Temporally structured plasticity in death-feigning behavior in response to nutritional conditions in Tribolium castaneum

Investment in antipredator behavior and foraging both directly influence fitness, yet these investments are often subject to trade-offs. In income-breeding species, individuals may initially prioritize foraging after adult emergence and subsequently increase investment in antipredator behavior as their nutritional condition improves. In this study, we investigated temporal changes in death-feigning behavior, an antipredator response, in the red flour beetle Tribolium castaneum from immediately after adult emergence. Both fed and starved individuals exhibited an increase in death-feigning duration with time after emergence. However, in starved individuals, this trend reversed after approximately 15 days, with a marked decline in duration. These results suggest that the increase in investment in death-feigning behavior early in adulthood is relatively inflexible, whereas behavioral responses become highly plastic in response to environmental conditions around day 15. Furthermore, individuals that were fed until day 18 before starvation showed a less pronounced behavioral change than those subjected to starvation from the beginning of the experimental period, suggesting that the timing of environmental exposure may influence subsequent behavioral responses. Together, these findings suggest that behavioral plasticity is not constant over time but is instead structured across developmental stages. We propose a novel conceptual framework, termed temporally structured plasticity (TSP), to describe this pattern.