Jump now, pay later: saltatory behavior trades off with body mass and facilitates shelter repair in a seed-dwelling insect

Abstract

Many animals inhabit spatially confined shelters that provide protection but impose sensory and energetic constraints. In the Mexican jumping bean moth, Cydia saltitans , larvae use saltatory (“jumping”) movements to relocate their shelters (i.e., parasitized seeds) away from aversive stimuli, potentially at a high energetic cost. We tested whether these movements trade off with larval energetic reserves, development, and shelter repair. We placed larvae in one of two treatments: a control group allowed to move freely, and a stationary group in which shelter movement was physically prevented, and we quantified seed wall repair time following induced damage, larval body mass as a proxy for fat reserves, and head capsule width as a developmental stage proxy. Stationary larvae exhibited significantly higher body mass than control larvae, suggesting an energetic cost to saltatory behavior, although developmental stage did not differ between treatments. However, control larvae repaired shelter damage significantly more quickly than stationary individuals. Free movement might enable larvae to optimize positioning and leverage for repair, highlighting another adaptive function of saltatory movements, or might better promote hormone levels that support silk production for repair. Our findings highlight how individuals may prioritize energy allocation for movement, despite the energetic costs, in spatially confined and resource-limited systems. Understanding this balance provides broader insight into the evolution of behavioral and physiological strategies in species adapted to spatial or energetic constraints.

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