Habitat Characteristics in Created Vernal Pools Impact Spotted Salamander Water-Borne Corticosterone Levels

Water‐borne and plasma corticosterone are not correlated in spotted salamanders

“…Despite the lack of correlation between water‐borne and plasma corticosterone; we have evidence that water‐borne corticosterone is biologically meaningful in spotted salamanders. In a previous study, water‐borne corticosterone was associated with salamander body size as well as the water temperature and diameter of vernal pools (Millikin et al, ). If water‐borne corticosterone was a random signal, there likely would not have been an association with the body size or the environment.…”

“…This is because dividing water‐borne corticosterone by body size can produce artificial differences if the groups differ greatly in body size (Scott & Ellis, ). Also, we have evidence that dividing by body size does not completely correct for body size differences even among animals of a similar body size (Millikin et al, ). We found after dividing corticosterone pg by total body length, larger animals still had higher corticosterone levels making it necessary to include body size in models to control for its impact when determining predictors of corticosterone levels (Millikin et al, ).…”

“…Also, we have evidence that dividing by body size does not completely correct for body size differences even among animals of a similar body size (Millikin et al, ). We found after dividing corticosterone pg by total body length, larger animals still had higher corticosterone levels making it necessary to include body size in models to control for its impact when determining predictors of corticosterone levels (Millikin et al, ). Another limitation is that perhaps water‐borne hormones should not be compared across different amphibian life stages.…”

“…It is possible that laboratory‐reared metamorphs had elevated baseline corticosterone due to confinement, captivity, or growth and development during metamorphosis, preventing a detectible response (de Assis, Titon, Barsotti, Titon, & Gomes, ; Belden, Wingfield, & Kiesecker, ; Chambers, Wojdak, Du, & Belden, ). It seems these were not influential factors for laboratory‐reared larvae because water‐borne corticosterone levels of laboratory‐reared larvae were similar to those of larvae caught in the field (Millikin et al, ). Our field‐caught adults also had baseline plasma corticosterone levels that were similar to other studies (Homan et al, ).…”

“…Recovery was calculated by observed concentration divided by expected concentration. Minimum observed recovery was 64% (Millikin, Woodley, Davis, & Anderson, ). Observed and expected values were linearly related (slope = 1.40, F (1,7) = 3,945, R 2 = .998, p < .0001; Millikin et al, ).…”