Developmental environment has lasting effects on amphibian behavior and thermal physiology

Environmental challenges early in development can result in complex
phenotypic trade-offs and long-term effects on individual physiology,
performance, and behavior, with implications for disease and predation
risk. We examined the effects of simulated pond-drying and elevated water
temperatures on development, growth, thermal physiology, and behavior in a
widespread North American amphibian, the Southern leopard frog, Rana
sphenocephala. Tadpoles were raised in outdoor mesocosms under warming and
drying regimes based on projected climatic conditions in 2070. We
predicted that amphibians experiencing the rapid pond drying and elevated
pond temperatures associated with climate change would accelerate
development, be smaller at metamorphosis and demonstrate long-term
differences in physiology and exploratory behavior post-metamorphosis.
While both drying and warming accelerated development and reduced survival
to metamorphosis, only drying resulted in smaller animals at
metamorphosis. At approximately one month post-metamorphosis, animals from
the control (ambient no-drying) treatment jumped relatively farther at
high temperatures in jumping trials. In addition, across all treatments,
frogs with shorter larval periods had lower critical thermal minima and
maxima. We also found evidence that developing under warming and drying
resulted in a less exploratory behavioral phenotype, and that drying, but
not warming, resulted in warmer thermal preferences. Furthermore, behavior
predicted thermal preference, with less exploratory animals selecting
higher temperatures. Our results underscore the multi-faceted effects of
early developmental environments on behavioral and physiological
phenotypes later in life. For example, thermal preferences can influence
disease risk through behavioral thermoregulation, and exploratory behavior
may increase risk of predation or pathogen encounter. By impacting thermal
physiology, behavior, and various physiological traits, climatic stressors
during development may mediate amphibian exposure and susceptibility to
predators and pathogens into adulthood.