Houston C. Chandler | Search USGS

USGS2024

Predicting the persistence of salamanders: consequences of phenological shifts for species of management concern on DoD lands

As climate change effects intensify, key life history events may become decoupled from necessary biotic and abiotic resources. For species of management concern on Department of Defense (DoD) lands, these shifts in phenology may prove difficult to address without a mechanistic understanding of the drivers of such changes. We sought to determine the causes and effects of phenological shifts on species of management concern by using observational and experimental data to develop and test population viability models. Our objectives were to (i) identify the patterns and drivers of adult breeding and juvenile emigration phenology for four pond-breeding salamanders (three of management concern), (ii) determine how shifts in phenology and abiotic resources affect the strength of species interactions, community structure, and population viability, and (iii) provide management options to mitigate shifts in phenology that may impact ongoing conservation and recovery efforts.

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USGS2023

Evaluating growth rates of captive, wild, and reintroduced populations of the imperiled Eastern Indigo Snake (Drymarchon couperi)

Reintroduction of species at sites where populations have been extirpated has become a common technique in wildlife conservation. To track progress towards reintroduction success, effective postrelease monitoring is needed to document vital rates of individuals and the corresponding impact on population trajectories. We assessed growth and body size in Eastern Indigo Snakes (Drymarchon couperi) using a data set from multiple projects across the species' distribution, including free-ranging wild snakes, snakes reared in captive-breeding programs, and snakes released at two reintroduction sites. We used these data to fit a von Bertalanffy growth model in a Bayesian framework to quantify differences in growth among three broad categories of snakes (wild, captive, and reintroduced), while accounting for measurement error across various projects. We also compared changes in body mass of captive-born individuals from four captive rearing facilities. Asymptotic snout–vent length across all groups was 185 cm (95% credible interval = 177–194 cm) for males and 157 cm (95% credible interval = 153–161 cm) for females. Reintroduced snakes had a higher growth coefficient than either captive or wild snakes (e.g., captive females = 1.20 [1.06–1.35] d –1 ; wild females = 1.22 [0.95–1.49] d –1 ; reintroduced females = 1.62 [1.21–2.05] d –1 ), indicating that current captive-breeding and rearing efforts for indigo snakes produce similar or faster growth trends compared to wild populations. Furthermore, daily changes in juvenile body weight relative to body size were similar in three of the four captive rearing facilities (mean for females at Orianne Center for Indigo Conservation = 0.57 [0.48–0.65]; Zoo Atlanta = 0.55 [0.37–0.72]; Welaka National Fish Hatchery = 0.55, [0.36–0.73]; Auburn University = 0.39 [0.21–0.58]). Long-term project success for indigo snake reintroductions will depend on continuing to implement best practices in an adaptive management framework.

Herpetologica↗