Florida researchers' plan to cull iguana populations? Smash their heads.

Researchers are taking a controversial approach as they try to rid Florida of invasive iguanas overtaking residents' yards: Bashing in their brains.

A team from the University of Florida is using a captive gun that sends a bolt into the brain, similar to what's used in the livestock industry. They're also smashing the creatures' heads against solid objects to cause blunt force trauma. They've killed 249 so far.

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UF wildlife biologist Jenny Ketterlin told the Sun Sentinel it's the most humane way to kill them.

Their work is part of a $63,000 research project contracted by the Florida Fish and Wildlife Conservation Commission. Officials say iguanas are an invasive species that feed on native plants and wildlife.

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The earliest report of iguanas existing in Florida dates to Miami-Dade County in 1965, according to the FWC. The population exploded over several decades.

Now, iguanas have shown up in Florida residents' toilets. They have been known to damage sidewalks, consume native plant life and can spread salmonella by defecating in swimming pools.

Veterinarian Dr. Susan Kelleher says the head-bashing method is cruel. She suggests sedating and then euthanizing them.

Gary Fishman, a Boynton Beach resident, told the Sun Sentinel that he's killed more than 100 iguanas with a pellet gun. He believes the pellet gun is a more humane extermination option.

"The iguana does not belong here," Fishman said. "They need to be annihilated. They can't be relocated. So they must be destroyed."