Bat use of abandoned mines in the Pryor Mountains : a report to Montana Department of Environmental Quality, Mine Waste Cleanup Bureau

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Bat use of Abandoned Mines
in the Pryor Mountains

A Report to:

Montana Department of Environmental Quality
Mine Waste Cleanup Bureau

2209 Phoenix Avenue
Helena, Montana 59620-0901

Submitted by:

Paul Hendricks and John Carlson

October 2001

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MONTANA STATE LIBRARY

1515 E. 6th AVE.
HELENA, MONTANA 59S20

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MONTANA STATE LIBRARY

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Bat use of Abandoned Mines
In the Pryor Mountains

©2001 Montana Natural Heritage Program

Montana State Library P.O. Box 201800 Helena, Montana 59620-1800 (406) 444-3009

DEQ Agreement No. 480008 Task Order No.

This document should be cited as:

Hendricks, P., and J.C. Carlson. 2001 . Bat use of abandoned mines in the Pryor
Mountains. Report to the Montana Department of Environmental Quality, Mine Waste
Cleanup Bureau. Montana Natural Heritage Program, Helena. 8pp.

Summary

We surveyed ten workings at six abandoned mine sites (Swamp Frog, Marie, Dandy, Roberts
Incline, CM & M, Lisbon) on the southern slope of Big Pryor Mountain in the Pryor Mountains,
Carbon County, Montana, for evidence of use by bats in the summer of 2001 . This aggregation
of mines, spread along two linear miles between 5380-6800' elevation, was "reclaimed" in 1989,
but reclamation involved primarily the posting of warning signs at portals and construction of
fence barriers around open shafts and pits. Thus, several mine workings were still accessible to
bats.

We inspected and trapped at mines during three visits: 17-18 July, 24-29 July, and 4-6
September, 2001 . We made complete or partial internal inspections of eight workings and found
scattered bat droppings in seven of these. During eight nights of trapping at six portals of four
mines we captured 48 bats of three species: 21 Western Small-footed Myotis {Myotis
ciliolahnim), 15 Western Long-eared Myotis (Myotis evotis), and 12 Big Brown Bats (Eptesicus
fusciis). The two Myotis species are U.S. Fish and Wildlife Service species of special concern.
No Townsend's Big-eared Bats (Corynorhimis townsendii), another special concern species,
were captured or detected, although this species has been documented in winter at two of these
mine workings. We heard the audible calls of Spotted Bats [Euderma maculatiim), another
special concern species, early in the morning of 18 July, 25 July, and 29 July over the Swamp
Frog, Dandy, and Roberts hicline mines, respectively, but found no evidence of mine use by this
species.

We recommend that the Dandy Upper West Adit #4 and the Marie, two workings with extensive
underground passage, be considered for bat-accessible gating. Summer bat activity was
significant at the Dandy working (83% of our total captures), a documented Townsend's Big-
eared Bat hibemaculum. The Marie site, although currently experiencing relatively little summer
use by bats (4% of our total captures), has the potential to become a significant site for bats if
protected from human intrusion.

Ill

Acknowledgments

We thank Vic Anderson and Jack Yates, Montana Department of Environmental Quality Mine
Waste Cleanup Bureau, for their continued interest and support in the evaluation of abandoned
mines in Montana as bat habitat. Montana DEQ Mine Waste Cleanup Bureau provided the funds
necessary to conduct the assessment covered in this report. We thank Doug Keinath (Wyoming
Natural Heritage Program), Erin Riley (BLM), and Dustin Rodgers (BLM) for assistance in the
field trapping bats, and Jay Parks (BLM) for advice on access to the mines and additional
support for the field work. Whitney Weber (Montana Natural Heritage Program) downloaded
GPS data and produced the map. Joy Lewis (Montana Natural Heritage Program) edited an
earlier draft of this report and escorted the final draft through the production process, where
credit is due to Katrina Dixon (Natural Resources Infomiation System).

IV

INTRODUCTION

Exploration and exploitation of uranium deposits on the southern exposures of the Pryor
Mountains in Carbon County of south-central Montana, quickly developed in the 1950's and
declined about as rapidly in the 1960's. Although the majority of workings are little more than
prospect pits or scrapes and most underground workings extend only a few yards, a few
abandoned mine sites include workings with more extensive underground passageway.
Reclamation of abandoned mine workings in 1989 included postmg warning signs at portals and
construction of fencing around open pits and shafts at sites with the most significant underground
workings. Thus, several underground workings remain accessible both to bats and humans
despite reclamation efforts.

Perhaps because of the abundance of natural caves in the Pryor Mountains (Campbell 1978), the
area is occupied by a relatively large diversity of bat species, ten species documented so far
(Worthington 1991 ). Six bat species that could occupy abandoned mines in the Pryor Mountains
(Western Small-footed Myotis [Myotis ciliolabnaii]. Western Long-eared Myotis [M. evotis].
Little Brown Myotis [A/, luclfiigiis]. Long-legged Myotis [M. volans]. Big Brown Bat [Eptesiciis
fuscus], Townsend's Big-eared Bat [Coiynorhiints townsendii]) are known from Pryor Mountain
caves (Worthington 1991 ). Of these six species, four (excepting Little Brown Myotis and Big
Brown Bat) are considered species of special concern by the U. S. Fish and Wildlife Service
(Hai-vey et al. 1999).

There have been few efforts to systematically document bat use of caves in the Pryor Mountains,
with the notable exception of Worthington (1991 ). Documenting bat use of abandoned
underground mines in the Pryor Mountains has received less attention, even though mines have
supplemented or replaced caves as key year-round bat habitat in many regions of the United
States (Tuttle and Taylor 1994). The primary objectives of our field work in summer 2001 were
to: 1 ) assess the use by bats of several mine sites with underground workings still accessible to
them, and 2) offer suggestions for protection of significant bat roosting habitat from human
disturbance, should such habitat be identified.

STUDY AREA AND METHODS

The Pryor Mountains of Carbon County, Montana lie near the Wyoming border to the west of
the Big Horn River, and are separated from the Big Horn Mountains by the impressive gorge of
Big Horn Canyon. The Pryor Mountains are a series of asymmetric anticlines forming four
major uplifted mountain blocks (Campbell 1978), one of which is the Big Pryor Mountain block
where a series of abandoned uranium mines are located. Nearly all of the surface rock of the
Pryor Mountains is uplifted Madison Group limestone, which harbors numerous solution caves
in the upper portions of the Mission Canyon Formation. Base elevation on the southern slopes of
Big Pryor Mountain in Montana is 4600', reaching 8786' at the summit.

A series of abandoned uranium mines are found between Gypsum Creek to the west and
Crooked Creek to the east. They range in elevation from 5380-7800' and are located on the
south-facing slope of a spur ridge leading to Red Pryor Mountain on the summit ridge of Big
Pryor Mountain. This cluster of abandoned mines was the focus of reclamation activity in 1989

by Spectrum Engineering (Spectrum Engineering 1990), but reclamation did not include
evaluation of the mine workings for use by bats.

Our 2001 assessment focused on the mine workings on BLM lands between the Swamp Frog
(5380') and the Lisbon (6800') mines, and also included the Marie, Robert's Incline, Dandy, and
CM & M mines, all within T9S, R27E (Fig. 1). We excluded visits to the highest-elevation
mines, on U.S. Forest Service lands in T 8S, R 27E (Old Glory [=Ponderosa] and Sandra mines),
because of deteriorated roads and prior indication of limited or low potential for use by bats
(Madson and Hanson 1993, Martinez 1995). Landscapes at all mine sites we visited were
dominated by limber pine-juniper-sagebnish habitat, with some Douglas-fir intermixed at the
higher sites.

We inspected mine workings and trapped bats during three visits in summer 2001: 17-18 July,
24-29 July, and 4-6 September. For each mine site, we documented the presence of open portals
and noted portal dimensions, obstructions, and the presence of bat spoor. Workings deemed safe
for entry were examined for the presence of bats or bat sign, and internal dimensions measured
with a cloth tape or estimated. Mine ambient temperature and relative humidity, when recorded,
were measured with a sling-psychrometer.

Bats were captured at portals using 50-denier mist nets of various lengths (usually 8' or 18'),
depending on dimensions of the portal. We used an electronic bat detector (ANABAT II; Titley
Electronics, Ballina, Australia) to aid with detecting the presence of bats in the area while we
operated mist nets. Typically, nets were deployed at dusk and operated for at least 3-4 hours
(often until midnight or later). Captured bats were identified with aid of keys in Nagorsen and
Brigham (1993) and Foresman (2001b); individuals were sexed, aged, measured (forearm,
weight), reproductive status noted, then released.

RESULTS

The sequence of mines presented below is arranged from lowest to highest elevation. Names for
mine workings and reclamation sites follow Spectrum Engineering (1990).

Swamp Frog (T9S, R27E, Sec. 17NESE). We visited this mine site (5380' elevation) on 17
July, and netted at the two shallow adits of the "Central 1 Site." The two adits are approximately
8-10' apart. The north adit is very shallow (10') with passage about 8' x 8' in height and width,
the south adit is a simple relatively level working of same dimensions about 85' in extent with a
partially collapsed entrance about 3' x 8'. A few scattered bat droppings were present in the
south adit, but no bats were seen.

We deployed a net across the portal of the south adit, but captured no bats in three hours.
However, we noted 8-10 passes at and into the north adit by perhaps 3-4 individuals of an
unidentified Myotis species. During our walk out (at 00:15 on 18 July) we briefly heard the
audible clicking of a Spotted Bat [Euderma maculatum) flying above us in the Swamp Frog
"Central 3" area.

Figure 1 . Mine workings surveyed for bats during the summer of 2001 .

Robert's Incline (T9S, R27E, Sec. 9NWSW). We trapped the portal of this site (5865'
elevation) on the night of 28 July. The portal (about 6' tall x 8' wide) is in a matrix of unstable
rock, supported by a partially collapsed headframe. This working, actually a decline, was not
inspected internally because of the partial collapse of the passage, but from the portal appeared to
be a simple working extending at least 80' (Martinez [1995] states the adit extends >200').

We recorded slight activity in the area during three hours, and captured only two male Western
Small-footed Myotis entering the portal (Table 1). We briefly heard Spotted Bat calls upslope
from the portal at 00:20 on 29 July.

Table 1. Summary of bats captured at abandoned mines in the Pryor
Mountains, Carbon County, Montana in summer 2001. MYCI = Myotis
ciliolabrum (Western Small-footed Myotis), MYEV = Myotis evotis
(Western Long-eared Myotis), EPFU = Eptesicus fusciis (Big Brown Bat).
M = male, F - female.

Mine working

Date

MYCI

MYEV

EPFU

Robert's Incline

28 Jul

2M

Marie

24 Jul

1 M

1 M

Dandy West "Adit 4"

25 Jul

4 Sep

5 Sep

3M

13M, 1 F

2M, 3F
5M, 1 F

3M, 1 F

1 M
4M, 3F

Dandy West "Adit 5"

25 Jul

3M

Dandy West "Adit 6"

27 Jul

1 M

Total

20M, 1 F

lOM, 5F

9M, 3F

Marie (T9S, R27E, Sec. 8SENE). This mine (6000' elevation) has over 950' of workings on two
levels. From the portal (8.5' tall x 14' wide) the mine descends at a moderate angle for 440'
where it intersects perpendicular passage mnning east and west. There is a second level of
workings at this point, accessed through a dome-like stope or nearby ore chutes in both sections
(east and west) of perpendicular passage. Mine temperature and relative humidity at the
intersection on 25 July were 46.5 °F and 90%, respectively. There are several side workings off
of the west passage, which is level and extends 242' to the drift face, where it was 47.0 °F with
85% relative humidity. The east passage ascends slightly for 121' to the drift face, where it was
49.5 °F with 84% relative humidity. We found scattered Myotis droppings in both sections of
the east-west perpendicular passage, but saw no bats on either visit underground (25 July and 5
September). There was also evidence of recent human visitation throughout the mine, but
especially in the decline from the portal to the perpendicular passage. Evidence included spent
fireworks, charred firewood, boot prints, and discarded beer cans.

We netted the portal for four hours on the night of 24 July. There was slight bat activity at the
portal, and we captured only two bats (Table 1), a male Western Small-footed Myotis and a male
Big Brown Bat attempting to enter the mine.

Dandy (T9S, R27E, Sec. 8NENE). This mine includes numerous workings spread over a
relatively wide area. Our attention was focused on two workings (adits 4 and 5) in the "Dandy
West Upper" site (61 10' elevation) and one working (adit 6) in the "Dandy West Lower" site
(6030' elevation). Most other sites in the Dandy Mine area are very shallow or lack underground
workings. We inspected the three adits on 25 July and 5 September.

"Adit4" is the most extensive of the three workings, apparently with three levels (Madson and
Hanson 1993), the portal being on the upper-most level. We were unable to explore the working
beyond the first 120' (where we detected a lower level) because of standing water and deep mud
that accumulated in early July from a severe thunderstorm; standing water and mud were still
present on 5 September. The portal is immediately adjacent to a dry gully that directs ninoff into
the mine working, which is a decline beyond the portal. The adit splits about 70' beyond the
portal (and about 40' beyond a ceiling opening to the surface), with the left branch leading to the
lower workings, and the right branch about 60' long leading to a drift face. Water pools in the
right branch on this upper level of the mine. "Adit 5" is about 65' east of "Adit 4", and declines
slightly beyond the portal for about 120' to the drift face (deep mud prevented complete
inspection of this working). Passageways in both adits are large (at least 8-10' wide x 8-10' high,
and the portals of both are unobstructed. We found evidence of recent human visitation (boot
prints in the mud), but conditions made it difficuh to detect bats or bat droppings

"Adit 6", down-slope from the other two, is a single level decline extending 345' to the drift face.
There are no significant side-workings off of the main passage, but there are two areas where
domes have been created along the passage. The passage declines 177' to the first dome (46 °F
and 94% relative humidity on 25 July), then is level thereon to the drift face (same temperature
and relative humidity). The portal is partly blocked by a wooden head frame and cross-bracing.
We found some evidence of recent human visitation (boot prints and trash). We found not bats
during our two inspections but noted scattered Myotis droppings below a dome near the portal
and at the drift face.

At "Adit 4" we captured nine bats in four hours on 25 July (Table 1): three male Western Small-
footed Myotis, two male and three lactating female Western Long-eared Myotis, and one male
Big Brown Bat. On 4 September we captured 27 bats in three hours: 1 3 male and one female
Western Small-footed Myotis, five male and one female Western Long-eared Myotis, and four
male and three female Big Brown Bats. On 5 September netting ceased after two hours because
of rain, but we captured three male and one female Western Long-eared Myotis. At "Adit 5",
netted only on 25 July, we captured tliree male Big Brown Bats. At "Adit 6", netted only on 27
July, we captured a single male Western Small-footed Myotis in three hours, hi all cases, bats
were entering the mine workings when caught, although some bats at "Adit 4" entered via the
ceiling opening and then were caught exiting the portal. We also heard Spotted Bat clicking
overhead at the "Dandy West Upper" site (near adits "4" and "5") for about 5 seconds at 01:45
on 26 July.

CM & M (T9S, R27E, Sec. 4SW). On 27 July we checked two workings at this mine site, both
adits, for evidence of use by bats: "CM & M West" in Sec. 4SWSW (6500' elevation), and "CM
& M Pif in Sec. 4SESW (6470' elevation). The "Wesf adit is short (28' of level passage) with a
walk-in portal 9' tall x 9' wide leading to an open pit at the other end. Scattered Myotis

droppings were present in the passage, but no bats. The adit at the "CM & M Pit" is more
substantial. The portal, behind barb-wire fencing, is an open timbered headframe leading to a
simple decline about 8' tall x 10' wide extending about 360' to the drift face. There are no side
passages. We found scattered Myotis droppings and a few larger bat droppings (Eptesicus?) near
the drift face. Neither of the CM & M workings were monitored overnight.

Lisbon (T9S, R27E, Sec. 4NESW). Two workings at this mine site, both adits, were visited on
25 and 26 July: "Lisbon Point East" and "Lisbon Point West." The "East" adit (6800' elevation)
is a level working extending about 92' beyond an open portal 6.5' tall x 16' wide. There are three
areas of side-workings extending only a few feet along the passage. No bats or bat droppings
were noted. The "West" adit (6800' elevation) is apparently an active working once again,
renamed "Pack Rat Load Claim" and posted on 31 October 1997 by the claimant, C Tucker (P.O.
Box 22575, Billings, MT 59104). The portal is blocked by a locked gate of rebar (20 x 20 cm
spacing) in a wooden frame. Beyond the portal is a decline visible for about 100' (Madson and
Hanson [1993] state the passage extends about 200'), in which are stored a variety of mining
supplies. Outside of the portal is a generator protected by a plywood barrier. The site is posted
"No Trepassing", and the entire Lisbon Mine site is behind a BLM Closed Road sign. There
were recent ATV tracks in the road to the "East" adit.

DISCUSSION

Our summer trapping at the abandoned mines on the south side of the Pryor Mountains in T9S,
R27E resulted in capture of three species of bats at five workings (Table 1): Western Small-
footed Myotis, Western Long-eared Myotis, and Big Brown Bat. In addition, we heard Spotted
Bat on three nights at three sites, but these animals were probably passing between foraging
areas and roosting clitTs, as this bat is not thought to be a mine-dwelling species (Tuttle and
taylor 1994, Foresman 2001a). The three species of bats we captured at the mines are found
throughout Montana, although there exist large gaps between documented locations (Foresman
2001a), even for the cosmopolitan Big Brown Bat. Despite broad continental distributions,
Western Small-footed Myotis and Western Long-eared Myotis are U.S. Fish and Wildlife
Service species of special concern (Harvey et al. 1999) because of unknown or declining
population trends and overall vulnerability. Sites where significant activity of these two species
is documented probably should be considered for protection, if such measures are not already in
place.

Our 2001 assessment showed that most of the abandoned mine workings still accessible to bats
were used by them in summer to greater or lesser extent, corroborating the findings of Martinez
(1995) based on bat detector surveys. Most of the mine workings we inspected were likely used
primarily as temporary summer night roosts, as mines affording the greatest protection for
maternity roosts were generally too cold, and other workings were too shallow to offer stable
environments for hibernating bats during extreme fluctuations in winter weather. Furthermore,
most workings appeared to be visited by humans often enough to disturb any summer colonies
that might otherwise develop in warmer locations near portals. This is especially true for
Townsend's Big-eared Bat (Coiynorhiniis towusendii), another bat species of special concern
that is resident year-round in the Pryor Mountains ( Worthington 1991, Madson and Hanson
1993).

It was evident to us that the Dandy West Upper "Adit 4" was an significant source of summer
water for three species of bats in this arid landscape, as we saw several bats drinking from the
standing water visible beyond the portal. The presence of water may contribute to the abundance
of bat activity at this mine working, but it may be attractive to bats in summer for reasons other
than just access to water. The relatively extensive underground workings offer significant
roosting habitat, and this adit is a documented hibemaculum for Townsend's Big-eared Bat and
at least one species of Myotis (Madson and Hanson 1993). All evidence indicates that the Dandy
West "Adit 4" is important habitat for bats in this area of the Pryor Mountains.

The Marie Mine is another extensive working of size and complexity comparable to the Dandy
"Adit 4" (Madson and Hanson 1993) that appears to provide important stable winter roosting
habitat for bats, even though summer activity was close to minimal during our field assessment.
No bats were found during the only winter inspection (Madson and Hanson 1993), but the
amount of disturbance caused by human visitation to this mine in September and October, after
bats in Montana normally enter hibemacula (Hendricks et al. 2000), may preclude bats from
using the mine as a hibernaculum.

We can say little about cun'ent use by bats of the Lisbon "West" adit, because it is now locked in
relation to recent mining activity. Nevertheless, bats are capable of passing through the locked
gate and may still use the mine as a night roost in summer and a hibemaculum in winter.
Madson and Hanson (1993) found a Townsend's Big-eared Bat and at least one species of
Myotis hibernating in this working in March 1992, indicating it provided important bat habitat to
a limited number of individuals. Martinez (1995) documented moderate activity at the portal of
this mine in summer 1995.

We documented limited bat activity at the Swamp Frog "Central 1 Adits", Robert's hicline, and
Dandy West "Adit 6", and found some sign of bat use at the "CM & M Pit" adit. Our
obsei"vations are similar to survey results by Martinez (1995) for the same workings, indicating
their use by bats is mostly for summer night roosts. All workings are susceptible to unauthorized
human intrusion.

MANAGEMENT SUGGESTIONS

Based on our summer 2001 assessments of these abandoned mines and limited infomiation from
previous surveys (Madson and Hanson 1993, Martinez 1995) we suggest the following;

1 ) Install bat-friendly gates secure from vandalism on the Marie Adit and Dandy West Upper
"Adit 4." These two workings are the most extensive and complex and offer the widest
variety of bat roosting habitat in the collection of mines surveyed. Human visitation to these
sites appears to be a regular occurrence, and probably will increase with continued ATV
recreation in the Pryor Mountains. The Dandy "Adit 4" has a history of bat use at all seasons
and is a documented Townsend's Big-eared Bat hibemaculum, and the Marie has the
potential to be used in like manner if protected from unauthorized human intmsion.

2) Consider installing bat-friendly gates on the Robert's Incline, Dandy "Adit 6" and "CM & M
Pit" adit. Each is extensive enough to offer bat habitat for small numbers of bats, and bat
activity has been documented at each working. These workings could be used more often by
bats if protected from unauthorized human intrusion.

3) Support addition surveys at each of these workings to fully document their seasonal use and
significance for bats. For workings where bat-friendly gates are installed, conduct surveys
both before and after gate installation to document the utility of the gate design.

Literature Cited

Campbell, N. F. 1978. Caves of Montana. Montana Bureau of Mines and Geology Bulletin
105. 169 pp.

Foresman, K. R. 2001a. The wild mammals of Montana. The American Society of
Mammalogists Special Publication No. 12. 278 pp.

Foresman, K. R. 2001b. Key to the mammals of Montana. University of Montana Bookstore,
Missoula, Montana. 92 pp.

Harvey, M. J., J. S. Altenbach, and T. L. Best. 1999. Bats of the United States. Arkansas Game
& Fish Commission and the U.S. Fish & Wildlife Service. 64 pp.

Hendricks, P., D. L. Genter, and S. Martinez. 2000. Bats of Azure Cave and the Little Rocky
Mountains, Montana. Canadian Field-Naturalist 114:89-97.

Madson, M., and G. Hanson. 1992. Bat hibemaculum search in the Pryor Mountains, south-
central Montana, February and March, 1992. Montana Natural Heritage Program.
Helena, MT. 35 pp. + appendices.

Martinez, S. 1995. Evaluation of selected bat habitat sites in south-central and northwestern
Montana, 1995. Montana Natural Heritage Program. Helena, Montana. 11 pp. +
appendices.

Nagorsen, D. W., and R. M. Brigham. 1993. The bats of British Columbia. University of
British Columbia Press, Vancouver, British Columbia. 164 pp.

Spectrum Engineering. 1990. Final report, Pryor Mountain 89, Carbon County, Montana. MT
A/E 88-46-1 19. January 25, 1990.

Tuttle, M. D., and D. A. R. Taylor. 1994. Bats and mines. Bat Conservation International
Resource Publication Number 3. 41 pp.

Worthington, D. J. 1991 . Abundance and distribution of bats in the Pryor Mountains of south
central Montana and north eastern Wyoming. Montana Natural Heritage Program.
Helena, MT. 23 pp.