Behavioral and physiological responses of the terrestrial life stages of the Jefferson salamander, Ambystoma jeffersonianum, to low soil pH

Abstract

Terrestrial metamorphs of the salamander, Ambystoma jeffersonianum, were exposed to four levels of pH on artificial substrates in the laboratory. Short-term exposure (7 d) to pH levels between 3.5 and 5.0 had no effect on total body mass, Na⁺, K⁺, Ca²⁺, and Mg²⁺ concentrations. However, at 14 d in both laboratory experiments and in field microcosms, whole body water and Na⁺ concentrations were significantly lower at the lower pH level. Terrestrial metamorphs and adults of the Jefferson salamander preferred artificial substrates that were higher in pH. Ponds not utilized for breeding all had adjacent soil pH below 3.7. Pond water and soil pH were directly and highly correlated. Soil pH may indirectly affect breeding success of Jefferson salamanders by influencing pond pH or directly by physiologically stressing the terrestrial life stages. Laboratory data implicate direct effects on the physiology of terrestrial young of the year salamanders by induction of loss of body water and Na⁺. Apparently, soil pH is a critical factor not only in the selection of vernal ponds by Jefferson salamander adults for breeding, but in determining the likelihood of reproductive success as judged by recruitment into the adult population.