Since January, the Arizona conservation biologist has taken on a specialized role that has him descending into mine shafts to ensure bats living underground don't become casualties of efforts to close abandoned mines across the Southwest.
"It's easy enough to exclude bats from mines. There's no reason for them to be entombed," said Corbett, who works out of Tucson as a coordinator for the nonprofit group Bat Conservation International.
As someone designated to stick up for the little - albeit furry - guy, the bat buff travels around Arizona and other states offering inspections and recommendations. He is getting more companies and agencies to agree that doing nothing would be senseless.
Bats occupy a very important niche as nocturnal predators. They help the ecosystem by eating insects, including pests that eat crops like cotton and corn.
Angie McIntire, bat management coordinator for the Arizona Game & Fish Department, said mines can house thousands of bats. They may only use a mine for a couple months but it could be during a critical time such as giving birth or feeding young.
Both McIntire and Corbett said there is no way to gauge how many bats have been lost in mines. There is no official survey.
"I'm sure sites have been closed without any thoughts to bats or even knowledge they're in there," McIntire said.
Bat Conservation International started a national bats and mines program about 12 years ago. It was only a couple years ago that officials decided it would be better to have a coordinator devoted specifically to the Southwest.
Corbett's mine visits generally occur when government agencies and groups approach him with a mine location. But sometimes he will learn about a site and initiate contact. The real work begins once he and a support team, usually a trio of land officials and wildlife biologists, decide to go in.
While Corbett often inspects caves and horizontal shafts, it's vertical shafts that involve more work. Corbett uses a variety of ropes and a harness to lower himself into the shafts - some have been more than 500 feet deep. Corbett will hang a few feet before touching down in a shaft, using a pole or tracking stick to probe for other critters. He once came down near a rattlesnake and was able to gently move it away.
Once he's landed, Corbett looks for signs of bat life, such as bat droppings, also known as guano, or meal leftovers in the form of insect parts. But the research doesn't stop there.
"I'm looking at the bigger picture - how does that one mine fit into the larger landscape in terms of providing quality of habitat," Corbett said.
If other factors like temperature and exposure to predators show the mine to be habitable bat space, Corbett will recommend constructing a steel gate that would be narrow enough to keep humans out but let bats flit freely.
"If a mine is unsafe, putting a bat gate on is twofold; it keeps people out and also protects bats," Corbett said. "The two goals are not mutually exclusive."
If the danger to people is too great, they can drive bats out before filling up a mine. The process, called exclusion, involves putting a chicken wire netting over an entry point for several days. Bats can fly out through the netting but can't squeeze back in.
If no bats are found, then mine owners will likely be free to seal up a mine however they see fit.
Closing deserted mines has long been a public concern.
The issue took on more urgency in Arizona last year when a girl fell to her death in a mine shaft in the northwestern part of the state. The Arizona State Mine Inspector's Office estimates there are more than 9,500 abandoned mines statewide. There are hundreds of thousands more in neighboring states.
Chris Ross, leader of an abandoned mines program for the Bureau of Land Management in Nevada, praised Corbett for his understanding of not just the science, but the social and demographic issues. He said Corbett makes assessments that are economical but don't compromise public safety.
"He'll prioritize and spend big bucks on expensive bat gates on the ones that are important," Ross said. "The rest of them, we can chase the little dears out and fill them (the mines) up cheaply."
Corbett hopes to continue building relationships in more states such as Colorado and Utah. Most mining companies have been cooperative when it comes to finding a way to let bats roost in peace.
"They're happy to have some help on these issues," he said. "They want to do the right thing but like everyone else, they are strapped on resources."