Bat Conservation International Surveys Abandoned Mines for Bat Roosts


Mojave National Preserve is 1.6 million acres of rough and rugged desert terrain, stretched between Los Angeles, California, and Las Vegas, Nevada. It is the kind of stark desert landscape that makes for spectacular photos and travel stories, a gem in the National Park System.   

Jackson Bain rappels into an incline. Photo by Nathan Breece.

Traveling through, you witness one of the largest and densest forests of spikey Joshua trees found anywhere in the world, towering mountains that rise steeply thousands of feet above the desert floor, volcanic lava beds that cover more than 200 square miles, a sea of sand dunes, and an exceptional array of flora and fauna. Yet, it’s what beneath the surface that draws Nathan Breece and his colleagues Shawn Thomas and Jackson Bain from Bat Conservation International’s Subterranean Team. 

Throughout the Preserve, abandoned mines – remnants of bygone days when the extraction of tons of gold, copper, silver, zinc, lead, and other minerals attracted fortune seekers –  now serve as roosts to Townsend’s Big-eared Bats (Corynorhinus townsendii) and other bat species in the western United States, as well as harbor other wildlife.  Today, in the Preserve, there remain more than 1,400 abandoned mine openings that lead to underground spaces.  The abandoned mines in the Preserve, as well as the Preserve’s natural caves and karst, are vital for migrating western bats and maternity colonies, says Breece. 

A Townsend’s big-eared bat (Corynorhinus townsendii) perched in an inclined shaft. Photo by Nathan Breece.

Commissioned by the National Park Service to determine how bats and other wildlife are inhabiting abandoned mine sites, Breece recently led his fellow bat conservationists and David Tibor and Trinity Smith, environmental scientists from the California Department of Conservation, into Mojave National Preserve’s underground.  During a week in the field, the team surveyed nearly two dozen abandoned mines – hauling in high-tech devices for recording climate and structural data; adjusting their headlamps; clipping into harnesses to rappel into dark shafts (vertical passageways) that sometimes dropped dozens of feet; and suiting up in protective gear to crawl into unknown adits (horizontal passageways) that often twisted and turned.   

What they discovered were live animals – snakes, barn owls, woodrats, beetles, spiders, a federally endangered desert tortoise, and roosting bats, including a bat with a sharp spike of cholla cactus protruding from its back.  They also found and recorded additional evidence of wildlife inhabitation including bat guano, bird pellets, other forms of scat, middens, nesting materials, and the skeletal remains of lizards, snakes, small- to medium-sized mammals, and the carcass of a mountain lion.   

Finding the mountain lion carcass, says Breece, was not surprising.  In his twelve years of subterranean research for Bat Conservation International, Breece has come across the remains of mountain lions several times, leading him to a conclusion that old or sick mountain lions may seek out caves and abandoned mines for their final days.  Over the past two years, Bat Conservation International has worked in Glacier, Death Valley and Capitol Reef National Parks, Lava Beds National Monument, and other federally managed lands as part of BCI’s commitment to implement bat conservation on over 258 million acres of land owned and managed by the U.S. government. 

“These kinds of projects with the National Park Service and other federal agencies represent the epitome of partnership,” Breece says.  “Surveys commissioned by federal land managers provide bat conservationists with access to evaluate the health and viability of bat habitat, up close.  And land managers benefit from our expertise in mapping and recording often unknown underground spaces.”  

Looking down a shaft from the collar. Photo by Nathan Breece.

Per Bat Conservation International’s agreement in Mojave National Preserve, Breece and his team recorded the precise GPS coordinates of each mine feature; measured each mine’s entry points; and made note of the site’s elevation. Inside, the team documented temperatures and humidity; logged indications of human visitation; and recorded all evidence of bats and all other wildlife species.   

In some of the surveyed mine features, the team used a handheld LIDAR device that enables remote sensing of the mine’s interior by sending out laser beams that return to the device to produce a precise composite image of distance, height, width, and geological features –  once the data is uploaded onto high-powered computers and translated by synthesizing software.    

“Mojave National Preserve has documented 10 bat species within its boundaries, but as many as 17 species could be present based on habitat preferences and biology of these bats.  Projects conducted by Bat Conservation International help us to inventory and potentially detect undocumented bat species,” says Neal Darby, Wildlife Biologist, Mojave National Preserve, National Park Service. “Most importantly, Bat Conservation International helps provide information that can lead to protection and preservation strategies to conserve and enhance bat habitat, as well as other wildlife.”