Herp Workshop: Radio Telemetry & Funnel Traps

One of my favorite parts of the herp workshop was tracking threatened turtles and snakes that had been fitted with transmitters. Radio telemetry looks a bit ridiculous, and I can imagine that it would drive me crazy if I were searching fruitlessly for something for hours or days on end, which I know has happened to scientists in the field. But for a few afternoons, it’s just like a game of hide and seek with some wonderful reptiles!

You hold the receiver, attached to a large antenna, and as you get closer to the animal, the receiver makes regular and increasingly loud beeping sounds. But it’s trickier than that–water, slopes and trees can all cause bounceback. And you can find yourself crossing through head-high brambles and waist-deep swamps or streams in pursuit of the signal. Often you find a pretty good signal coming from almost 180 degrees in front you, and you have to adjust what’s called the gain lower to differentiate between whether it’s strongest straight ahead, or veering to the left or right. I found the visual representation of the beeps to be the most helpful when comparing–they look like rising bars in a bar chart, and I often paused to compare which direction was showing a slightly higher bar.

If you’re lucky and/or persistent, you can find your target!

To find animals that haven’t been fitted with a transmitter, there are various approaches. One that we used for both amphibians and water snakes is the funnel trap. It’s a pretty basic design–one or more funnels direct animals into the trap, then it’s hard for them to locate the small hole to get out.

Froglets and tadpoles in a plastic funnel trap
Northern water snake in a metal funnel trap

My dad and I actually designed and built a variation on the funnel trap that I’m looking forward to using once my amphibian survey project gets off the ground… In other news of things that have been simmering for a while, I finally got my New York Master Naturalist certification today! I’m celebrating by hiding inside from the heat and painting.

A northern water snake after being trapped, processed and released

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