R.B. Pape – Biology and ecology of Bat Cave, Grand Canyon National Park, Arizona. Journal of Cave and Karst Studies, v. 76, no. 1, p. 1–13. DOI: 10.4311/2012LSC0266 BIOLOGY AND ECOLOGY OF BAT CAVE, GRAND CANYON NATIONAL PARK, ARIZONA ROBERT B. PAPE Department of Entomology, University of Arizona, Tucson, Arizona 85721, [email protected] Abstract: A study of the biology and ecology of Bat Cave, Grand Canyon National Park, was conducted during a series of four expeditions to the cave between 1994 and 2001. A total of 27 taxa, including 5 vertebrate and 22 macro-invertebrate species, were identified as elements of the ecology of the cave. Bat Cave is the type locality for Eschatomoxys pholeter Thomas and Pape (Coleoptera: Tenebrionidae) and an undescribed genus of tineid moth, both of which were discovered during this study. Bat Cave has the most species-rich macro-invertebrate ecology currently known in a cave in the park. INTRODUCTION Cave. A review of cave-invertebrate studies in the park, which included 9 reports addressing 16 caves, was prepared This paper documents the results of a biological and by Wynne et al. (2007). Their compilation resulted in a list ecological analysis of Bat Cave on the Colorado River of approximately 37 species of cave macro-invertebrates within Grand Canyon National Park conducted during currently known from caves there. Wynne and others have four expeditions to the cave between 1994 and 2001. The recently performed invertebrate surveys in caves in the study focused on the macro-invertebrate elements present Grand Canyon–Parashant National Monument, and have in the cave and did not include any microbiological already encountered several undescribed cave-inhabiting sampling, identification, or analysis. Access to caves in macro-invertebrate species, including three new genera. the park is strictly regulated and requires either an These include a camel cricket (Rhaphidophoridae), a approved research permit or a cave entry permit, granted barklouse (Psocoptera), and a macrosternodesmid millipede, through the Grand Canyon Division of Science and Pratherodesmus (Shear et al., 2009; Wynne and Drost, 2009). Resource Management. BAT CAVE CAVE INVERTEBRATES IN GRAND CANYON NATIONAL PARK Bat Cave is located in the north wall of the main gorge of the Colorado River within Grand Canyon National Grand Canyon National Park has extensive cave Park (Fig. 1, insert). The entrance is at an elevation of resources, but there has been little research on cave- 580 meters, approximately 260 meters above the river. The inhabiting invertebrates in the park. The earliest effort was cave is formed along a major vertical fault in the Cambrian conducted by the Cave Research Foundation at Horseshoe Muav limestone and consists of just over one thousand Mesa in 1977 and 1978 (Welbourn, 1978). The scope of that meters of surveyed passage, mostly along the single main project was not strictly biological, but did include a search trunk passage. From the entrance, the cave trends a few for invertebrates in eight caves contained in the Mooney degrees east of north (Fig. 1). The cave is essentially Falls member of the Redwall limestone. The effort produced horizontal, with a total vertical relief of only 75 meters. a total of fourteen invertebrate species, including a new Bat Cave is named for the large maternity colony of species of garypid pseudoscorpion (Archeolarca cavicola Mexican free-tailed bats (Tadarida brasiliensis I. Geoffroy) Muchmore). The lack of species diversity was attributed to that resides there. The first record of the cave is from the the lack of available moisture in the caves. Peck (1980) 1930s. Shortly thereafter, there were efforts to mine the looked at three caves in the Grand Canyon, all of which, like bat guano for fertilizer. These early efforts were mostly Bat Cave, were in the Muav limestone. All three of these unproductive. In 1958, the property was purchased by the caves contain active streams that have their outfall in major U.S. Guano Corporation. U.S. Guano invested 3.5 million tributaries to the main gorge of the Colorado River below dollars in the setup of the mining operation, only to find the North Rim of Grand Canyon. Peck’s effort identified a that the extent of the guano deposit was only 1 percent of total of 15 invertebrate species from the 3 caves. One of those their original estimate. Difficulties with the haul system caves, Roaring Springs Cave, was revisited by Drost and across the canyon, and specifically the lack of a significant Blinn in 1994 and 1995 (Drost and Blinn, 1997), and their guano deposit, forced the abandonment of the mining effort increased the invertebrate species recorded from that operation in 1960 (Billingsley et al., 1997). The support cave from the original 10 found by Peck to 19, including the towers for the haul system’s cables are still present on the first records of aquatic invertebrates from a Grand Canyon top of the south rim of the canyon and below the cave on the Journal of Cave and Karst Studies, April 2014 N 1 BIOLOGY AND ECOLOGY OF BAT CAVE,GRAND CANYON NATIONAL PARK,ARIZONA Figure 1. Map of the biologically active front portion of Bat Cave, Grand Canyon National Park, showing regional location (inset) and survey stations mentioned in the text. north side of the river. A wooden plank-way, portions of MATERIALS AND METHODS which are elevated, traverses approximately the first 145 me- ters of the cave from an elevated entrance platform. Sections The four expeditions to Bat Cave were conducted on of large flanged pipe approximately 30 cm in diameter and March 12, 1994; March 29 and 30, 1996; October 24, 1997; other mining equipment remain in the cave. Most of the and October 26, 2001. Access to the cave was made up the animal species associated with the cave are arthropods tied river by boat from Lake Mead. Visits to the cave were directly to the bat guano-supported food web. scheduled seasonally and temporally to avoid disturbance 2 N Journal of Cave and Karst Studies, April 2014 R.B. PAPE to the resident bat population. Even so, at least some bats or phytophage), and relative abundance (abundant, com- were present on all visits to the cave. During the March mon, uncommon, or rare) for each species. Ecological visits, no more than a few hundred bats were present at any groups used in this paper are defined as follows: A time, mostly around the roost at survey station D1 (Fig. 1). trogloxene is an animal that enters caves to fill some All efforts were made to keep disturbance to the bats at a ecological need, such as obtaining food, water, shelter, etc., minimum. This roost is at the east edge of the main trunk but that cannot survive without returning to the surface to passage, and the roost area can be skirted with minimal meet some of its life-cycle requirements. A troglophile is an disturbance to the bats. animal that is capable of completing its life cycle within The 5 visits involved approximately 34 hours of caves, but may also do so elsewhere. A troglobite is an observation and sampling of invertebrates in the cave. obligate cave animal, which cannot live outside of the cave The methods were low impact, consisting of a visual search environment. The occurrence of parasites in the cave is in of passage floors, walls, crevices, ledges, and breakdown- association with other species of animals, but because of boulder accumulations. Additional habitat niches have their presence in the cave during part of their life cycle we been created in Bat Cave by the presence of wooden consider them to be trogloxenes. Accidentals are just what walkways and machinery remaining from the abandoned the label implies, animals that wander or fall into the cave, mine operation. Particular attention was paid to floor would not normally occur in such habitats, and obtain no debris, under which many invertebrates commonly shelter. benefit from their presence in the cave. Debris that was overturned was replaced after examination to minimize impact to microhabitats. The principal benefits SPECIES ACCOUNTS of this type of documentation are minimal habitat Phylum: Chordata disturbance, low animal population impact, and ease of Class: Aves sampling in the cave environment. Since obligate cave Order: Passeriformes invertebrate populations may be small and may be Family: Troglodytidae adversely impacted by over-sampling, no pitfall or other Catherpes mexicanus Swainson trapping devices were used. Pitfall traps should only be A single canyon wren was observed in the entrance utilized where the traps can be regularly monitored. room of the cave on October 26, 2001. Canyon wrens are Initial sampling of specimens was kept to a minimum, common in cave entrance areas, where they forage, shelter, and no more than six individuals of each type were taken. and occasionally nest. Both males and females were included in these samples for species where their sex was readily evident. Additional Class: Mammalia sampling for type-series specimens was later performed for Order: Chiroptera the tenebrionid beetle and the undescribed tineid moth. Family: Vespertilionidae Specimens were sampled with forceps or a camel hair brush Myotis californicus Audubon & Bachman dampened with ethanol. Specimens were placed in vials of The presence of this insectivorous bat at Bat Cave is ethanol for transport to the laboratory. known from acoustic monitoring that was conducted at the Two approximately 0.3 kg samples of fresh bat guano entrance in 1997 (Charles Drost, pers. comm). It is were taken on March 29, 1996, for Berlese extraction. Each assumed that only small numbers of these bats use the of these samples was a composite of smaller sub-samples cave.