Here's one advantage to armadillos' steady northward march across the Southeast United States:

They're awfully handy to have as bait if, say, you're a wildlife biologist looking to trap an alligator that has inexplicably settled into your local pond in north Georgia.

That's what happened last month near Atlanta: A biologist with Georgia's Department of Natural Resources, on the way to trap an alligator scaring residents, stopped en route to pick up some fresh road kill.

Now it's true that the armadillo was more of a random choice. "Our biologist just happened to see it on the side of the road," said agency spokeswoman Robin Hill. "It could've been a squirrel."

And it's also true the southern fare failed to tempt the alligator. "No," said Hill, "there was so much attention on that pond that the alligator just got spooked, and we haven't seen him since."

But there's no question armadillos - and other small mammals - are on the move in the United States, expanding into terrain biologists thought highly unlikely just a few years ago.

Some of that migration can be attributed to opportunity: The armadillo in particular has been moving northward since it arrived in Texas in the 1880s and Florida in the 1920s, according to Colleen McDonough, a biology professor at Valdosta State University in Georgia.

Some, however, is clearly triggered by a changing climate. Armadillos have settled into southern Illinois, Indiana, Kansas and Missouri - all areas that were "totally unexpected," McDonough said.

They're not the only ones. White-footed mice and southern flying squirrels have expanded their range northward some 140 miles in Michigan, according to University of Michigan biology professor Philip Myers, who described the migration in a recent paper as "an unusually clear example of change that is likely to be the result of climatic warming."

"As with any range extension, it's a complicated situation having to do with people, migration corridors and so forth," Myers said in an interview.

Like coyotes, armadillos are opportunistic creatures, unquestionably moving north for reasons unrelated to climate change, cautioned McDonough. That explains their spread into northern Georgia, South Carolina, Oklahoma and other southern states. But biologists never thought the winters of North Carolina, Indiana, or Missouri were mild enough to support an armadillo population; seeing the animal establish itself in those reasons is thought to be a sign of climate change, though a harsh winter or two could knock them back.

"That northern border is going to fluctuate," McDonough said.

The consequences of such changes are unclear.

Armadillos are a welcome help to residents dealing with fire ants, a big concern in the South, McDonough said. But they're also a nest predator and could put added pressure on local quail populations already trying to defend against possums, raccoons and snakes.

Myers' research in Michigan, meanwhile, suggests southern species are replacing northern ones, rather than simply slotting into the local fauna.

"To predict the impact of adding a chipmunk or subtracting a mouse, you have to know a lot more about the natural history of the communities than we do," Myers said.

What is certain, Myers added, is that the most common animals in many ecosystems are changing. These creatures play key roles: They disperse seeds, dig burrows that provide habitat for others, prey on insects, serve as reservoirs for hantavirus and other diseases.

"Potentially there are huge changes that could be a consequence of messing around with the species present," Myers said.

"Basically all we can do is ... sit back and measure the change as it happens, whether we like it or not."

This article originally appeared at The Daily Climate, the climate change news source published by Environmental Health Sciences, a nonprofit media company.