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A Survey of the Herpetofauna of the Comanche National Grasslands in Southeastern Colorado

Study Region, Methods and Personnel


Study region

The Comanche National Grasslands is divided into a northern portion (primarily in Otero County, immediately south of La Junta; essentially bounded by the Arkansas and Purgatoire River drainages) and a southern portion (primarily in Baca County, in the general vicinity of Springfield, and extending into extreme eastern Las Animas County; see Appendix 3). Within the boundaries of both portions, in addition to shortgrass prairie, extensive canyonlands habitat is included. These areas provide unique and ecotonal habitat which is excellent habitat for many species of amphibians and reptiles, and abundance of many species was observed to be highest in these parts of the Grasslands. Most of the accessible areas of the Grasslands were included during the survey period. However, given the resources dedicated to this subset of the larger herpetofaunal survey of southeastern Colorado, all areas were not visited in a systematic manner; selected areas were more heavily visited at various times during the active season (roughly 1 April-15 October), and many private holdings were inaccessible. Several landowners within the confines of the Grasslands did give permission to enter their land, and their help is appreciated. Most of the field work was conducted by our "B" crew, headquartered around the Two Buttes Reservoir region in extreme northcentral Baca Co. This crew spent considerable time camped in the Cottonwood Canyon/Carrizo Canyon and Vogel Canyon/Picketwire Canyon areas of the Grasslands, and surveys were also conducted on foot in these areas.

Survey methods

Several field methods were utilized to evaluate the presence/absence of amphibian and reptile species in southeastern Colorado. Since the area is large and because horned lizards in particular utilize burms along dirt roads as basking sites, roads were driven extensively at low speeds. This method is very effective for finding amphibians and reptiles and allows large areas to be surveyed rapidly, and many snake, lizard and frog species were encountered (as well as box turtles and tiger salamanders). Different species are encountered during the day versus at night and during rainstorms versus dry spells, and roads were surveyed during many different times of day and climatic conditions. One potential problem with this method is that it may oversample species which move frequently and undersample those which are secretive or rarely cross roads. To offset this potential bias, extensive fieldwork on foot was also conducted, particularly in areas with greater habitat complexity (such as Cottonwood and Carrizo Canyons in southeastern Baca Co) and around areas such as ponds which were likely to contain non-vagile forms. Many species are secretive, and rocks, logs, boards and other cover were turned to search for species such as night snakes, ground snakes, skinks, red-spotted toads, etc. Streams, ponds and small bodies of water were also checked for adult amphibians and larvae and water-dependent reptiles such as soft-shelled turtles, lined and garter snakes. Specimens collected were usually examined, measured and then released at the site of capture. Locality data was collected for all specimens encountered, live or dead. Massasauga rattlesnakes were returned to the lab at UNC for processing (see below). Road killed specimens were collected and preserved in buffered formalin; these specimens were then entered into the UNC Museum of Natural History preserved Herpetology Collection. In 1997, GPS units were available, and latilong coordinates (not differentially corrected) were obtained for each locality (as well as standard fixed distance localities).

In a few sites in Baca County during the 1996 season, hoop and net turtle live traps were installed along creeks or small ponds for up to 24 hr. The intent was to sample for rarely seen species such as the yellow mud turtle (Kinosternon flavescens). Trapping was initiated relatively late in the season, and few turtles (only Chrysemys picta) were encountered.

PIT-tagging of species of primary concern

The use of passive injectable transponder (PIT) tags for identifying animals has seen a tremendous increase in the last five years. These glass-encased microchips are capable of providing an animal with a unique digitized code which is read upon recapture with a hand-held scanning reading device. Individual chips can be read at least 100,000 times and remain permanently implanted. Thus, if an animal is implanted during one study, it can be followed in subsequent studies several to many years later. This method of marking animals is ideal for use in long-term population assessment and management, and PIT-tagged animals do not appear to suffer greater mortality than untagged animals (Camper and Dixon, 1988). PIT tags (11 mm x 2.1 mm, 125 kHz, part #TX1400L), injectors, 12-gauge needles and Mini Portable Readers (part #HS5900L) were purchased from BioSonics, Inc. of Seattle, WA. All PIT tags were scanned before and after implantation and the unique ID number was recorded. Unfortunately, BioSonics no longer supplies tags or readers, and these supplies are now purchased from Avid, Inc. In general, we have found Avid products to be superior and we are now using them exclusively. BioSonic tags can be read by Avid readers, but Avid tags, because they are encrypted, are assigned a different but unique code when read by BioSonic (Destron-Fearing) readers. Horned lizards (subadult and adult only) were injected with 11 mm x 2.1 mm tags, measured and then immediately released at the site of capture. Lizards were turned on their back, and the skin on the right ventrolateral surface was gently grasped to move internal organs out of the way. A PIT tag was then injected subcutaneously. The small wound produced by the 12-gauge needle was sealed with cyanoacrylate glue. The animal was inspected to ensure that no bleeding occurred and the lizard was then released. Massasaugas required more careful handling and were returned to the lab at UNC for processing. Snakes were restrained manually by Dr. S. Mackessy, and PIT tags were injected subcutaneously on the right side two-thirds down the length of the body and the small wound was sealed with cyanoacrylate glue. Venom and blood samples (caudal vein) were also taken at this time, and several morphometric data were collected. Snakes were housed for a minimal amount of time (usually less than 72 hr) and were released at the site of capture. Neonate animals were not PIT-tagged.

Remote Data Loggers

StowAway remote temperature data loggers (purchased from Onset Computers) were installed in 6 locations in early July 1996. Three each were installed in areas central and peripheral to the distributions of Texas horned lizards and massasaugas. Two of these areas were within the Comanche National Grasslands: one was placed near the junction of David Canyon Road and Rourke Road in the northern section (Otero Co.), and the other was placed just off Road M in Cottonwood Canyon in the southern section (Baca Co.). Data loggers were placed in 1l Nalgene plastic bottles with desiccant, and an 18" temperature sensor was extended from the lid. The exit hole was sealed with silicon adhesive (inside and out) and the edge of the lid was wrapped with Parafilm and then duct tape. This assembly was then placed approximately 6-8" below the surface and buried. The temperature sensor was run up the northern side of a wooden fence post (to minimize conductive and convective heat biases) to a height of 6" above ground. Care was taken to assure that the sensor tip would be in the shade. Temperature data was uploaded to a portable IBM laptop computer in early September 1996, early December 1996, May 1997 and late October 1997. Data typically was recorded at 30 minute intervals, and at this recording frequency, 336 days of continuous data could be collected before uploading was required. This data is not included in this report.

Personnel

Most field work was conducted by field crew "B" members, and their work has been exemplary. The 1995 field crew "B" consisted of Chad Montgomery, a Master's candidate in Biological Sciences at UNC, and Kevin Waldron, an undergraduate in Biological Sciences at UNC. In 1996, Chad Montgomery, Scott Boback (a recent graduate of the Master's program) and Ben Hill, an undergraduate student in Biological Sciences at UNC were members of the "B" field crew. In 1997, The "B" field crew consisted of Chad Montgomery and Theresa Childers, also an undergraduate in Biological Sciences at UNC. From 1995-1997, several other members of the survey and telemetry crews, including Enoch Bergman, Ron Donoho, Justin Hobert, Jerry Manzer and James Sifert, also made occasional forays into the Grasslands areas. In 1995, the assistance of two volunteers, Brandon Quinn and Neal Sacheck, also provided additional information on the northern portion of the Grasslands.

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