Date of Award
Anthropogenic activities caused by urbanization have considerably altered our world’s ecosystems which has led to a global amphibian population decline. Encroaching and unyielding urbanization by humans has contributed to a rise in artificial light at night due to light pollution as well as increased temperature due to climate change. Both rising temperatures and artificial light at night (ALAN) have been shown to individually have negative effects on amphibian physiology such as increased stress and decreased behavior. However, due to the drastic nature of human imposition, amphibians typically encounter these anthropogenic stressors in combination. Therefore, it is important to understand how both individual and multiple stressors impact amphibian physiological responses and fitness so that we can predict how future populations will be affected and improve conservation efforts. To determine the relationship between anthropogenic stress and physiological fitness, we designed an experiment that exposed 60 southern leopard frog (Lithobates sphenocephalus) tadpoles for three weeks to elevated temperatures and artificial light at night both individually, combined, and with a control of normal temperatures and light/dark conditions. We then determined their predator evasion abilities by recording their swimming performance via turn-around time and burst swimming speed with a high-speed go-pro camera and a simulated predator. We then determined their total stress hormone levels by performing a whole-body corticosterone (CORT) assay using an ELISA to acquire the corticosterone concentrations within each tadpole. We found that neither ALAN nor increased temperature had any significant impact on either turn-around time or burst swimming speed (P>0.05). However, we found that ALAN caused an increase in whole-body corticosterone concentrations, but increased temperature had no effect. Finally, we found that increased temperature significantly decreased body mass, and increased temperature combined with ALAN marginally decreased body mass. Overall, we found that an increase in temperature had a stronger negative impact on growth, while ALAN increased whole-body corticosterone. However, swimming performance was largely unimpacted after three weeks of exposure to both stressors. An increase in whole-body corticosterone levels with only three-weeks of exposure to ALAN may indicate that longer-term exposures could be more detrimental to larval amphibians.
Alexander, Skylar, "Evaluating the impact of temperature and artificial light at night on the growth, swimming performance, and corticosterone levels of southern leopard frog (Lithobates sphenocephalus) tadpoles" (2023). Honors Theses. 2979.
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