Wildlife in Abandoned Mines

Many different types of wildlife use abandoned mines for either permanent or temporary habitat.

BatsBats
Abandoned mines provide very good bat habitat. Contrary to their much-maligned image, bats are ecologically and economically critical to the well being of the nation. The Mexican free-tailed bat weighs approximately one ounce and will consume one-half its body weight in insects each night. The mathematical result is that one large (20-million) colony of bats consumes over 150 tons of insects each night. A much smaller colony may consume almost 2 tons of insects each night. Seed production from an agave plant (the source for tequila) drops to a fraction of the normal without bats as pollinators. And yet, over half of the 43 species living in the U.S. are endangered or on the candidate list for endangered species. As their traditional habitats such as caves and tree hollows are being disturbed by human intrusion, bats are becoming more and more dependent on abandoned mine sites for suitable habitat. Many of the 43 species, including endangered species, have been observed using abandoned mines either as permanent roosts or temporary stops during migration. Abandoned mines provide microclimates similar to caves, suitable for rearing young, hibernation, and rest stops during migration in the spring and fall. Closure of mine openings without a biological survey can trap and destroy an entire colony of bats.

Bat Conservation International (BCI) is a non-profit organization formed to promote the conservation of bats and bat habitat. The Office of Surface Mining signed a Memorandum of Understanding with BCI in 1998 to address the significance of protecting bat habitat while closing abandoned mines.

New Mexico is home to 27 species of bats; 19 are listed as a Species of Concern, three species are considered threatened and one species is considered endangered. The various species found in New Mexico include:

Common Name (Species Name)  
Pallid Bat (Antrozous pallidus)  
Mexican Long-tongued Bat (Choeronycteris mexicana)  
Townsend's Big-eared Bat (Corynorhinus townsendii)  
Big Brown Bat (Eptesicus fuscus)  
Spotted Bat (Euderma maculatum)  
Greater Mastiff Bat (Eumops perotis)  
Allen's Big-eared Bat (Idionycteris phyllotis)  
Silver-haired Bat (Lasionycteris noctivagans)  
Western Red Bat (Lasiurus blossevillii)  
Eastern Red Bat (Lasiurus borealis)  
Hoary Bat (Lasiurus cinereus)  
Western Yellow Bat (Lasiurus xanthinus)  
Lesser Long-nosed Bat (Leptonycteris curasoae)  
Greater Long-nosed Bat (Leptonycteris nivalis)  
Southwestern Bat ( Myotis auriculus)  
California Bat (Myotis californicus)  
Western Small-footed Bat (Myotis ciliolabrum)  
Western Long-eared Bat (Myotis evotis)  
Little Brown Bat (Myotis lucifugus)  
Fringed Bat (Myotis thysanodes)  
Cave Bat (Myotis velifer)  
Long-legged Bat (Myotis volans)  
Yuma Bat (Myotis yumanensis)  
Pocketed Free-tailed Bat (Nyctinomops femorosaccus)  
Big Free-tailed Bat (Nyctinomops macrotis)  
Western Pipistrelle Bat (Pipistrellus hesperus)  
Brazilian Free-tailed Bat (Tadarida brasiliensis)  
A biological survey is conducted in coordination with bat expert Dr. J. Scott Altenbach of the University of New Mexico to check for bat habitation prior to closure of a mine opening. If bat activity is confirmed, the typical response is to construct a bat gate or bat cupola. Bat gates may be different sizes, shapes, or designs but usually involve a steel grid with openings large enough to allow passage for the bats, yet small enough to prevent human entry. Gates often are installed on mine openings with no visible signs of bat habitation in order to maintain ventilation patterns which may be essential to adjacent or connecting areas which do contain bats. The type of gate installed depends on the size of the opening and the species of bat using it. While most species tolerate gates and readily adapt to them, some species do not. For these bats a concrete wall blocking most of the opening is effective so long as a horizontal opening is left at the top of the closure to accommodate the bats. Other type gates may include a lockable gate to provide for future human entry if necessary. Bat gates must meet the primary objective of protecting the public from a hazardous condition and are sometimes more economical than conventional mine closure methods.

The New Mexico AML Program often constructs cupolas over shafts used by bats to access mines. The steel bars of the cupolas are spaced appropriately to allow bats to fly through while keeping a majority of humans out. View an abandoned mine shaft from a bat's perspective.
Bats of the Western United States (front) Bats of the Western United States (back)
Examples of Bat Cupolas
Cerrillos South bat cupola (AML 340.18) Lordsburg/Gore Canyon AML 33
Real de Dolores Ortiz cupola Lake Valley Phase I   AML 835-14
Examples of Adit Closures
When bats are found in a mine, a bat gate will often be constructed if the rock is deemed stable. When rock at an adit entrance is considered unstable, the bat gate will sometimes be placed inside a corrugated steel pipe.

OwlsBarn owl
Barn owls (Tyto alba) are commonly found in abandoned mines in the southern part of New Mexico. A mine shaft provides a relatively safe nesting location difficult for predators to access. The AML Program preserves existing barn owl habitat when feasible.

Snakes in a mine aditSnakes
Rattlesnakes are a danger commonly associated with abandoned mines in New Mexico.. Rattlesnakes can sometimes be found near the entrance to a mine adit, going in and out of the mine depending on their temperature preference.


Other

Some other species that find temporary homes in abandoned mines include ringtails (Bassariscus astutus) and javelina (Tayassu tajacu). 

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