Located in western New Mexico, El Malpais National Monument encompasses approximately 1,522 km² [~588 mi²]. Featuring at least eight major volcanic eruptions ranging in age from 100,000 to 3,000 years old (Cascadden et al. 1997), the national monument is a dramatic landscape comprising vast expanses of pahoehoe and ‘a‘ā lava flows, cinder cones, ice caves, and at least 290 lava tube caves (fig. 1). Despite the large number of lava tube caves, this region has received little scientific attention with regard to bat and arthropod populations that occur within these features.
Bats are often considered keystone species of cave ecosystems. When bats populate caves in large numbers, they transport a significant amount of organic material (as guano) from the surface into the cave. Although bats have been studied throughout most of the western United States, how these animals use caves remains underresearched. Bat maternity roosts (sites where female bats rear their pups) and hibernacula (winter hibernation sites) are highly sensitive to human disturbance (Brown et al. 1993; McCracken 1989; Elliott 2000; Hamilton-Smith and Eberhard 2000). With the westward advance of white-nose syndrome, a disease responsible for the mortality of more than five million bats in eastern North America (USFWS 2012), inventory and monitoring of all roost sites will be critically important to the long-term management of bats at El Malpais National Monument.
Other animals of high conservation and management value are arthropods that occur exclusively in caves. Prior to this study, at least five cave-adapted arthropods (presumed sensitive species) were known from six lava tube caves at El Malpais (Northup and Welbourn 1997). Many troglomorphic (cave-adapted) animals are endemic to a single cave or region (Reddell 1994; Culver et al. 2000; Christman et al. 2005) and are generally characterized by low population numbers (Mitchell 1970). Additionally, numerous human-induced impacts threaten subterranean ecosystem health and the very persistence of cave-obligate species. Many cave-obligate species are therefore considered imperiled. Nonnative species introductions (Elliott 1992; Reeves 1999; Taylor et al. 2003; Howarth et al. 2007), global climate change (Chevaldonné and Lejeune 2003; Badino 2004), and recreational use (Culver 1986; Howarth and Stone 1993; Pulido-Bosch et al. 1997) are among the impacts that present challenges for the long-term management of cave-obligate arthropod populations at El Malpais.
An all taxa biological inventory focusing on bats, cave-dwelling arthropods, and other vertebrates was not only important to characterizing the fauna that use El Malpais lava tubes, but also was required to provide resource managers with the information necessary to best conserve and manage these sensitive resources. My objectives for this study were to (1) catalog all taxa using caves, including the identification of endemic and sensitive cave-adapted invertebrates, (2) apply and examine a systematic sampling protocol for inventorying arthropods, (3) draw comparisons across the national monument to gain inference into patterns of invertebrate species distributions, biodiversity, biogeography, and endemism, and (4) provide recommendations to enhance management of El Malpais lava tube caves. I addressed objectives 1 and 4 in this article and will address objectives 2 and 3 in subsequent publications.
Wynne, J. J. 2013. Inventory, conservation, and management of lava tube caves at El Malpais National Monument, New Mexico. Park Science 30(1):45–55.
Available at http://www.nature.nps.gov/ParkScience/archive/PDF/Article_PDFs/ParkScience30(1)Summer2013_45-55_Wynne_3651.pdf.