A lizard turf war is underway in New Orleans, according to the Louisiana Illuminator, and researchers at Tulane University recently identified a contributing factor. 

What's happening?

Green anoles are the only anoles native to North America and are a well-known presence in and around New Orleans.

The invasive brown anole didn't show up in the United States until the 1950s, but the species has since become established in the Southeast.

Researchers at Tulane University, aware that invasive species significantly disrupt and displace their native cousins, noted that "behavioral aggression" is one factor in the displacement of native species such as the green anole. 

"Invasive species cause a lot of ecological and economic damage, so biologists are really interested in understanding what makes these species so successful," Tulane researcher Alex Gunderson explained.

He and co-author Julie Rej published a study in the Journal of Thermal Biology, examining whether high temperatures were a factor in the brown anoles' displacement of green anoles. 

As the Louisiana Illuminator noted, they first suspected the species' startlingly high blood-lead levels could be to blame, but their findings said otherwise.

"Since we haven't seen lead affecting them in other ways, my guess is that it's probably not the cause. What we can say for certain is that their aggression increases with warmer temperatures," Gunderson said of the brown anoles.

Why is this study concerning?

Brown anoles weren't firmly established in Louisiana until about 25 years ago, but their numbers have since exploded.

In 2024, the Illuminator noted that, in that time, the green anole rapidly evolved, as the species had "never faced pressure like they do from brown anoles today." As green anoles began migrating to higher tree branches to evade brown anoles, their toe pad size increased.

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That behavior is called "resource partitioning," according to the Houston Arboretum, a defensive measure adopted as the more aggressive brown anoles outcompeted them for vital resources.

Invasive species are known to reproduce aggressively and deprive native wildlife of food, water, and sunlight, but the study's findings cited another factor working against native green anoles: rising temperatures.

In other words, brown anoles already have unfair biological advantages, which allowed them to crowd out the native green anole, and as the planet continues overheating, that advantage sharpens, further threatening these beloved native lizards.

Left unchecked, rising average temperatures could accelerate the decline of the green anole population.

What's being done about it?

As the researchers explained, understanding critical climate issues, such as the impact of higher average temperatures on native and invasive species, is key.

The Houston Arboretum had an interesting suggestion for dealing with the invasive brown anole, one particularly apt for New Orleans, a city known for daring cuisine: eat them.

"As one of our conservation staff members, Chris Garza, pointed out, the Cuban brown anole is edible," the Arboretum advised, recommending an increasingly popular approach to invasive species.

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