Organ Pipe Cactus National Monument in southern Arizona is a vast and rugged stretch of desert that supports a remarkable diversity of creatures. Resident species include at least 60 mammals, 14 of them bats, plus 350 bird species and more than 100 reptiles. This remote region also has become popular with drug smugglers. A team of scientists recently surveyed the monument because of the bats; they were protected by elite park rangers armed with assault weapons because of the smugglers. Conserving desert bats of the U.S.-Mexico borderlands raises unique challenges.
The monument, known as ORPI, is home to the largest-known maternity colony of the endangered lesser long-nosed bats (Leptonycteris yerbabuenae) in the United States. The bats spend their summers at ORPI’s abandoned Copper Mountain Mine.
BCI Caves Coordinator Jim Kennedy and colleagues spent two weeks last year hiking around the monument to assess 72 abandoned mines that are slated for closure because of their potential danger to humans and wildlife.
BCI was asked to examine the old mines for current or potential use by bats, then to design and recommend the best methods for closure. Those could range from simply filling insignificant pits with dirt to planning elaborate systems of gates for mines that host large bat colonies – with a lot of options in between.
The Copper Mountain colony – an estimated 40,000 bats – has grown steadily over the years, so much so, apparently, that this endangered species has formed smaller, satellite colonies that moved into other old mines in the area. This is an exciting turn of events for the recovery of the species, but it dramatically complicates management. A single site is much easier to protect, gate and monitor than a half-dozen remote backcountry sites, but the broader effort is essential to protecting the species’ long-term recovery.
This complex population helped convince BCI to emphasize comprehensive conservation planning and action on a landscape scale rather than focus on individual sites as crises arise.
Among cave- and mine-roosting bats, when conditions allow colonies to grow, subpopulations will often move out of primary roosts and colonize other subterranean sites. The satellite colonies are vital for continued population growth, maintaining genetic diversity within the species and as reservoirs that could escape catastrophic incidents at the main roost and rebuild the population. Losing current and potential satellite mines would have serious impacts on the long-term success of the Copper Mountain colony.
More than a century of mining for gold, silver, copper and other minerals has left the landscape littered with hundreds of abandoned mines and prospects, many of which provide shelter for bats and other wildlife. Unfortunately, many of these open and untended shafts present a hazard to humans.
Lesser long-nosed bats migrate into southern Arizona from central Mexico in April and May, timing their arrival with the blooming of desert agave and cacti, such as saguaro, organ pipe and senita. The bats are essential for pollinating these plants and for dispersing their seeds.
We identified 15 openings of various mines that require bat-friendly gates or similar closures of varying complexity. With the surprising success so far of this species throughout the Organ Pipe Cactus National Monument, this federal commitment to conserving vital habitat sparks real optimism that lesser long-nosed bats may ultimately graduate off the Endangered Species list.