Survey Protocols and Spatial Ecology of the Western Chicken Turtle (Deirochelys reticularia miaria)

The behaviors, activity season, and spatial ecology of Deirochelys reticularia miaria (Western Chicken Turtle) are poorly understood in Texas. Though its distribution within the state is widespread, turtle assemblage studies conducted within its range in Texas have seldom documented presence. Formal protection is lacking for the subspecies, and past research suggests that its remaining habitat within the state is threatened by increasing urbanization. The U.S. Fish and Wildlife Service issued a 90-day finding that listing the subspecies as threatened or endangered may be warranted. I designed two studies to meet two primary objectives: (1) standardize survey protocols and (2) assess the turtles’ spatial ecology and examine how its prolonged aestivation period affects model fit when selecting an annual home range estimation method. For the first objective, I reviewed capture techniques from the literature, identified an activity season and period of highest capture success within that season for D. r. miaria in Texas, and evaluated the efficacy and biases of capture methods. I compared capture methods consisting of both active (i.e., road surveys, dipnet surveys, seine surveys, night wading surveys) and passive techniques (i.e., two types of unbaited fyke net). Among passive capture techniques, fyke nets were effective in every study that deployed them and had the highest number of captures in the Texas field study. Dipnet surveys had the highest capture rate among active survey methods. Body size biases were apparent among all methods with enough captures to compare. For the second objective, I analyzed telemetry data to understand annual home range, core area, and movements, or collectively the spatial ecology of the species at two Texas sites. I evaluated the applicability of several home range estimators. The 95% kernel density estimators provided the most consistent estimates of annual home range. Traditional 50% core activity area estimators had questionable utility because they either excluded aquatic areas that were frequently used or included aestivation sites. Managers should consider how extensive aestivation affects home range estimates, how periods of drought affect movement, and how the longevity of the species, the potential to make long migrations, and landscape characteristics could affect spatial resource requirements