Juvenile Salamanders Do Not Exhibit Compensatory Growth Post-metamorphosis in an Experimental Setting
Compensatory growth, where an organism can grow faster during recovery from low resource periods, is a mechanism used by a wide variety of taxa to mitigate previous deficiencies. Here we present experimental data to test whether pond-breeding salamander juveniles raised in different quality larval habitats can catch up to larger cohort members after metamorphosis. We reared larval Spotted Salamanders (Ambystoma maculatum) in ponds of differing habitat quality resulting in large size differences at metamorphosis. We then kept juveniles in the lab for a year, fed them ad libitum, and measured their growth at three time points post-metamorphosis. We found large differences in size at metamorphosis related to larval habitat, but salamanders that were small at metamorphosis remained smaller a year later and relative growth rates were equal across all metamorphic sizes. Thus, we have little evidence that juveniles can compensate for small size by growing more in the year after metamorphosis, even in conditions of unlimited food. Our data suggest compensatory growth in amphibians may be species-specific, and that poor quality larval environments may be a disadvantage during subsequent life stages.

Change in individual Spotted Salamander mass (mg) over time by leaf litter addition treatment. Size at metamorphosis collected 4 June–8 August 2015, and individuals were weighed on 16–17 January 2016, 1–2 March 2016, and 1–7 April 2016. Each line corresponds to an individual, and the numbers above each panel indicate the larval pond leaf litter quantity (kg/1000 L).

Posterior probability densities of mass at (A) metamorphosis and (B) the end of the experiment approximately one year later, and (C) relative growth rates (in days−1) as predicted by the Bayesian models. We define growth rate as (ln(massfinal)−ln(massinitial))/days between measurements. Each histogram highlights the 90% credible intervals, with the thick vertical line indicating the median.

Mass at metamorphosis vs. relative growth rate (d−1) between metamorphosis and last juvenile measurement. Points are color-coded by larval pond litter quantity treatment.
Contributor Notes
Associate Editor: D. S. Siegel.