Herpetological Conservation and Biology 6(2):312–323. Submitted: 2 March 2011; Accepted: 14 July 2011. HABITAT USE AND HOME RANGE OF LONG-NOSED LEOPARD LIZARDS (GAMBELIA WISLIZENII) IN CANYONS OF THE ANCIENTS NATIONAL MONUMENT, COLORADO 1,3 1 2 ROBERT A. SCHORR , BRAD A. LAMBERT , AND ERIC FREELS 1Colorado Natural Heritage Program, Colorado State University, Fort Collins, Colorado 80523, USA 2Dolores Public Lands Office, San Juan Public Lands, 100 North Sixth Street, Box 210, Dolores, Colorado 81323, USA 3Corresponding author, e-mail: [email protected] Abstract.—An understanding of species’ habitat requirements is needed for effective land management decisions, but for many North American reptiles, habitat use information is lacking. Gambelia wislizenii (Long-nosed Leopard Lizard) is a predatory lizard of most North American deserts, and, although common in the interior of its range, appears to be declining at some peripheral populations. To understand habitat use and movement patterns, we used telemetry and two habitat comparison methods to study a G. wislizenii population at the eastern boundary of the range. Gambelia wislizenii home ranges at Canyons of the Ancients National Monument, Colorado, are the largest recorded. Habitat analysis using microsite-attribute comparisons and compositional analysis documented second-order habitat preference for Big Sagebrush- or Utah Juniper-dominated landscapes. Gambelia wislizenii were found in areas with moderate shrub and forb cover with much bare ground, but were not found in areas dominated with grass cover. Incorporating management strategies that limit grass encroachment and maintain bare ground cover with moderate tree and shrub cover may help sustain G. wislizenii populations. Key Words.—bare ground; Colorado; Gambelia wislizenii; grass cover; habitat use; home range; Long-nosed Leopard Lizard; shrub cover INTRODUCTION some time actively hunting (Pietruszka 1986) and may subdue active prey, such as small rodents (Pietruszka et Gambelia wislizenii (Long-nosed Leopard Lizard) is a al. 1980). medium-sized, carnivorous lizard that occurs in the In Colorado, G. wislizenii is restricted to the western Chihuahuan, Great Basin, Mojave, and Sonoran deserts border of the state (Hammerson 1999). Surveys in (Stebbins 2003) and ranges from southern Idaho and Colorado have produced several dozen records from the southeastern Oregon to northern Mexico, and east to west-central part of the state (McCoy 1967), but efforts Colorado and Texas (McGuire 1996; Orange et al. to locate G. wislizenii in previously occupied areas of 1999). Gambelia wislizenii inhabit Greasewood southwest Colorado have been less successful (Sarcobatus vermiculatus), sagebrush (Artemisia spp.), (Hammerson 1999). In Canyons of the Ancients saltbush (Atriplex spp.), and rabbitbrush (Chrysothamnus National Monument (Monument), Montezuma County, spp.) shrublands, seeming to prefer areas where there is the few G. wislizenii records are from the mesa tops of little or no grass cover (McCoy 1967; Baltosser and Best Cannonball Mesa and the surrounding areas (R. Bruce 1990; Steffen and Anderson 2006). Because of its broad Bury, unpubl. report; Brad Lambert, unpubl. report). range in North American deserts and its affinity for areas Because G. wislizenii is found in shrubland habitats devoid of grass cover (Stebbins 2003), G. wislizenii is a with minimal grass cover, and these habitat types are model species for understanding the impacts of invasive declining throughout its range (West 1999), we initiated grasses on habitat use. a habitat use study. The objectives were to understand Habitat changes that limit G. wislizenii abundance or G. wislizenii ecology, movement patterns, and habitat distribution may have consequences for other desert use, and provide management guidance for maintaining species. Gambelia wislizenii are higher-order carnivores habitats for a species that may be declining in abundance in southern deserts where they feed primarily on lizards, and distribution (Nussbaum et al. 1983; Hammerson and have been known to ingest prey nearly as large as 1999). Such information can be invaluable for themselves (Gracie and Murphy 1986). In northern addressing leopard lizard conservation prior to legally- desert systems, G. wislizenii diet consists of more mandated management (U. S. Fish and Wildlife Service invertebrate prey, including grasshoppers, beetles, and 1998). flies (McCoy 1967; Tanner and Krogh 1974; Mitchell 1984). They are sit-and-wait predators that will spend 312 Herpetological Conservation and Biology FIGURE 1. Map of Cannonball and Risley mesas on Canyons of the Ancients National Monument in southwestern Colorado, USA. Inset is the State of Colorado and Canyons of the Ancients National Monument in the southwest corner. MATERIALS AND METHODS wislizenii. Biologists searched between 0800 and 1200 to match lizard activity patterns (McCoy 1967; Parker Study site.—We studied G. wislizenii on Cannonball and Pianka 1976). After capture, we recorded sex and and Risley mesas within the Monument (Fig. 1), which took measurements of snout-to-vent length (SVL), tail is managed by the Bureau of Land Management (BLM). length, and mass. We placed a 1.1-g transmitter with a Declared a national monument in 2000, the 66,370 ha battery life of approximately 4–5 weeks (Holohil area provides habitat for much herpetofaunal diversity, Limited Ltd., Carp, Ontario, Canada) over the pelvic and this diversity motivated the BLM to establish the girdle of the lizard and attached the transmitter using McElmo Rare Snake and Lizard Area in Bridge Canyon elastic cord (Knapp and Owens 2005). Transmitter of the Monument in 1976. Pinyon Pine (Pinus edulis) masses ranged from 1.8–6.5% of the lizards’ body with intermixed Big Sagebrush (Artemisia tridentata), masses and fell within the tested weight loads of other saltbush, Skunkbush (Rhus trilobata), and Utah Juniper lizards (Knapp and Owens 2005; Knapp and Abarca (Sabina osteosperma) dominate the mesas on the 2009). Individuals > 90 mm SVL and showing orange Monument (Fig. 2). Vegetation along the lowland coloration on the sides and under the tail were drainages is a complex of Greasewood, saltbush, considered females. Individuals > 80 mm SVL, not Skunkbush, and rabbitbrush, with mesic areas supporting showing orange coloration, and having enlarged postanal Cottonwood (Populus angustifolia), willow (Salix spp.), scales were categorized as males (Parker and Pianka and Tamarisk (Tamarix ramosissima). 1976; Mitchell 1984; Hammerson 1999). We located lizards 2–5 times a week (mean = 3.2 locations/7 d) from Telemetry and home range estimation.—In late June 19 June to 1 August 2006, and 23 June to 30 July 2008 of 2006 and 2008, a crew of 4–9 biologists walked the to match peak G. wislizenii seasonal activity (McCoy mesas to locate, capture, and attach transmitters to G. 1967) and increase capture success. Gambelia wislizenii 313 Schorr et al.—Habitat and Home Range of Long-nosed Leopard Lizards. FIGURE 2. Gambelia wislizenii habitat (foreground) on Cannonball Mesa (left) and the area adjacent to and north of Gambelia wislizenii habitat on Cannonball Mesa (right). (Photographed by Robert Schorr). emerge from hibernation as early as April and May in asymptote is reached for KHR estimation have not been the southern regions of their range (Baltosser and Best established (Laver and Kelly 2008). 1990), but in Colorado do not emerge until mid-May (McCoy 1967; Hammerson 1999). Habitat use.—We assessed habitat use at various We estimated individual home ranges and an scales using a hierarchical approach of habitat selection aggregated (all individuals) home range using minimum (Johnson 1980). We compared second-order selection convex polygons (MCP) and kernel estimators (KHR; (home range within study area) and third-order selection Seaman and Powell 1996). We used HRT: Home Range (habitat patches within home range) using compositional Tools for ArcGIS (Rodgers et al. 2007) in a geographic analysis outlined by Aebischer et al. (1993). The information system (ArcGIS 9.3.1, Environmental sampling units for compositional analysis were the Systems Research Institute, Redlands, California, USA) individuals’ MCPs. We based habitat types on the for estimation and visualization of home range and dominant vegetation groupings (DOM_VEG_1) in the movement patterns. For individual lizard KHR Canyons of the Ancients National Monument Vegetation estimates, we used fixed kernels with least squares cross Database (2003; Dolores Public Lands Office, Dolores, validation. Kernel home range estimators can be Colorado, USA). Range ecologists at the Dolores Public advantageous because they are probability-based and Lands Office interpreted vegetation types using 1:24,000 give information about the relative use of an area stereographic true-color aerial photograph pairs, then (Seaman and Powell 1996). However, kernel estimators verified vegetation types by assessing ground cover and have undergone much criticism because of the shrub cover along 30-m transects. For assessment of subjectivity of smoothing parameter choice and its landscape vegetation cover in second-order habitat use, impact on estimates and the decreased accuracy with we defined the study area as the area encompassed by a small number of observations per individual (Seaman et 100-m buffer around the aggregated MCP. The study al. 1999; Laver and Kelly 2008). Seaman et al. (1999) area on Cannonball Mesa has five habitat types: recommended obtaining ≥