The Lizard Log

The Langkilde Lab in Action

To Catch a Fence Lizard

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Almost every time I talk to people about our research with lizards, I get asked the question: “But how do you catch so many lizards?” or some variant of it. In general fence lizards are fast, and, while we do sometimes catch them with our hands (especially juveniles), we mostly use the time-honored technique of noosing lizards. This involves creating a small noose, putting it on a pole, slowly lowering it over a lizard’s head, and tightening the noose by lifting upwards.

While it seems as though a lizard should run away if a large human being is trying to put a tickly noose over its head, fence lizards will often stay stock still to the surprise of most first time noosers. The probable reason for this is that fence lizards are generally well-camouflaged animals; they rely on their cryptic patterning for protection from predators. Many of these predators, such as birds of prey and some snakes, are visually-oriented. So if a fence lizard is threatened by a predator, running away, or otherwise moving to avoid a small distraction (like our nooses), might just serve to attract the predator and reduce a lizard’s chances of survival. When we are catching lizards, we often see their eyes following our movements but not the noose’s; in other words, they seem to recognize a human 8 feet away as a potential threat, but ignore the small noose near their head.

To noose lizards, we use collapsible panfish poles (like this or this), which allow us to say outside of a lizard’s flight initiation distance, the distance from a predator at which the lizard will run to shelter. We also use waxed dental floss to make our small nooses. The waxed floss holds its shape well and is very tough, allowing it to be used over and over. Last week while catching lizards at Raystown Lake in PA, I hooked up our lab’s GoPro camera to my lizard pole so I could show y’all what it looks like to catch a lizard with a noose (watch in HD if you can!).

Another question I often get is: doesn’t this hurt the lizard? The answer is, thankfully, no! First of all, fence lizards’ necks are a strong region of their body, and secondly, fence lizards weigh very little. They rarely exceed 20 gms (and that only in very gravid females). The combination of low weight and a strong support means that fence lizard necks can easily support their body weight. Our nooses don’t tighten enough to cut off circulation, and we can generally free a lizard from a noose in under 15 seconds. Catching lizards by hand is actually more risky than noosing them, since there is a higher risk of pressing on a lizard’s tail and having it break. In short, I’ve noosed hundreds of lizards and never had any appear injured.

I hope you enjoyed our quick lizard catching video, and maybe now, as I walk through various parks and forests, I won’t get so many questions from people asking what the heck I’m doing strolling around in the middle of the woods with a fishing pole!

 

 

 

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Author: Chris Thawley

Postdoctoral Fellow at University of Rhode Island; ecologist, herper, discslinger

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