Re-evaluating the reproductive ecology of the endangered Houston Toad (Bufo [=Anaxyrus] houstonensis) using automated audio monitoring techniques
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The Houston Toad (Bufo [=Anaxyrus] houstonensis) has been a species of conservation concern for approximately a half-century, yet many aspects of its life history are not well known. Technological innovations in the form of automated recording devices and automated detection have enabled all aspects of this dissertation. Monitoring for species that are difficult to detect, or become detectable within a narrow temporal window, such as the Houston Toad, has historically been done by human observers. This dissertation seeks to illustrate that through application of technological innovations, remotely monitoring populations of Houston Toads has given us the opportunity to re-evaluate the species’ life history entirely, using data that are collected more frequently, by more reliable observers: automatons.
Populations of Houston Toads have been brought to the brink of extirpation in recent years, then returned to above average local abundances through captive propagation in select localities. These changes in demography are the result of anthropogenic disturbance, above all else, and changes to the landscape continue to occur within this species’ remaining critical habitat. As a part of this study I sought to include data collected throughout these shifts in demography, across landscapes ranging in their relative quality as optimal habitat for the Houston Toad, and from portions of their range in which they are rarely found.
My research has resulted in a successful long-term study of the environmental abiotic correlates to male Houston Toad chorusing behavior, providing crucial information to researchers, biological consultants, and governing agencies about the seasonal and diurnal behavior of this endangered species. It has re-defined the approach human surveyors must take when attempting to detect this species’ vocalization using auditory surveys, and for the first time offers researchers an understanding of how the length, and frequency, of these auditory surveys impacts the probability of detection. I evaluated the sound dampening qualities of the varying microhabitats surrounding Houston Toad breeding locations, and the influence these qualities have on probability of detection for a variety of animal vocalizations, including the Houston Toad. Finally, I review the Houston Toad’s historical range and its relationship with its nearest congeneric relative the Dwarf American Toad (Bufo [=Anaxyrus] americanus charlesmithi) by reviewing past literature, museum vouchers, and comparing the general morphology and vocal repertoire of each species. These data fill gaps in the present knowledge we hold for this species, and provide a foundation for future research to base its hypotheses upon.