Ontogenetic modulation of risk perception and decision making in larval anurans

Abstract To select cost-effective defensive strategies, prey must fine-tune defensive responses by integrating reliable information about predation risk with their own physiological state and energetic needs. Although the actual perceived level of risk is difficult to assess, we hypothesized that stage-related variation in defensive responses to different predation cue concentrations may offer insight into decision-making under predation risk. To test this hypothesis, we examined the sensitivity of Italian agile frog (Rana latastei) tadpoles to both fed and fasted predator cues at 4 concentrations (pure stimulus, 1:10, 1:100, 1:500, including tap water as control), testing individuals at 2 developmental stages (26 to 28 and 30 to 31 Gosner stages). Young tadpoles responded similarly to both fasted and fed predator cues, by markedly lowering activity levels when exposed at pure and 1:10 cues, while no significant difference from the control was recorded at low cue concentrations. Old tadpoles, in contrast, showed heightened sensitivity to fed predator cues, responding even at 1:100, while largely ignoring cues from fasted predators. These results highlight a developmental shift in risk assessment, consistent with changing tradeoffs between predator avoidance and other life-history priorities. This shift suggests that ontogenetic changes shape not only the strength but also the selectivity of perceived risk, reflecting more nuanced decision-making as developmental priorities evolve.