South Dakota Bat Working Group
Bats & Mines

Last update 12/2009

Updated December 2009

Abandoned Mines Are Wildlife Habitat
By Joel Tigner of Batworks - A Chiropteran Consultancy

Generally speaking, open underground abandoned mines are viewed as blight on the landscape.
In the Black Hills region, open underground mines have been part of the terrain for over one hundred years. As such, they have come to serve as an integral part of sustaining habitat for many wildlife species, including South Dakota’s bats. At least ten species of bats roost in underground mines in South Dakota. Bats live in a variety of locations that can vary by season. These locations are called roosts. Unlike many birds, bats do not build nests, so a bat roost is not a nest, but rather a location where bats gather temporarily.

Bats…who needs them anyway? And on top of that, why don’t they roost where they did before the mines were here? Abandoned mines can pose public safety hazards!

All the bats in South Dakota eat nothing but insects.
And bats are insect-eating machines. Many of the insects that bats eat are agricultural and forestry pests. Bats are the main predator of night-flying insects. Bats also eat nuisance insects and help to control insects such as mosquitoes that can impact public health. Many species can eat their weight in insects during an evening. (One local example: During a survey at a roost in the Black Hills, a Townsend’s Big-eared Bat was netted emerging at sunset. The bat was weighed, banded, and released. Less than three hours later, this same bat was captured re-entering the roost with a 40% increase in body weight.) Without bats, insect populations would increase, largely unchecked. An effective natural control, bats live only where the insect population will support them.

The roosting question is more complex
. There is virtually no historical information on bat population size and distribution in South Dakota. This notwithstanding, many of the naturally occurring underground roosting sites (natural caves) have been lost as bat habitat (commercial development of large caves, high levels of disturbance in natural caves). Many of South Dakota's abandoned mines have likely served as a buffer against the decline of available natural roosting sites. Bat surveys of underground roosts begun in the early 1990’s have shown significant declines in bat numbers when compared with surveys conducted at the same sites since 2000. While a variety of factors have likely contributed to the decline in bat numbers, disturbance at and loss of roosting sites is a main cause of this decline.

Safety hazards? Absolutely, no question about it. All abandoned mines can pose significant safety hazards. Underground mines can be particularly dangerous places. In addition to the more obvious hazards, collapse and fall hazards for example, many abandoned underground mines contain toxic gases. Many of these are colorless, odorless and heavier than air. They can accumulate at low places within the mine or pool along the floor of the mine. A person entering the mine walking through these pooled gases can stir them up into the good air being breathed where they are inhaled. Conditions can change over time within the mine. Lacking adequate ventilation, air quality will deteriorate. Previous visits into a site are no guarantee that conditions will not have deteriorated to lethal levels.
Abandoned mine entry should only be undertaken by trained individuals using appropriate safety equipment.
Assessing abandoned mines and protecting them, where appropriate, serves to mitigate these hazards.

At some point during the year, at least ten bat species in South Dakota depend on underground roosting sites. Many abandoned mines have been closed in recent years, either intentionally or through natural erosion and /or deterioration. Not all mines, just as not all caves, provide the conditions bats need to survive. Using SDGFP funding, abandoned mines can be evaluated as bat habitat. In circumstances where the habitat is determined to be significant, specially designed bat gates can be installed to protect the roost for bats. These gates are designed to prevent unauthorized human entry, mitigating liability for the landowner while providing “bat-friendly” access. If the landowner decides to close open underground workings, advice can be provided as to how and when this should be done to prevent unnecessarily putting bats at risk. All of these are done at no cost to the landowner.

No property rights are affected by this program. If the site is used by bats as a hibernation site, owners must agree to refrain from entry of the site during the hibernation season. Each site is evaluated on a case-by-case basis.

For additional information on participation in this project,
Contact: Joel Tigner at
605-390-2061 (Rapid City, South Dakota).

We are actively seeking locations of mines that provide potential roosting habitat in the Black Hills region. Site evaluation can be provided at no cost to individuals interested in determining whether their site(s) provide potential roosting habitat. There is no obligation or further commitment required to participate in this service. Should you elect to permanently close an underground site, advice and protocol can be given to prevent placing bats unnecessarily at risk. 


Gating Information - Updated Dec. 25th, 2008

At the end of 2008, a total of 38 bat gates have been installed to protect underground bat roosting habitat in the Black Hills region (31 at abandoned mines; 7 at natural caves). All of these locations are used by bats as hibernation sites as well as night roosts during the active season.  Sites are located on private and public land and are located in Lawrence, Meade, Pennington, and Custer Counties in SD with one mine located in Wyoming.

Currently, there are 5 gates pending construction in the Spring of 2009, all of which are located at abandoned mines on private property. Evaluation of newly identified sites continues through funding provided through SD Department of Game, Fish and Parks.

Before & After photographs: Portal-stabilizing culvert & gate in place
in the Hell Canyon Ranger District of the Black Hills National Forest.

Photo by Joel Tigner

Photo by Brad Phillips

For additional information or to report a location, contact:

Joel Tigner, BATWORKS
605-390-2061 (Rapid City)

Photos by Joel Tigner

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