RADIOTELEMETRY AND POPULATION MONITORING OF SAND DUNE LIZARDS (SCELOPORUS ARENICOLUS) DURING THE NESTING SEASON, 2006

Transcription

1 Share With Wildlife Project Title: Dispersal and radio tracking of the Sand Dune Lizard, Sceloporus arenicolus RADIOTELEMETRY AND POPULATION MONITORING OF SAND DUNE LIZARDS (SCELOPORUS ARENICOLUS) DURING THE NESTING SEASON, 2006 Michael T. Hill and Lee A. Fitzgerald Department of Wildlife and Fisheries Sciences Texas A&M University College Station, TX 77843

2 Hill and Fitzgerald Sand dune lizard interim report. 2 INTRODUCTION The sand dune lizard (Sceloporus arenicolus) is endemic to a small, yet well-defined area in southeastern New Mexico and to a relatively unknown area in adjacent west Texas (Fitzgerald et al. 1997, USFWS 2004, 04 May CFR 17 69[86]:24888 Federal Register Candidate Notice of Review-Sand dune lizard). In June 2002, the Center for Biological Diversity petitioned the U.S. Fish and Wildlife Service (USFWS) to list S. arenicolus as a Threatened or Endangered species under the Endangered Species Act. In March 2004, the USFWS reviewed available information and renewed the Candidate Status of S. arenicolus as a Listing Priority of 2 (High and Imminent Threat to the Species) (USFWS 2004). During 2005, New Mexico Department of Game and Fish considered arguments for and against changing the status of S. arenicolus from State Threatened to State Endangered, and the decision was taken to list the lizard species as State Endangered. The Shinnery Oak Stakeholders Group met several times during to identify and resolve conflicts revolving around the sand dune lizard and sympatric lesser prairie chicken. State and federal agencies charged with natural resource conservation in southeastern New Mexico need basic ecological information on the sand dune lizard in order to formulate scientifically defensible conservation plans. In particular, there is a clear and urgent need for information on sand dune lizard movements and nesting ecology, because land managers and user groups need to know to what extent sand dune lizards use the shinnery oak matrix as well as sand dune blowouts for dispersal and nesting. Nesting habits have never been described for sand dune lizards. We do not know what microhabitats females use for nesting, nor do we understand movements of gravid females. It is critical to learn to what extent nesting females traverse the shinnery oak habitat and leave sand dune blowouts during nesting. During the 2004 field season, we tested the feasibility of radio tracking sand dune lizards using the smallest miniature radio transmitters available. We radiotracked 8 sand dune lizards and proved the feasibility of tracking detailed movements of lizards in the shinnery oak landscape. It appears females may leave their home range and travel to other blowouts or into the shinnery oak matrix to nest, but this is not yet clear, because nests were not been found. We are continuing the study in 2005 for the second season with increased effort. Because of the meticulous nature of this work, 3 seasons of field data will be required to piece together a picture of dispersal and nesting movements of individual lizards. Funding from this proposal would allow us to continue this research for the third season in In addition to the obvious need for natural history and population biology information to inform policy decisions regarding of S. arenicolus, natural history information and population estimates should be useful to more fully address potential conflicting issues of shinnery habitat management for lesser prairie chickens (Tympanuchus pallidicinctus) and S. arenicolus. Lesser prairie chickens (LPC) are also a Candidate species under the ESA (USFWS 2003) and current practices for conservation and management of LPCs often involves reduction of shrub components through the use of herbicide to control shinnery oak. These practices, although likely beneficial to LPCs, are known to be detrimental to S. arenicolus which occupies localized and fragmented habitats within the shinnery system. Herbicide spraying in New Mexico resulted in disappearance of S. arenicolus from sprayed areas within 4 years (Snell et al. 1997). Moreover, the shinnery habitat shows no signs of recovery 18 years post-spraying (Fitzgerald

3 Hill and Fitzgerald Sand dune lizard interim report. 3 and Painter, pers. comm.) Therefore, understanding variability in S. arenicolus population density, and relationships between habitat and population density is necessary for effective management of LPCs that occupy similar habitats. The findings of this project will be immediately applicable to conservation plans for sand dune lizards developed by Endangered Species Program of New Mexico Department of Game and Fish. Information on dispersal and nesting movements of sand dune lizards will be used to develop criteria for protecting areas of shinnery oak habitat that surrounds areas with sand dune blowouts and to establish corridors of shinnery oak habitat that connect dune complexes. Biologists from NMGF, BLM, and other entities will use information from this study to refine stipulations for oil and gas development and herbicide spraying in areas that impact sand dune lizards (Painter et al. 1999; C. Painter pers. comm.). METHODS Study Area The study area is located at Caprock Wildlife Area in east-central Chaves County, New Mexico on Bureau of Land Management lands (Figure 1). The area is dominated by shinnery oak (Quercus havardii) with big bluestem (Andropogon gerardii), little bluestem (Schizachyrium scoparium), and sand sage (Artemisa filifolia) characterizing the vegetative community (Dick- Peddie 1993). Radiotelemetry Radiotelemetry is an effective method for tracking the small-scale movements of organisms (Garton et al. 2001). We used radiotelemetry to monitor the movements of gravid female sand dune lizards from late May to mid July. The following protocol was tested by us in 2003 and 2004 (Fitzgerald et al. 2005). Lizard positions were monitored 3 times per day, morning before activity, during the daily activity period, and after dark when the lizards are in their nocturnal refugia (they usually bury themselves under sand). The transmitters (Blackburn Transmitters, Nacogdoches, Texas) weigh 0.25 g which is within the normally accepted 5% body mass of marked subjects (Kenward 2001). The transmitters have a battery life of 14 days but to ensure retrieval, we recovered the transmitters after 11 days or as soon as there was a noticeable change in signal. Gravid females were caught starting in late May through late June. Females with large eggs, determined by gently palping the abdomens of the subjects, were outfitted with transmitters. The transmitters were attached to the dorsum of the lizards at or directly posterior to the pectoral girdle with a small amount of cyanoacrylate glue (e.g. Super Glue). The whip antenna was directed towards the posterior of the subject with care given to alignment of the antenna with the longitudinal axis of the subject. Transmitters were removed by soaking the lizard, with transmitter, in water to soften the adhesive. After the adhesive had sufficient time to soften, the transmitter was carefully removed by hand. Tracking was performed with a Telonics (Mesa, Arizona) TR-2 receiver, a Telonics RA- 2A directional antenna, and a home-made unidirectional wand antenna used for tracking at a fine scale. Care was taken while tracking so as to minimize disturbance to the subjects. When care was taken while tracking inactive subjects (buried for the night or under shade during midday)

4 Hill and Fitzgerald Sand dune lizard interim report. 4 the observer was often able to approach the subjects position closely without flushing them. In previous work with this species, observers were able to locate the subject in nearly all instances (M.T. Hill, pers. obs.). Locations were marked with a pin flag with lizard number, time, and date written on the flag for insurance against equipment failure (e.g. the GPS losing multiple points). Differentially corrected UTM coordinates were collected for each position with a Trimble GeoExplorer (Sunnyvale, California) GPS unit. Surface temperature (T s ) measured with the thermometer bulb inserted in the substrate, air temperature (T a ) measured in the shade 1 m above the ground, lizard activity observations (e.g. active, buried, basking, stationary), exposure observations (e.g. shade, partial sunlight, full sunlight), and position in the habitat (e.g. blowout center, blowout margin) were collected immediately after finding the lizard to identify any microhabitat preferences that the lizards may exhibit. For all nocturnal lizard locations microhabitat variables were collected in the same manner as Fitzgerald et al. (1997). Microhabitat variables measured at the lizards location and at the paired random point were: air temperature (T a ) measured 2 cm above the substrate, substrate temperature (T s ), distance to cover, and aspect. Aspect was measured as the compass bearing of the slope to the nearest degree. The cosine and sine of the aspect measure the north-south and east-west orientations of points, respectively. Cover was measured from the points where resting lizards are seen to the nearest clump of vegetation providing refuge. Random points were located 10 paces along a random compass bearing from the point where the individual is tracked to. Variables at both points were measured immediately. The microhabitat and behavior of the lizard were noted, and if the lizard was resting or nesting in a sand dune blowout, the largest dimension of the blowout was measured to the nearest meter by pacing. Dune blowouts were classified according to 4 depth categories: Class I blowouts are 0-2 feet (0-60 cm) deep at their deepest point; Class II blowouts are 2-5 feet ( cm) deep, Class III blowouts are 5-10 feet ( cm) deep, and Class IV blowouts are > 10 feet (> 300 cm) deep. When nesting occurred the presumed nest site was carefully excavated to collect data on the orientation of the nest chamber and on the eggs. Aspect of the nest site (i.e. west facing slope) was determined with a KB-14 azimuth compass (Suunto, Finland). PRELIMINARY RESULTS Seven female sand dune lizards were tracked at the study area from May to July These lizards were tracked for a longer period of time than in the past with multiple radios used on individual lizards. One nest laid on the night of 27/28 May 2006 was recovered and found to contain three eggs. During the 2005 field season another nest was recovered which also contained three eggs. These two nests are the only described nests of sand dune lizards. Three other nest sites were identified during 2006 although the nests were not recovered. Six nest sites were identified during 2005 bringing the total number of nest sites identified to 10 with two nests recovered. Open sand and clear exposure seem to be related to nest site selection. All identified nest sites were on open sand slopes with little vegetation within blowouts. During the 2006 season, two individuals were lost to snake predation. One of the transmitters was recovered from a coachwhip (Masticophis flagellum) while the other transmitter

5 Hill and Fitzgerald Sand dune lizard interim report. 5 was eventually unearthed from a burrow encased in snake feces. During 2005 three of the 14 tracked lizards were lost to coachwhips. Mark-recapture Study Two 36-bucket pitfall grids were put into place 2006, to compliment 2 other grids established in 2005 (Figure 2). The pitfall trapping grids are used to estimate population density of sand dune lizards and other lizard species in the study area, and obtain additional data on lizard movements. Lizards of all species were marked with individually identifying toe clips as discussed in Ferner (1979). Movements will be assessed based on the trap locations of recaptured lizards. The Jolly-Seber method in program MARK will be used to generate abundance estimates (Krebs 1999). Tables 1 and 2 summarize the captures made with the four pitfall grids during 2005 and Only two grids were operated during 2005 while four grids were operated during These grids have captured most of the lizard species found at the study area with the exception of collared lizards (Crotaphytus collaris) and Texas horned lizards (Phrynosoma cornutum) although these two species are often encountered in close proximity to the grids. LITERATURE CITED Dick-Peddie, W. A New Mexico vegetation: past, present, and future. University of New Mexico Press, Albuquerque. Fitzgerald, L. A., M. W. Sears, and C. W. Painter Interdune dispersal of sand dune lizards (Sceloporus arenicolus) in the Mescalero Sands ecosystem. Report to New Mexico Department of Game and Fish. Garton, E. O., M. J. Wisdom, F. A. Leban, and B. K. Johnson Experimental design for radiotelemetry studies. Pages in J. J. Millspaugh and J. M. Marzluff, editors. Radio tracking and animal populations. Academic Press, San Diego. Kenward, R. E A manual for wildlife radio tagging. Academic Press, San Diego.

6 Hill and Fitzgerald Sand dune lizard interim report. 6 Figure 1. The range of Sceloporus arenicolus in New Mexico. The green star indicates the location of the study area at Caprock Wildlife Area, ~40 miles east of Roswell Figure 2. Graphical representation of a pitfall grid used during 2005 and Four such grids were employed during 2006 for lizard capture. Buckets are spaced 15 m apart for a total sampled area of 5625 m 2 per grid.

7 Hill and Fitzgerald Sand dune lizard interim report. 7 Table 1. Summary of four pitfall grids operated during 2005 and 2006 at Caprock Wildlife Area, Chaves County, New Mexico. Pitfall grid 2005 total captures 2006 total capture Days run for 2005 Days run for 2006 No. of species TOTAL No. of S. arenicolus marked Species Table 2. Summary of marks by species for four pitfall grids operated during 2005 and 2006 at Caprock Wildlife Area, Chaves County, New Mexico. Aspidoscelis marmorata A. sexlineata Eumeces obsoletus Holbrookia maculata Sceloporus arenicolus S. consobrinus Uta stansburiana Grid Grid Grid Grid Total Total