TEXAS J. OF SCI. 63(2): MAY, 2011 (PUBLISHED AUG 2014) HERPETOFAUNAL SURVEY OF THE GRIFFITH LEAGUE RANCH IN THE LOST PINES ECOREGION OF TEXAS

Transcription

1 TEXAS J. OF SCI. 63(2): MAY, 2011 (PUBLISHED AUG 2014) HERPETOFAUNAL SURVEY OF THE GRIFFITH LEAGUE RANCH IN THE LOST PINES ECOREGION OF TEXAS Donald J. Brown 1, Todd M. Swannack 2, James R. Dixon 2 and Michael R. J. Forstner 1 1 Department of Biology, Texas State University-San Marcos 601 University Drive, San Marcos, TX Department of Wildlife and Fisheries Sciences Texas A&M University, 2258 TAMU College Station, TX Abstract. The Lost Pines ecoregion is a 34,400 ha remnant patch of pinedominated forest located in central Texas. The ecoregion is currently under intense development pressure due to its aesthetic value and close proximity to the city of Austin. A survey-intensive herpetofaunal assessment was conducted on the Griffith League Ranch (GLR) between 2001 and 2004 to determine what species utilize the habitat, and obtain baseline activity patterns. A total of 35 herpetofaunal species were documented on the GLR: five lizards, three turtles, 15 snakes, and 12 amphibians, including the endangered Houston toad (Bufo houstonensis). In general, herpetofaunal detection was highest in spring and summer, and lowest in winter. The survey showed there is a rich herpetofaunal community in the Lost Pines ecoregion, which warrants consideration in its future development and land-use planning. The Lost Pines ecoregion of central Texas is a 34,400 ha remnant patch of pine-dominated forest that was isolated from the East Texas Piney Woods ecoregion during the Pleistocene (Bryant 1977; Al-Rabab ah & Williams 2004). Due to its aesthetic value and close proximity to the city of Austin and recently constructed Austin-Bergstrom International Airport, the Lost Pines ecoregion is currently under tremendous development pressure. The number of residents in Bastrop County increased by 29.7% between 2000 and 2009 (U. S. Census Bureau 2010), along with a substantial increase in commercial development. The Lost Pines houses a diverse array of wildlife. White (2003) and Marcum (2005) collectively documented 116 bird species between the 1,948 ha Griffith League Ranch (GLR) and the 2,400 ha Bastrop State Park. Rebhorn (2004) and Ferguson et al. (2008) collectively found 20 native mammal species on the GLR. Over 300 invertebrate species have been identified in the ecoregion, two of

2 102 THE TEXAS JOURNAL OF SCIENCE-VOL. 63, NO. 2, 2011 which could be endemic (Taber & Fleenor 2003; Taber 2008). However, in terms of wildlife conservation the Lost Pines is well known for being the last remaining stronghold for the federally endangered Houston toad (Bufo houstonensis; Gottschalk 1970). Garnering public and political support for protection of wildlife habitat is contingent upon knowing what wildlife utilize the habitat. Because of the increasingly rapid development in the Lost Pines, the U. S. Fish & Wildlife Service launched a landowner and developer-inclusive initiative to preserve Houston toad habitat. The culmination of this initiative was a county-wide habitat conservation plan for Bastrop (KES Consulting et al. 2007), now implemented as the Lost Pines Habitat Conservation Plan. Herpetofaunal surveys have been conducted in this unique habitat prior to this investigation (Dronen 1989; Dixon et al. 1990). However, this paper represents, to our knowledge, the first published herpetofaunal survey focused exclusively within the Lost Pines ecoregion. An extensive multi-year data set is used to show that conserving the Lost Pines is important not only for the Houston toad, but for a wide array of herpetofaunal species. In addition, temporal detection patterns are summarized to assist landowners in choosing timeframes for habitat manipulation that minimize disturbance and mortality potential, particularly for amphibians around breeding ponds. METHODS Study Site. This study was conducted on the GLR in Bastrop County, Texas (N , W ). The property is underlain by deep sandy soils of the Patilo-Demona-Silstid Association (Baker et al. 1979). The forest overstory is dominated by loblolly pine (Pinus taeda), post oak (Quercus stellata), blackjack oak (Quercus marilandica), and eastern red cedar (Juniperus virginiana). The understory is dominated by yaupon

3 BROWN, ET AL. 103 Figure 1. Location of the Griffith League Ranch (GLR) within the Lost Pines ecoregion in Bastrop County, and trapping locations on the GLR. Trapping occurred from 12 March 2001 to 30 June 2004 using 13 Y-shaped (15 m arms) and 5 ( m) linear arrays. The Lost Pines boundary was modified from Texas Parks and Wildlife Department (2010), and is a soft boundary, excluding some small loblolly pinedominated patches and including some developed and cleared patches.

4 104 THE TEXAS JOURNAL OF SCIENCE-VOL. 63, NO. 2, 2011 holly (Ilex vomitoria), American beautyberry (Callicarpa americana), and farkleberry (Vaccinium arboreum). Data Collection. The GLR has been surveyed and trapped extensively since For this study the intensive, daily trap data collected from 12 March 2001 to 30 June 2004 were used to provide species capture summaries and temporal detection (i.e., inferred activity) patterns. Herpetofaunal species detected on the GLR through 2010, but not captured in traps, were also noted. Scientific and common names follow Dixon (2000). In March 2001 three 153 m and two 121 m aluminum drift fences were placed along forest edges, with 19 L buckets placed every 30 m along each fence. One Y-shaped array was placed in a forest opening to capture grassland-associated species. Two Y- shaped arrays were placed in forested habitat. Y-shaped arrays consisted of three 15-m arms, with a 19 L center bucket and a 19 L bucket at each arm terminus. A double-throated funnel trap was placed on each side of each arm of Y-shaped arrays to trap species that can evade capture in pitfall traps. Pitfall traps were equipped with predator exclusion devices (Ferguson & Forstner 2006). Pitfall traps contained flotation devices to mitigate mortality during bucket flooding, and both pitfall and funnel traps contained sponges to provide a moist environment for amphibians. In February 2002 an additional seven Y-shaped arrays were placed in forested habitat, and an additional two Y-shaped arrays were placed in forest clearings (Fig. 1). Traps were checked daily throughout the study, with the exception of being closed for seven non-consecutive days in July 2002 due to excessive rainfall, and 1 August 2003 through 9 August 2003, and 20 August 2003 through 1 September 2003, both due to excessive temperatures. Heavy rainfall and unusually high temperatures posed substantial mortality risks from bucket flooding or desiccation, respectively. Captured individuals were either individually or cohort marked using toe-clips or passive integrative

5 BROWN, ET AL. 105 transponder (PIT) tags for amphibians, toe-clips for lizards and salamanders, carapace notches for turtles, and scale-clips for snakes. Photographs and standard measurements were taken, and individuals were released near their site of capture. Analyses. Number of captures and recaptures over the entire study period was tallied for each species. Total number of amphibian, lizard, and snake captures in 2002 and 2003 were plotted by month to determine general herpetofaunal activity patterns. Species-specific activity patterns were investigated for species with > 40 captures in 2002 and RESULTS A total of 35 herpetofaunal species (12 amphibians, five lizards, three turtles, and 15 snakes) were documented on the GLR (Table 1) during a total of 411,768 trap hours using pitfall and funnel traps between 12 March 2001 and 30 June The pitfall traps (n=48) and funnel traps (n=72) were open for the entire period excepting 29 days of severe cold, heat, or flooding. In general, amphibian captures were highest from April to July and September to October (Fig. 2). Lizard captures were highest between April and September. Snake captures were highest in May, but were fairly consistent throughout the year. Total monthly captures for seven amphibians and three lizards are shown in Table 2. Houston toads were captured primarily from February through April. The remaining amphibians all had high captures in June. Bullfrogs (Rana catesbeiana) and Hurter s spadefoot toads (Scaphiopus hurterii) had high captures between May and November. Tiger salamanders (Ambystoma tigrinum) had no clear temporal activity patterns. Most Ground skink (Scincella lateralis) captures occurred between March and May. Six-lined race runners (Cnemidophorus sexlineatus) and Southern prairie lizards (Sceloporus consobrinus) had a similar activity trend, with a substantial capture increase beginning in April, and a rapid decrease

6 106 THE TEXAS JOURNAL OF SCIENCE-VOL. 63, NO. 2, 2011 Table 1. Herpetofaunal species observed or captured on Griffith League Ranch (GLR) between 12 March 2001 and 30 June 2004, or documented in the Lost Pines ecoregion (LPE) but not on GLR (Dronen 1989; this author MRJF), or documented in Bastrop County (BACO) but outside of the LPE, Texas (Dixon 2000). Site Scientific Name Common Name Captures a (Recapture) AMPHIBIANS GLR Acris crepitans Blanchard s cricket frog 89 (1) LPE Ambystoma texanum Smallmouth salamander 0 GLR Ambystoma tigrinum Eastern tiger salamander 90 (90) BACO Bufo debilis Green toad 0 GLR Bufo houstonensis Houston toad 67 (6) BACO Bufo speciosus Texas toad 0 GLR Bufo valliceps Gulf coast toad 197 (19) GLR Bufo woodhousii Woodhouse s toad 1 GLR Bufo spp b Toad species 41 (1) GLR Gastrophryne carolinensis Eastern narrowmouth toad 6 GLR Gastrophryne olivacea Great plains narrowmouth toad 50 (2) GLR Hyla cinerea Green tree frog 3 LPE Hyla chrysoscelis Cope s gray tree frog 0 GLR Hyla versicolor Gray tree frog 15 LPE Pseudacris clarki Spotted chorus frog 0 BACO Pseudacris fouqettei Cajun chorus frog 0 LPE Pseudacris streckeri Strecker s chorus frog 0 LPE Rana berlandieri Rio Grande leopard frog 0 GLR Rana catesbeiana American bullfrog 68 LPE Rana clamitans Bronze frog 0 GLR Rana sphenocephala Southern leopard frog 695 (9) LPE Scaphiopus couchi Couch s spadefoot 0 GLR Scaphiopus hurterii Hurter s spadefoot 402 (40) LPE Syrrhophus marnocki Cliff chirping frog 0 LIZARDS GLR Anolis carolinensis Green anole 9 (1) LPE Cnemidophorus gularis Texas spotted whiptail 0 GLR Cnemidophorus sexlineatus Six-lined race runner 1538 (444) BACO Crotaphytus collaris Eastern collared lizard 0 BACO Eumeces septentrionalis Prairie skink 0 BACO Holbrookia lacerata Plateau earless lizard 0 BACO Ophisaurus attenuatus Slender glass lizard 0 LPE Phrynosoma cornutum Texas horned lizard 0 GLR Sceloporus consobrinus Southern prairie lizard 898 (199) GLR Sceloporus olivaceus Texas spiny lizard 2 GLR Scincella lateralis Ground skink 114 (6) BACO Urosaurus ornatus Eastern tree lizard 0

7 BROWN, ET AL. 107 Table 1. cont. Site Scientific Name Common Name Captures a (Recaptures) SNAKES GLR Agkistrodon contortrix Broad-banded copperhead 26 GLR Agkistrodon piscivorus Western cottonmouth 0 LPE Arizona elegans Texas glossy snake 0 LPE Coluber constrictor Eastern yellow-bellied racer 0 BACO Crotalus atrox Western diamondback 0 rattlesnake GLR Crotalus horridus Canebrake rattlesnake 1 BACO Elaphe emoryi Southwestern rat snake 0 GLR Elaphe obsoleta Texas rat snake 16 (1) GLR Heterodon platirhinos Eastern hog-nosed snake 23 BACO Lampropeltis calligaster Prairie king snake 0 BACO Lampropeltis getula King snake 0 GLR Leptotyphlops dulcis Plains blind snake 4 GLR Masticophis flagellum Western coachwhip 27 (3) GLR Micrurus tener Texas coral snake 4 GLR Nerodia erythrogaster Blotched water snake 2 GLR Nerodia fasciata Broad-banded water snake 0 GLR Nerodia rhombifer Diamondback water snake 0 LPE Opheodrys aestivus Rough green snake 0 BACO Pituophis catenifer Bull snake 0 BACO Rhinocheilus lecontei Texas long-nosed snake 0 BACO Salvadora grahamiae Texas patch-nosed snake 0 BACO Sonora semiannulata South Texas ground snake 0 GLR Storeria dekayi Texas brown snake 18 GLR Tantilla gracilis Flatheaded snake 1 BACO Thamnophis marcianus Checkered garter snake 0 GLR Thamnophis proximus Ribbon snake 3 GLR Virginia striatula Rough earth snake 0 TURTLES GLR Chelydra serpentina Common snapping turtle 1 BACO Graptemys versa Texas map turtle 0 LPE Kinosternon flavescens Yellow mud turtle 0 LPE Pseudemys texana Texas river cooter 0 GLR Terrapene Carolina Three-toed box turtle 5 (1) BACO Terrapene ornata Ornate box turtle 0 GLR Trachemys scripta Red-eared slider 3 BACO Trionyx spiniferus Guadalupe spiny soft-shelled turtle 0 a Total first captures, of which 93.5% of live first captures were marked (recaptures in parentheses); Species listed for GLR with 0 captures were recorded but not captured. b Morphologically unidentifiable juveniles.

8 108 THE TEXAS JOURNAL OF SCIENCE-VOL. 63, NO. 2, 2011 Figure 2. Activity patterns of herpetofaunal taxonomic groups in the Lost Pines ecoregion, Bastrop County, Texas, inferred from pitfall and funnel trap captures in 2002 and The figure shows percentage of total captures by month within taxonomic groups. in October. All lizards and amphibians other than Southern leopard frogs (Rana sphenocephala) had very low captures from November through January. DISCUSSION A rich herpetofaunal diversity was found in the Lost Pines ecoregion of Texas. Temporal capture patterns indicated herpetofauna in this region are active most of the year, with the highest activity in spring and summer. Therefore, major habitat manipulation, such as culling pine engraver beetle (Ips spp.) infested trees, should be restricted to the late fall and winter (i.e., November to January) when possible. In addition, we recommend restricting cattle usage of ponds to the late fall and winter due to negative effects on water quality and terrestrial habitat for amphibians (Schmutzer et al. 2008). We made direct observation of

9 BROWN, ET AL. 109 Table 2. Cumulative monthly captures from 1 January 2002 to 31 December 2003 for nine herpetofaunal species on the Griffith League Ranch, Bastrop County, Texas. Amphibians Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Acris crepitans Rana catesbeiana Bufo valliceps Bufo houstonensis Scaphiopus hurterii Rana sphenocephala Lizards Scincella lateralis Cnemidophorus sexlineatus Sceloporus consobrinus Table 3. Herpetofaunal diversity in Bastrop County compared to the four surrounding counties. County records for Caldwell, Fayette, Lee, and Travis were obtained from the Texas Cooperative Wildlife Collection (2010). County Size (km 2 ) Species Species per km 2 Bastrop Caldwell Fayette Lee Travis

10 110 THE TEXAS JOURNAL OF SCIENCE-VOL. 63, NO. 2, 2011 improvements in water quality and pond edge integrity after cattle exclusion from ponds on the GLR, followed by subsequent use of those same ponds by Houston toads for chorusing and breeding in the years that followed. In general, the capture data reflect what are probably realistic relative abundance differences among species within herpetofaunal categories. However, based on pond surveys we have conducted, gray tree frogs (Hyla versicolor) and green tree frogs (Hyla cinerea) are more abundant than is reflected in our capture data. This is likely due to their arboreal nature and their ability to climb out of pitfall traps. Texas spiny lizards are also probably underrepresented due to arboreal habitat preferences. Cottonmouths and water snakes are certainly under-represented due to strong preferences for aquatic habitats. Indeed, snakes in general are likely under-represented due to their secretive nature and ability to escape pitfall traps. Employing other sampling techniques (e.g., coverboards) would likely have resulted in more representative relative abundance differences for snakes. In addition to the herpetofauna documented on the GLR, there are numerous other species that may occur regularly in the Lost Pines ecoregion (Table 1). Additional species were recorded by Dronen (1989) during a herpetofaunal survey at the Bastrop- Buescher State Park complex, and by one of the authors (MRJF) while conducting Houston toad survey work. Also listed in Table 1 are species documented in Bastrop County (Dixon 2000), inclusive of those species not occurring within the Lost Pines. This and the other studies cited herein have shown that the Lost Pines houses an extensive wildlife community, showing this is clearly an ecoregion worth conserving. Compared to the surrounding counties (Caldwell, Fayette, Lee, and Travis), only Travis County has greater herpetofaunal diversity than Bastrop County (Table 3). When diversity is scaled by county size, Bastrop County still ranks second behind Caldwell County. Most land in the

11 BROWN, ET AL. 111 Lost Pines is privately owned; thus, preserving the ecological integrity of the Lost Pines will require substantial landowner support. This will become increasingly difficult as property values continue to increase. However, with high public and political support, and development plans that minimize further encroachment into the forest, we can ensure the Lost Pines retains its ecological and cultural significance for future generations. ACKNOWLEDGEMENTS The Boy Scouts of America provided funding and access to the GLR and we are grateful for their support. ALCOA provided preliminary funding for this study. Additional funding and handling permits were provided by the Texas Parks and Wildlife Department (permit SPR ), and the United States Fish and Wildlife Service (permit TE ). A portion of this research was funded by a Texas Academy of Science student research grant (awarded to TMS). We thank all of the individuals who assisted in trapping for this study, and the individuals who have conducted herpetofaunal surveys in the Lost Pines. This research was approved by the Texas State University-San Marcos Institutional Animal Care and Use Committee (0810_0208_11). LITERATURE CITED Al-Rabab ah, M. A. & C. G. Williams An ancient bottleneck in the Lost Pines of central Texas. Molecular Ecology 13(5): Baker, F. E Soil survey of Bastrop County, Texas. U. S. Department of Agriculture, Soil Conservation Service. Washington, D. C., 73 pp. Bryant, V. M., Jr A 16,000 year pollen record of vegetational change in central Texas. Palynology 1(1): Dixon, J. R Amphibians and reptiles of Texas. 2 nd edition. Texas A&M Univ. Press, College Station, 432 pp. Dixon, J. R., N. O. Dronen, J. C. Godwin & M. A. Simmons The amphibians, reptiles, and mammals of Bastrop and Buescher State Parks: With emphasis on the Houston toad (Bufo houstonensis) and the Short-tailed shrew (Blarina sp.). Final report, Texas Parks and Wildlife Department, Austin, Texas, 82 pp. Dronen, N. O Herpetofauna inventory of Bastrop and Buescher State Parks. Interim report, Texas Parks and Wildlife Department, Austin, Texas, 6 pp. Ferguson, A. W. & M. R. J. Forstner A device for excluding predators from pitfall traps. Herpetol. Review 37(3):

12 112 THE TEXAS JOURNAL OF SCIENCE-VOL. 63, NO. 2, 2011 Ferguson, A. W., F. W. Weckerly, J. T. Baccus & M. R. J. Forstner Evaluation of predator attendance at pitfall traps in Texas. Southwest. Nat. 53(4): Gottschalk, J. S United States list of endangered native fish and wildlife. Federal Register 35, KES Consulting, Loomis Austin & M. R. J. Forstner Lost pines habitat conservation plan for Bastrop County, Texas. 147 pp. Available at Marcum, H. A The effects of human disturbance on birds in Bastrop State Park. Unpublished Ph.D. dissertation, Texas A&M Univ., College Station, 126 pp. Rebhorn, R. C Small mammal survey of Griffith League Ranch, Bastrop County, Texas. Unpublished M.S. thesis, Texas State Univ.-San Marcos, 51 pp. Schmutzer, A. C., M. J. Gray, E. C. Burton & D. L. Miller Impacts of cattle on amphibian larvae and the aquatic environment. Freshwater Biology 53(12): Taber, S. W Biogeographic characterization of a glacially relict pine forest in east central Texas as measured by invertebrate composition. Southwest. Entomol. 33(2): Taber, S. W. & S. B. Fleenor Insects of the Texas lost pines. Texas A&M Univ. Press, College Station, 296 pp. Texas Cooperative Wildlife Collection Herpetology: County records. Accessed 9 August Texas Parks and Wildlife Department Natural subregions (natsubpy) GIS data. Accessed 2 July U. S. Census Bureau Quickfacts: Bastrop County, Texas. Accessed 2 July White, C. J Avian habitat affinity in the lost pines region of Texas. Unpublished M.S. thesis, Texas State Univ.-San Marcos, 50 pp. DJB at: djb.ecology@gmail.com