SWEETWATER, Texas (Reuters) -

The Texas town of Sweetwater claims fame as home to the world's largest annual "rattlesnake roundup," where thousands of pounds of slithering venomous snakes are forced out of their dens and put on display.

The rattlesnakes are rounded up in the second weekend of March and then taken to a coliseum, where tens of thousands of visitors watch organizers milk their venom. They rattle, show their fangs and stun the crowd with their force before they are skinned for leather goods.

But the Sweetwater Rattlesnake Roundup, which dates back to 1958, is drawing criticism - not just for the killing, but also for the method employed to draw out the snakes: hunters inject gasoline into rocky crevices where the serpents spend the colder months.

"We'll put about a quarter of a cup, maybe a half a cup of gasoline in the back and they don't like the fumes," said rattlesnake hunter Jeffery Cornett.

"So what's going to happen is, you know, they'll come out to kind of get a breath of fresh air. And as they start moving towards the front, you know, we'll start snatching them." Matt Goode, a rattlesnake expert and research scientist at the University of Arizona, said such roundups were "absolutely horrific."

Hunting can be a good way to manage animal populations but needs to be properly regulated, he said, adding that putting gas in dens could hurt other wildlife.