Papers by Selma Glasscock
Journal of Mammalogy, Oct 1, 2008
We tested the influence of a change in food resource distribution on space use and diet of coyote... more We tested the influence of a change in food resource distribution on space use and diet of coyotes (Canis latrans). We focused on 2 facets of space use: maintenance of home ranges by residents, and establishment of home ranges by immigrants after a coyote removal program. The study was conducted on 2 populations of coyotes in southern Texas. In both populations, a clumped, high-quality food source was added to randomly selected feeding stations to measure the influence of food distribution and abundance on home-range patterns, trespassing rates, and consumption of native prey. In established home ranges, coyotes visited and foraged at stations regularly and were found closer to stations during the treatment period. Although there was no overall treatment effect on home-range size (F ¼ 1.66, d.f. ¼ 5, P ¼ 0.15), home ranges without supplemental food remained stable in size, whereas home ranges that had received supplemental food increased during the posttreatment period (t ¼ 2.09, d.f. ¼ 1, P ¼ 0.04). Core areas showed a similar trend; there was no overall treatment effect (F ¼ 1.51, d.f. ¼ 2, P ¼ 0.24); however, core areas of home ranges that received supplemental food were smaller than those of controls during the treatment period (t ¼ 2.71, d.f. ¼ 1, P , 0.01). There were no statistical differences in occurrence of any species, such as small mammals or white-tailed deer (Odocoileus virginianus), in scats of treatment versus control coyotes. Coyotes within the study site after removals were located closer to feeding stations during treatment than posttreatment (F ¼ 8.83, d.f. ¼ 1, P , 0.02, n ¼ 897) periods, yet homerange size with supplemental food was larger than home-range size during the posttreatment period. Our findings suggest that a resource other than food influences coyote spatial patterns.
Authorea (Authorea), Mar 16, 2023
Body condition is a frequently used physiological indicator of avian health and is affected by an... more Body condition is a frequently used physiological indicator of avian health and is affected by an array of environmental variables. Although a number of studies have investigated the specific effects of individual weather variables on body condition in birds, few have analyzed the effects of both temperature and precipitation within the context of an extreme weather event such as hurricanes. In this study we examined the relationship between breeding season body condition and daily maximum temperature, daily minimum temperature, and monthly total precipitation for three passerine bird species at the Welder Wildlife Refuge near Rockport, Texas. We also evaluated yearly changes in body condition over a twelve-year period for northern cardinals (Cardinalis cardinalis), painted buntings (Passerina ciris), and white-eyed vireos (Vireo griseus), focusing on the extreme precipitation event of Hurricane Harvey which caused heavy localized flooding. We found that body condition declined with average daily minimum and maximum temperatures, while precipitation had varied, species-specific effects in the three species analyzed. Our results also suggest that northern cardinals experienced a notable reduction in average body condition in the two years following Hurricane Harvey. Taken together, we conclude that short-term precipitation and temperature drivers can be important correlates of body condition in songbirds and that severe weather events may reduce body condition in some bird species.
Range change is occurring at a rapid rate for tropical, subtropical, and warm desert birds in Tex... more Range change is occurring at a rapid rate for tropical, subtropical, and warm desert birds in Texas . Comparisons between former (1974) and current avian distributions for the region show significant breeding range extension of 40-220 km to the N, NE, or E for at least 68 species, many of which cross major biogeographic boundaries . Fieldwork at the northern end of the subtropics along the coastal plain of the Gulf of Mexico has provided extensive documentation of breeding populations in new areas (e .g ., nests, eggs, nestlings, fledglings, pairs, singing males on territory, and response to playback) for nine subtropical species (e .g ., Green Jay Cyanocorax yncas and White-tipped Dove Leptotila verreauxi), as well as photographic evidence of seasonal persistence derived from use of a novel, web-based collaborative online robotic wildlife camera . Poor previous documentation, population change, habitat loss in the former range, and habitat change in the new range are considered as possible explanations . We conclude that change in key parameters of habitat, e .g . seasonal food availability, as affected by factors related to climatic change, e .g ., mean annual precipitation, temporal distribution of precipitation (monthly means), or monthly means for nighttime-low temperatures during the breeding season, provide the most likely explanations for observed range extensions . At present, movement of a large segment of the subtropical avian community into temperate habitats has not been met with a corresponding shift of temperate species as had been predicted by a number of models; rather the communities now overlap, creating, in effect, novel communities . Results of this overlap are likely to produce profound changes that may first be evident in the genetics of subtropical/temperate species pairs, e .g ., Black-crested Titmouse Baeolophus atricapillus and Tufted Titmouse Baeolophus bicolor .
Body condition is a frequently used physiological indicator of avian health and is affected by an... more Body condition is a frequently used physiological indicator of avian health and is affected by an array of environmental variables. Although a number of studies have investigated the specific effects of individual weather variables on body condition in birds, few have analyzed the effects of both temperature and precipitation within the context of an extreme weather event such as hurricanes. In this study we examined the relationship between breeding season body condition and daily maximum temperature, daily minimum temperature, and monthly total precipitation for three passerine bird species at the Welder Wildlife Refuge near Rockport, Texas. We also evaluated yearly changes in body condition over a twelve-year period for northern cardinals (Cardinalis cardinalis), painted buntings (Passerina ciris), and white-eyed vireos (Vireo griseus), focusing on the extreme precipitation event of Hurricane Harvey which caused heavy localized flooding. We found that body condition declined with...
PLOS ONE
Copper (Cu), iron (Fe), and zinc (Zn) are essential trace minerals for the reproduction, growth, ... more Copper (Cu), iron (Fe), and zinc (Zn) are essential trace minerals for the reproduction, growth, and immunity of mammalian herbivore populations. We examined the relationships between Cu, Fe, and Zn in soils, common plants, and hepatic stores of two wild herbivores to assess the effects of weather, sex, and population density on the transfer of trace minerals from soils to mammals during the growing season. Soils, grasses, woody browse, hispid cotton rats (Sigmodon hispidus), and white-tailed deer (Odocoileus virginianus) were sampled across 19 sites. Concentrations of Cu, Fe, and Zn in grasses and browse species were not correlated with concentrations of those minerals in soils sampled from the same areas. Leaves of woody browse were higher in Cu, lower in Fe, and similar in Zn when compared with grasses. Available concentrations of soils were positively related to liver Cu and Zn in hispid cotton rats, which was consistent with the short lives and high productivity of these small ...
Journal of Urban Ecology, 2018
Previous studies have explored spatial ecology and habitat use of alligators and other crocodilia... more Previous studies have explored spatial ecology and habitat use of alligators and other crocodilian species. However, few studies have explored these characteristics in urban environments. We studied an alligator population that occurred in an urban-influenced ecosystem, a habitat that has received little scientific attention. Our objectives were to determine spatial ecology and habitat use of American alligators within this urban system and to provide a template of methodology and analytical techniques that can be used by urban biologists, planners and researchers in order to assess and study urban crocodilian populations. We recorded 653 observations of alligators and their locations during 19 alligator surveys at an encounter rate of 0.6 alligators per km/survey. Results indicated that alligators exhibited clustering patterns of distribution. Thirteen different wetland types occurred within our survey area, but alligators were only observed in 10 of the 13. We found few difference...
Herpetological Monographs, 2018
The American Alligator (Alligator mississippiensis) is a crocodilian species that was once listed... more The American Alligator (Alligator mississippiensis) is a crocodilian species that was once listed as endangered in the United States but is now harvested both recreationally and commercially throughout its range in the southeastern United States. Harvest of alligators typically includes egg collecting and hunting. However, review of scientific literature reveals that the effects of harvest on alligator populations have received little scientific scrutiny. We built a theoretical simulation model to evaluate the impact of several harvest strategies on long-term (i.e., 100 yr) alligator population trends. We used system dynamics software to develop the model and acquired data for the model from literature and field studies on alligator ecology. Although widely applicable across the species range and for other crocodilians, we used the Texas alligator management program as an example for model use. Results of model simulations showed that current harvest (50% egg harvest, 2% subadult harvest, 2% adult harvest) is sustainable, but alligator populations will stabilize at levels below population potential. The best harvest scenario for a sustainable harvest that maintains alligator populations at a relatively unchanging level is a 38% egg harvest, 2% subadult harvest, and 2% adult harvest. An elevated egg harvest (80%) can be sustained if no hunting harvest occurs. Contrarily, an increased hunting harvest (4% subadult, 4% adult) can be sustained with no egg harvest. This model identifies the function of current alligator harvest within populations and provides a tool for future use in determining the effect of changes in harvest or life-history characteristics on alligator population dynamics.
Wildlife Society Bulletin, 2016
ABSTRACTEnvironmental education programs have been evaluated to assess short‐term effects on part... more ABSTRACTEnvironmental education programs have been evaluated to assess short‐term effects on participants; however, few studies have examined long‐term effects. We quantified how the Texas Chapter of The Wildlife Society's Wildlife Conservation Camp (WCC), Texas, USA, has affected high school students. A web‐based survey questionnaire measured attitudes and behaviors of participants toward wildlife conservation and natural resources. A subset of questions was taken from the 2011 National Survey of Fishing, Hunting, and Wildlife‐Associated Recreation to provide a comparison population (USDI, USFWS, USDC, and USCB 2011). The majority of respondents reported moderate to large increases in knowledge (89%) and interest (80%) of wildlife conservation and observation from the WCC and major influence on the course of their lives (85%). Most respondents (86%) who went into a conservation‐related field reported the WCC influenced their career path. The majority of WCC respondents took spe...
The Wilson Journal of Ornithology, 2013
BioOne sees sustainable scholarly publishing as an inherently collaborative enterprise connecting... more BioOne sees sustainable scholarly publishing as an inherently collaborative enterprise connecting authors, nonprofit publishers, academic institutions, research libraries, and research funders in the common goal of maximizing access to critical research.
Journal of Mammalogy, 2008
We tested the influence of a change in food resource distribution on space use and diet of coyote... more We tested the influence of a change in food resource distribution on space use and diet of coyotes (Canis latrans). We focused on 2 facets of space use: maintenance of home ranges by residents, and establishment of home ranges by immigrants after a coyote removal program. The study was conducted on 2 populations of coyotes in southern Texas. In both populations, a clumped, high-quality food source was added to randomly selected feeding stations to measure the influence of food distribution and abundance on home-range patterns, trespassing rates, and consumption of native prey. In established home ranges, coyotes visited and foraged at stations regularly and were found closer to stations during the treatment period. Although there was no overall treatment effect on home-range size (F ¼ 1.66, d.f. ¼ 5, P ¼ 0.15), home ranges without supplemental food remained stable in size, whereas home ranges that had received supplemental food increased during the posttreatment period (t ¼ 2.09, d.f. ¼ 1, P ¼ 0.04). Core areas showed a similar trend; there was no overall treatment effect (F ¼ 1.51, d.f. ¼ 2, P ¼ 0.24); however, core areas of home ranges that received supplemental food were smaller than those of controls during the treatment period (t ¼ 2.71, d.f. ¼ 1, P , 0.01). There were no statistical differences in occurrence of any species, such as small mammals or white-tailed deer (Odocoileus virginianus), in scats of treatment versus control coyotes. Coyotes within the study site after removals were located closer to feeding stations during treatment than posttreatment (F ¼ 8.83, d.f. ¼ 1, P , 0.02, n ¼ 897) periods, yet homerange size with supplemental food was larger than home-range size during the posttreatment period. Our findings suggest that a resource other than food influences coyote spatial patterns.
IFAC Proceedings Volumes, 2009
The scientific field study of wildlife often requires vigilant observation of detailed animal beh... more The scientific field study of wildlife often requires vigilant observation of detailed animal behavior over extended periods. In remote and inhospitable locations, observation can be an arduous, expensive, and dangerous experience for field scientists. We are developing a new class of networked teleoperated robotic "observatories" that allows "citizen scientists" and professional scientists to remotely observe, record, and index animal activity and behaviors via the internet. This paper describes CONE-Welder, installed at the Rob & Bessie Welder Wildlife Foundation in Texas to gather photographic and quantitative data for a biological study of avian activity and hypothesized range change for selected subtropical bird species. Since the system was deployed on 12 May 2008, over 600 users ("players") have participated online. Players have requested over 2.2 million camera frames and captured over 29,000 photographs. Within these photos, citizen scientists have classified 74 unique species, including eight avian species previously unknown to have breeding populations within the region. The collected dataset quantifies seasonal presence of birds of particular interest, e.g., the Green Jay (Cyanocorax incas). This paper describes the system architecture, the game interface that provides incentives for player participation, and initial data collected. CONE-Welder
Journal of Environmental Management, Jun 1, 2005
In this paper, we describe a model designed to simulate seasonal dynamics of warm and cool season... more In this paper, we describe a model designed to simulate seasonal dynamics of warm and cool season grasses and forbs, as well as the dynamics of woody plant succession through five seral stages, in each of nine different plant communities on the Rob and Bessie Welder Wildlife Refuge. The Welder Wildlife Refuge (WWR) is located in the Gulf Coastal Prairies and Marshes ecoregion of Texas. The model utilizes and integrates data from a wide array of research projects that have occurred in south Texas and WWR. It is designed to investigate the effects of alternative livestock grazing programs and brush control practices, with particular emphasis on prescribed burning, the preferred treatment for brush on the WWR. We evaluated the model by simulating changes in the plant communities under historical (1974-2000) temperature, rainfall, livestock grazing rotation, and brush control regimes, and comparing simulation results to field data on herbaceous biomass and brush canopy cover collected on the WWR over the same period. We then used the model to simulate the effects of 13 alternative management schemes, under each of four weather regimes, over the next 25 years. We found that over the simulation period, years 1974-2000, the model does well in simulating the magnitude and seasonality of herbaceous biomass production and changes in percent brush canopy cover on the WWR. It also does well in simulating the effects of variations in cattle stocking rates, grazing rotation programs, and brush control regimes on plant communities, thus providing insight into the combined effects of temperature, precipitation, cattle stocking rates, grazing rotation programs, and brush control on the overall productivity and state of woody plant succession on the WWR. Simulation of alternative management schemes suggests that brush canopy removal differs little between summer and winter prescribed burn treatments when precipitation remains near the long-term average, but during periods of low precipitation canopy removal is greater under winter prescribed burning. The model provides a useful tool to assist refuge personnel with developing long-term brush management and livestock grazing strategies.
Journal of Environmental Management, 2005
In this paper, we describe a model designed to simulate seasonal dynamics of warm and cool season... more In this paper, we describe a model designed to simulate seasonal dynamics of warm and cool season grasses and forbs, as well as the dynamics of woody plant succession through five seral stages, in each of nine different plant communities on the Rob and Bessie Welder Wildlife Refuge. The Welder Wildlife Refuge (WWR) is located in the Gulf Coastal Prairies and Marshes ecoregion of Texas. The model utilizes and integrates data from a wide array of research projects that have occurred in south Texas and WWR. It is designed to investigate the effects of alternative livestock grazing programs and brush control practices, with particular emphasis on prescribed burning, the preferred treatment for brush on the WWR. We evaluated the model by simulating changes in the plant communities under historical (1974-2000) temperature, rainfall, livestock grazing rotation, and brush control regimes, and comparing simulation results to field data on herbaceous biomass and brush canopy cover collected on the WWR over the same period. We then used the model to simulate the effects of 13 alternative management schemes, under each of four weather regimes, over the next 25 years. We found that over the simulation period, years 1974-2000, the model does well in simulating the magnitude and seasonality of herbaceous biomass production and changes in percent brush canopy cover on the WWR. It also does well in simulating the effects of variations in cattle stocking rates, grazing rotation programs, and brush control regimes on plant communities, thus providing insight into the combined effects of temperature, precipitation, cattle stocking rates, grazing rotation programs, and brush control on the overall productivity and state of woody plant succession on the WWR. Simulation of alternative management schemes suggests that brush canopy removal differs little between summer and winter prescribed burn treatments when precipitation remains near the long-term average, but during periods of low precipitation canopy removal is greater under winter prescribed burning. The model provides a useful tool to assist refuge personnel with developing long-term brush management and livestock grazing strategies.
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Papers by Selma Glasscock