Effects of artificial light at night (ALAN) on the physiology, growth, and behavior of two common Texas anurans

Forsburg, Zachery R.
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Artificial light at night (ALAN) alters the natural light dark patterns in ecosystems and is a growing problem, as 40% of the world’s population lives in areas continually illuminated and area exposed to ALAN is increasing at an estimated 6% per year. ALAN can have a suite of effects on the behavioral, developmental, and physiological traits of organisms. Amphibians are the most imperiled vertebrate class, as over 40% of known species are threatened with extinction, yet our understanding of how ALAN affects amphibians is lacking compared to our knowledge of how ALAN affects other organisms. My dissertation research explored how ALAN affects the physiology, growth, and behavior of the larvae of two common Texas anurans, the Rio Grande leopard frog (Rana berlandieri) and the Gulf Coast toad (Bufo valliceps). Chapter 1 is an introduction to ALAN, how ALAN affects other groups of organisms, and an overview of the main topics of my research. I validate a non-invasive water-borne hormone collection method for Rana berlandieri, explore the physiology of R. berlandieri tadpoles, and compare rearing methods in Chapter 2. Chapter 3 discusses the results of laboratory reaction norm studies showing that short term exposure to ALAN affects the physiology, but not the behavior or growth of R. berlandieri and B. valliceps tadpoles. The last chapter explores if ALAN acts synergistically with a natural environmental stressor for tadpoles, the presence of predators, using a semi-natural outdoor mesocosm experiment. Additionally, I examined how long-term exposure to ALAN affected the growth and anti-predator behavior of R. berlandieri Rio Grande leopard frog tadpoles. My results show that both short-term and long-term exposure to environmentally relevant levels of ALAN affect the physiology of anuran larvae. Short-term ALAN exposure did not affect behavior, but long-term exposure to ALAN diminished anti-predator behavior. Long-term exposure decreases the growth of tadpoles and increases the rate of metamorphosis. My research also suggests that ALAN interacts synergistically with other environmental stressors to negatively affect the physiology of tadpoles. Together, my research suggests that urban planners should include ways to remove ALAN, or mitigate the effects of ALAN, when building around wildlife areas to decrease the consequences of ALAN on amphibian populations.
ALAN, Light pollution, Conservation physiology, Stress physiology, Corticosterone, Amphibians
Forsburg, Z. R. (2020). <i>Effects of artificial light at night (ALAN) on the physiology, growth, and behavior of two common Texas anurans</i> (Unpublished dissertation). Texas State University, San Marcos, Texas.