We went to Costa Rica to look for the “velvet killer,” a very dangerous, aggressive, unpredictable snake called the fer-de-lance. These snakes are pit vipers, which means that they have two heat-sensitive pits on the front of their face that detect minute differences in temperature; that’s how they detect their warm-blooded prey.

We wanted to get the fer-de-lance to strike right at the camera, but for whatever reason we could not get this one snake to strike. We had the camera right up in the snake’s face and moved it all around to make it look like the camera was an animal jumping along the ground. Still, this snake would have nothing to do with the camera.

So I happened to mention to the crew that it’s a shame the camera doesn’t put out any heat, since the fer-de-lance detects its prey through these heat-seeking organs on the front of its face. I said if the camera put out some kind of heat, we could probably get the snake to strike at it.

The sound guy said, “Wow, you know, a possibility is I’ve got a lot of these nine-volt batteries with me that we run our microphones off of.” He said, “If we taped a penny across both of the terminals on the battery, the positive and the negative, it would complete the circuit and the battery should heat up.”

And sure enough, he gets out a nine-volt battery, tapes a penny over the top of it, and the thing is so hot you can’t even hang onto it. They get the camera with the heated battery hanging off the front of it and they move it up towards this fer-de-lance coiled up in the ground, and suddenly the snake is on that camera like you wouldn’t believe.

Obviously the pits actually work, because that snake struck at the camera, grabbed the whole lens in its mouth, repeatedly striking—we couldn’t even get the camera away from the snake. The snake probably thought that it was my foot or a rat or something like that.

It was amazing to see how the snake ignored the camera when it wasn’t emitting heat, yet just the heat of the added battery seemed to have the snake figuring out, hey, that’s a warm-blooded animal, something good to eat.

It was ingenious on the sound man’s part for coming up with the battery idea, and we got some incredible footage of this fer-de-lance coming straight at the camera. You can look right down its throat as it grabs the camera lens in its mouth—and we all have a nine-volt battery to thank for that shot.

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