Contract Research Findings: Reptiles
| Title: | Texas tortoise (Gopherus berlandieri) consumed by a mountain lion (Puma concolor) in southern Texas |
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| Journal/Year: | The Southwestern Naturalist/2006 |
| View: | Download Adams_etal_2006_TortoiseMountainLion.pdf |
| Author(s): | R. Bill Adams|James C. Pitman|Louis A. Harveson |
| Abstract: | Mountain lions (Puma concolor), throughout their distribution, eat a variety of prey, but primarily consume large prey (e.g., cervids). While monitoring radio-collared mountain lions, we saw a mountain lion kitten consuming a Texas tortoise (Gopherus berlandieri). Small prey might increase survival of young mountain lions developing predation skills required for solitary survival as adults. |
| Management Implications: | Texas tortoises are listed as threatened by the State of Texas, but Hellgren et al. (2000) reported a density of 0.26 tortoises/ha in southern Texas. Hellgren et al. (2000) suggested that the Texas tortoise population could withstand predation by coyotes (Canis latrans), raccoons (Procyon lotor), crested caracaras (Polyborus plancus), and other predators. Logan and Sweaner (2001:305-306) reported turtle remains in 1 of 832 scats examined in southern New Mexico. Additionally, Harveson et al. (2000) found no tortoise remains from 25 mountain lion scats, so there is no indication that mountain lions negatively impact the tortoise population in southern Texas. Small prey items, such as the Texas tortoise, are relatively abundant and might increase survival of juvenile mountain lions still developing predation skills required for solitary survival as an adult. |
| Citation: | Adams, R. B., J. Pitman, and L. A. Harveson. 2006. Texas tortoise (Gopherus berlandieri) consumed by a mountain lion (Puma concolor) in southern Texas. The Southwestern Naturalist 51:586-587. |
| Title: | Geographic distribution. Graptemys pseudogeographica kohni |
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| Journal/Year: | Herpetological Review/2008 |
| View: | Visit Society For the Study of Amphibians and Reptiles Herpetological Review 1967–2015: Complete Editions (Open Access) |
| Author(s): | Donald J. Brown | James R. Dixon | Michael R. J. Forstner |
| Citation: | Brown, D. J., J. R. Dixon, and M. R. J. Forstner. 2008. Geographic distribution. Graptemys pseudogeographica kohni. Herpetological Review 39:481. |
| Title: | Short-term response of herpetofauna to various burning regimes in the South Texas plains |
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| Journal/Year: | The Southwestern Naturalist/2008 |
| View: | Download Ruthven_etal_2008_BurningRegimes.pdf |
| Author(s): | Donald C. Ruthven, III | Richard T. Kazmaier | Michael W. Janis |
| Abstract: | Data on effects of fire on herpetofauna generally are lacking. With increased use of prescribed fire to manage rangelands in South Texas for wildlife and livestock, a better understanding of effects of fire on the herpetofauna is needed. We investigated effects of combinations of winter and summer prescribed fire on rangeland sites on the Chaparral Wildlife Management Area in southern Texas. Dormant-season fires had little effect on diversity and abundance of the herpetofauna. Inclusion of growing-season fire into the burning regime tended to increase diversity and abundance of grassland species, such as the six-lined racerunner (Cnemidophorus sexlineatus). Although our experimental design limits interpretation of results to the study site, our data suggest that prescribed fire may be used to manage rangelands in South Texas without negative effects on the herpetofauna. A varied burning regime is recommended to increase herpetofaunal diversity. |
| Management Implications: | In the short-term, burning rangelands in South Texas during winter appears to have little effect 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 effects 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. |
| Citation: | Ruthven, D. C., III, R. T. Kazmaier, and M. W. Janis. 2008. Short-term response of herpetofauna to various burning regimes in the South Texas plains. The Southwestern Naturalist 53:480-487. |
| Title: | Distribution and status of the Brazos water snake (Nerodia harteri harteri) |
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| Journal/Year: | Thesis/2009 |
| View: | Download McBride_2009_WaterSnake.pdf |
| Author(s): | Dustin Lee McBride |
| Abstract: | Nerodia h. harteri (Brazos Water Snake) is a state threatened endemic Texas snake found along the upper Brazos River drainage in north-central Texas. A range-wide survey was conducted from 2006-2008 to determine the current distribution and relative abundance of N. h. harteri, identify potential habitat, and investigate habitat relationships of the snake. While the range of N. h. harteri and suitable habitat remain intact, the snake is now rare. Logistic regression analysis indicated the likelihood of finding the snake was positively related to both the amount of rock (>10 cm) at a site and surrounding a site. Reasons for the population decline remain unclear; however, results illustrate the importance of riffle habitat for the future conservation of this Texas snake. |
| Management Implications: | This study investigated the current status and distribution of N. h. harteri throughout its range and modeled the relationship between the abundance of rocky habitat and the likelihood of finding the snake. Results suggest that N. h. harteri is now a rare snake and the presence of riffle habitat is crucial for its continued persistence. Education and public awareness will be key in mitigating direct human impacts on N. h. harteri populations and habitat. In light of ever increasing human densities and demands for water and the climatic uncertainties of global climate change, the assurance of adequate instream flows and maintenance of the river channel will be critical for the conservation of this Texas endemic snake. Given the rate at which this snake has declined, future conservation efforts need to be implemented in a timely manner, and consideration of a captive breeding program and potential reintroductions may be warranted. Future research should focus on assessment of local population dynamics, as well as the feasibility of reintroduction efforts. Other research should include an accurate survey of Lake Granbury, an assessment of the flow regime necessary for maintenance of riffle habitat, and the prevalence of fish kills caused by the microalga P. parvum within the upper Brazos River drainage and the response of forage fish populations. Finally, if construction of Cedar Ridge Reservoir is approved, there will be a unique opportunity to investigate the response of N. h. harteri to a major impoundment project. |
| Citation: | McBride, D. L. 2009. Distribution and status of the Brazos water snake (Nerodia harteri harteri). Thesis, Tarleton State University, Stephenville, TX, USA. |
| Title: | Effects of summer and winter burning on vegetation and wildlife in a sand sagebrush/honey mesquite savanna |
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| Journal/Year: | Thesis/2009 |
| View: | Download Poole_etal_2009_BurningVegetation.pdf |
| Author(s): | Matthew W. Poole |
| Abstract: | There is substantial information on the generalized effects of fire in some grassland ecosystems. However, studies addressing seasonality of fire are less common. The Rolling Plains have high climatic variability with periodic droughts; however, little information is available on the potential role of burning in these communities under these conditions. Therefore, I initiated a project to explore the effects of seasonality of fire on a sand prairie ecosystem. We established 5 blocks of 3 18-ha plots at Matador Wildlife Management Area (WMA) in Cottle County, Texas. Each plot, within a block, was randomly assigned to a summer burn (August), winter burn (February), or a control (no fire) treatment. Herbaceous vegetation cover and frequency were measured twice annually (May-June and August-September) using 0.1 m² quadrats, while woody cover was measured during late summer using the line-intercept method. Invertebrates, herpetofauna, and small mammals were sampled utilizing drift fence arrays during the spring and summer. Invertebrates were also sampled in late summer using sweep nets and small mammals were also sampled twice annually using Sherman live traps. Summer burning appeared to benefit forbs, species richness, evenness and diversity. In general, forbs were not affected by winter burning, but forbs were similar to grasses, in that individual species' responses to winter burning were variable. My results indicated that prescribed summer burning appears to be effective at reducing, but not eliminating sand sagebrush, honey mesquite, prickly pear, yucca, and total woody canopy cover. Summer burning was the most effective treatment at reducing honey mesquite and sand sagebrush, which may have promoted the observed increases in herbaceous vegetation by making resources, such as light and water, available to grasses and forbs. However, many of the wildlife species examined did not respond to the application of summer and winter burning, but responded to onset of drought conditions. Therefore, a combination of both summer and winter burning treatments are recommended for suppressing woody plant cover and increasing overall plant diversity by promoting desirable herbaceous species for a wide variety of wildlife and livestock. Longer term research on the effects of summer and winter burning on herbaceous and woody vegetation, especially in drought years, is needed to fully evaluate the effects of burning in the Rolling Plains of Texas. |
| Citation: | Poole, M. W. 2009. Effects of summer and winter burning on vegetation and wildlife in a sand sagebrush/honey mesquite savanna. Thesis, West Texas A&M University, Canyon, USA. |
| Title: | Geographic distribution. Hidalgo County. Chelydra serpentina serpentina |
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| Journal/Year: | Herpetological Review/2009 |
| View: | Visit Society For the Study of Amphibians and Reptiles Herpetological Review 1967–2015: Complete Editions (Open Access) |
| Author(s): | Brian E. Dickerson | Amanda D. Schultz | Donald J. Brown | Bei DeVolld | Michael R. J. Forstner | James R. Dixon |
| Citation: | Dickerson, B. E., A. D. Schultz, D. J. Brown, B. DeVolld, M.R.J. Forstner, and J.R. Dixon. 2009. Geographic Distribution (Hidalgo County). Chelydra serpentina serpentina. Herpetological Review 40:448. |
| Title: | Impact of reduced flooding on herpetofauna in a TPWD bottomland |
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| Journal/Year: | TPWD Final Report/2009 |
| View: | Download Ford_etal_2009_Flooding.pdf |
| Author(s): | Neil B. Ford | Shaun Crook | Stephen Lange |
| Abstract: | Floodplain forests are among the most threatened habitats in North America. We used the species richness, ranked abundance, and diversity of amphibians and reptiles to assess the effects of flood suppression at the Old Sabine Bottom Wildlife Management Area (OSBWMA) in Smith County, Texas, USA. Amphibians and reptiles were surveyed using visual surveys, cover boards, and with minnow traps at ephemeral pools: in undisturbed bottomland forest, in maintained openings, and a bottomland hardwood regeneration site (Baker Tract). We observed a total of 3343 amphibians and reptiles representing 45 species in 2007 through 2009 (sample period two) whereas 2280 records of 42 species were made in 1998 and 1999 (sample period one). Species diversity indices and rarefaction adjusted richness were not different between years of sample period one (1998-1999) and years of sample period two (2007-2009) but community comparison indices indicated that changes occurred for some species. The ranked abundance of each species was compared to their ranking in the datasets of each sample period. The number of southern leopard frogs increased and the number of small-mouthed salamanders decreased during sample period one. Turtles and lizards did not vary much between sampling periods. Terrestrial snake species such as king snakes and earth snakes became more abundant in the later period. We used GIS to assess how collections of amphibians and reptiles differed in a year with reduced (less winter) flooding to one with a more normal (winter) flood pattern. Overall, the presence of amphibians varied according to the flooding patterns and these animals were restricted to more permanent water if the floods were reduced. The change in the herpetofaunal communities suggests that changes in flooding have a measurable effect on the surveyed makeup of amphibians and reptiles in this floodplain. One caveat, however, is that during the same period, hog activity increased dramatically and may have had impacts on the same fauna in ways that cannot be interpreted with this data. |
| Management Implications: | An increase in the impact of feral hogs on the OSBWMA was evident from the first study in 1998 and 1999 to the current research. Some of this may just be the result of an increased population of feral hogs on the WMA. In addition, hunters have increased success during flooding, as the hogs are restricted to higher ground during that time. However, it also appeared that during reduced flooding years, hogs were concentrating foraging around ephemeral pools and the edges of creeks and streams due to dryer conditions. This may be a result of the reduced flooding in that the interior sites were dryer than in the years with flooding. Turning the vegetation around pools where the ground is softer appeared to be a foraging strategy that hogs were employing in this area. Therefore the impact of the hogs on amphibians and other animals living near ephemeral pools was acerbated by the reduction in flood regimes. Wood duck predation in bottomland hardwood is reduced during floods. Predators such as Texas rat snakes appear to have difficulty locating nests when a floodplain is inundated by water (Carfagno and Weatherhead, 2009, Roy Neilsen and Gates, 2007). Since duck reproduction is often in the spring when the flooding is normally occurring, a reduction in flooding periodicity or duration could have an impact on the ability of wood duck populations to recruit young of the year. Monitoring wood duck boxes in years with normal flood patterns and those of reduced frequency would be an important project for this WMA. It is also likely that predation on other cavity nesting species, like Eastern Grey Squirrels, might be impacted by reduced flooding and should be monitored also. |
| Citation: | Ford, N. B., S. Crook, and S. Lange. 2009. Impact of reduced flooding on herpetofauna in a TPWD bottomland. Texas Parks and Wildlife Department Final Report, Austin, USA. |
| Title: | American alligator (Alligator mississippiensis) ecology in inland wetlands of east Texas |
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| Journal/Year: | Dissertation/2010 |
| View: | Download Saalfeld_2010_AlligatorGrowthRates.pdf |
| Author(s): | David Thomas Saalfeld |
| Citation: | Saalfeld, D. T. 2010. American alligator (Alligator mississippiensis) ecology in inland wetlands of east Texas. Dissertation, Stephen F. Austin State University, Nacogdoches, TX, USA. |
| Title: | Demography and habitat selection of the alligator snapping turtle, Macrochelys temminckii, in the Middle Trinity River ecosystem |
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| Journal/Year: | TPWD Final Report/2010 |
| View: | Download Kazmaier_etal_2010_AlligatorSnappingTurtle.pdf |
| Author(s): | Richard T. Kazmaier | J. Daren Riedle | Jeffrey Gunnels |
| Abstract: | Because of apparently declining populations throughout its range, there is considerable conservation concern for alligator snapping turtles. Despite their status as the largest freshwater turtle in the United States, we lack baseline data on populations throughout much of their geographic range. Focusing on Gus Engeling Wildlife Management Area (WMA) and Keechi Creek WMA in the Middle Trinity River Basin, we sampled for turtles using modified fyke traps, hoop nets and box traps. Between 2006 and 2009 we had a total effort of 1,239 net nights at Gus Engeling WMA and 88 net nights at Keechi Creek WMA. We have captured a total of 13 alligator snapping turtles at Gus Engeling WMA and 3 at Keechi Creek WMA. Alligator snapping turtles occur in very low densities at both sites and are also represented by very young age class turtles. The shallow water habitats at both sites may preclude higher densities and larger individuals. We used gradient analysis to determine habitat use by alligator snapping turtles in relation to other species of turtles at Gus Engeling WMA. The turtle community at Gus Engeling WMA is structured along gradients based on flow, substrate, and emergent vegetation, and is tied to Catfish Creek. Turtle communities at Keechi Creek WMA, which has lower habitat diversity, exhibit lower species richness and increased overlap of resource use than Gus Engeling WMA. |
| Citation: | Kazmaier, R. T., J. D. Riedle, and J. Gunnels. 2010. Demography and habitat selection of the alligator snapping turtle, Macrochelys temminckii, in the Middle Trinity River ecosystem. Texas Parks and Wildlife Department Final Report, Austin, USA. |
| Title: | Spatial ecology and demography of the ornate box turtle in a seasonally burned sand prairie matrix |
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| Journal/Year: | Thesis/2010 |
| View: | Download Grant_2010_OrnateBoxTurtle.pdf |
| Author(s): | Steven David Grant |
| Abstract: | Box turtles (Terrapene spp.) are declining throughout their range, but there is a lack of information on general ecology and the influence of common land management practices on populations of these terrestrial turtles. Because of these inadequacies, I initiated the first phase of a long-term ornate box turtle (Terrapene ornata) research project at Matador Wildlife Management Area in Cottle County, Texas. To examine spatial ecology, a 273-ha primary study site dominated by sand sagebrush (Artemisia filifolia) grasslands was divided into 15 ~18-ha plots (5 blocks x 3 plots). Within each block, there were randomly assigned burning treatments: winter burn, summer burn, and unburned. Thirty-one turtles were captured within the plots and outfitted with radio transmitters and followed from June 2007 to April 2010. Using GIS, I assigned treatments to radio locations and calculated minimum convex polygon (100%, 95%), fixed kernel (95%), and bivariate normal (95%) home ranges. I compared male and female total, annual, monthly, seasonal, and average daily activity using analysis of variance. I used second and third order compositional analysis to evaluate habitat selection based on treatment. Turtle movement was significantly less in April than in May, June, July, June, August, and September. Whereas males and females had similar home range sizes, males had greater daily movement. Turtles did not appear to have a preference for burn treatment. Thus, in the short term, box turtles did not appear to be influenced by burning regime in this habitat. I also examined data from 477 ornate box turtles captured at Matador Wildlife Management Area from 2004 - 2010 to assess the demography of this population. The population of ornate box turtles was significantly female biased at 1.65:1. Adult female turtles were heavier than males but no difference was detected in turtle carapace length or body condition. Based upon regression of age against both mass and carapace length, growth was basically linear. Both Kaplan-Meier and ln(frequency) regression methods produced annual survival estimates near 80%, but adult female survival was higher than that of adult males. Ornate box turtles at Matador Wildlife Management Area had a staggered entry into hibernation beginning in October with all turtles underground by the end of December. However, turtles displayed rather synchronous emergence from hibernation in mid-April. Ornate box turtles demonstrated reproductive activity throughout the active season, but such activity was most pronounced in September. The overall pattern of relatively high survival, high capture rates, linear growth, and small home ranges suggests that the ornate box turtle population at Matador Wildlife Management Area is very robust. |
| Citation: | Grant, S. D. 2010. Spatial ecology and demography of the ornate box turtle in a seasonally burned sand prairie matrix. Thesis, West Texas A&M University, Canyon, USA. |
| Title: | The effects of winter burning and grazing on resources and survival of Texas horned lizards in a thornscrub ecosystem |
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| Journal/Year: | Journal of Wildlife Management/2010 |
| View: | Visit BioOne - The effects of winter burning and grazing on resources and survival of Texas horned lizards in a thornscrub ecosystem |
| Author(s): | Eric C. Hellgren | Anna L. Burrow | Richard T. Kazmaier | Donald C. Ruthven, III |
| Keywords: | grazing | habitat | harvester ants | Phrynosoma cornutum | prescribed fire | survival | Texas horned lizard |
| Abstract: | The ecological effects of land-use practices on reptiles, especially endangered or threatened species, are of conservation and scientific interest. We describe the effects of rotational livestock grazing and prescribed winter burning on resources and survival of the Texas horned lizard (Phrynosoma cornutum) during the summers of 1998 to 2001 in southern Texas, USA. We evaluated survival rates of Texas horned lizards (n = 111) on 6 study sites encompassing 5 different burning and grazing treatments. We also measured indices of cover (i.e., vegetation) and food abundance (i.e., harvester ants [Pogonomyrmex rugosus]). We telemetered and relocated adult lizards daily. We divided the study into 2 seasons, spring (15 Apr-30 Jun) and summer (1 Jul-15 Aug), corresponding to the relative activity of horned lizards. Winter burning provided an increase in food resources and led to increased survival of Texas horned lizards in the second growing season after fire, but grazing-induced changes in vegetation cover reduced survival, likely by increasing lizard vulnerability. Fire and grazing reduced litter and increased bare ground and forb cover but did not affect woody vegetation. Ant activity was greater in burned sites and varied with grazing level, season, and year. Summer survival functions of horned lizards varied by burning treatment, with higher survival observed on burned sites in the second year after burning. Survival rates were ordered from highest in ungrazed sites to lowest in heavily grazed sites. We recognize the limitations of our work resulting from a lack of spatial replication of treatments. However, our mensurative study provides fertile ground for future hypothesis testing regarding the effects of land management on shrubland and grassland reptiles. We propose that future studies focus on the population consequences of variation in burn frequency, burn timing, and grazing intensity. |
| Management Implications: | We add to the growing literature indicating that prescribed burning creates suitable habitat and food resources (i.e., vegetation, ants) for Texas horned lizards, and we documented a positive response in survival during the second year after burning. However, replication in the form of additional studies and meta-analyses are necessary to determine whether the differences that we observed are related to site or are truly driven by burning or grazing effects. We recommend that managers monitor the effects of burning treatments in a systematic way. Desired timing and frequency of burning on horned lizard populations await the results of such monitoring of replicated management treatments. The management relevance of our results regarding grazing effects is less clear. We recommend managers of Phrynosoma spp. in more xeric environments (e.g., P. modestum, P. mcallii) be cautious about implementing grazing. Measuring responses of target species to varying grazing intensities likely is more useful to wildlife managers. |
| Citation: | Hellgren, E. C., A. L. Burrow, R. T. Kazmaier, and D. C. Ruthven, III. 2010. The effects of winter burning and grazing on resources and survival of Texas horned lizards in a thornscrub ecosystem. Journal of Wildlife Management 74:300-309. |
| Title: | Assessing Texas freshwater turtle populations: project status and results from selected studies |
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| Journal/Year: | TPWD Final Report/2011 |
| View: | Download Mali_etal_2011_FreshwaterTurtles.pdf |
| Author(s): | Ivana Mali | Donald J. Brown | Melissa Jones | Michael R. J. Forstner | James R. Dixon |
| Citation: | Mali, I., D. J. Brown, M. Jones, M. R. J. Forstner, and J. R. Dixon. 2011. Assessing Texas freshwater turtle populations: project status and results from selected studies. Texas Parks and Wildlife Department Final Report, Austin, USA. |
| Title: | Escapes from hoop nets by red-eared sliders (Trachemys scripta) |
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| Journal/Year: | The Southwestern Naturalist/2011 |
| View: | Download Brown_etal_2011_HoopNetsRedEaredSliders.pdf |
| Author(s): | Donald J. Brown | Bei DeVolld | Michael R. J. Forstner |
| Abstract: | We investigated the influence of sex and depth of body on escapes from hoop nets by red-eared sliders (Trachemys scripta) to assess if escapes from traps potentially biased estimates of structure of populations. Turtles remained in traps ≥ 34 h and traps were checked at ca. 12-h intervals. Depth of body was not a significant variable in escapes from hoop nets, but sex was a significant variable, with only females escaping. This study provides evidence that previous reports on the inefficiency of hoop nets and on rates of captures that are male-biased could result from escapes rather than differential attraction to traps. |
| Management Implications: | This study provides evidence that previous reports on the inefficiency of hoop nets and on rates of captures that are male-biased could be, at least partially, a result of escapes rather than attraction. Further investigations should focus on taxa more prone to escapes, such as C. picta. It is possible that hoop nets are equally efficient or more efficient than basking traps if the investigator employs a rigorous trap-checking routine. |
| Citation: | Brown, D. J., B. DeVolld, and M. R. J. Forstner. 2011. Escapes from hoop nets by Red-eared sliders (Trachemys scripta). The Southwestern Naturalist 56:124-127. |
| Title: | Freshwater turtle conservation in Texas: harvest effects and efficacy of the current management regime |
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| Journal/Year: | Journal of Wildlife Management/2011 |
| View: | Visit Wiley Online Library - Freshwater turtle conservation in Texas: harvest effects and efficacy of the current management regime |
| Author(s): | Donald J. Brown | Vincent R. Farallo | James R. Dixon | John T. Baccus | Thomas R. Simpson | Michael R. J. Forstner |
| Keywords: | Apalone spp. | commercial harvest | freshwater turtles | Geographic Information System (GIS) | red-eared sliders | softshells | Texas | Trachemys scripta |
| Abstract: | The collapse of Asian turtle populations led to the creation of a worldwide freshwater turtle market in the 1990s. Texas is one of several states in the United States that has capitalized on this market. The Texas Parks and Wildlife Department (TPWD) recently instituted regulations designed to protect turtles from commercial harvest in public waters. Two counties in the Lower Rio Grande Valley (LRGV) accounted for 66.1% of known wild turtle harvest in 1999, with no reported harvest in subsequent years. We sampled 60 sites in the LRGV to determine if we could detect harvest effects. We also investigated the potential for sustainable harvest under the new harvest guidelines using source-sink dynamics implemented in a Geographic Information System (GIS) approach. We detected differences congruent with harvest effects for red-eared sliders (Trachemys scripta) and Texas spiny softshells (Apalone spinifera). Based on a GIS analysis of water bodies throughout the entire state, we estimated that only 2.2% of water bodies are protected under the current commercial harvest regulations. We determined source water bodies could supply 30.5% of sink water bodies in the LRGV, and we concluded that long-term sustainable turtle harvest is unlikely under the current management regime due to the intensity of commercial harvests, the low number of protected water bodies, and non-robust or non-interactive protected populations. One solution to this would be modification of the regulations to include season and bag limits, a management strategy currently implemented in various forms by 14 states in the eastern half of the United States. |
| Management Implications: | The commercial take of turtles in Texas is now managed analogously to stocked fish when in actuality turtle population ecology is more analogous to that of waterfowl as a wildlife resource. Consequently, we recommend that a more conservative approach be taken for commercial harvest management. In addition to the spatial control already enforced, harvest regulations should be modified to prevent turtle harvest during breeding and nesting seasons. Furthermore, bag and size limits should be enforced for female turtles due to their substantially greater influence on population viability. This typical game management approach is currently being utilized in various forms by 14 states in the eastern half of the United States (Lowe 2009). Eight other states have banned commercial turtle harvest. Only Oklahoma has a turtle management regime similar to that of Texas. It may be possible to harvest Texas’ freshwater turtles sustainably, but it will require greater regulatory effort from TPWD, and probably a much lower harvest-rate. |
| Citation: | Brown, D. J., V. R. Farallo, J. R. Dixon, J. T. Baccus, T. R. Simpson, and M. R. J. Forstner. 2011. Freshwater turtle conservation in Texas: harvest effects and efficacy of the current management regime. Journal of Wildlife Management 75:486-494. |
| Title: | No difference in short-term temporal distribution of trapping effort on hoop-net capture efficiency for freshwater turtles |
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| Journal/Year: | Southeastern Naturalist/2011 |
| View: | Download Brown_etal_2011_HoopNetTurtles.pdf |
| Author(s): | Donald J. Brown | Ivana Mali | Michael R. J. Forstner |
| Abstract: | We investigated the influence of trapping duration on freshwater turtle captures using baited hoop-nets. We trapped 9 ponds in the Lower Rio Grande Valley and 6 ponds in the Lost Pines ecoregion areas of Texas in the summer of 2010 using high-intensity, short-duration trapping (40 traps/1 day) and low-intensity, longer-duration trapping (10 traps/4 days). We found that the number of captures was not different between sampling schemes. However, the mean capture rate was twice as high after the first day of low-intensity trapping. This study showed that researchers seeking to maximize captures per-unit-effort (CPUE) should focus on the least time-intensive, labor-intensive, and expensive way to complete the trapping effort, rather than short-term temporal distribution of trapping effort. |
| Citation: | Brown, D. J., I. Mali, and M. R. J. Forstner. 2011. No difference in short-term temporal distribution of trapping effort on hoop-net capture efficiency for freshwater turtles. Southeastern Naturalist 10:245-250. |
| Title: | Population characteristics of diamondback terrapin at the Deer Island Complex: Galveston, Texas during 2008 |
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| Journal/Year: | TPWD Final Report/2011 |
| View: | Download Haskett_Guillen_2011_Diamondback.pdf |
| Author(s): | Kelli Haskett | George Guillen |
| Abstract: | A total of 134 diamondback terrapin were captured on North and South Deer Islands between November 16, 2007 and February 17, 2009. Additionally, 15 terrapin were recaptured during this period. One terrapin was recaptured twice during the study period. Of the 15 terrapin that were collected a more than once, the average time period between captures was 94 days, ranging between 1 and 258 days. Prior to March 27, 2008 no terrapin were captured. In addition, from November 3, 2008 to December 23, 2009, no terrapin were observed at South Deer Island. The average travel distance was 168 meters and ranged between zero and 1,453.5 meters. Two terrapin travelled between North and South Deer Island. Specimen 80 travelled from North Deer Island to South Deer Island at least once during the survey. The total minimum distance travelled between islands by this terrapin was 1,339.4 meters after 259 days. Terrapin 63 travelled a minimum distance of 1,453.5 meters from North Deer Island. Nearly 60% of terrapin captures occurred within the channels that span the length of South Deer Island. The average terrapin catch per hour of effort was 1.2. Greater numbers of terrapin were found throughout April and May, while population counts dramatically dropped from September 2008 through February 2009. Biological data collected on terrapin indicated a male to female sex ratio of 1.1 to 1. The average carapace length for male terrapin was 131.7 cm versus 186 cm for female terrapin. The average male and female weight was .38 kg and 1.2 kg, respectively. The estimated population size based on mark recapture data ranged between Estimates the population size of terrapin on North Deer Island were not attempted due to the insufficient numbers of marked and recaptured terrapin. Estimates of the terrapin population size at South Deer Island for two periods (4/12-5/9/08) and (5/10-8/4/08) ranged between 595 and 1,365 terrapin respectively. However the 95% confidence interval for the number of terrapin present during these time periods were large ranging between 145 to 5,563, and 271 to 16,283 terrapin respectively. As a result of this research, a large number of terrapin in West Bay have been individually marked and documented. This will provide future researchers and managers essential baseline population data needed for the further study and management of Diamondback terrapin populations residing on North and South Deer Islands. It also provides baseline information that will enable researchers to track the continued movement, habitat use and population status of this local population. Furthermore, this research provides critical environmental and habitat data that can be used to define habitat needs for this species coast wide and methodology needed to locate populations of this subspecies throughout the coastal areas of the state. It is essential that monitoring of Diamondback terrapin be continued at the Deer Island complex to monitor long term trends associated with changes in climate, habitat and water quality. It is critical that habitat models be developed for Texas terrapin to identify critical habitat needs for this species. This will require additional years of data collection and intensive studies. Expanded monitoring to the entire Texas coast is needed to identify other populations and the larger demographic characteristic of this species. |
| Management Implications: | As a result of this research, a large number of terrapin in West Bay have been individually marked and documented. This will assist future researchers wishing to further study the terrapin population on North and South Deer Islands by providing a starting point for each terrapin's location. Future researchers will then be able to track the movement of these animals, along with changes in sex ratios and population increases or declines. It also provides baseline information on population status of these animals, which will allow researchers to track the status of this population. Furthermore, this research provides critical environmental and habitat data that can be used to define habitat needs for this species and locate populations of this subspecies throughout the coastal areas of the state. The most important conservation action to protect diamondback terrapin in Galveston Bay would be to protect South Deer Island from erosion and conservation and restoration of marsh habitat on the island. North Deer Island, being such an important bird rookery island, is already protected and partially owned by the Texas and Houston Audubon Societies. In addition to numerous no trespassing signs throughout the island, Audubon employs a warden that frequently patrols the island for violators. Additionally, an 8-year, $3.2 million protection and restoration project was implemented to provide erosion control structures and marsh restoration for the island. Measures being taken to protect bird habitat on North Deer Island including exclusion of predators, reduction of human disturbance and protection and enhancement of wetlands should also enhance terrapin habitat. South Deer Island also supports numerous colonial waterbirds and appears to possess both foraging and nesting areas for the largest known population of the Texas diamondback terrapin subspecies and the only known terrapin population in Galveston Bay. It is essential that this critical terrapin habitat be protected. It is essential that continued monitoring of Diamondback terrapin be continued at the Deer Island complex to monitor long term trends associated with changes in climate, habitat and water quality. Along the east coast several states have monitoring programs that have collected data on known terrapin populations for over 30 years. These programs have documented severe declines associated with crab bycatch, automobile and vessel collisions and loss nesting habitat. No such program existing in Texas despite having an extensive coastline and historical occurrences of terrapin spanning over 80% of the coast. The majority of habitat models for terrapin have been developed in the east coast. It is critical that similar habitat models be developed for Texas terrapin to identify critical habitat needs for this species. This will require additional years of data collection and intensive studies. Currently, the only monitoring that occurs for terrapin are the incident bycatch data reported from the annual derelict blue crab collection program and the TPWD Coastal Fisheries fishery independent sampling program. Both of these efforts have yielded very low numbers of terrapin because of gear bias and in the case of crab traps, the inability to sample active commercial fishing traps due to legal restrictions. The traps that are collected are typically old and frequently show evidence of terrapin bycatch although only pieces of skeletal remains are present, which reduces our ability to estimate numbers caught in these gear. |
| Citation: | Haskett, K., and G. Guillen. 2011. Population characteristics of diamondback terrapin at the Deer Island Complex: Galveston, Texas during 2008. Texas Parks and Wildlife Department Final Report, Austin, USA. |
| Title: | Trade in non-native amphibians and reptiles in Texas: lessons for better monitoring and implications for species introduction |
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| Journal/Year: | Herpetological Conservation and Biology/2011 |
| View: | Download Prestridge_etal_2011_NonNativeSpecies.pdf |
| Author(s): | Heather L. Prestridge | Lee A. Fitzgerald | Toby J. Hibbitts |
| Keywords: | exotic species | invasive species | LEMIS database | wildlife trade |
| Abstract: | In the United States, trade is monitored at different levels of government, and state level insight requires combining federal, state, and local sources of information. Trade in wildlife and their products has implications on wild populations of species involved, and introduction of non-native vertebrates, especially amphibians and reptiles, is linked to the commercial trade in these animals. We used: (1) federal databases; (2) surveys of pet owners at live animal expositions; (3) observations of sales at live animal expositions; and (4) data collected from dealers on the Internet to quantify imports, exports, and use of exotic herptiles traded in Texas. We recorded 1,192 unique taxonomic entities of amphibians and reptiles in commercial trade in Texas. A total of 949,901 live specimens were imported to Texas from 2002 to 2008. The top 16 imported taxa made up 73.36% of the trade. Internet and exposition-based trade was dominated by few species of common pets, with others represented in small numbers. Much trade persists in known invasive species and others that must have the potential to become invasive. We documented trade in 36 known invasive species, three of which are invasive in Texas. Our approach could serve as a template for assessing trade in non-native species at regional scales. Modifications to national databases would allow exports to be distinguished from re-exports, and adoption of standardized taxonomy would improve understanding of impacts of trade on species. State level management changes should be consistent across all 50 states to add continuity to laws governing non-native amphibians and reptiles kept as pets. |
| Management Implications: | Shortcomings of the USFWS reporting system have previously been pointed out and include allowance of multiple codes for the same taxonomic entity, partial codes, and generalized codes. Schlaepfer et al. (2005) noted that non-identified shipments could include imperiled species or non-natives known to be invasive. Ceballos and Fitzgerald (2004) recommended that precise information on origin of specimens is needed to understand impact of the trade on wild populations as well as to achieve accurate monitoring. We avoided some of these problems by cross-referencing our database queries and developing criteria for estimating the total number of taxa. However, partial codes, generalized codes, and poor nomenclature posed problems that impeded our ability to precisely identify the number of species and subspecies in the trade. We recommend that vague entries in trade databases such as "Non-CITES Reptile or Amphibian", "Reptile", or "Amphibian" not be permissible for commercial shipments. Utilization of the Taxonomic Serial Number (TSN) provided by the Integrated Taxonomic Information System, would be a positive step towards clarifying identities of species in the trade, but recommendations to adopt the TSN have yet to be implemented (Gerson et al. 2008). Benefits of standardized nomenclature for traded species would enable more complete analysis of trade data and enhance the ability of inspectors to identify species in shipments. Standard nomenclature is also needed to develop enforceable criteria for the level of taxonomic identification required for different types of shipments. Gerson et al. (2008) claimed that through the adoption of the TSN system, traders would be forced to become more knowledgeable and forthcoming about the taxonomic status of species traded. It is unrealistic to expect commercial traders to keep up with changes in current scientific nomenclature. Government agencies and NGOs should work together to develop standard names or TSN codes that commercial traders are required to use for reporting. This requirement would improve trade monitoring systems and reduce confusion caused by reporting old and new names for the same species. The problem of importing regulated species under false names would still exist as well as incorrect identifications. Nevertheless, trade monitoring systems would be greatly improved if the TSN coding system were adopted or standardized genus and species names were required for commercial trade shipments. Our results indicated the growing role of Internet-based sales of live animals in the pet trade. It is increasingly important to monitor Internet trade, as the use of e-commerce has created a global market for wildlife and their products. The pet trade is very risky for species invasion problems because the number and suite of species used as pets changes over time and the magnitude of the pet trade overall is growing. In contrast, the number of species used for food and skins is relatively stable. Kraus (2009) draws interesting correlations between the pathway of introduction of an invasive species with geographic region of the introduction noting pet trade is the most common pathway for live, non-native reptiles and amphibians to be introduced to North America. When considering these factors combined with our results showing that Internet and exposition trade in live, non-native species is flourishing in Texas, it is clear that management should focus on specimens that are traded live for pets. Our study is among the first to use multiple data sources at the national level, state level, data on Internet-based trade, and targeted interviews to reveal detailed patterns of trade among a large number of genera, species, and subspecies of amphibians and reptiles. Our approach could be used as a template for assessing trade in non-native species in other states, especially those with a high volume of documented dealers, breeders, or enthusiasts. We showed that much trade persists in known invasive species and others that must have the potential to become invasive. Continued monitoring of species involved in trade and quantities imported is critical in developing management strategies for all species traded live but also conservation practices for those traded as products. |
| Citation: | Prestridge, H. L., L. A. Fitzgerald, and T. J. Hibbitts. 2011. Trade in non-native amphibians and reptiles in Texas: lessons for better monitoring and implications for species introduction. Herpetological Conservation and Biology 6:324-339. |
| Title: | Nest success and hatchling survival of American alligators within inland wetlands of east Texas |
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| Journal/Year: | Journal of Wildlife Management/2012 |
| View: | Visit Wiley Online Library - Nest success and hatchling survival of American alligators within inland wetlands of east Texas |
| Author(s): | David T. Saalfeld | Warren C. Conway | Gary E. Calkins |
| Keywords: | Alligator mississippiensis | American alligator | harvest models | hatchling survival | nest success | Texas |
| Abstract: | Because of liberalization of American alligator (Alligator mississippiensis) harvest management in Texas, estimates of nest success and hatchling survival for inland populations are essential for long-term, sustainable population and harvest management. To date, few studies have examined American alligator nest success and hatchling survival. We initiated a 3-year study from 2006 to 2008 to document alligator nest success and hatchling survival within several wetlands in east Texas. From June 2006 to August 2008, we located 30 nests from 3 wetlands within east Texas, where overall nest success was 44.2% (95% CI = 25.1-63.1%), irrespective of year. Nest circumference and day during the nesting season exerted the greatest influence on nest success. Additionally, from August 2006 to August 2008 we captured, marked, and released 271 hatchling alligators at Little Sandy National Wildlife Refuge, and recaptured an additional 192 hatchling alligators during this time. We estimated yearly apparent survival at 6.0% (95% CI = 2.0-14.6%) for hatchling alligators born in 2006 and 43.0% (95% CI = 28.4-57.8%) for those hatched in 2007. Variation in nest success and hatchling survival was likely attributed to fluctuating water levels and habitat management practices. Alligator harvest regulations need to account for variability in nest success and hatchling survival by including site-specific estimates of these metrics into harvest models. Failing to account for spatial and temporal variation in nest success and hatchling survival may result in unsustainable harvest and/or overharvest. |
| Management Implications: | Alligator harvest regulations should accommodate variability in nest success and hatchling survival by including site-specific estimates into harvest models. Not accounting for spatial and temporal variation in nest success and hatchling survival could potentially result in unsustainable harvest and/or overharvest. For example, at Dam B WMA, alligators have been studied extensively since 2003, and during this time span, < 10 nests and < 60 hatchlings have been documented. Conversely, >38 nests and >250 hatchlings were documented in 3 years at Little Sandy NWR. Additionally, 211 alligators have been harvested from Dam B WMA since 1997 (approx. 17 alligators/year); however, < 15 alligators (approx. 1 alligator/year) were harvested at Little Sandy NWR during the same time frame. Therefore, the additive effects of poor recruitment, poor hatchling survival, few successful nests, and greater hunting pressure (compared to Little Sandy NWR) may lead to unsustainable harvest at Dam B WMA. However, obtaining yearly or site-specific estimates of nest success remains unlikely, difficult, time consuming, and expensive. As such, spotlight surveys of pods could provide the next best index of nest success. By modifying spotlight counts currently being conducted to set harvest restrictions to include shallow marsh habitats, pods could easily be counted and used to establish harvest models. Therefore, to sustainably harvest American alligators, annual water levels and hatchling abundance (as determined from pod counts) should be included into harvest models, from which, harvest quotas can be modified on a yearly basis to account for annual variation in nest success and hatchling survival. |
| Citation: | Saalfeld, D. T., W. C. Conway, and G. E. Calkins. 2012. Nest success and hatchling survival of American alligators within inland wetlands of east Texas. Journal of Wildlife Management 76:1568-1575. |
| Title: | Genetic determination of the desert massasauga distribution in Texas |
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| Journal/Year: | TPWD Final Report/2013 |
| View: | Download Ryberg_etal_2013_Massasauga.pdf |
| Author(s): | Wade A. Ryberg | Anna Blick | Johanna A. Harvey | Toby J. Hibbitts | Gary Voelker |
| Abstract: | The Massasauga (Sistrurus catenatus) maintains a fragmented distribution comprised of three subspecies distinguished on the basis of morphological variation and geographic isolation. Recent genetic work supported the distinction of the geographically isolated Eastern Massasauga (S. c. catenatus) from both Western (S. c. tergeminus) and Desert Massasaugas (S. c. edwardsii), but the exact relationships among geographically isolated S. c. tergeminus and S. c. edwardsii populations remained unresolved due to poor sampling throughout the species range (Kubatko et al. 2011). The unresolved geographic relationship between these subspecies poses a difficult challenge for the conservation and management of this species in Texas where both subspecies exist, because S. c. tergeminus has no special state or federal status and S. c. edwardsii has been petitioned for listing and is currently under 12-month review for candidacy under the US Endangered Species Act. To address this challenge, we used nuclear and mitochondrial DNA variation to 1) define the geographic relationships between S. c. tergeminus and S. c. edwardsii in Texas and adjacent states, 2) determine baseline population structure throughout the state and 3) discuss the establishment of potential management units for S. c. edwardsii should listing occur. We found strong evidence that S. c. tergeminus and S. c. edwardsii are genetically indistinguishable for the nuclear and mitochondrial genes investigated. We also found strong evidence supporting earlier conclusions that S. c. catenatus is highly divergent from the S. c. tergeminus-edwardsii group. Within the S. c. tergeminus-edwardsii group, we found some evidence of population structure, which included populations of Massasaugas from 1) Arizona and New Mexico, 2) Colorado and Kansas, 3) Missouri, 4) Oklahoma, and 5) south Texas. These 5 distinct population segments could be considered for listing, but with no clear evidence suggesting relationships among these disjunct populations, we recommend that more research using other molecular markers (e.g., SNP's, microsatellites) be conducted to provide a measure of genetic connectivity capable of revealing more detailed taxonomic and population level structure for identifying potential conservation units. Regardless of federal ruling, we feel that the overall rarity of Massasaugas in south Texas and their geographic isolation from other populations in the S. c. tergeminus-edwardsii group means that they deserve continued attention. We recommend continued survey efforts in this region to provide information on the distribution and abundance of this Massasauga population and to monitor changes to its habitat over time. |
| Management Implications: | Across the range, population sizes and trends for S. c. edwardsii are largely unknown (but see Mackessy 2005 for CO populations). However, through our survey efforts we have anecdotal data that indicate this species is common in some localities and extremely rare others. For Texas in particular, several collectors searching in north-central and west Texas found multiple individuals in a single night or over several consecutive nights of searching in 2013. These collectors describe this searching success as consistent with past years in those areas. Alternatively, a single collector from south Texas found 2 individuals this year after regularly searching for the last 17 years with only one observation. We lack such anecdotal data from the other distinct population segments listed above, although the petition provides evidence that S. c. edwardsii has undergone some range reduction over time as a result of population declines in those portions of its range. In addition, information is presented that indicates these population declines are associated with habitat degradation from land conversion to cultivated croplands and heavy livestock grazing as well as heavy road mortality (US Federal Register August 9, 2012). The disjunct south Texas population segment occupies a region of the state where such land use practices are common, often on large, privately owned ranches 10,000 to 100,000 acres or more. If USFWS determines that listing (entire subspecies group or population segments) is warranted, we anticipate that conservation easement agreements with private property owners in this region are likely to be a productive means of providing broad protection for this disjunct population in the state. Regardless of federal ruling, we feel that the overall rarity of these snakes in south Texas and the fact that they appear to have recently (~100 ybp) undergone geographic isolation from other populations in the S. c. tergeminus-edwardsii group throughout the state means that they deserve continued attention. We strongly recommend continued survey efforts in this region to provide baseline information on the distribution and abundance of this Massasauga population and to monitor potential changes to its habitat over time. |
| Citation: | Ryberg, W. A., A. Blick, J. A. Harvey, T. J. Hibbitts, and G. Voelker. 2013. Genetic determination of the desert massasauga distribution in Texas. Texas Parks and Wildlife Department Final Report, Austin, USA. |
| Title: | Plant and small vertebrate composition and diversity 36-39 years after root plowing |
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| Journal/Year: | Rangeland Ecology and Management/2013 |
| View: | Visit BioOne - Plant and small vertebrate composition and diversity 36-39 years after root plowing |
| Author(s): | Timothy E. Fulbright | E. Alejandro Lozano-Cavazos | Donald C. Ruthven, III | Andrea R. Litt |
| Keywords: | amphibians | brush management | Prosopis glandulosa | reptiles | rodents | woody plants |
| Abstract: | Root plowing is a common management practice to reduce woody vegetation and increase herbaceous forage for livestock on rangelands. Our objective was to test the hypotheses that four decades after sites are root plowed they have 1) lower plant species diversity, less heterogeneity, greater percent canopy cover of exotic grasses; and 2) lower abundance and diversity of amphibians, reptiles, and small mammals, compared to sites that were not disturbed by root plowing. Pairs of 4-ha sites were selected for sampling: in each pair of sites, one was root plowed in 1965 and another was not disturbed by root plowing (untreated). We estimated canopy cover of woody and herbaceous vegetation during summer 2003 and canopy cover of herbaceous vegetation during spring 2004. We trapped small mammals and herpetofauna in pitfall traps during late spring and summer 2001-2004. Species diversity and richness of woody plants were less on root-plowed than on untreated sites; however, herbaceous plant and animal species did not differ greatly between treatments. Evenness of woody vegetation was less on root-plowed sites, in part because woody legumes were more abundant. Abundance of small mammals and herpetofauna varied with annual rainfall more than it varied with root plowing. Although structural differences existed between vegetation communities, secondary succession of vegetation reestablishing after root plowing appears to be leading to convergence in plant and small animal species composition with untreated sites. |
| Management Implications: | A concern regarding use of root plowing to manage woody plants is that it can cause permanent changes in vegetation structure and composition that are undesirable for wildlife. Based on our long-term (>three decades) data, root plowing should be avoided if land managers wish to maintain woody plant species richness and diversity. Effects of root plowing, however, do not appear to be a conservation concern for small vertebrate communities on the Chaparral Wildlife Management Area in Texas. |
| Citation: | Fulbright, T. E., E. A. Lozano-Cavazos, D. C. Ruthven, III, and A. R. Litt. 2013. Plant and small vertebrate composition and diversity 36-39 years after root plowing. Rangeland Ecology and Management 66:19-25. |