Using gasoline to drive animals out of their burrows is strictly against the rule of law, if you abide by EPA regulations. Most of the folks don't care... it's all a joke to them. Catching the snakes is the important thing. They justify their environmentally destructive practices by insisting they are performing a public service.... removing those nasty rattlesnakes.
The technique goes something like this: They take a garden hose, or similar hose and put a teaspoon or so of raw gasoline in the hose. insert the hose into the burrow and "blow" the fumes into the burrow by placing their mouth on the hose... it doesn't put *that* much gas into the burrow that the snakes smell like gasoline for a long time, but it can make the burrow uninhabitable for the tortoise that created the opening in the earth in the first place. I have also hear it rumored that the tortoises will not evacuate the burrow, even in the presense of all that noxious fumes...and have been reported to end up dying as a result... I do not have factual evidence to support the tortoise dying in the burrow anecdote.... just something an old timer told me.
It is pretty awful to consider the environmental impact of removing as many snakes from an area as roundups can in a year's time. It is pretty significant if the use of gasoline actually kills gopher and or other species of endangered tortoises and Indigos.... I've never been able to get my brain around the rattlesnake roundup mentality, nor the indiscriminant killing of any species (even homo sapiens, like in many examples of genocide over the history of the world) just for the sake of the killing.
If you ask the participants, I'm sure they'll tell you that they're just doing the public good... afterall, what if it was your little boy or girl that got bit by one of them snakes??? or if your livestock were in jeopardy of getting bit??? Frankly, I live in an area where it is more the rule than the exception to find venomous snakes, and we don't round them up, sell them, or kill them.... my kids all know what the local species look like, as well as many exotics. They know not to fool around with a snake anymore than they would take a gun and mess with it.... Why is it that these people can't educate their young people not to play with animals that can kill instead of trying to wipe them off the face of the earth as an excuse to get together to drink a few beers?????
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"Seek first to understand, then to be understood"