Short-term response of herpetofauna to various burning regimes in the South Texas plains.
Beginning in the mid-20th century, landowners in South Texas began to convert thorn woodlands back to grasslands to enhance rangelands for livestock production. Mechanical treatments such as root plowing were commonly used methods for achieving this goal. Mechanical brush-manipulation practices can significantly reduce woody plant cover while increasing herbaceous vegetation (Scifres et al., 1976; Bozzo et al., 1992). However, upon recolonization by woody species, their diversity may be dramatically reduced (Fulbright and Beasom, 1987; Ruthven et al., 1993), which may negatively impact diversity of wildlife.
Land ownership and land-use practices in South Texas have changed in recent years. Size of individual landholdings has decreased and revenues derived from those properties have become increasingly dependent on wildlife rather than traditional livestock operations. Many wildlife-management programs are directed toward game species such as the white-tailed deer (Odocoileus virginianus) and northern bobwhite (Colinus virginianus). Prescribed burning in the Rio Grande plains of southern Texas can reduce brush cover while maintaining diversity of woody plants (Box and White, 1969; Ruthven et al., 2003), increase herbaceous vegetation for wildlife (Hansmire et al., 1988; Ruthven et al., 2000; Ruthven and Synatzske, 2002), increase bare ground, and decrease litter (Burrow, 2000; Ruthven et al., 2002x). As a result of these reported benefits, prescribed fire is recommended to enhance wildlife habitat on rangelands of South Texas (Guthery, 1986; Fulbright and Ortega-S., 2006).
Management and conservation of reptiles and amphibians generally has fallen behind other species (Scott and Seigel, 1992). Of particular concern, is the possible decline of amphibian populations (Blaustein and Wake, 1990; Pechmann and Wilbur, 1994), but recent observations suggest that reptile populations may be declining at a rate similar to amphibians (Gibbons et al., 2000). Although most herpetofauna appear to avoid direct impacts of fire (Means and Campbell, 1981; Floyd et al., 2002), there are concerns that hibernating reptiles in southern Texas, such as the Texas horned lizard (Phrynosoma cornutum), might suffer direct mortality from management activities, including prescribed fire (Fair and Henke, 1997). In xeric environments, reptiles that depend on open, early successional habitats can increase in abundance following fires (Mushinsky, 1985; Greenberg et al., 1994; Pianka, 1996).
Most investigations into effects of burning on herpetofauna are from Australia and forested environments of the eastern United States (Russell et al., 1999; Pilliod et al., 2003). In South Texas, dormant-season prescribed fire had a positive effect on the ecology of P. cornutum by increased rates of survival and greater abundance of prey (Burrow et al., 2002); yet, few data are available on effects of fire on other herpetofauna in the region. Objectives of this study were to investigate effects of various burning regimes on diversity and abundance of the herpetofauna, which would assist managment of wildlife resources on semiarid rangelands in the Tamaulipan Biotic Province.
MATERIALS AND METHODS--Study Area--The study area was on the Chaparral Wildlife Management Area (28[degrees]20'N, 99[degrees]25'W) in the western South Texas plains (Gould, 1975; Hatch et al., 1990) and northern portion of the Tamaulipan Biotic Province (Blair, 1950). Climate is characterized by hot summers and mild winters with an average daily minimum winter January) temperature of 5[degrees]C, an average daily maximum summer (July) temperature of 37[degrees]C, and a growing season of 249-365 days (Stevens and Arriaga, 1985). Average annual precipitation is 54 cm with peaks occurring in late spring (May June) and early autumn (September-October; Texas Parks and Wildlife Department, unpublished data).
Soils consist of Duval fine sandy loam, gently undulating, Duval loamy fine sand, 0-5% slopes, and Dilley fine sandy loam, gently undulating (Stevens and Arriaga, 1985; Gabriel et al., 1994). The Duval series are fine-loamy, mixed, hyperthermic Aridic Haplustalfs and the Dilley series are loamy, mixed, hyperthermic shallow Us talfic Haplargids. Topography is nearly level to gently sloping and elevation is 168-180 m.
Plant communities are characteristic of the mesquite-granjeno (Celtis pallida) association (McLendon, 1991). Within this association are two primary communities, the mesquite-colima (Zanthoxylum fagara)-granjeno community, in which colima and bluewood brasil (Condalia hookerz) are the subdominants, and the mesquite-granjeno/hog-plum (Colubrina texana) community, in which hogplum is the subdominant. Woody plant canopy cover and dominant species composition was similar among study plots prior to application of burning treatments (Gabor, 1997). Prominent herbaceous species include Lehmann lovegrass (Erogrostis lehmanniana), an introduced perennial, hooded windmill-grass (Chloris cucullata), hairy grama (Bouteloua hirsuta), partridge pea (Chamavcrista fasciculata), and croton (Croton).
The study area had been grazed by domestic livestock since the 18th century (Lehmann, 1969). Cattle were the major species of livestock since about 1870, whereas sheep were grazed from about 1750 to 1870. Before 1969, grazing by cattle was continuous (G. Light, pers. comm.). From 1969 to 1984, cattle (cow-calf) were grazed yearlong using a four-pasture rotation system. In response to persistent drought conditions, grazing was discontinued on the entire study site in 1984. Grazing resumed in 1990 using stocker-class animals (two steers [less than or equal to] 227 kg = one animal unit) under a high-intensity, low-frequency, grazing system in which cattle, in two separate herds, rotated once through six pastures on each one-half of the area 1 October through 30 April. Stocking rates were considered low and averaged 15 animal-unit days (AUD) x [ha.sup.-1] x [year.sup.-1]. Beginning in autumn 1997, cattle were combined into one herd and rotated through the 12 pastures making up the core of the study area under light-to-moderate (15-25 AUD x [ha.sup.-1] x [year.sup.-1)] stocking rates.
Dormant-Season Burn--Three sites subjected to prescribed burns were paired with three untreated sites using a randomized-block design. Burned plots were located within larger areas (>40 ha) that had been burned. Rangeland fire in southern Texas typically produces a mosaic of burned and nonburned areas as a result of uneven fuel loads (Box and White, 1969). All burned plots received 100% coverage by burns. Study sites were burned during winter (December-February) 1997-1998 and again in winter 1999-2000. Study plots were ca. 2 ha in size. Burning conditions were similar among study plots and years (Ruthven et al., 2000, 2002 a). Study plots and surrounding rangeland had no previous history of prescribed burning or wildfires, for [greater than or equal to] 40 years.
We captured herpetofauna in drift fence-pitfall arrays as described by Ruthven et al. (2002b). Three arrays were installed on each study plot. Arrays were <100 m apart and from the edge of study plots. As spring and summer are peak activity periods for most herpetofauna on the study area (Ruthven et al., 2002b), each array was monitored for 13 days in spring (May-June) 1998, 7 days in summer (August) 1998, 14 days in spring 1999, and 21 days in spring 2000. Arrays were checked twice daily. Captured animals were identified to species, sex was determined when possible, and snout vent and total lengths recorded. Lizards and amphibians were marked by toe clipping. Because of low rates of encounters, snakes were identified as recaptures by comparing snout-vent length. Species diversity was estimated with Shannon's index (Pielou, 1975). Scientific nomenclature and common names of reptiles and amphibians follow Dixon (2000).
Growing-Season Burns--Five sites subjected to prescribed burns were paired with five nontreated sites using a randomized-block design. Study plots were ca. 2 ha in size. Burned plots were located within larger areas (>40 ha) that had been burned. All study sites received 100% coverage by burns. Fire was applied to study plots and surrounding rangeland in August 1999 and burning conditions were similar among plots (Ruthven and Synatzske, 2002). Study plots and surrounding rangeland had been subjected to prescribed burning during winter (January-March 1997) under conditions similar to dormant season, burned plots.
One drift fence-pitfall array was established in the center of each study plot and monitored for 14 days each during Spring 2000 and 2001 and Summer (July-September) 2000 and 2001. Data-collection methods followed those in the dormant-season plots.
Data Analyses--We analyzed burn data for summer using a two-way analysis of variance (ANOVA) with repeated measures (PROC GLM; SAS Institute, Inc., 1999). Treatment (burned or nonburned) was a between-subjects factor and year was a within-subjects factor. We also tested for a treatment-by-year interaction effect to indicate a possible differential response to time since burning. Response variables tested were the number of captures by species and taxonomic group, and computed diversity indices for each plot.
We analyzed burn data for winter similarly, except we used average captures/day as response variables because sampling effort was not equal among all study plots. Standard errors and P-values are reported to facilitate interpretation of practical significance (Gould and Steiner, 2002). All statistical comparisons were considered significant at P [less than or equal to] 0.05 with trends towards significance at P [less than or equal to] 0.1.
We realize the implications of pseudoreplication (Hurlbert, 1984); however, Wester (1992) suggested that pseudoreplication is a matter of scale and that statistical analyses of single-treatment studies in which samples are taken within a relatively small area can be useful in assessing impacts of treatments. Although conclusions of these analyses were limited to the study site and may not be extrapolated to other populations, they may be helpful in explaining potential effects of temporal factors on results of this study.
RESULTS--Dormant-Season Burns--We captured 1,861 individuals representing 23 species during trapping sessions in 1998, 1999, and 2000 (Table 1). Great Plains narrowmouth toad (Gastrophryne olivacea) and Texas spotted whiptail (Cnemidophous gularis) were the dominant species encountered making up 61 and 10% of total captures, respectively. Diversity did not exhibit (P > 0.3) a year or treatment-by-year interaction and was similar (P = 0.824) among burned (1.18 [+ or -] 0.08; mean [+ or -] SE) and nonburned (1.26 [+ or -] 0.09) plots. Cnemidophorus gularis (P = 0.092) and total number of lizards (P = 0.084) tended to be greater on nonburned plots (Table 1). Total captures of amphibians (P = 0.022) and lizards (P = 0.005), as well as abundance of Texas toads (Bufo speciosus; P = 0.001) was greatest in 1999 (Table 1). Total captures also tended (P = 0.083) to be greatest in 1999. The Great Plains skink (Eumeces obsoletos) was most abundant (P < 0.001) in 1998, whereas total captures of snakes (P = 0.027) was greatest in 2000. The six-lined racerunner (Cnemidophorus sexlineatus) exhibited a slight (P = 0.094) treatment-by-year interaction with greatest abundance on burned plots in 1998 (Table 1).
Growing-Season Burns--We encountered a total of 495 individuals representing 18 species during trapping sessions in 2000 and 2001 (Table 2). Cnemidophorus gularis and G. olivacea were the dominant species encountered making up 42 and 21% of total captures, respectively. Diversity did not show (P > 0.5) a year or treatment-by-year interaction, but generally was greater, although non-significant (P = 0.115), on burned (1.55 [+ or -] 0.06; mean [+ or -] SE) than nonburned (1.28 [+ or -] 0.01) plots. Abundance of lizards (P= 0.058), total captures of herpetofauna (P = 0.081) and flathead snakes (Tantilla gracilis; P = 0.065) tended to be greatest on burned plots (Table 2). Abundance of C. sexlineatus was greater, though non-significant (P = 0.123), on burned plots compared to unburned plots. Total captures (P = 0.040), total encounters of amphibians (P = 0.016), and abundance of G. olivacea was greatest in 2000 (Table 2). Snakes were encountered most commonly in 2001 (P = 0.007).
DISCUSSION--Prescribed-burning regimes incorporating both dormant-season and growing-season fire appeared to have little short-term effect on diversity of the herpetofauna and were consistent with other investigations (Keyser et al., 2004; Wilgers and Horne, 2006). Overall, abundance of lizards, snakes, and amphibians appeared unaffected by dormant-season fires. Cnemidophorus gularis showed slight decreases in abundance in response to winter burns, whereas C. sexlineatus demonstrated a positive response during the first year post burn in 1998. In contrast, inclusion of summer fires had little effect on C. gulafis, yet encounters of C. sexlineatus were 10-times greater on burned sites compared to unburned areas. The positive response of C. sexlineatus to fire is similar to previous studies (Mushinsky, 1985; Greenberg et al., 1994). Cnemidophorus sexlineatus typically inhabits open, xeric habitats (Carpenter, 1959; Greenberg et al., 1994) and increases following fire are likely the result of increases in bare ground and reductions of woody plant cover, which occur following fire (Ruthven et al., 2002 a, 2003). Little is known of the habitat preferences of C. gulafis, however, it is a common denizen of South Texas shrublands. Prior to initiation of prescribed burning, C. sexlineatus rarely was encountered on the study area (Texas Parks and Wildlife Department, unpublished data). Fire suppression has been a driving factor in the conversion of grasslands and savannas in South Texas to thorn woodlands (Archer et al., 1988; Archer, 1994) and historically C. sexlineatus may have been the dominant teiid in this ecosystem.
In the tallgrass prairie of Kansas, prescribed fire can increase abundance of P. cornutum and E. obsoletos through changes in vegetational structure and increases in bare ground, which facilitate thermoregulatory activities (Wilgers and Home, 2006). On our study area, previous studies have demonstrated that P. cornutum positively responds to prescribed fire by reductions in size of home range (Burrow et al., 2002). The lack of a treatment effect by P. cornutum, and possibly other species, in the present study may be a result of sampling methods. Reductions in size of home range may decrease vulnerability of certain species to be captured in drift fencepitfall arrays.
Sampling methods limited most captures of snakes to diminutive species. However, rates of capture were relatively low making inferences about treatment effects difficult. Even so, four species (Arizona elegans, Masticophis flagellum, Thamnophis marcianos, Salvadora grahamiae) were encountered only on burned sites, whereas no species of snake was encountered solely on unburned plots.
Effects of prescribed fire on amphibians are highly variable (Pilliod et al., 2003). The lack of a treatment effect in this study was similar to that reported in semi-arid rangelands in Australia, where the fossorial nature of most amphibians appears to provide a degree of resilience to fire (Friend, 1993). Gastrophryne olivacea and B. speciosus are active borrowers and readily use burrows of other vertebrates and invertebrates as refugia. Friend (1993) also suggested that abundance of amphibians was more closely related to moisture than fire regimes. This may explain yearly variation in abundance that we observed that was associated with greater precipitation prior to and during sampling sessions in 1999 and 2000. Effects of fire on sedimentation of breeding ponds is also of concern (Pilliod et al., 2003); however, it is unclear how this process might affect the ephemeral ponds on which G. olivacea and B. speciosus depend for their reproductive cycle.
Most ecological investigations into the effects of habitat-altering practices are short-term, and as with this study, may not be of sufficient duration to accurately assess the full impacts of range-management practices such as prescribed fire. Long-term investigations into the response of lizards in Australia suggest most species exhibit an ebb and flow pattern following wildfire, which produces a mosaic of large burned landscapes with islands of unburned vegetation (Pianka, 1996). Species that predominate in early successional seres tend to increase following fire, whereas species that depend on later sera] stages or climax vegetation decrease following fire. However, species that rely on later sera] stages or climax vegetation persist on burned landscapes through retention of unburned areas and may later increase as succession progresses on burned areas. Prescribed fires on rangelands in South Texas typically produce a mosaic affect on the landscape (Box and White, 1969). Although study plots received 100% coverage by prescribed burns, adjacent burned areas produced a typical mosaic of burned and nonburned areas, which may have impacted our results. Braithwaite (1987) found that intensity of fire influenced post-fire selection of habitats by lizards and that a varied fire regime may increase overall diversity of lizards. The landscape of South Texas lends itself to varying degrees of fire intensity within a single burn. The herbaceous-dominated interspace between clusters of shrubs can produce low-intensity fires, while stands of volatile shrubs such as whitebrush (Aloysia gratissima) can produce high-intensity burns.
In the short-term, burning rangelands in South Texas during winter appears to have little affect on the herpetofauna, whereas fire in summer provided slight increases in diversity and an increase in abundance of grassland species. Our data suggested that land managers can use fire as a management tool without deleterious effects on herpetofaunal communities. We concur with the findings of Braithwaite (1987), that a mosaic of burning regimes may promote overall faunal diversity. Research investigating affects of land-use practices, such as prescribed fire, on herpetofauna lag behind other vertebrates (Friend, 1993; Russell et al., 1999; Pilliod et al., 2003). To fully understand impacts of prescribed fire on the herpetofauna of rangelands in South Texas, long-term research and monitoring of a wide variety of burning regimes with broader sampling methods to increase sample sizes and species encountered is warranted.
We thank J. Franco for the translation of the Spanish resumen.
Submitted 20 August 2007. Accepted 1 May 2008. Associate Editor was William I. Lutterschmidt.
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DONALD C. RUTHVEN, III, * RICHARD T. KAZMAIER, AND MICHAEL W. JANIS
Chaparral Wildlife Management Area, Texas Parks and Wildlife Department, P.O. Box 115, Artesia Wells, TX 78001 (DCR)
Department of Life, Earth, and Environmental Sciences, West Texas A&M University, Box 60808, Canyon, TX 79016 (RTK)
Matador Wildlife Management Area, Texas Parks and Wildlife Department, 3036 FM 3256, Paducah, TX 79248 (MWJ)
Present address of DCR: Matador Wildlife Management Area, Texas Parks and Wildlife Department, 3036 FM 3256, Paducah, TX 79248
* Correspondent: firstname.lastname@example.org
TABLE 1--Mean ([+ or -] SE) captures per array day of herpetofauna on dormant season burned (n = 3) and unburned sites (n = 3) on the Chaparral Wildlife Management Area, Dimmit and LaSalle counties, Texas, 1998-2000. Different letters within rows indicate differences (P < 0.05) among years. 1998 Herpetofauna Burned Unburned Amphibians Bufo debilis 0 0.02 (0.02) Bufo speciosus 0.29 (a1) (0.13) 0.32 (a) (0.11) Bufo valliceps 0 0 Gastrophryne olivacea 5.11 (2.62) 2.95 (1.06) Rana belandieri 0.02 (0.02) 0 Scophiopus couchii 0.05 (0.05) 0 Total 5.46 (a) (2.45) 3.29 (a) (0.93) Lizards Cnemidophorus gularis 0.60 (a) (0.08) 0.56 (a) (0.08) Cnemidophorus sexlineatus 0.06 (0.04) 0 Coleonyx brevis 0 0 Eumeces obsoletus 0.17 (a) (0.02) 0.17 (a) (0.04) Phrynosoma cornutum 0.16 (0.06) 0.25 (0.07) Sceloporus olivaceus 0.02 (0.02) 0.02 (0.02) Sceloporus undulatus 0.08 (ab) (0.02) 0.16 (ab) (0.11) Total 1.10 (a) (0.10) 1.16 (a) (0.21) Snakes Arizona elegans 0.06 (0.03) 0 Heterodon nasicus 0.02 (0.02) 0.02 (0.02) Hypsiglena torquata 0 0.02 (0.02) Leptotyphlops dulcis 0.02 (0.02) 0.06 (0.06) Masticophis flagellum 0.02 (0.02) 0 Rhinocheilus lecontei 0.03 (0.02) 0.03 (0.02) Sonora semiannulata 0.03 (0.02) 0 Tantilla gracilis 0.02 (0.02) 0 Tantilla nigriceps 0 0 Thamnophis marcianus 0.02 (0.02) 0 Total 0.21 (a) (0.02) 0.13 (a) (0.08) Total herpetofauna 6.76 (2.46) 4.57 (0.79) 1999 Herpetofauna Burned Unburned Amphibians Bufo debilis 0.33 (0.33) 0 Bufo speciosus 2.31 (b) (0.98) 2.48 (b) (0.23) Bufo valliceps 0.02 (0.02) 0 Gastrophryne olivacea 3.26 (1.65) 3.98 (1.19) Rana belandieri 0 0 Scophiopus couchii 0 0 Total 5.93 (b) (1.22) 6.45 (b) (0.99) Lizards Cnemidophorus gularis 0.17 (b) (0.05) 0.43 (b) (0.11) Cnemidophorus sexlineatus 0.02 (0.02) 0 Coleonyx brevis 0.02 (0.02) 0 Eumeces obsoletus 0.02 (b) (0.02) 0.07 (b) (0.04) Phrynosoma cornutum 0.12 (0.02) 0.14 (0.14) Sceloporus olivaceus 0 0.02 (0.02) Sceloporus undulatus 0.02 (a) (0.02) 0.l0 (a) (0.02) Total 0.38 (b) (0.06) 0.76 (b) (0.02) Snakes Arizona elegans 0 0 Heterodon nasicus 0 0 Hypsiglena torquata 0.02 (0.02) 0.05 (0.02) Leptotyphlops dulcis 0 0.02 (0.02) Masticophis flagellum 0 0 Rhinocheilus lecontei 0.05 (0.02) 0 Sonora semiannulata 0 0.02 (0.02) Tantilla gracilis 0 0.02 (0.02) Tantilla nigriceps 0 0.02 (0.02) Thamnophis marcianus 0 0 Total 0.07 (ab) (0.04) 0.14 (ab) (0.04) Total herpetofauna 6.38 (1.12) 7.36 (0.97) 2000 Herpetofauna Burned Unburned Amphibians Bufo debilis 0 0 Bufo speciosus 0.29 (a) (0.02) 0.14 (a) (0.07) Bufo valliceps 0 0 Gastrophryne olivacea 3.28 (1.74) 2.30 (1.16) Rana belandieri 0 0 Scophiopus couchii 0.05 (0.05) 0 Total 3.62 (a) (1.74) 2.43 (a) (1.09) Lizards Cnemidophorus gularis 0.52 (a) (0.12) 0.79 (a) (0.1) Cnemidophorus sexlineatus 0.03 (0.03) 0.02 (0.02) Coleonyx brevis 0 0 Eumeces obsoletus 0.05 (b) (0.03) 0.09 (b) (0.03) Phrynosoma cornutum 0.06 (0.04) 0.12 (0.04) Sceloporus olivaceus 0.05 (0.03) 0.02 (0.02) Sceloporus undulatus 0.205 (0.03) 0.36 (b) (0.10) Total 0.91 (a) (0.18) 1.39 (a) (0.19) Snakes Arizona elegans 0 0 Heterodon nasicus 0 0 Hypsiglena torquata 0.03 (0.02) 0.02 (0.02) Leptotyphlops dulcis 0.14 (0.07) 0.14 (0.09) Masticophis flagellum 0 0 Rhinocheilus lecontei 0 0.02 (0.02) Sonora semiannulata 0.08 (0.05) 0.05 (0.03) Tantilla gracilis 0 0.02 (0.02) Tantilla nigriceps 0.03 (0.02) 0 Thamnophis marcianus 0 0 Total 0.28 (c) (0.05) 0.23 (c) (0.05) Total herpetofauna 4.81 (1.78) 4.05 (1.28) P-values Herpetofauna Treatment Year Amphibians Bufo debilis 0.395 0.426 Bufo speciosus 0.973 <0.001 Bufo valliceps 0.374 0.410 Gastrophryne olivacea 0.733 0.233 Rana belandieri 0.374 0.410 Scophiopus couchii 0.116 0.683 Total 0.638 0.022 Lizards Cnemidophorus gularis 0.092 0.013 Cnemidophorus sexlineatus 0.350 0.214 Coleonyx brevis 0.374 0.410 Eumeces obsoletus 0.472 <0.001 Phrynosoma cornutum 0.350 0.373 Sceloporus olivaceus 0.909 0.496 Sceloporus undulatus 0.102 0.029 Total 0.084 0.005 Snakes Arizona elegans 0.116 0.063 Heterodon nasicus 1.000 0.198 Hypsiglena torquata 0.562 0.361 Leptotyphlops dulcis 0.706 0.081 Masticophis flagellum 0.374 0.410 Rhinocheilus lecontei 0.411 0.331 Sonora semiannulata 0.593 0.215 Tantilla gracilis 0.417 0.952 Tantilla nigriceps 0.829 0.423 Thamnophis marcianus 0.374 0.410 Total 0.746 0.027 Total herpetofauna 0.740 0.083 P-values Herpetofauna Interaction Amphibians Bufo debilis 0.394 Bufo speciosus 0.914 Bufo valliceps 0.410 Gastrophryne olivacea 0.163 Rana belandieri 0.410 Scophiopus couchii 0.683 Total 0.355 Lizards Cnemidophorus gularis 0.233 Cnemidophorus sexlineatus 0.094 Coleonyx brevis 0.410 Eumeces obsoletus 0.290 Phrynosoma cornutum 0.899 Sceloporus olivaceus 0.305 Sceloporus undulatus 0.784 Total 0.331 Snakes Arizona elegans 0.063 Heterodon nasicus 1.000 Hypsiglena torquata 0.567 Leptotyphlops dulcis 0.877 Masticophis flagellum 0.410 Rhinocheilus lecontei 0.156 Sonora semiannulata 0.568 Tantilla gracilis 0.394 Tantilla nigriceps 0.122 Thamnophis marcianus 0.410 Total 0.242 Total herpetofauna 0.288 TABLE 2--Mean ([+ or -] SE) captures per array day of herpetofauna on growing-season burned (n = 5) and unburned sites (n = 5) on the Chaparral Wildlife Management Area, Dimmit and LaSalle counties, Texas, 2000-2001. 2000 Herpetofauna Burned Unburned Amphibians Bufo speciosus 1.8 (0.97) 0.6 (0.40) Gastrophryne olivacea 5.2 (0.92) 8.4 (1.36) Total 7.0 (1.61) 9.0 (1.58) Lizards Cnemidophorus gularis 10.6 (1.54) 10.8 (2.35) Cnemidophorus sexlineatus 4.8 (2.96) 0.4 (0.25) Eumeces obsoletus 0.2 (0.20) 1.0 (0.45) Eumeces tetragrammus 0 0.2 (0.20) Phrynosoma cornutum 0.6 (0.40) 0 Sceloporus olivaceus 0 0.4 (0.40) Sceloporus undulatus 3.6 (0.40) 2.0 (0.77) Total 19.8 (1.62) 14.8 (2.71) Snakes Heterodon nasicus 0 0 Hypsiglena torquata 0 0 Leptotyphlops dulcis 0.2 (0.20) 0.6 (0.25) Rhinocheilus lecontei 0.2 (0.20) 0 Salvadora grahamiae 0.4 (0.25) 0 Sonora semiannulata 1.4 (0.68) 0.4 (0.25) Tantilla gracilis 0.2 (0.20) 0 Tantilla nigriceps 0 0 Total 2.4 (0.87) 1.0 (0.45) Total herpetofauna 29.2 (0.97) 24.8 (1.66) 2001 Herpetofauna Burned Unburned Amphibians Bufo speciosus 0 0.2 (0.20) Gastrophryne olivacea 2.8 (0.73) 4.2 (1.83) Total 2.8 (0.73) 4.4 (1.73) Lizards Cnemidophorus gularis 9.6 (2.06) 10.4 (1.25) Cnemidophorus sexlineatus 4.6 (2.50) 0.2 (0.20) Eumeces obsoletus 1.0 (0.32) 0.4 (0.25) Eumeces tetragrammus 0 0 Phrynosoma cornutum 0.4 (0.25) 0.4 (0.25) Sceloporus olivaceus 0.2 (0.20) 0.4 (0.40) Sceloporus undulatus 2.4 (0.93) 1.8 (0.49) Total 18.2 (1.32) 13.6 (1.81) Snakes Heterodon nasicus 0.6 (0.40) 0 Hypsiglena torquata 0.2 (0.20) 0 Leptotyphlops dulcis 0.8 (0.37) 0.8 (0.58) Rhinocheilus lecontei 0.2 (0.20) 0.2 (0.20) Salvadora grahamiae 0 0 Sonora semiannulata 1.0 (0.32) 0.6 (0.25) Tantilla gracilis 0.8 (0.37) 0.2 (0.20) Tantilla nigriceps 0 0.2 (0.20) Total 4.0 (0.63) 2.2 (0.97) Total herpetofauna 24.8 (1.53) 20.2 (3.29) P-values Herpetofauna Treatment Year Amphibians Bufo speciosus 0.364 0.080 Gastrophryne olivacea 0.131 0.025 Total 0.267 0.016 Lizards Cnemidophorus gularis 0.833 0.591 Cnemidophorus sexlineatus 0.123 0.850 Eumeces obsoletus 0.785 0.725 Eumeces tetragrammus 0.347 0.347 Phrynosoma cornutum 0.273 0.725 Sceloporus olivaceus 0.290 0.771 Sceloporus undulatus 0.124 0.360 Total 0.058 0.425 Snakes Heterodon nasicus 0.172 0.172 Hypsiglena torquata 0.347 0.347 Leptotyphlops dulcis 0.636 0.291 Rhinocheilus lecontei 0.545 0.608 Salvadora grahamiae 0.141 0.141 Sonora semiannulata 0.211 0.725 Tantilla gracilis 0.065 0.182 Tantilla nigriceps 0.347 0.347 Total 0.148 0.007 Total herpetofauna 0.081 0.040 P-values Herpetofauna Interaction Amphibians Bufo speciosus 0.237 Gastrophryne olivacea 0.473 Total 0.893 Lizards Cnemidophorus gularis 0.817 Cnemidophorus sexlineatus 1.000 Eumeces obsoletus 0.034 Eumeces tetragrammus 0.347 Phrynosoma cornutum 0.305 Sceloporus olivaceus 0.771 Sceloporus undulatus 0.508 Total 0.907 Snakes Heterodon nasicus 0.172 Hypsiglena torquata 0.347 Leptotyphlops dulcis 0.587 Rhinocheilus lecontei 0.608 Salvadora grahamiae 0.141 Sonora semiannulata 0.305 Tantilla gracilis 0.486 Tantilla nigriceps 0.347 Total 0.620 Total herpetofauna 0.958
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|Author:||Ruthven, Donald C., III; Kazmaier, Richard T.; Janis, Michael W.|
|Date:||Dec 1, 2008|
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