Thousands of Arizona mines have boomed and busted in the state’s history.
Now, decades after the heyday, the federal government and scientists are working to keep humans out of abandoned sites while still inviting bats in.
“In the absence of these abandoned mine habitats, these bat populations would crash,” said Arizona Game and Fish research ecologist Joel Diamond.
Diamond spoke as he drove through the desert near Buckeye. The area’s popular with recreational shooters and four-wheelers.
The opening to a former silver mine appears without warning. It’s a 90-foot drop to the bottom.
“The shaft's deep enough that it’s a one-way trip,” Diamond said. “If you fall in the shaft, you’re probably not going to make it back out.”
Game and Fish worked with federal partners to block off the mine last year. The opening is ringed by a metal culvert and rebar forms a grid pattern on the top.
The design lets bats fly through and keeps desert tortoises and other animals, including people, from walking in.
“Before we gated it, it was something you could drive your ATV right into and not notice because it was level with the ground,” Diamond said.
Bats need a variety of habitats to live out their lives. Caves often have multiple microclimates, which makes them suitable for multiple purposes such as a nursery for pups or daytime hangout.
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Mines are less complex and usually only serve a single purpose for bats. This particular mine shaft is a late-night snacking spot for California leaf nosed bats.
“They fly in there, hang off the wall, pluck the wings off whatever they’re eating that day and then have their dinner,” Diamond said.
Scientists monitor the sites with audio recorders that pick up the bat's unique calls to measure how frequently they're used.
Diamond focused on bats in both his graduate and doctorate degrees. Arizona is home to 28 bat species including one of his favorites, pallid bats.
“They’re very cute, big long ears, they have a little pig nose,” Diamond said.
The winged creatures are cute, but fierce. Pallid bats can stalk and kill scorpions and are among few that hunt prey on the ground.
Arizona Game and Fish, along with the Bureau of Land Management (BLM) and non-governmental organizations keep an eye on thousands of mine sites across the state.
Since 2009, Game and Fish alone took stock of 4,200 mines. The organization began installing bat gates in 2016 and have placed 44 with another 25 in the works.
Nonprofit Bat Conservation International reports it’s helped facilitate 400 mine gates in Arizona in the last decade.
“We usually prioritize on if it seems like there’s a lot of public access where people could get hurt,” said Misty Shafiqullah, who manages Arizona’s abandoned-mine lands program for the BLM. “That’s where we’re going to put our money first.”
There’s estimated to be more than 100,000 abandoned mines in Arizona.
“A lot of these things can be picked up with satellite imagery, but you’re not going to see all of them that way and so you really do have to get out on the ground to find a lot of them,” Shafiqullah said.
On a recent January day, BLM staffers joined contractors and Jason Corbett from Bat Conservation International to walk through a planned mine gate site near Parker.
BLM geologist Vince Beresford points out a stripe of turquoise-colored mineral on the rocks.
“When they started out prospecting, they probably noticed a vein of some sort of Chrysocolla at the surface and then wanted to follow that into the ground.”
The Chrysocolla vein marked a copper deposit.
The miner’s pursuit of the metal left the hillside pitted with openings.
Contractor Tom Gilleland measures each one for a custom-fit gate. His business Mine Gates Environmental relies almost solely on federal contracts. He said funding for these types of projects has dried up under the current federal administration.
“I literally just did my taxes and our revenues were half of what they were last year,” Gilleland said.
The walkthrough that brought everyone to Parker was almost canceled because of the government shutdown.
After donning a helmet, Corbett leads the group into a rocky crevice where the ceiling is just a few feet overhead.
The cramped space is full of trash — a sign that people are also drawn to the area. A nearby gate is riddled with holes like someone used it for target practice.
“It seems like when a gate goes up, folks get pretty convinced that the federal gold reserves are behind that,” Corbett said laughing. “People love attacking them.”
The contractors who build the gates often clear trash from the area. Corbett said it’s not uncommon for bat usage to increase once the gates are up because people are no longer intruding.
He tipped his head up to look at the mine’s ceiling.
“Nobody home, but there's a little pile of guano,” Corbett said. “So bats are, you know, using the site.”
