Meeting Abstract
Compensatory growth is accelerated growth that occurs after a period of growth depression. Such growth can be advantageous because it allows organisms to obtain a larger body size than they otherwise would. Previous amphibian studies suggest that compensatory growth may occur when larval growth is depressed by food availability, but not when it is depressed by predation threat. The purpose of this study was to determine if such a pattern occurs in larval leopard frogs, Lithobates pipiens. We reared larvae at low and high densities in 410 L outdoor mesocosms (5 and 50 individuals per mesocosm, respectively). Each density was replicated 10 times, and half of the mesocosms at each density contained a caged Libellulid predator. Each tank received a standard amount of food, so per capita resources varied with density. Predators were fed three L. pipiens larvae every other day to generate kairomones. Once larvae reached a standard size, we transferred three individuals from each mesocosm to a set of predator-free mesocosms with ad libitum food. We monitored growth before and after larvae were transferred. During the initial growth period, the presence of a predator depressed larval growth, but only at the low density. Larvae from the high density grew at the same rate as those from the low-density mesocosms with predators. This suggests that predators depressed growth at low density, but food availability did at high density. When larvae were transferred to the second set of mesocosms, individuals from the low-density grew significantly faster than those from the high-density. Those from predator-free mesocosms also tended to grow faster than those from mesocosms with predators. Compensatory growth therefore did not occur. However, larvae did exhibit a high degree of growth-rate plasticity, which warrants further investigation.
