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The legacy of Colorado’s historic abandoned mines includes new, and critical, habitat for opportunistic bats

In "Gold!" the author journeys to an old mining spot in the Sangre de Cristos to witness the creatures' massive nightly exodus

A 2018 finalist for Colorado Authors League award for General Non-fiction

Chapter 18

Bat Country


“So what can you tell me about the boots?” I asked the room full of clothing-optional enthusiasts. It was late afternoon, I’d been driving for hours, and I had to know. There was a moment where several volunteers at the hot springs looked around at one another, unsure how to respond. One man shrugged and admitted he had no idea, adding that the shoes have always been there as long as anyone could remember.

I had found the mysterious footwear along a lonely stretch of road at the northern end of the San Luis Valley, cutting between acres of golden farmland. The road leads to the base of the Sangre de Cristo Mountain Range for some miles before reaching the hot springs resort. On the southern side, there’s perhaps a mile of fencing with posts topped with hundreds of old cowboy boots and shoes.

At first glance, the tattered footwear slowly rotting in the dying light brought to mind unfortunate images of late ’70s horror movies and cheery cannibal family traditions. In the surreal late afternoon light of the valley reflecting off my vehicle’s windshield, the site did come across as mighty peculiar.

“Gold! Madness, Murder, and Mayhem in the Colorado Rockies” by Ian Neligh.

“You would have noticed if any of your guests went missing?” I asked the group. Many looked a tad uncomfortable wearing clothes, which was apparently required in the visitors center, or possibly at my line of questioning.

In point of fact, the unusual display of boots is something of a tradition dating back generations. In the time-honored Western practice of both paying tribute and letting nothing go to waste, worn-out boots were sometimes retired to serve as protection for the tops of fence posts. In this way, the boots continued to serve their owners by keeping water from destroying the wooden posts. While unusual to see without a complete and helpful understanding of the tradition, it is effective and a form of early recycling. As it turned out, I was at the clothing-optional resort not to partake in the area’s well-known hot springs but to pass through it along an old road leading to one of the most efficient and important examples of natural recycling in the state. From the time of the gold rush, there are some thirty thousand mine-related openings across the state today. The bats in Colorado have followed suit by repurposing abandoned mines for their homes.

As the sun set in an ominous red and orange splash across the dreamlike landscape of the valley, distant rainstorms shouldered their way ever closer as I began my two-mile hike. If I hurried, I could see the largest known bat population in the state emerge from an abandoned mine called the Orient.

Very Bat Behavior

I wasn’t disappointed when I got to Tina Jackson’s office in Denver. A taxidermied bat hung from the wall, rubber Halloween bats hung from the ceiling, and stuffed animal bats were scattered around. Jackson is a species conservation coordinator with Colorado Parks and Wildlife who is responsible for keeping an eye on the state’s bat populations. As it happens, former mines across Colorado are essential to maintaining bats, which have a very direct correlation to the people in the state, their economy, and health.

This relationship began once the gold rush and the fever to burrow into the mountains for precious minerals slowed, and the sounds of picks and rock drills went largely silent. The mines didn’t stay that way long; a variety of bat species soon began setting up their hibernation havens and roosting spots.  Jackson said as the state began closing the mines in the early ’90s someone realized that bats were living in them.

Ian Neligh, author of “Gold! Madness, Murder, and Mayhem in the Colorado Rockies.”

“Closures make a lot of sense. They are for human safety, which definitely should be done,” Jackson explained. “But these mine openings have been around for potentially a hundred-plus years—and the bats have figured that out.”

Bats, mountain lions, bears, rodents, and a host of different types of wildlife began making use of what were essentially man-made caves. The state decided to determine which mines were providing essential habitat and which weren’t. Bats were one of the animals that the state wanted to encourage in their use of old mines. As such, special gates were installed; like giant Venetian blinds they allowed bats to fly in and out and only restricted humans from entering. Jackson said that some mines are too dangerous even for bats to live in, due to poisonous gases or other hazards, but often they find a way to adapt.

“We have Townsend’s big-eared bats that use the uranium mines over in the southwest, so you kind of would think that would be a bad thing, but they’re using them,” Jackson said. Some believe that the bat populations finding and using mines is a result of their species being pushed by humans into new areas, but Jackson believes the bats appropriating the abandoned mines is more of an opportunistic move than one forced upon them.

“We’ve just provided a new place,” Jackson said. “It was a lot like building a birdhouse. We didn’t cut the bird’s tree down and then put the birdhouse up; we just put a birdhouse up and now there’s another bird that can go, ‘Oh, wow, here’s a home.’”

“And the bats have certainly jumped on that,” Jackson said. A survey of more than six thousand mines in Colorado, Arizona, California, and New Mexico shows that anywhere from 30 percent to 70 percent are being used by bats.  According to Jackson, the Townsend’s big-eared bats are the ones most often seen by state biologists making use of the abandoned mines. The big-eared bats are also a species of “special concern” to the state because they are so sensitive to human disturbance. The gradual closure of abandoned mines and loss of caves for bat habitat is thought to have largely contributed to the declining populations of this species in the United States. Jackson added the other poster child of mine-living bat species is the opportunistic Brazilian free-tailed bat, also known as the Mexican free-tailed bat, or Tadarida brasiliensis.

“That one is using abandoned mines in the San Luis Valley and there we have a bachelor colony of a quarter of a million bats in one abandoned mine,” she said.

That same mine is called the Orient, and I was about a quarter of a mile away when I smelled it—long before I reached it. The massive size of the colony can be measured by the smell of guano. Like an old-time restorative of cruel smelling salts, the bouquet of some 250,000 bat droppings is quite powerful. The air becomes heavy with a smell like ammonia, urine, and something akin to moss.

“They’re hugely beneficial,” Jackson said of bats, and she’s not kidding. They are the only flying mammal on the planet to catch and eat some six hundred mosquitoes an hour and put a serious dent in hazardous crop-eating insects. The bats living in the Orient Mine eat two tons of bugs every evening, including the Heliothis moth, which makes victim of a host of crops including everything from corn to pumpkins. And the serious dent they put on mosquito populations is not a bad thing either with the rise of charming mosquito-borne illnesses such as dengue, West Nile, and the Zika virus—to name a few.

“Bats are super beneficial. There’s been some research recently that says billions of dollars every year are saved,” Jackson said of the bat contribution. “They eat agricultural pests, they eat mosquitoes, they eat all sorts of things—and mosquitoes are important from a human disease vector issue.”

Protecting the Batcave

The small party of resort goers and myself reached the top of the climb, with a view of the massive cave-in on the upper levels of the Orient Mine. The iron mine was started in the early 1870s and, while not specifically related to gold, is the largest known example of a mine repurposed by bats in the state.

In my time traversing the mountains and talking with prospectors, I’ve come across more than a few mines specially sealed off with a grate-like structure to allow the passage of bats. But nothing I’ve seen is on this scale. Too large to block off with a small gate, the “Glory Hole” falls away dangerously into the darkness of the mountain. A giant gaping mouth appeared after the mine closed in the 1930s and silently yawns out over the San Luis Valley. The valley is known for its unusual, often jaw-dropping features such as its colorful gator ranch, UFO Watchtower, and its Great Sand Dunes, but nothing could prepare me for what I was about to see. As the sun sank in what can only be described as an apocalyptic smorgasbord of colors, we waited, whispering only when necessary. They would soon arrive.

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Jackson told me protecting mines from humans was essential for the bats’ survival. “Waking up a colony of hibernating bats, if it happens often enough, can cause them either to abandon the site or actually die from not having enough fat reserves to make it through the winter,” Jackson explained. “So we’re protecting the people from the mine, but we’re also protecting the bats from the people.”

Biologists will go to a mine site eligible for closure and look for signs of bats, such as guano or bug parts, littering the ground. Failing that they’ll wait for winter and do their best to sneak inside, which is always a dangerous proposition in an abandoned mine.

In 2010 the state worked on nine abandoned mine projects involving bats. These projects consisted of 118 mine openings. That year fifty-five bat gates were installed. In Clear Creek County some thirty-six mines near Dumont were investigated for bats. Of those, twenty-two mines were closed and fourteen received bat gates.

Jackson said white-nose syndrome, a malignant fungal disease that eats away at hibernating bats and brings with it a high mortality rate, hasn’t yet reached Colorado. Biologists are regularly and vigorously monitoring for it in Colorado’s abandoned mines. The fungus was first observed in 2006 and has since affected at least nine species of hibernating bats and spread to twenty-nine states. And there are a lot of abandoned mines in Colorado that still need to be checked and closed every year. Of the roughly thirty thousand mine-related openings across Colorado, ten thousand of them have been made bat friendly in the last twenty years.

“So we’re looking at about another forty years before we get to the remainder of them,” Jackson said. “But on the other hand we’re building closures, but those fail at times. Those fail because people make them fail.”

Indeed, the locations of mines with bats living in them are something of a secret. I’d seen a few, but they were pretty far off the beaten path. Jackson said work to repair and maintain bat gates is a never-ending process. She added that a mine with bats on private property is never fully off-limits.

“When gold prices get high enough . . . it makes sense for people to open them back up,” Jackson said. “We have had cases where our biologists go up to survey, and the gate is open, and there are people working on it.”

Staring up at the sky I spotted two bats fly overhead. Then a few more, then hundreds came twisting out of the mouth of the mine like a single living thing. The bats flew in a thick black column, not far above where I stood, stretching in the cool evening air like a snake. They made some sounds, the flap of a wing or a random squeak, but mostly remained silent in their single-minded purpose to drift over the valley. Thousands of bat wings sounded not unlike the wind whispering over the ocean. For nearly half an hour bats got in line and took their turn entering the giant formation, leaving the mine for their nightly hunting grounds. It seemed to me that it was a sight as valuable as any gold or other precious metal ever removed from the mountains of Colorado.

From “Gold! Madness, Murder, and Mayhem in the Colorado Rockies,” ©2017 by Ian Neligh, West Margin Press, reprinted by permission.


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Interview with “Gold! Madness, Murder, and Mayhem in the Colorado Rockies” author Ian Neligh.

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