Abstracts for 2005 HLCS Workshop, Texas Tech University
Artificial Hibernation as Part of a Long-term Captive Management Plan of Texas Horned Lizards.
Dickey, Aaron and Grant Ashmore
Fort Worth Zoo, 1989 Colonial Pkwy., Fort Worth, TX, 76114. mountainsndesert@fortworthzoo.org
Hibernation is an important aspect of captive horned lizard care and required for both lizard health and reproductive success (Montanucci 1989; Baur pers. com). Horned lizards will slow metabolically and stop eating both in the presence and absence of environmental cues such as shortening day length and lowering night-time temperatures (pers. obs). After experiencing a negative result when subjecting a lizard to a traditional cooling method and faced with the improbability of success with a second natural cooling method, the Fort Worth Zoo employed a modified version of a method used by wildlife rehabilitators in the 1990s for hibernating temperate bat species (Barnard 1995). The outdoor horned lizard enclosure at the Zoo is located in an area subject to flooding due to both rising creek levels and storm run-off. This influenced both the design of our outdoor enclosure and the subsequent inability to use the outdoor enclosure as a natural hibernaculum. The solution is an inexpensive dorm-style refrigerator modified to provide air exchange, a light cycle, and the ability to monitor temperature fluctuations in the refrigerator. These modifications maximize environmental control while minimizing both fiscal cost to the zoo and disturbance to the hibernaculum. The limited data thus far indicate success in both survivability and hibernation-induced weight loss. Four lizards have been successfully over-wintered in this way over 2 winters (6 total hibernation events). Hibernaculum temperatures ranged from 44-64 over the course of 6 months but stayed between 48 and 58 degrees for most of the time. Weight loss has been 2-10% of body weight but has probably been mostly due to water loss.
Keywords: Captive Management, Artificial Hibernation, Phrynosoma cornutum
Red Imported Fire Ant Impact and Management Considerations for Preserving Red Harvester Ants
Drees. Bastiaan M.
Professor and Extension Entomologist, Texas Cooperative Extension, Department of Entomology, 412 Minnie Belle Heep Bldg., College Station, TX, 77843-2475. b-rees@tamu.edu
The red imported fire ant, Solenopsis invicta Buren (Hymenoptera: Formicidae) is an exotic pest that now infests more than the eastern half of Texas. Natural spread through Texas began in the 1950's and since then, populations of the red harvester ant, Pogonomyrmex sp., and the Texas horned lizard, Phrynosoma cornutum, declined. This correlation causes many people to infer that S. invicta caused their decline. Field observations have shown that although imported fire ants coexist with harvester ants some times, harvester ant colonies ultimately decline, are overrun by fire ants, and not replaced. Newly mated red harvester ant queens, and perhaps even very young horned lizards, are vulnerable to predation by fire ants under certain environmental conditions favoring fire ant foraging. However, other factors can also explain, in part, declines in red harvester ant and horned lizard populations throughout their range. The Texas Cooperative Extension publication L-5314, “Red Harvester Ants” available from http://tcebookstore.org/pubinfo.cfm?pubid=1090 discusses both control and preservation of this primary horned lizard food source. Applied research conducted to document imported fire ant control in relation to preserving red harvester ants is available by searching http://fireant.tamu.edu, for “red harvester ants” and specifically two reports: 1) “Target-specific fire ant suppression for preservation of native species and non-target organisms such as the horned lizard” by J. L. Cook; and, 2) “Exclusion of ants using holes of various diameters” by B. M. Drees. Application methods, even using insecticides such as hydramethylnon ant bait (Amdro® and others) labeled for harvester ant control, can be modified to specifically target fire ants. Other theoretical approaches will be discussed, but applied research will be necessary to provide data supporting their effectiveness.
Keywords: red imported fire ants, harvester ants, horned lizards, management
Habitat Ecology and Conservation of Texas Horned Lizards at an Urban Air Force Base.
Hellgren, E. C., D. A. Endriss, S. F. Fox, and R. Moody
Oklahoma State University, 430 LSW, Department of Zoology, Oklahoma State University, Stillwater, OK, 74078. ehellgr@okstate.edu
The unique management issues surrounding reptile populations in urban areas are unexplored. The Texas horned lizard (Phrynosoma cornutum) has been suspected to be in rangewide decline for decades, in part due to urban development. However, due to the small spatial requirements of P. cornutum, populations may be viable in protected areas within an urban environment. We used radio telemetry and fluorescent powder-tracking to collect data on micro- and macrohabitat use, home range size, seasonal movements, and survival rates of P. cornutum within a wildlife reserve (ca. 15 ha) at Tinker Air Force Base in Oklahoma City. We captured 41 females, 29 males, and 27 hatchlings in 2003- 2004. Lengths of movement trails obtained through fluorescent powder tracking were longer for adult males during the breeding season than after the breeding season. We collected habitat data for 836 capture locations and paired random, available locations from 20 transmittered lizards that were relocated for 1-8 months. Microhabitats used by lizards had more bare ground than available microhabitats. Therefore, these lizards may benefit if more open area were interspersed within the dense vegetation required for cover. At a macro-scale, lizard locations were tied closely to trails and disturbed ground in areas of native grassland. Survival rate from May- December was 0.65 (95% CI: 0.37- 0.92). Lizard entry into hibernation ranged widely from late September to mid-December (n=11). Lizards hibernated shallowly (5-12 mm) on S- and SW-facing slopes (<5-30 deg.). Our work has implications for predicting effects of future base development projects on the lizard population, facilitating development of habitat management techniques to improve urban habitat, and predicting occurrence of lizards in unsampled areas.
Keywords: Air Force base, habitat use, Phrynosoma cornutum, Texas horned lizard, urban
Reintroduction of Texas Horned Lizards to Central Texas.
Hodges, Wendy L.
Department of Science and Mathematics, University of Texas of the Permian Basin, 4901 E. University Blvd., Odessa, TX, 79762. hodges_w@utpb.edu
Texas horned lizards have been introduced in 22 states over 130 years with several populations persisting for 30 or more years, suggesting the species may be amenable to reintroductions where it has disappeared. The goals of this project were to establish a population that could persist for one year, insure no net loss of harvester ant colonies, establish reintroduction protocols, and gather data on habitat characteristics important for choosing appropriate sites. Forty-seven lizards were released at a private ranch in Hays County, Texas: 30 juveniles raised from captive parents and 7 adults were released in May 2002 followed by ten more over 2 years. The first cohort was acclimated to the site in outdoor enclosures. Afterward, the site was revisited to record recaptures and track adults. Most surveys were conducted by 1-2 field volunteers, but groups of 9-12 people were also deployed to search the area. Ant activity and vegetation cover were quantified concurrently. Most lizards were recaptured in close proximity to outdoor enclosures, and one female laid eggs within one day of leaving the enclosures. In 2003, only one adult lizard was seen, and all tracked lizards were eventually found dead or transmitters were found with signs of predation. Harvester ant colonies remained active and stable over the study period. Rainfall in 2002 that caused flooding had a negative impact on lizards both directly and indirectly: one adult was found entombed in mud and ant colony activity was reduced for two weeks. While we were unsuccessful at establishing a horned lizard population, harvester ant colonies persisted, general relocation protocols were outlined and locality information should allow continued progress for relocation efforts. Future sites should have stable harvester ant populations and mixed vegetation types and open ground located outside of low lying areas or potential flood plains.
Keywords: reintroduction, harvester ants, radio telemetry, vegetation sampling, flooding
Where are Horned Lizards in Texas? A Current Distribution Based on Citizen Scientist Monitoring.
Linam, Lee Ann J.
Texas Parks & Wildlife Department, 200 Hoots Holler Rd., Wimberley, TX 78676. lalinam@wimberley-tx.com
In 1997 Texas Parks and Wildlife Department launched the Texas Horned Lizard Watch, relying on two premises: Texas citizens are interested in the status of the Texas horned lizard (Phrynosoma cornutum), and these same citizens are capable of gathering scientifically significant data regarding its status. The program, one of many “citizen science” programs now emerging in Texas and elsewhere, offers participants a choice of participating at several levels representing varying degrees of complexity and scientific rigor. Since its inception, over 170 volunteers have returned species and habitat data from over 250 total locations in 157 counties, while less detailed sighting data has been accumulated from 201 of Texas’ 254 counties. Results to date have helped to refine our understanding of Texas horned lizard distribution, showing widespread occurrence in West and South Texas; reduced occurrence in Central Texas, North Texas and the Lower Rio Grande Valley; and very rare occurrence in Southeast Texas and the upper coastal counties. Anecdotal accounts identify the 1970s as the median period of horned lizard decline; however, at least 150 counties have reported sightings of Texas horned lizards since 2000. Statistical comparisons (chi-square) of volunteer data have shown that presence of the Texas Horned Lizard is related to presence of harvester ant species (Pogonomyrmex) and absence of the red imported fire ant (Solenopsis invicta). Data to date have failed to detect a relationship between horned lizard presence and land use, habitat type, or soil type. As additional years of data accumulate, it is hoped that this program may track trends in horned lizard populations, as well as the variables that affect the abundance and conservation of this popular species.
Keywords: Texas horned lizard, distribution, volunteer monitoring
The Texas Landowner Incentive Program: Helping Landowners Improve Texas Horned Lizard Habitat.
Miller, Michael S.
Texas Parks and Wildlife Department, Box T-0070, Stephenville, TX 76402 mike.miller@tpwd.state.tx.us
The Texas Parks and Wildlife Department (TPWD) created the Landowner Incentive Program (LIP) in 1997 to provide grants for private landowners to improve habitat for threatened and endangered species. The idea was to encourage landowners to manage for these species and their associated habitats through incentives rather than coercive regulations. Over the last 8 years, over $2 million in state and federal funds have been allocated by TPWD to 108 projects, benefiting 20 species of concern and 135,000 acres of habitat on private lands. Although many projects have probably improved Texas Horned Lizard (Phrynosoma cornutum) habitat, only 3 project applications have been submitted specifically for improving habitat for the lizard. In 2003, LIP became a federal grant program, administered by U.S. Fish and Wildlife Service and implemented by individual state wildlife agencies. With this change came a new emphasis on funding projects that benefited federal candidate and state-listed species, rather than federally endangered or threatened species. TPWD’s FY05 LIP funding proposal requests almost $950,000 to improve habitat for 15 at-risk species, including the Texas Horned Lizard. Prescribed burning, selective brush removal, cross fence construction, native plant reseeding, and creation of small, bare soil sites (to attract harvester ants) are among the management practices that can be funded by LIP to improve Texas Horned Lizard habitat.
Keywords: Landowner Incentive Program, Phrynosoma cornutum
Ecological effects of prescribed fire on Texas horned lizards
Moeller, Beth A., Hellgren, Eric C., Kazmaier, Richard T., and Ruthven, Donald C.
Fort Worth Zoo, 1989 Colonial Pkwy, Fort Worth, TX 76110 bmoeller@fortworthzoo.org
The Texas horned lizard (Phrynosoma cornutum) has experienced apparent large-scale declines throughout its range, particularly in Texas. We studied the effect of prescribed burning (a habitat management practice of increasing popularity) on the ecology of the Texas horned lizard in a thornscrub savanna. We assessed home range size, woody vegetation selection, and survival rates of horned lizards in 4 treatments. Home ranges in the summer-burned-grazed treatment were smaller than those in the other treatments (winter-burned-grazed, unburned-grazed, and unburned-ungrazed). Survival rates in burned sites were higher than in unburned sites. The survival functions also differed between burning treatments, with survival declining in early summer in the unburned areas and in late summer in the burned areas. Lizards selected for whitebrush (Aloysia gratissima) and avoided Texas persimmon (Diospyros texana) consistently across treatments. Selection or avoidance of other woody species was not consistent among treatments. Ant activity, used as a surrogate of ant abundance, has been shown previously to be higher on burned sites on our study area. Therefore, more food, or better food-cover interspersion, may explain the higher survival in burned areas and the smaller home ranges in summer-burned areas. We conclude that prescribed burning in a thornscrub savanna provided favorable ecological conditions for Texas horned lizards.
Keywords: burning, conservation, habitat use, home range, land management, prescribed fire
Horned Lizard Research on the Chaparral Wildlife Management Area
Mostyn, Chris; Gallagher, Jim; Synatzske, David; Ruthven, Chip
Texas Parks and Wildlife Department, 64 Chaparral WMA Drive, Cotulla, TX 78014 cwma@granderiver.net
In recent decades, Texas horned lizard populations have shown dramatic declines throughout the eastern portion of their range. Declines have been linked to application of pesticides, loss of habitat, over-collection by the pet trade, and the accidental introduction of the imported fire ant, but a single cause is unlikely. To address Texas horned lizard population declines and gain a better understanding of horned lizard ecology, collection of horned lizard data began on the Chaparral Wildlife Management Area (CWMA) in the South Texas Plains in 1991. Vegetation on the area is dominated by mesquite/mixed-brush communities characteristic of the South Texas Plains. Horned lizards are captured by hand during fortuitous encounters on roads and in the brush and in drift fence arrays. Monitoring revolves around a mark-recapture study. Individuals are measured by snout/vent length (SVL) and total length, sexed, and marked by either a series of toe clippings or the implantation of passive integrated transponder (PIT) tags which, when scanned, provides an identification number for each lizard. Over 3000 horned lizards have been marked on Chaparral WMA. The primary objectives of Horned Lizard (Phrynosoma cornutum) research on the CWMA are to examine the effects of common land use practices, including grazing and prescribed burning on ecological characteristics of horned lizards (range size, habitat preferences, and population parameters) and expand a long-term ecological monitoring of horned lizards to include temporal responses of the horned lizard population to anthropogenic (e.g. increased public use, road-building, prescribed burning, disking, fire ant invasion) impacts. The data may help to refute any concerns or potential arguments that suggest that common land management practices essential to enhancement of wildlife habitat exacerbate Horned Lizard population declines.
Keywords: Monitoring, mark-recapture, decline, ecology
Development of Survey Protocols for Regional Estimates of Horned Lizard Densities
Mueller, James M.
Sul Ross State University, Department of Biology, Alpine, TX 79832 jmueller@sulross.edu
The historic range of the Texas horned lizard included the entire state of Texas, but the species has been extirpated throughout most of the eastern one-half of the state. Recent surveys suggested that the species is doing best in north, south, and west Texas, but little monitoring is being conducted to accurately assess Texas horned lizard population trends in these areas. We are developing protocols for measuring densities of Texas horned lizards in west Texas using line transect sampling. This method assumes that sightability decreases monotonically as the distance from the survey line increases, and a program is available for fitting curves to the observed data. Another component of sightability, however, is related to temporal changes in lizard activity. One objective of our research is to determine if lizard sightability can be inferred from temperatures logged from radiomarked lizards and their environment. Results suggest that this approach can work. However, a much greater sampling effort will be required than what I have been able to conduct to obtain reasonably precise estimates. Other methods are probably more efficient for small scale (i.e., a single study site such as a WMA or ranch) estimates of density.
Keywords: horned lizards, monitoring, temperature, activity, survey
The Utility of WW.B-Dahl grass for Reducing Fire Ant Densities in Pastures
Gad Perry, Carlton Britton, and Troy Sternberg
Department of Range, Wildlife, And Fisheries Management, Texas Tech University, Lubbock, TX 79409 gad.perry@ttu.edu
The Red Imported Fire Ant (RIFA) is an invasive pest that causes both ecological and economic damages. Among other concerns, it appears to negatively impact populations of horned lizards (genus Phrynosoma) over large geographic area. Conventional RIFA control methods have not proven effective or long lasting, and are not feasible for use on the large scales that would be required to aid horned lizard populations. This has led to research on alternative methods for repelling or reducing RIFA populations. We used a correlation approach to test preliminary observations that WW-B.Dahl, an introduced pasture grass used over much of Texas, can reduce RIFA infestations. Study sites ranged from Fredericksburg and Seguin in the south to Sherman in the north and Abilene in the west. We found that WW-B.Dahl grass had about one third the mound density found in neighboring plots, a statistically significant difference and are currently testing to see whether this translates into differences in the presence of other insects, reptiles, and birds. Reduced RIFA densities will improve efficiency of harvesting operations for growers, decrease vegetation loss due to RIFA mounds, and prevent reduction of property values due to high RIFA mound infestation. Research on the mechanisms by which WW-B.Dahl inhibits RIFA infestations, and on additional effects that might also occur, is also ongoing. Further study may identify WW-B.Dahl traits or chemicals that are repellent to RIFA.
Horned Lizards and Nature Tourism Development
Plante, Shelly
Nature Tourism Coordinator, Texas Parks and Wildlife Department, 4200 Smith School Road, Austin, TX 78744shelly.plante@tpwd.state.tx.us
We will look at nature tourism trends in Texas in recent years, development of nature tourism enterprises on private and public lands and other available opportunities based on a site’s natural resources. This will be a great overview and introduction to nature tourism in Texas and should help guide landowners in the initial steps necessary to start a nature tourism business, determine their target market, and learn what resources are available to get them started.
Keywords: nature tourism
Texas Horned Lizard Biology and Management
Ruthven, Donald C. "Chip" and Kazmaier, Richard T.
Matador WMA, Texas Parks and Wildlife Department, 3036 FM 3256, Paducah, TX 79248 cruthven@caprock-spur.com
Much of our knowledge of the biology of the Texas Horned lizard is based on small sample sizes and anecdotal observations. Recent studies throughout the range of this charismatic reptile in Texas, in particular radio telemetry studies in southern Texas, have yielded new information of the ecology of this species. This species prefers grassland and savanna habitats on sandy soils with a mixture of bare ground and herbaceous and woody vegetation for thermoregulation and refugia from predation. Body size decreases from south to north through their Texas range. In South Texas they can remain active from late January through late December; however, the primary period of activity is May through July. Hibernacula are generally associated under or near the drip line of shrubs and lizards bury themselves to a depth of about 1 inch. Home range size can be as much as 50 acres but are typically between 2 to 10 acres. Mating has been observed from March to October. Nesting has been observed from late April through July. Females frequently move outside their core home range to excavate nests and clutch size can range from 6 to 40 eggs. Females can produce more than one clutch in a given year. Hatching interval averages seven weeks. Growth of hatchlings is rapid with lizards reaching maturity within one year. Harvester ants are their primary fodder but other ant species, as well as termites appear to be important food sources. Survival during the active season can vary between 35 and 80%. Primary predators include snakes, greater roadrunner, and grasshopper mouse. Prescribed fire and moderate grazing by cattle can be utilized to manage habitat for Texas horned lizards. Additional research, especially the ecology of hatchlings, is needed to fully understand the biology of this species and aid in its management and conservation.
Keywords: Texas horned lizard, home range, reproduction, survival, habitat, management
Artificial Hibernation as Part of a Long-term Captive Management Plan of Texas Horned Lizards.
Dickey, Aaron and Grant Ashmore
Fort Worth Zoo, 1989 Colonial Pkwy., Fort Worth, TX, 76114. mountainsndesert@fortworthzoo.org
Hibernation is an important aspect of captive horned lizard care and required for both lizard health and reproductive success (Montanucci 1989; Baur pers. com). Horned lizards will slow metabolically and stop eating both in the presence and absence of environmental cues such as shortening day length and lowering night-time temperatures (pers. obs). After experiencing a negative result when subjecting a lizard to a traditional cooling method and faced with the improbability of success with a second natural cooling method, the Fort Worth Zoo employed a modified version of a method used by wildlife rehabilitators in the 1990s for hibernating temperate bat species (Barnard 1995). The outdoor horned lizard enclosure at the Zoo is located in an area subject to flooding due to both rising creek levels and storm run-off. This influenced both the design of our outdoor enclosure and the subsequent inability to use the outdoor enclosure as a natural hibernaculum. The solution is an inexpensive dorm-style refrigerator modified to provide air exchange, a light cycle, and the ability to monitor temperature fluctuations in the refrigerator. These modifications maximize environmental control while minimizing both fiscal cost to the zoo and disturbance to the hibernaculum. The limited data thus far indicate success in both survivability and hibernation-induced weight loss. Four lizards have been successfully over-wintered in this way over 2 winters (6 total hibernation events). Hibernaculum temperatures ranged from 44-64 over the course of 6 months but stayed between 48 and 58 degrees for most of the time. Weight loss has been 2-10% of body weight but has probably been mostly due to water loss.
Keywords: Captive Management, Artificial Hibernation, Phrynosoma cornutum
Red Imported Fire Ant Impact and Management Considerations for Preserving Red Harvester Ants
Drees. Bastiaan M.
Professor and Extension Entomologist, Texas Cooperative Extension, Department of Entomology, 412 Minnie Belle Heep Bldg., College Station, TX, 77843-2475. b-rees@tamu.edu
The red imported fire ant, Solenopsis invicta Buren (Hymenoptera: Formicidae) is an exotic pest that now infests more than the eastern half of Texas. Natural spread through Texas began in the 1950's and since then, populations of the red harvester ant, Pogonomyrmex sp., and the Texas horned lizard, Phrynosoma cornutum, declined. This correlation causes many people to infer that S. invicta caused their decline. Field observations have shown that although imported fire ants coexist with harvester ants some times, harvester ant colonies ultimately decline, are overrun by fire ants, and not replaced. Newly mated red harvester ant queens, and perhaps even very young horned lizards, are vulnerable to predation by fire ants under certain environmental conditions favoring fire ant foraging. However, other factors can also explain, in part, declines in red harvester ant and horned lizard populations throughout their range. The Texas Cooperative Extension publication L-5314, “Red Harvester Ants” available from http://tcebookstore.org/pubinfo.cfm?pubid=1090 discusses both control and preservation of this primary horned lizard food source. Applied research conducted to document imported fire ant control in relation to preserving red harvester ants is available by searching http://fireant.tamu.edu, for “red harvester ants” and specifically two reports: 1) “Target-specific fire ant suppression for preservation of native species and non-target organisms such as the horned lizard” by J. L. Cook; and, 2) “Exclusion of ants using holes of various diameters” by B. M. Drees. Application methods, even using insecticides such as hydramethylnon ant bait (Amdro® and others) labeled for harvester ant control, can be modified to specifically target fire ants. Other theoretical approaches will be discussed, but applied research will be necessary to provide data supporting their effectiveness.
Keywords: red imported fire ants, harvester ants, horned lizards, management
Habitat Ecology and Conservation of Texas Horned Lizards at an Urban Air Force Base.
Hellgren, E. C., D. A. Endriss, S. F. Fox, and R. Moody
Oklahoma State University, 430 LSW, Department of Zoology, Oklahoma State University, Stillwater, OK, 74078. ehellgr@okstate.edu
The unique management issues surrounding reptile populations in urban areas are unexplored. The Texas horned lizard (Phrynosoma cornutum) has been suspected to be in rangewide decline for decades, in part due to urban development. However, due to the small spatial requirements of P. cornutum, populations may be viable in protected areas within an urban environment. We used radio telemetry and fluorescent powder-tracking to collect data on micro- and macrohabitat use, home range size, seasonal movements, and survival rates of P. cornutum within a wildlife reserve (ca. 15 ha) at Tinker Air Force Base in Oklahoma City. We captured 41 females, 29 males, and 27 hatchlings in 2003- 2004. Lengths of movement trails obtained through fluorescent powder tracking were longer for adult males during the breeding season than after the breeding season. We collected habitat data for 836 capture locations and paired random, available locations from 20 transmittered lizards that were relocated for 1-8 months. Microhabitats used by lizards had more bare ground than available microhabitats. Therefore, these lizards may benefit if more open area were interspersed within the dense vegetation required for cover. At a macro-scale, lizard locations were tied closely to trails and disturbed ground in areas of native grassland. Survival rate from May- December was 0.65 (95% CI: 0.37- 0.92). Lizard entry into hibernation ranged widely from late September to mid-December (n=11). Lizards hibernated shallowly (5-12 mm) on S- and SW-facing slopes (<5-30 deg.). Our work has implications for predicting effects of future base development projects on the lizard population, facilitating development of habitat management techniques to improve urban habitat, and predicting occurrence of lizards in unsampled areas.
Keywords: Air Force base, habitat use, Phrynosoma cornutum, Texas horned lizard, urban
Reintroduction of Texas Horned Lizards to Central Texas.
Hodges, Wendy L.
Department of Science and Mathematics, University of Texas of the Permian Basin, 4901 E. University Blvd., Odessa, TX, 79762. hodges_w@utpb.edu
Texas horned lizards have been introduced in 22 states over 130 years with several populations persisting for 30 or more years, suggesting the species may be amenable to reintroductions where it has disappeared. The goals of this project were to establish a population that could persist for one year, insure no net loss of harvester ant colonies, establish reintroduction protocols, and gather data on habitat characteristics important for choosing appropriate sites. Forty-seven lizards were released at a private ranch in Hays County, Texas: 30 juveniles raised from captive parents and 7 adults were released in May 2002 followed by ten more over 2 years. The first cohort was acclimated to the site in outdoor enclosures. Afterward, the site was revisited to record recaptures and track adults. Most surveys were conducted by 1-2 field volunteers, but groups of 9-12 people were also deployed to search the area. Ant activity and vegetation cover were quantified concurrently. Most lizards were recaptured in close proximity to outdoor enclosures, and one female laid eggs within one day of leaving the enclosures. In 2003, only one adult lizard was seen, and all tracked lizards were eventually found dead or transmitters were found with signs of predation. Harvester ant colonies remained active and stable over the study period. Rainfall in 2002 that caused flooding had a negative impact on lizards both directly and indirectly: one adult was found entombed in mud and ant colony activity was reduced for two weeks. While we were unsuccessful at establishing a horned lizard population, harvester ant colonies persisted, general relocation protocols were outlined and locality information should allow continued progress for relocation efforts. Future sites should have stable harvester ant populations and mixed vegetation types and open ground located outside of low lying areas or potential flood plains.
Keywords: reintroduction, harvester ants, radio telemetry, vegetation sampling, flooding
Where are Horned Lizards in Texas? A Current Distribution Based on Citizen Scientist Monitoring.
Linam, Lee Ann J.
Texas Parks & Wildlife Department, 200 Hoots Holler Rd., Wimberley, TX 78676. lalinam@wimberley-tx.com
In 1997 Texas Parks and Wildlife Department launched the Texas Horned Lizard Watch, relying on two premises: Texas citizens are interested in the status of the Texas horned lizard (Phrynosoma cornutum), and these same citizens are capable of gathering scientifically significant data regarding its status. The program, one of many “citizen science” programs now emerging in Texas and elsewhere, offers participants a choice of participating at several levels representing varying degrees of complexity and scientific rigor. Since its inception, over 170 volunteers have returned species and habitat data from over 250 total locations in 157 counties, while less detailed sighting data has been accumulated from 201 of Texas’ 254 counties. Results to date have helped to refine our understanding of Texas horned lizard distribution, showing widespread occurrence in West and South Texas; reduced occurrence in Central Texas, North Texas and the Lower Rio Grande Valley; and very rare occurrence in Southeast Texas and the upper coastal counties. Anecdotal accounts identify the 1970s as the median period of horned lizard decline; however, at least 150 counties have reported sightings of Texas horned lizards since 2000. Statistical comparisons (chi-square) of volunteer data have shown that presence of the Texas Horned Lizard is related to presence of harvester ant species (Pogonomyrmex) and absence of the red imported fire ant (Solenopsis invicta). Data to date have failed to detect a relationship between horned lizard presence and land use, habitat type, or soil type. As additional years of data accumulate, it is hoped that this program may track trends in horned lizard populations, as well as the variables that affect the abundance and conservation of this popular species.
Keywords: Texas horned lizard, distribution, volunteer monitoring
The Texas Landowner Incentive Program: Helping Landowners Improve Texas Horned Lizard Habitat.
Miller, Michael S.
Texas Parks and Wildlife Department, Box T-0070, Stephenville, TX 76402 mike.miller@tpwd.state.tx.us
The Texas Parks and Wildlife Department (TPWD) created the Landowner Incentive Program (LIP) in 1997 to provide grants for private landowners to improve habitat for threatened and endangered species. The idea was to encourage landowners to manage for these species and their associated habitats through incentives rather than coercive regulations. Over the last 8 years, over $2 million in state and federal funds have been allocated by TPWD to 108 projects, benefiting 20 species of concern and 135,000 acres of habitat on private lands. Although many projects have probably improved Texas Horned Lizard (Phrynosoma cornutum) habitat, only 3 project applications have been submitted specifically for improving habitat for the lizard. In 2003, LIP became a federal grant program, administered by U.S. Fish and Wildlife Service and implemented by individual state wildlife agencies. With this change came a new emphasis on funding projects that benefited federal candidate and state-listed species, rather than federally endangered or threatened species. TPWD’s FY05 LIP funding proposal requests almost $950,000 to improve habitat for 15 at-risk species, including the Texas Horned Lizard. Prescribed burning, selective brush removal, cross fence construction, native plant reseeding, and creation of small, bare soil sites (to attract harvester ants) are among the management practices that can be funded by LIP to improve Texas Horned Lizard habitat.
Keywords: Landowner Incentive Program, Phrynosoma cornutum
Ecological effects of prescribed fire on Texas horned lizards
Moeller, Beth A., Hellgren, Eric C., Kazmaier, Richard T., and Ruthven, Donald C.
Fort Worth Zoo, 1989 Colonial Pkwy, Fort Worth, TX 76110 bmoeller@fortworthzoo.org
The Texas horned lizard (Phrynosoma cornutum) has experienced apparent large-scale declines throughout its range, particularly in Texas. We studied the effect of prescribed burning (a habitat management practice of increasing popularity) on the ecology of the Texas horned lizard in a thornscrub savanna. We assessed home range size, woody vegetation selection, and survival rates of horned lizards in 4 treatments. Home ranges in the summer-burned-grazed treatment were smaller than those in the other treatments (winter-burned-grazed, unburned-grazed, and unburned-ungrazed). Survival rates in burned sites were higher than in unburned sites. The survival functions also differed between burning treatments, with survival declining in early summer in the unburned areas and in late summer in the burned areas. Lizards selected for whitebrush (Aloysia gratissima) and avoided Texas persimmon (Diospyros texana) consistently across treatments. Selection or avoidance of other woody species was not consistent among treatments. Ant activity, used as a surrogate of ant abundance, has been shown previously to be higher on burned sites on our study area. Therefore, more food, or better food-cover interspersion, may explain the higher survival in burned areas and the smaller home ranges in summer-burned areas. We conclude that prescribed burning in a thornscrub savanna provided favorable ecological conditions for Texas horned lizards.
Keywords: burning, conservation, habitat use, home range, land management, prescribed fire
Horned Lizard Research on the Chaparral Wildlife Management Area
Mostyn, Chris; Gallagher, Jim; Synatzske, David; Ruthven, Chip
Texas Parks and Wildlife Department, 64 Chaparral WMA Drive, Cotulla, TX 78014 cwma@granderiver.net
In recent decades, Texas horned lizard populations have shown dramatic declines throughout the eastern portion of their range. Declines have been linked to application of pesticides, loss of habitat, over-collection by the pet trade, and the accidental introduction of the imported fire ant, but a single cause is unlikely. To address Texas horned lizard population declines and gain a better understanding of horned lizard ecology, collection of horned lizard data began on the Chaparral Wildlife Management Area (CWMA) in the South Texas Plains in 1991. Vegetation on the area is dominated by mesquite/mixed-brush communities characteristic of the South Texas Plains. Horned lizards are captured by hand during fortuitous encounters on roads and in the brush and in drift fence arrays. Monitoring revolves around a mark-recapture study. Individuals are measured by snout/vent length (SVL) and total length, sexed, and marked by either a series of toe clippings or the implantation of passive integrated transponder (PIT) tags which, when scanned, provides an identification number for each lizard. Over 3000 horned lizards have been marked on Chaparral WMA. The primary objectives of Horned Lizard (Phrynosoma cornutum) research on the CWMA are to examine the effects of common land use practices, including grazing and prescribed burning on ecological characteristics of horned lizards (range size, habitat preferences, and population parameters) and expand a long-term ecological monitoring of horned lizards to include temporal responses of the horned lizard population to anthropogenic (e.g. increased public use, road-building, prescribed burning, disking, fire ant invasion) impacts. The data may help to refute any concerns or potential arguments that suggest that common land management practices essential to enhancement of wildlife habitat exacerbate Horned Lizard population declines.
Keywords: Monitoring, mark-recapture, decline, ecology
Development of Survey Protocols for Regional Estimates of Horned Lizard Densities
Mueller, James M.
Sul Ross State University, Department of Biology, Alpine, TX 79832 jmueller@sulross.edu
The historic range of the Texas horned lizard included the entire state of Texas, but the species has been extirpated throughout most of the eastern one-half of the state. Recent surveys suggested that the species is doing best in north, south, and west Texas, but little monitoring is being conducted to accurately assess Texas horned lizard population trends in these areas. We are developing protocols for measuring densities of Texas horned lizards in west Texas using line transect sampling. This method assumes that sightability decreases monotonically as the distance from the survey line increases, and a program is available for fitting curves to the observed data. Another component of sightability, however, is related to temporal changes in lizard activity. One objective of our research is to determine if lizard sightability can be inferred from temperatures logged from radiomarked lizards and their environment. Results suggest that this approach can work. However, a much greater sampling effort will be required than what I have been able to conduct to obtain reasonably precise estimates. Other methods are probably more efficient for small scale (i.e., a single study site such as a WMA or ranch) estimates of density.
Keywords: horned lizards, monitoring, temperature, activity, survey
The Utility of WW.B-Dahl grass for Reducing Fire Ant Densities in Pastures
Gad Perry, Carlton Britton, and Troy Sternberg
Department of Range, Wildlife, And Fisheries Management, Texas Tech University, Lubbock, TX 79409 gad.perry@ttu.edu
The Red Imported Fire Ant (RIFA) is an invasive pest that causes both ecological and economic damages. Among other concerns, it appears to negatively impact populations of horned lizards (genus Phrynosoma) over large geographic area. Conventional RIFA control methods have not proven effective or long lasting, and are not feasible for use on the large scales that would be required to aid horned lizard populations. This has led to research on alternative methods for repelling or reducing RIFA populations. We used a correlation approach to test preliminary observations that WW-B.Dahl, an introduced pasture grass used over much of Texas, can reduce RIFA infestations. Study sites ranged from Fredericksburg and Seguin in the south to Sherman in the north and Abilene in the west. We found that WW-B.Dahl grass had about one third the mound density found in neighboring plots, a statistically significant difference and are currently testing to see whether this translates into differences in the presence of other insects, reptiles, and birds. Reduced RIFA densities will improve efficiency of harvesting operations for growers, decrease vegetation loss due to RIFA mounds, and prevent reduction of property values due to high RIFA mound infestation. Research on the mechanisms by which WW-B.Dahl inhibits RIFA infestations, and on additional effects that might also occur, is also ongoing. Further study may identify WW-B.Dahl traits or chemicals that are repellent to RIFA.
Horned Lizards and Nature Tourism Development
Plante, Shelly
Nature Tourism Coordinator, Texas Parks and Wildlife Department, 4200 Smith School Road, Austin, TX 78744shelly.plante@tpwd.state.tx.us
We will look at nature tourism trends in Texas in recent years, development of nature tourism enterprises on private and public lands and other available opportunities based on a site’s natural resources. This will be a great overview and introduction to nature tourism in Texas and should help guide landowners in the initial steps necessary to start a nature tourism business, determine their target market, and learn what resources are available to get them started.
Keywords: nature tourism
Texas Horned Lizard Biology and Management
Ruthven, Donald C. "Chip" and Kazmaier, Richard T.
Matador WMA, Texas Parks and Wildlife Department, 3036 FM 3256, Paducah, TX 79248 cruthven@caprock-spur.com
Much of our knowledge of the biology of the Texas Horned lizard is based on small sample sizes and anecdotal observations. Recent studies throughout the range of this charismatic reptile in Texas, in particular radio telemetry studies in southern Texas, have yielded new information of the ecology of this species. This species prefers grassland and savanna habitats on sandy soils with a mixture of bare ground and herbaceous and woody vegetation for thermoregulation and refugia from predation. Body size decreases from south to north through their Texas range. In South Texas they can remain active from late January through late December; however, the primary period of activity is May through July. Hibernacula are generally associated under or near the drip line of shrubs and lizards bury themselves to a depth of about 1 inch. Home range size can be as much as 50 acres but are typically between 2 to 10 acres. Mating has been observed from March to October. Nesting has been observed from late April through July. Females frequently move outside their core home range to excavate nests and clutch size can range from 6 to 40 eggs. Females can produce more than one clutch in a given year. Hatching interval averages seven weeks. Growth of hatchlings is rapid with lizards reaching maturity within one year. Harvester ants are their primary fodder but other ant species, as well as termites appear to be important food sources. Survival during the active season can vary between 35 and 80%. Primary predators include snakes, greater roadrunner, and grasshopper mouse. Prescribed fire and moderate grazing by cattle can be utilized to manage habitat for Texas horned lizards. Additional research, especially the ecology of hatchlings, is needed to fully understand the biology of this species and aid in its management and conservation.
Keywords: Texas horned lizard, home range, reproduction, survival, habitat, management