drive along with the antenna out the window. When we start to hear beeps instead of just static, we stop the car, jump out, and turn the antenna around 360 degrees. As we turn, we determine in which direction the signal is the loudest. Then we take a bearing with a compass and record our position and the bearing to the bat. If possible, we try to move closer to the bat and take another bearing.



This is me using the radiotracking gear to find Carter's roost tree. He has roosted for the day in three different locations and we have been able to find two of them. Both were in dead standing pines quite close to the road where we caught him.

We often lose Carter's signal for minutes at a time. He usually reappears after about 10 minutes without us going anywhere, but if he's gone for much longer than that then we hop in the car and drive down the road to see if he's at one of his roosts.

Last night we were driving along searching in the rain for his signal when we suddenly heard it again. Kerry stopped the car and I jumped out to take a bearing. I landed in a squishy spot and moaned about my misfortune to land in a muddy spot along the road. The Carter's signal was really strong and it sounded like he was quite close to us and actually flying down the road. I stepped aside to take the bearing when I smelled something terrible. I looked back at where I had been standing and saw a big pile of entrails writhing with maggots! Of all the places to stop along the road, I had stepped smack in the middle of a three foot (1 m) wide mass of possum guts. It smelled so foul.

Possum trappers can get permits to trap in the forest. Then they pluck the fur to sell to textile manufacturers or sell the skins. A few days ago we met a possum trapper who'd set heaps of traps down this particular road. I'd stepped right into his gutting pile where he'd dealt to all the possums he trapped.

Carrie