In South Florida, iguanas had better watch their backs. That's because scientists are on an unusual hunt to kill them, with the help of captive bolt guns and a $63,000 research grant, according to the Sun Sentinel.

It's not as cruel as it might seem at first glance. The green iguana, native to Central and South America, is an invasive species in Florida. The large lizards—which can grow up to 6 feet long—first made it to Florida in the 1960s, and as their population has exploded, they have expanded farther north. The reptiles damage roads, sidewalks, sea walls, and flood-control canals with their burrows; chomp their way through landscaping; spread Salmonella, largely by pooping in people's backyard pools; and compete with the endangered Miami blue butterfly for precious food resources.

The population boom has caused an uptick in complaints from residents, Florida Fish and Wildlife's Sarah Funck told the Sun Sentinel in 2017, pushing the state to find new strategies to deal with the reptiles. One approach? Hire scientists to hunt them down and kill them.

As part of the Florida Fish and Wildlife research project, 15 University of Florida biologists have been tasked with executing as many iguanas as possible in Broward County (home to Fort Lauderdale and parts of the Miami metropolitan area), setting out in teams of two at night. Armed with flashlights and captive bolt guns—which are often used on animals in slaughterhouses and are considered a humane way of killing an animal instantly and painlessly—the researchers attempt to sneak up on sleeping lizards and shoot them before they can scurry away. They also sometimes dispatch the iguanas by smashing their heads against a hard surface, including the side of a truck or a boat.

They've exterminated 249 lizards so far. They take the dead animals back to the lab to be weighed and measured for their dataset, then deposit the carcasses in a landfill. The iguana killing spree is expected to last into May.

While they have tried trapping the iguanas in county parks, they haven't succeeded in capturing any with that method.

As part of the Fish and Wildlife Conservation Commission's iguana-eradicating efforts, the agency has also been hosting public workshops on how to deter and trap iguanas and has hired a dedicated trapper to control populations on public lands in the Florida Keys. 

[h/t Sun Sentinel]