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Caves and human-made equivalents are important diurnal and nocturnal shelters for many species of bats (Hill and Smith, 1984), and selection of suitable maternity sites within those shelters is critical to reproductive success of bats (Altringham, 1996). Important criteria for selection by cavernicolous species include warm temperatures that assure rapid growth and development of young (McNab, 1982; Tuttle and Stevenson, 1982), moist air that reduces problems of water balance (Bassett, 1982), and secluded areas that provide protection from adverse weather, reduce risks of predation, and diminish disturbances by humans (Kunz, 1982; McCracken, 1989). Choosing maternity roosts close to foraging areas also provides benefits including reduced commuting distance, more time and energy available for feeding and care of young (Altringham, 1996), less evaporative water loss incurred during flight (Bassett, 1982), and less time exposed to aerial predators (Altringham, 1996).

Carlsbad Cavern contains a small maternity colony (~100 individuals) of fringed myotis (Myotis thysanodes) that regularly roosts >200 m below the surface of the ground and >1.5 km from the nearest opening to the cavern (Baker, 1962; Geluso and Geluso, 2004). With many passageways and rooms in the cavern that are closer to surface openings, we questioned why females selected a remote area to bear and raise their young. From among factors known to influence roost selection, we compared the microclimate at the roost site with other areas in the cavern, estimated potential risks to young at the roost site, and investigated human disturbance to the maternity colony. We also determined the route taken by bats from their roost to the surface because of possible unknown passageways or openings in the cavern that would make commutes to the surface and back shorter than predicted.

Materials and Methods--We conducted our study in Carlsbad Cavern, Carlsbad Caverns National Park, Eddy Co., New Mexico, in 1995, 1998, and 2001. Passageways in the cavern were formed millions of years ago when slightly acidic water seeped through cracks in the massive bedrock and gradually dissolved the rock (Jagnow and Jagnow, 1992). As of 2001, 48.3 km of passageways (including tunnels, rooms, and chambers) have been surveyed in the cavern, with new passageways continually being discovered (e.g., the discovery of Halloween Hall in 2013). The cavern has two known openings to the surface, both of which are natural (Fig. 1). The larger one is situated in a sinkhole (32[degrees]10.623'N, 104[degrees]26.462'W) and is perpendicular to the surface of the ground; its dimensions are ~21x12 m. The smaller opening lies in the same plane as the surface, and its dimensions are ~6.4x3.4 m. The small opening is located 0.4-km east of the large opening (photographs of openings in Geluso and Geluso, 2004). The deepest part of the cavern lies at the end of Left Hand Tunnel in a chamber named Lake of the Clouds (Fig. 1); this chamber lies ~315 m below the surface when measured as the vertical distance from the bottom surface of the upper lip of the large opening of the cavern to the floor of the chamber (pocket map 3 in Hill, 1987).

Maternity colonies of two species of bats are present in Carlsbad Cavern--M. thysanodes in Left Hand Tunnel and the Brazilian free-tailed bat (Tadarida brasiliensis) in Bat Cave (Fig. 1; Geluso and Geluso, 2004). Since the early 1950s, summer colonies of no more than 100 individuals of M. thysanodes have been reported in areas at the end of Left Hand Tunnel, including Lake of the Clouds (Baker, 1962). During the present study, the maternity colony of M. thysanodes was located in the passage leading into Lake of the Clouds (Figs. 1 and 2), and that section of passage is known as the Balcony (Hill, 1987, p. 90). The vertical distance from the bottom surface of the upper lip of the large opening of the cavern to the floor of the Balcony is ~240 m. Although pools of water occur on the floor of the Balcony, most (>90%) of the floor is dry (see pocket map 2 in Hill, 1987). In 1995, we observed the colony (~100 individuals) about 9 m above the floor in an area containing no standing water below the roost.

Determining the Underground Route--We initially used radiotelemetry to investigate probable areas traveled by M. thysanodes to reach the surface. On 9 July 1995, we placed mist nets (Avinet, Inc., Dryden, New York) across the entrance to the Balcony and captured 13 M. thysanodes 13-97 min after sunset. Bats were placed individually in a 0.35-L drinking cup, and cups were covered with plastic lids and marked with time of capture. Sex, reproductive condition, body weight, and age (adult or young of the year) were recorded for each bat. A radiotransmitter was attached to one pregnant female, 10 lactating females, and two adult males using methods and materials described by Best and Geluso (2003). Bats were released at the capture site. Each radiotransmitter (Type BD-2A with reed switch, Holohil Systems Ltd., Woodlawn, Ontario, Canada), including a whip antenna (13.8 cm in length) and battery (expected to last ~3 wk), weighed 0.73 g and was tuned to a different frequency within a range of 172.615-172.891 MHz. Radiotransmitters were 7.7-8.6% of body weight of lactating females, 6.3% for the pregnant female, and 8.1 and 10.4% for males.

We tracked bats with a hand-held antenna (3-element Yagi style, Wildlife Materials, Inc., Carbondale, Illinois) and a multichannel receiver (TRX-2000S and Falcon-Five models, Wildlife Materials, Inc.). Seven radioreceivers were used each night to monitor locations in the cavern and at its openings. At each station, we manually and repeatedly punched in radiofrequencies of the 13 transmitters as we waited to record the passage of bats. Using this method, some radioequipped bats likely passed undetected. We monitored both openings to the cavern on 11 and 12 July 1995, the Main Corridor near Devil's Spring on 11 July, and the Lunch Room on 12 July (Fig. 2). Each night monitoring commenced before sunset. We also used radioreceivers to verify the presence of radioequipped bats inside the Balcony during daylight hours.

Because bats left the maternity site and passed through the Lunch Room in single file, we could track and count the number of passes via ultrasonic calls at various locations near and in the Lunch Room. On 14 July 1995, we listened for bats with narrowband ultrasonic bat detectors (Mini-2, Ultra Sound Advice, Birmingham, United Kingdom) set at 35-40 kHz. Bats were monitored (1) in Left Hand Tunnel near its entrance, (2) 38-m deep in the Secondary Stream Passage, (3) between elevators and restrooms in the Lunch Room, and (4) on the hill near the Grape Arbor at the west end of the Lunch Room (Fig. 2). Although most, if not all, bats passing overhead likely were fringed myotis (the only species captured on 9 July), some calls might have been produced by other species that occasionally use deep portions of the cavern (e.g., T. brasiliensis and the cave myotis [Myotis velifer], see below and Geluso and Geluso, 2004).

Unfortunately, radiotelemetry and ultrasonic detectors used in 1995 did not allow us to discern direction of flight at any single station. For example, we could not be certain which opening an individual used to exit the cavern. Perhaps a bat exited one opening undetected and then was detected at the other opening as it flew overhead. However, light tags used in 2001 (see below) allowed us to visually follow the underground routes. We used the netting methods described above to capture 15 M. thysanodes, seven M. velifer (five adult males, one young of the year, and one adult female), and one T. brasiliensis (adult male) at the entrance to the Balcony on 4 July 2001. We attached a green, mini-light stick (2.9 mm in diameter by 23 mm in length, Chemical Light, Inc., Vernon Hills, Illinois) to 14 M. thysanodes (10 lactating females, one pregnant female, one nonreproductive female, one adult male, and one young of the year). After activating each light stick, its tip was dipped in a nontoxic adhesive (Skin-Bond Cement, Smith and Nephew United, Inc., Largo, Florida) and gently pressed between the bat's scapulae for 30-45 s. We let the glue cure for at least 4 min before releasing bats at the capture site.

Prior to release, assistants were positioned at the following locations: (1) 54 m east of entrance to Left Hand Tunnel; (2) on breakdown rocks in the Lunch Room; (3) near Devil's Spring in the Main Corridor; (4) at Bat Cave Sign in Bat Cave; (5) in mouth of large opening to cavern; and (6) on surface near the small opening (Fig 2). Assistants watched for green "flying" lights and recorded time and direction of each passing bat. We also confirmed that M. thysanodes was roosting in the Balcony in July 2001 by placing a radiotransmitter on a lactating female captured exiting the small natural opening to the cavern on 2 July and by locating that individual in the Balcony the next morning. We used pocket maps 2 and 3 in Hill (1987) to determine distances traveled by M. thysanodes from its roost site to the surface. The Institutional Animal Care and Use Committee at Auburn University approved procedures involving radiotelemetry and the use of light tags.

Measurements of Microclimate--We took measurements of ambient air temperature with a quick-reading mercury thermometer and of relative humidity with a thermohygrometer (model WD-35612-00, Oakton[R], Chicago, Illinois) throughout the cavern to compare the microclimate in the Balcony with areas not selected as roost sites in the cavern. Instruments were held about 1.4 m above the cave floor. When temperatures vary, as they did in the cavern, water vapor pressure is more appropriate than relative humidity to describe the drying power of air and to estimate potential water loss from bats via evaporation (Kurta, 2014). Therefore, we used values of temperature and relative humidity to obtain actual measures of moisture in the air (i.e., water vapor pressure; mmHg). We also compared our measurements of air temperature and humidity with those taken throughout the cavern by another biologist in 1985 (Hill, 1987).

From 1400-1855h on 22 July 1995, we took spot readings of temperatures in the Lunch Room and at four locations in Left Hand Tunnel (its entrance, the Beach Area, west lead into Right Hand Fork, and the Balcony; Fig. 2). At 1415h the next day, we recorded temperature in Bat Cave under four small domes located 21 m west of the small opening to the cavern (Fig. 1); those domes had been occupied by T. brasiliensis from the 1950s-1983 (Geluso and Geluso, 2004). From 0842-1550h on 9 October 1995, we recorded temperatures at locations listed above plus those at Devil's Spring and Iceberg Rock, in the Bell Cord Room and Lake of the Clouds, and under the present-day roost of T. brasiliensis in a large dome at the end of Bat Cave (Fig. 1). In subsequent surveys, we recorded relative humidity and temperature at most locations listed above in early morning (0001-0500h) and in the afternoon (1232-1707h) on 20 July 1998 and again in the afternoon (1250-1423h) on 6 July 2001.

Evidence of Predators and Disturbance by Humans-Sightings of carnivores in Bat Cave and along the route from the large opening of the cavern to the underground Lunch Room have been reported by Geluso and Geluso (2004). In the present study, therefore, we concentrated our efforts to locate signs of predators (e.g., observation of scat) as we walked back and forth many times from the Lunch Room to the maternity site of M. thysanodes. People must pass through the area containing the maternity colony of M. thysanodes to reach Lake of the Clouds at the end of Left Hand Tunnel (Figs. 1 and 2), and through the years, trips to Lake of the Clouds have been made by park personnel and cavers for purposes of restoration, exploration, research, and orientation for new rangers. Therefore, to evaluate human disturbance to the colony, we gathered information on frequency and times of the year that visits have been made to Lake of the Clouds prior to our study.

Results--All 13 bats that were captured, radioequipped, and released near the maternity site on 9 July 1995 were present in the roost area by the following morning. However, we only tracked nine individuals in flight because radio signals of four lactating females were detected day and night only in the Balcony. We suspect that those individuals dropped or dislodged their radiotransmitters.

Underground Route--Radiotelemetry showed that the Main Corridor and Lunch Room were part of the underground route used by M. thysanodes. On 11 July 1995, nine bats were detected in the corridor at Devil's Spring from 2043-2246h, and soon after (<1, 1, 1, 2, 2, and 5 min), four lactating females, one pregnant female, and one adult male were detected on the surface. On 12 July, seven bats were detected in the Lunch Room from 2032-2257h, and 3-11 min later, five lactating females and one adult male were detected on the surface.

On 14 July 1995 (sunset occurred at 2005h), we counted 114 passes of bats from 1900-2330h near the entrance to Left Hand Tunnel using ultrasonic detectors. Some individuals might have been counted more than once (e.g., if ones detected before midnight were returning to their roost). None were heard in Secondary Stream Passage (a shortcut to the Main Corridor that contains narrow restrictions [76 cm wide], sharp bends [90%], and steep inclines [up to 60[degrees]]), and only four bats passed between the elevators and rest rooms (Fig. 2). That same evening, >100 passes were detected near the Grape Arbor at the west end of the Lunch Room, confirming that those individuals crossed the Lunch Room without using the Secondary Stream Passage.

On 4 July 2001 (sunset occurred at 2008h), 26 sightings of light-tagged individuals provided details about the underground route. Seven individuals traveled from Left Hand Tunnel into the Lunch Room from 2112-2328h, and two flew in the opposite direction at 2310 and 2336h. Three bats bypassed Secondary Stream Passage in the Lunch Room, continued over breakdown rocks behind the concession stands, and went toward Iceberg Rock from 2206-2210h. Four bats flew from the lower portion of the Main Corridor, passed Devil's Spring, and went toward Bat Cave Sign from 2127-2332h, and one individual flew in the opposite direction at 2334h. Three bats flew from the Main Corridor, passed Bat Cave Sign, and went deep into Bat Cave toward the small opening from 2128-2222h. Two individuals flew from the Main Corridor and went toward the base of the large opening at 2209 and 2335h. One individual exited the large opening at 2209h, and three exited the small opening from 2129-2223h.

Microclimate--Air temperatures in the cavern ranged from 13.6-20.0[degrees]C and increased as depth below the surface increased (Table 1). The highest readings occurred at the end of Left Hand Tunnel in the Balcony (19.3-19.5[degrees]C), Bell Cord Room (19.0-19.6[degrees]C), and Lake of the Clouds (19.7-20.0[degrees]C). Air temperatures were stable, even when readings taken in 1985 (Hill, 1987) were included (e.g., 15.4-15.7[degrees]C in Lunch Room, 19.319.5[degrees]C in Balcony, and 19.7-20.0[degrees]C in Lake of the Clouds, Table 1). In the cavern, water vapor pressure ranged from 9.9-17.0 mmHg (Table 2). Air moisture also increased with depth and remained within a narrow range at all locations. The highest vapor pressures occurred in the Balcony (16.1-16.9 mmHg), Bell Cord Room (15.8-16.6 mmHg), and Lake of the Clouds (16.5-17.0 mmHg). Driest air was recorded in areas close to entrances of the cavern in Bat Cave (9.9-11.1 mmHg) and at Devil's Spring (11.1 mmHg, Table 2; Fig. 2).

Relative humidity ranged from 84-94% in Bat Cave, 94-98% in the Main Corridor, 88-96% in the Lunch Room, and 90-100% in Left Hand Tunnel. As noted in the METHODS, the drawback of using relative humidity when temperatures vary is demonstrated by our measurements at Devil's Spring. Relative humidity at the spring (94-98%) was similar to the Balcony (96-100%; t-test: df = 4, P > 0.4), but on the basis of water vapor pressure, air at Devil's Spring (11.1-11.5 mmHg) was significantly drier than at the roost site (16.1-16.9 mmHg, Table 2; t-test: df = 4, P < 0.001).

Predators and Human Disturbance-On 3 July 2001, we observed fresh scat of a carnivore (likely a ringtail [Bassariscus astutus] or northern raccoon [Procyon lotor]) along Left Hand Tunnel, 0.53 km from the maternity roost of M. thysanodes near the end of the tunnel. In the decade prior to our study, there were probably no more than 10 trips per year taken by people through the area containing the maternity colony of M. thysanodes, and some of those trips occurred during summer months (D. L. Pate, pers. comm.).

Discussion--Tracking results show that M. thysanodes reaches the surface from its roost by flying along Left Hand Tunnel, crossing the Lunch Room toward Iceberg Rock, proceeding along the Main Corridor, and exiting through one of two openings of the cavern (Figs. 1 and 2). Some bats traveled ~1.8 km and exited through the large opening while others traveled ~2.1 km and exited through the small opening. Why some individuals traveled an extra 0.3 km to use the small opening is unclear. Perhaps the choice relates to timing of exit flights of T. brasiliensis, which also uses both openings (Geluso and Geluso, 2004). Although not observed directly, we suspect that M. thysanodes uses the same route to return to its roost. Evidence of this is based on light-tagged individuals flying along the route in the opposite direction 3.0, 3.4, and 3.5h after sunset. Those sightings might reflect females returning to the maternity site to nurse their young (Kunz, 1982). For example, lactating Indiana bats (Myotis sodalis) return to their maternity roost 2-4 times per night, presumably to feed their young (Murray and Kurta, 2004).

High ambient air temperature in the passageway containing the maternity colony of M. thysanodes likely is the primary reason why females selected a remote section of the cavern to raise young. Temperatures at the end of Left Hand Tunnel (Bell Cord Room, Balcony, and Lake of the Clouds) were the warmest in the cavern (Table 1), and low airflow and geothermal gradients probably explain those high temperatures (Hill, 1987). In addition, temperatures were stable (Table 1). Growth rates of young bats are highly dependent on temperature, and warm-stable temperatures at a maternity site help assure rapid growth and development of young and their readiness for winter hibernation (Tuttle, 1975; Tuttle and Stevenson, 1982; Lausen and Barclay, 2006). Temperatures at the end of Left Hand Tunnel probably allow young M. thysanodes to grow faster in that section of the cavern than in any other area (Table 1; for more temperatures throughout the cavern, see Hill, 1987, pp. 26 and 28).

High levels of water vapor at maternity sites also are advantageous to developing young because moist air can minimize loss of water by evaporation and reduce problems of water balance (Webb et al., 1995); however, evidence of selectivity on the basis of humidity is scarce (e.g., Betts, 1997). Because air moisture and temperature were highest at the end of Left Hand Tunnel and lowest near openings to the cavern (Tables 1 and 2), we could not ascertain whether humidity was a factor in M. thysanodes selecting the Balcony. Nor could we determine whether one environmental factor was more important than the other in selectivity.

Females of T. brasiliensis also bear and raise young in Carlsbad Cavern, but unlike M. thysanodes, their maternity roost is located in a cooler, drier section of the cavern- when air temperature and moisture are measured near ground level (Tables 1 and 2; Fig. 1). Because of the large size of its colonies (e.g., ~439,000 individuals at Carlsbad Cavern in June 2005; Hristov et al., 2010), T. brasiliensis is able to raise air temperatures in large domes, rooms, and even entire caves by trapping the metabolic heat of its occupants (Humphrey, 1975). Thus, young T. brasiliensis in the cavern likely are kept warm by the collective body heat produced from all individuals present in the large dome at the end of Bat Cave. The young probably also benefit from evaporative water that accumulates from occupants in the dome. Accumulated body heat from small aggregations of bats also can modify ambient temperatures at roost sites. For example, a maternity colony of Yuma myotis (Myotis yumanensis) containing 50-60 adult females raised air temperature from 15 to 22[degrees]C in a small dome, enabling the species to use an otherwise cool mine as a maternity site (Betts, 1997). If the colony of M. thysanodes (~100 individuals) at Carlsbad Cavern also took advantage of a small dome or other cavity in the ceiling of the Balcony, it might also raise temperatures that surround its young to levels higher than what we recorded near the floor (i.e., higher than 19.5[degrees]C; Table 1). In 1995, we did not determine whether the colony was roosting in a flat area of the ceiling or in a concavity; however, M. thysanodes has used ceiling pockets in the cavern in the past (Baker, 1962).

When bats roost on ceilings of caves, they are well protected from most predators; however, when young fall to the floor they become vulnerable to predation (Hill and Smith, 1984). For species that retrieve their fallen young, such as M. thysanodes (O'Farrell and Studier, 1973), the length of time on the floor is directly related to level of risk. In Carlsbad Cavern, raccoons are known to enter Bat Cave and feed on fallen young T. brasiliensis, and ringtails have been sighted in Bat Cave and the underground Lunch Room (Geluso and Geluso, 2004). In addition, we observed scat of a carnivore in Left Hand Tunnel during the present study. Obviously, the safest roost from predators is where predators are never present, and this might be the situation for M. thysanodes in the recesses of the cavern, where carnivores must travel >1.5 km of passageways to reach the maternity colony after entering the large opening to the cavern.

Human-caused disturbances to maternity colonies can have many types of detrimental effects to bats including abandonment of roost sites to other less-favorable locations, an increase in activity resulting in greater expenditure of energy, and death to young by causing them to lose their grip (McCracken, 1989). In fact, M. thysanodes, especially females prior to parturition, is easily disturbed by the presence of humans in its roost (O'Farrell and Studier, 1973). Although disturbance of bats by people in passageways and rooms at the end of Left Hand Tunnel seems to have been minimal through the years (see RESULTS), we recommend to the National Park Service that trips to Lake of the Clouds not be allowed at the park from 1 May to 1 September, which includes periods prior to parturition and after lactation for M. thysanodes (Geluso and Geluso, 2004).

Young had no risk of drowning in 1995 because the colony was located over an area containing no standing water on the floor. Although all areas at the end of Left Hand Tunnel have pools of standing water (i.e., Balcony, Lake of the Clouds, and the Bell Cord Room; pocket map 2 in Hill, 1987), there is plenty of ceiling space available for bats to select roosting sites above dry areas. Nevertheless, M. thysanodes is known to form maternity colonies over standing water, and when it does, retrieval becomes difficult and many fallen young drown (Baker, 1962). Perhaps the risky choice of roosting above pools is a tradeoff for higher humidity over water in situations where air moisture would otherwise be low.

Apparent disadvantages for M. thysanodes roosting deep within the cavern include higher energy costs, an increase in flight time resulting in less time for care of young, and an increase in evaporative water loss incurred during flight (Bassett, 1982; Altringham, 1996). Another disadvantage relates to individuals possibly becoming lost in the cavern, especially young traveling to and from their natal roost for the first time. In contrast, probable advantages of the roost site selected by M. thysanodes include warm and stable air temperatures, high humidity, low predation risk to young and adults, and infrequent human disturbance. Those factors are especially suited for raising offspring and likely contribute to high roost site fidelity of M. thysanodes in this distant part of the cavern (see Lewis, 1995). For this colony of M. thysanodes, such advantages seem to outweigh energetic costs and other disadvantages of commuting to a remote area of the cavern on a nightly basis.

Many people contributed to the success of this project, and their assistance is greatly appreciated. For help in tracking bats, we thank J. Boans, T. Boans, K. Geluso, N. A. Hawkins, S. Howard, C. H. Kilgore, L. F. Lumsden, L. A. McWilliams, P. R. Moosman, J. Morris, J. O'Haver, S. Poche, D. B. Quigley, J. M. Richards, D. M. Roemer, V. W. Sartori, H. Thomas, and M. B. Tolbert. We also thank L. A. McWilliams for helping obtain microclimatic data in the cavern and C. A. Hill and D. E. Northup for providing additional information about places shown in the plan view of the cavern. We also are grateful to the following park personnel who gave much of their time, expertise, and technical support throughout the project: T. B. Bemis, A. H. Burgess, R. C. Kerbo, D. L. Pate, J. M. Richards, and D. M. Roemer. We thank A. Fox and T. E. Rodriquez for preparing the figures; C. Lopez-Gonzalez for providing a Spanish translation of the abstract; and K. Geluso, D. L. Pate, C. Lopez-Gonzalez, G. D. Schroder, and two anonymous reviewers for suggestions and comments that improved the final version of the manuscript. This project was funded by the Adopt-A-Bat program sponsored by the Carlsbad Caverns-Guadalupe Mountains Association in cooperation with the National Park Service.

Literature Cited

Altringham, J. D. 1996. Bats: biology and behaviour. Oxford University Press, New York.

Baker, J. K. 1962. Notes on the Myotis of the Carlsbad Caverns. Journal of Mammalogy 43:427-428.

Bassett, J. E. 1982. Habitat aridity and intraspecific differences in the urine concentrating ability of insectivorous bats. Comparative Biochemistry and Physiology A. Comparative Physiology 72A:703-708.

Best, T. L., and K. N. Geluso. 2003. Summer foraging range of Mexican free-tailed bats (Tadarida brasiliensis mexicana) from Carlsbad Cavern, New Mexico. Southwestern Naturalist 48:590-596.

Betts, B. J. 1997. Microclimate in Hell's Canyon mines used by maternity colonies of Myotis yumanensis. Journal of Mammalogy 78:1240-1250.

Geluso, K. N., and K. Geluso. 2004. Mammals of Carlsbad Caverns National Park, New Mexico. Bulletin of the University of Nebraska State Museum 17:1-180.

Hill, C. A. 1987. Geology of Carlsbad Cavern and other caves in the Guadalupe Mountains, New Mexico and Texas. New Mexico Bureau of Mines and Mineral Resources, Bulletin 117:1-150 (includes 9 separate pocket maps).

Hill, J. E., and J. D. Smith. 1984. Bats: a natural history. University of Texas Press, Austin.

Hristov, N. I., M. Betke, D. E. H. Theriault, A. Bagchi, and T. H. Kunz. 2010. Seasonal variation in colony size of Brazilian free-tailed bats at Carlsbad Cavern based on thermal imaging. Journal of Mammalogy 91:183-192.

Humphrey, S. R. 1975. Nursery roosts and community diversity of Nearctic bats. Journal of Mammalogy 56:321-346.

Jagnow, D. H., and R. R. Jagnow. 1992. Stories from stones: the geology of the Guadalupe Mountains. Carlsbad Caverns-Guadalupe Mountains Association, Carlsbad, New Mexico.

Kunz, T. H. 1982. Roosting ecology of bats. Pages 1-55 in Ecology of bats (T. H. Kunz, editor). Plenum Press, New York.

Kurta, A. 2014. The misuse of relative humidity in ecological studies of hibernating bats. Acta Chiropterologica 16:249254.

Lausen, C. L., and R. M. R. Barclay. 2006. Benefits of living in a building: big brown bats (Eptesicus fuscus) in rocks versus buildings. Journal of Mammalogy 87:362-370.

Lewis, S. E. 1995. Roost fidelity of bats: a review. Journal of Mammalogy 76:481-496.

McCracken, G. F. 1989. Cave conservation: special problems of bats. The NSS Bulletin 51:47-51.

McNab, B. K. 1982. Evolutionary alternatives in the physiological ecology of bats. Pages 151-200 in Ecology of bats (T. H. Kunz, editor). Press, New York.

Murray, S. W., and A. Kurta. 2004. Nocturnal activity of the endangered Indiana bat (Myotis sodalis). Journal of Zoology (London) 262:197-206.

O'Farrell, M. J., and E. H. Studier. 1973. Reproduction, growth, and development in Myotis thysanodes and M. lucifugus (Chiroptera: Vespertilionidae). Ecology 54:18-30.

Tuttle, M. D. 1975. Population ecology of the gray bat (Myotis grisescens): factors influencing early growth and development. Occasional Papers, Museum of Natural History, university of Kansas 36:1-24.

Tuttle, M. D., and D. Stevenson. 1982. Growth and survival of bats. Pages 105-150 in Ecology of bats (T. H. Kunz, editor). Plenum Press, New York.

Webb, P. I., J. R. Speakman, and P. A. Racey. 1995. Evaporative water loss in two sympatric species of vespertilionid bat, Plecotus auritus and Myotis daubentoni: relation to foraging mode and implications for roost site selection. Journal of Zoology, London 235:269-278.

Submitted 6 September 2016. Accepted 30 March 2017.

Associate Editor was Troy Landine.

Kenneth N. Geluso * and Troy L. Best

Department of Biology, University of Nebraska, Omaha, NE 68182 (KNG)

Department of Biological Sciences, 331 Funchess Hall, Auburn University, AL 36849 (TLB)

* Correspondent:

Caption: Fig. 1-Schematic representation of part of Carlsbad Cavern, Carlsbad Caverns National Park, New Mexico. X symbols mark locations of maternity sites in 1995 and 2001 for fringed myotis (Myotis thysanodes) near the end of Left Hand Tunnel and for Brazilian free-tailed bats (Tadarida brasiliensis) near the end of Bat Cave. The Lunch Room is 230 m below the Visitor Center (figure modified from Geluso and Geluso, 2004).

Caption: Fig. 2-Plan view of part of Carlsbad Cavern, Carlsbad Caverns National Park, New Mexico. The X symbol marks the location of the maternity site of fringed myotis (Myotis thysanodes) near the end of Left Hand Tunnel in July 1995 and 2001. The site is located in the balcony portion of the passage leading into Lake of the Clouds. The Lunch Room is the area containing concession stands (rectangle), rest rooms (squares), and elevators (triangle). Circles next to concession stands represent breakdown rocks. The black arrow shows the entrance into Left Hand Tunnel after passing through the Lunch Room, and the white arrow shows the location of the Bat Cave Sign that indicates the beginning of Bat Cave. The plan view is based on maps in Hill (1987).
Table 1--Ambient air temperature ([degrees]C) at various locations
in Carlsbad Cavern, Carlsbad Caverns National Park, New Mexico.
Measurements in 1985 were taken "near the floor" (Hill, 1987, p.
28); our measurements in 1995, 1998, and 2001 (this study) were
taken 1.4 m above the floor. Depth below surface (m) is shown in
brackets and represents the vertical distance from the bottom
surface of the upper lip of the large opening of the cavern to the
floor of the passage or room (distances based on pocket map 3 in
Hill, 1987). A dash in brackets [-] indicates that the depth below
the surface was not determined for that location, and a dash not in
brackets indicates that a temperature reading was not taken on that

Location                     October 1985   22-23 July 1995

Under small domes (a) [45]        --             14.5
Under large dome (b) [50]         --              --

Devil's Spring [60]               --              --
Iceberg Rock [-]                  --              --

LUNCH ROOM [205]                 15.5            15.5

Entrance into tunnel [205]        --             15.8
Beach Area [205]                 16.0            16.1
Right Hand Fork [205]             --             18.1
Bell Cord Room [-]               19.4             --
Balcony (c) [240]                19.4            19.5
Lake of the Clouds [315]         20.0             --

                                              20 July 1998

Location                     9 October 1995   Morning   Afternoon

Under small domes (a) [45]        14.2         13.7       13.8
Under large dome (b) [50]         15.4         14.5       14.2

Devil's Spring [60]               13.6         13.7        --
Iceberg Rock [-]                  14.4         14.0       14.6

LUNCH ROOM [205]                  15.4         15.6       15.7

Entrance into tunnel [205]        15.8         15.7       16.1
Beach Area [205]                  16.6         16.1       16.5
Right Hand Fork [205]             17.8         17.7       17.8
Bell Cord Room [-]                19.4         19.0       19.3
Balcony (c) [240]                 19.4         19.4       19.3
Lake of the Clouds [315]          19.8         20.0       19.7

Location                     6 July 2001

Under small domes (a) [45]       --
Under large dome (b) [50]        --

Devil's Spring [60]             13.7
Iceberg Rock [-]                14.8

LUNCH ROOM [205]                 --

Entrance into tunnel [205]      16.2
Beach Area [205]                16.5
Right Hand Fork [205]           18.0
Bell Cord Room [-]              19.6
Balcony (c) [240]               19.3
Lake of the Clouds [315]         --

(a) Maternity site of Tadarida brasiliensis, 1950s-1983.

(b) Present-day maternity site of T. brasiliensis.

(c) Area containing the maternity colony of Myotis thysanodes
in the present study.

Table 2--Amount of moisture in the air at various locations in
Carlsbad Cavern, Carlsbad Caverns National Park, New Mexico. Values
for humidity are expressed as water vapor pressure (mmHg).
Measurements in 1985 were taken "near the floor" (Hill, 1987, p.
28); our measurements in 1998 and 2001 (this study) were taken 1.4 m
above the floor. Depth below surface (m) is shown in brackets and
represents the vertical distance from the bottom surface of the
upper lip of the large opening of the cavern to the floor of the
passage or room. A dash in brackets [-] indicates that the depth
below the surface was not determined for that location, and a dash
not in brackets indicates that a moisture reading was not taken on
that date.

                                            20 July 1998

Location                     October 1985   Morning    Afternoon

Under small domes (a) [45]        --          9.9         11.1
Under large dome (b) [50]         --         10.8         10.8

Devil's Spring [60]               --         11.5          --
Iceberg Rock [-]                  --         11.4         12.0

LUNCH ROOM [205]                 11.6        12.1         12.8

Entrance into tunnel [205]        --         12.0         13.0
Beach Area [205]                 12.8        12.5         13.2
Right Hand Fork [205]             --         14.7         15.0
Bell Cord Room [-]               16.6        15.8         16.1
Balcony (c) [240]                16.9        16.4         16.3
Lake of the Clouds [315]         16.8        17.0         16.5

Location                     6 July 2001

Under small domes (a) [45]       --
Under large dome (b) [50]        --

Devil's Spring [60]             11.1
Iceberg Rock [-]                12.1

LUNCH ROOM [205]                 --

Entrance into tunnel [205]      13.1
Beach Area [205]                12.7
Right Hand Fork [205]           15.3
Bell Cord Room [-]              16.4
Balcony (c) [240]               16.1
Lake of the Clouds [315]         --

(a) Maternity site of Tadarida brasiliensis, 1950s-1983.

(b) Present-day maternity site of T. brasiliensis.

(c) Area containing the maternity colony of Myotis thysanodes
in the present study.
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Author:Geluso, Kenneth N.; Best, Troy L.
Publication:Southwestern Naturalist
Geographic Code:1U8NM
Date:Jun 1, 2017

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