2007 Abstracts for the 6th National HLCS Conference
Abstracts are listed in alphabetic order by first author’s last name. Presenting author is shown in bold. Contact information is for the presenter only.
Tests of Interactions in Texas Horned Lizards: Evidence of Territoriality?
Victor Bogosian III, Eric C. Hellgren, Debora A. Endriss, Raymond W. Moody
Southern Illinois University Carbondale, Life Science II Room 251, Southern Illinois University Carbondale, Carbondale, IL 62901-6504: firstname.lastname@example.org
The genus Phrynosoma contains a group of cryptic species with relatively large home ranges; consequently, their social behavior and its links to other aspects of life history are poorly understood. We examined spatial overlap in a population of Texas horned lizards (Phrynosoma cornutum) using simultaneous radiolocations. All locations that fell within a 12-hour simultaneity window for lizards with overlapping 95% minimum convex polygons were included in a paired-individual analysis using a spatial and temporal interaction test. An interaction among behaviors (attraction, avoidance or random), season (nesting, non-nesting), and cohort (male-male, male-female, and female-female) was observed (p=0.02, log-linear analysis). Males were attracted to areas of their home ranges shared with females, and these attractions occurred more often during the nesting than non-nesting season. There were 29 total pairs with significant spatial interaction, the prevalence of which was attraction to shared area (44 individuals). The proportion of the shared area averaged 2.5 ± 28.0 % of an individual’s home range, with proportions of shared areas within home ranges of individuals tending to vary by cohort pairing (p = 0.08, one-way ANOVA). Females in a male-female pairing had the largest proportion of their home ranges taken up by the shared area (35.9 ± 35.1 %). These results are consistent with previously reported behavior for the species, but a lack of spatial interaction among males during the nesting season suggested a high degree of mutual avoidance or low-level territorial defense.
Keywords: home range, territoriality, minimum convex polygon, spatial interaction
Home Range, Life History, and Activity Patterns of Texas Horned Lizards (Phrynosoma cornutum) in the High Plains region of Texas
Juan C. Diaz, Jacob Goldfarb, Sandra Rideout-Hanzak, Gad Perry
Department of Natural Resources Management, Texas Tech University, Box 42125, Lubbock, TX, 79409-2125: email@example.com
The Texas horned lizard is suffering ongoing declines throughout much of Texas. The main causes are anthropogenic pressures, including habitat loss, use of pesticides, and the arrival of the red imported fire ant. Data on many aspects of the biology of the lizard are limited, only a few locations within the broad distribution have been studied in any detail, and causes of local declines or survival are often unclear. We studied home range (HR), life history, and activity patterns of this species in the high plains region of Texas. The study was conducted in Garza County, in the Texas Panhandle, on a private ranch engaged in ongoing habitat restoration efforts. We radio-tracked lizards throughout 2005 and 2006. As previously reported, female Texas horned lizards (mean SVL = 90 mm) are bigger than males (SVL = 73 mm). Adult females also grow faster. Radio-tracking shows that the average HR at this location is 17,600m2, and male and female HRs were not statistically different. Females lose about 40% of their mass when they deposit a clutch. Both sexes are most likely to be active at ambient temperatures between 29 - 36 °C, making for a surprisingly short activity season, and are more active during the morning and afternoon, especially during the heat of the summer. As in other populations, natural mortality is high. Also of concern is the frequent use of roads, exposing lizards to increased risk of mortality.
Keywords: home range, growth, mass changes and activities
Horned Lizard Monitoring and Demographics on the Matador Wildlife Management Area, Cottle County, Texas
Michael W. Janis and Donald C. Ruthven
Texas Parks & Wildlife Department, 3036 FM 3256, Paducah, TX, 79248: firstname.lastname@example.org
The Matador Wildlife Management Area (MWMA) comprises 11,405 ha (28,183 acres) in the rolling plains ecological region of Texas. The MWMA supports a healthy population of Texas horned lizards (Phrynosoma cornutum), and in 2004 we initiated an intensive mark-recapture monitoring program. From 2004–2006 we made 1,157 captures of horned lizards, with 259 being recaptures. The MWMA received average and above average winter and spring precipitation in 2004 and 2005, respectively, whereas in 2006 drought conditions prevailed. We make descriptive comparisons of demographic parameters between the drought and non-drought years. Of particular interest, we observed a noticeable increase in juvenile horned lizards in the population in 2005. In 2006 we also implemented a system of established road-cruising routes, so effort can be standardized to facilitate comparisons through time and among different soil and habitat types that occur on MWMA. Preliminary results from those efforts suggest that road cruising for horned lizards is most productive during the first 2 weeks of June on the MWMA, and that morning versus evening road cruising produce similar encounter rates. Additionally, we compare our northern Texas population to a southern Texas population on the Chaparral Wildlife Management Area. Preliminary data suggest that horned lizards in southern Texas grow faster, possibly because they have a longer active season.
Keywords: Texas Horned Lizard, demographics, growth rate, road cruising
Texas Horned Lizard Diet Analysis: Evaluating the Effects of Burning and Grazing
Jeremy S. Lane and Richard T. Kazmaier
Department of Life, Earth, and Environmental Sciences, West Texas A&M University, Box 60808, Canyon, TX, 79016: email@example.com
Although the diet of the Texas horned lizard (Phrynosoma cornutum) has been characterized as being dominated by harvester ants (Pogonomyrmex spp.), little attempt has been made to quantify variation in diet or the influence of land management practices on diet. Such information would be valuable for conservation efforts. For this purpose, Texas horned lizard fecal samples, collected from Chaparral Wildlife Management Area in southern Texas from 1998-2003 in conjunction with a fire ecology project on this species, were dissected to identify their contents. Each sample was matched to a pre-existing burning (unburned or burned) and grazing (ungrazed, moderately grazed, or heavily grazed) treatment according to the area in which it was found. Dietary abundance, diversity, richness, and evenness were calculated and compared among burning and grazing treatments using ANOVA. Two hundred twenty-five fecal samples were dissected, with ants (Formicidae) and termites (Isoptera) comprising the majority of the samples with 76.37% and 23.05% respectively. Twenty-six invertebrate families and approximately 27 ant species were identified from the samples. Of the ants, honeypot ants (Myrmecocystus; 60.27%) and harvester ants (Pogonomyrmex; 31.64%) were the majority. While there was no effect of burning on diet observed, there was an apparent trend among the grazing treatments. Species diversity, richness, and evenness were not different between grazing treatments. However, dietary abundances were higher in fecal samples from moderately grazed areas than in heavily grazed or ungrazed areas at both family and genus levels of invertebrates. As samples from moderately grazed areas had the highest abundances of food items, including the taxa that formed the majority of the diet analyses, moderate grazing appears beneficial to this population.
Keywords: Texas horned lizard diet
Texas Horned Lizard Watch - Results of a Decade of Volunteer Monitoring
Lee Ann Linam
Texas Parks and Wildlife Department, 200 Hoots Holler Rd., Wimberley, TX, 78676: firstname.lastname@example.org
In 1997, the 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 people a choice of participating at several levels representing varying degrees of complexity and scientific rigor. Since its inception, over 185 volunteers have returned species and habitat data from over 250 locations in 165 counties. Data from these official volunteers have been combined with results of citizen interviews conducted as part of the Hometown Horned Toads essay contest, with results of a survey of TPWD biologists, and with incidental reports to produce a postulated current distribution map for the state. While P. cornutum has evidently decline from its former historical distribution, the monitoring program has not detected ongoing declines during the past decade. Urbanization, pesticide use, and the spread of red imported fire ants (Solenopsisinvicta) have been postulated by citizens as the primary causes of decline; however, the monitoring program data have only been able to statistically link the presence of red imported fire ants as a predictor of distribution.
Keywords: volunteer, monitoring, status, Phrynosoma cornutum
Hibernation Site Selection of Short-horned Lizards in Northeastern Colorado.
Daniel Martin and Tom Mathies
Colorado Division of Wildlife, USDA NWRC, 1907-D Ross Ct., Ft. Collins, CO, 80526: email@example.com
We radio-tracked 17 adult Short-horned Lizards to their individual overwintering sites on the Shortgrass Steppe Long-Term Ecological Research (SGS LTER) site in Weld County, Colorado. Above-ground habitat characteristics of 16 overwintering sites and 32 randomly selected points within the study area were assessed. All individuals entered overwintering between 29 August and 19 September with a mean estimated entrance date of 8 September. The first sub-zero nighttime air temperatures occurred shortly thereafter on 16 September. No lizard left its normal area of use to overwinter and there was no tendency to aggregate. Lizards did not necessarily overwinter on warmer south-facing slopes; the proportion of overwintering sites oriented southwards (0.62) was not different from random. Most lizards (75%) selected overwintering sites in the banks of washes that had steep slopes relative to random sites, and at locations where substrate was relatively bare and penetrable. Overwintering sites also had slightly greater coverage of Yucca glauca (0.02%) than the general study area (0.01%). Analyses of historical soil temperature data from the SGS LTER revealed that hibernating lizards would have to overwinter at a subsoil depth of approximately one meter to avoid freezing temperatures.
Keywords: Colorado, hibernation, microhabitat, Phrynosoma hernandesi
Research Notes on Pogonomyrmex barbatus and Pogonomyrmex comanche in North Central Texas
Ann B. Mayo
Department of Biology, University of Texas at Arlington, 501 South Nedderman Drive, LS Rm 337, Arlington, TX, 76019: firstname.lastname@example.org
Preliminary work on the ecology and behavior of the harvester ant species Pogonomyrmex barbatus and Pogonomyrmex comanchewas begun in the Metroplex area (Dallas-Fort Worth) of North Central Texas. To date, colonies of P. comanche have been mapped at four locations within the Fort Worth Wildlife Refuge and Nature Center (FWNC) in Fort Worth and of P. barbatus at two locations, Veterans Park and Randol Mill Park in Arlington. Other locations in the Metroplex and surrounding area are also being mapped for more detailed information of the distribution of these species. The preliminary assessment of the preferred habitats and foraging activities of these ants in the FWNC and Arlington park sites has begun, including possible seasonal shifts in foraging, competition with other harvesting organisms (especially other ants, rodents, and birds), and resource partitioning between P. comanche and P. barbatus (This last is in preparation in conjunction with Dr. Jerry Cook (senior author) of Sam Houston University and NSF). Assessment of predation on these harvester ant species was also begun. Implications of this work should enhance management and conservation of these ant species in support of the conservation of the horned lizard (Phrynosoma).
Keywords: Pogonomyrmex, harvester ant, foraging, conservation
Horned Lizards in the Movies, Literature, and Music
We have certainly seen an abundance of photographs and art work with horned lizards. However, horned lizards have also been used and referenced in other media as well. They have even been used in some commercials to sell products. This talk will present some of the findings the Society has collected regarding the use and reference of horned lizards in movies, literature, and music.
Keywords: music, literature, movies, lizards
An Envirogram for the Texas Horned Lizard
Ellen Schwaller and Tony L. Burgess
Environmental Science, Texas Christian University, TCU Box 298830, Fort Worth, TX, 76129: email@example.com; firstname.lastname@example.org
We shall use Andrewartha and Birch’s envirogram model as the basis for an information platform to organize knowledge about the Texas Horned Lizard (Phrynosoma cornutum). Within this logical framework we will compile previous studies of P. cornutum, arranging environmental components affecting the organism into a dendrogram reflecting hypothetical causation sequences. Information is categorized into four component classes: resources and mates (positively acting on the organism); and predators and malentities (negatively acting on the organism). By organizing current knowledge in this way, we will more easily determine what is understood about P. cornutum, what questions should be answered to explain its recent contraction of populations in Texas, and what research should have priority in order to try experimental introductions. The envirogram will be designed so that each node links with attributed publications and sources. The project will be web-accessible to promote further collaboration, research, and education.
Keywords: envirogram, Phrynosoma cornutum, informatics
Don't Mess with the Texas Horned Lizard or Leave 'em Where You Find 'em
The Texas Horned Lizard is the Texas State Reptile. It is one of 13 horned lizard species in North America and is listed as threatened. There are many reasons for its decline. The fire ants invade harvester ant (the horned lizards’ main prey) territory, ravage their populations, decimate smaller horned lizards, and devour their eggs. As the fire ant populace mushrooms, the horned lizard population wanes. Humans also are culpable: they ruin natural habitats and seize the lizards away from native soil to stash as pets. Although horned lizards are charming, docile, magnetic, they are extremely demanding, arduous and thorny to keep alive. Another reason is that their diets are very specific. If this is disturbed, it may affect their health. They mostly eat harvester ants with an adult lizard consuming over 200 every day, which is a lot of ants to supply. Moving and handling a horned lizard stresses their immune systems, which makes them more susceptible to viruses. They can also potentially carry Salmonella bacteria that can cause human illnesses. If you were to try to keep them as a pet, you would need to build and maintain an expensive enclosure that simulates their own environment. It is also illegal to handle, pick up or move them without a scientific permit.
Keywords: pets, horned lizard, threatened
Ecology of Two Sympatric Species of Horned Lizards in Texas
Daniel P. Walker and Richard T. Kazmaier
Department of Life, Earth and Environmental Sciences West Texas A&M University, WTAMU Box 60808, Canyon, TX, 79016: email@example.com
As a result of population declines, horned lizards (Phrynosoma spp.) have received considerable attention with an emphasis on conservation and management. Texas horned lizards (P. cornutum) and roundtail horned lizards (P. modestum) are sympatric over a large portion of their ranges. We are examining the ecology of and niche partitioning of both species in the Texas Panhandle on the Cross Bar Ranch in Potter County. Lizards of both species are being captured through fortuitous encounters, road cursing and intensive searches. Upon each capture, morphological and microhabitat measurements are being taken. At each capture, microhabitat data are being taken at the actual lizard location and at a random point to compare use versus availability for each species to clarify microhabitat selection. Preliminary analyses suggest that both species are selecting for open areas, however Texas horned lizards are selecting for sites with more bare soil and roundtail horned lizards are selecting for rocky sites. Spatial distribution and diet are also being compared between the two species to evaluate these niche dimensions. We will also be expanding data collection to other regions where these two species are found to clarify regional variation in both morphology and niche partitioning.
Keywords: niche partitioning, Phrynosoma, microhabitat selection