Cheating death: Selection on digestive physiology overcomes expected growth costs of anti-predator defenses

Organisms often face a fundamental trade-off between growth and predator avoidance, especially when traits that enhance growth also increase predation risk. While many species reduce activity in response to predators, potentially constraining growth, this trade-off can be mitigated if alternative traits, such as digestive efficiency, compensate for reduced activity, enabling organisms to minimize growth costs while evading predators. To test this idea, we combined a mesocosm experiment with lab-based digestive physiological assays to examine survival selection and plasticity in damselfly larvae exposed to fish predators. We found that selection favored less active individuals, yet this reduction in activity did not suppress growth. Instead, plastic increases in consumption rate, selection for greater assimilation efficiency, and selection for weaker plastic digestive stress responses allowed individuals to maintain growth despite reduced activity and elevated metabolic rates. We provide here two datasets related to this study. The first, titled Mass.Data, contains the data used to determine the ratio of damselfly wet to dry mass that was necessary for calculating relative growth rate and other measures of digestive physiology in the experiment. The second dataset, Assimilation.Data, contains the data for activity rates, digestive physiology, and all other associated experimental measurements for comparing selective and plastic responses to predator presence in damselflies.