House cricket males reared at different perceived acoustic population densities differ in adult behaviour but not physiology

Abstract

If environments stay relatively constant over an individual's lifetime, a juvenile that accurately perceives environmental conditions, like population density, may adjust adult traits to better match their environment, thereby increasing success. While previous studies have explored how adult exposure to population density affects physiological and behavioural plasticity, the influence of juvenile density experience on adult traits is less studied. Using the common house cricket, Acheta domesticus, we explored whether perceived acoustic population density during development affected adult physiology and behaviour. We simulated high‐ and low‐densities using live ambient male song. Upon maturation, we measured metabolic (resting respiration) rate, reproductive investment (testes and accessory gland masses), calling song characteristics and aggressive behaviours from pairwise contests between males from different densities. Male rearing density did not affect resting metabolic rates or reproductive organ masses. However, high‐density males had significantly faster, longer chirps, with more pulses—known to be preferred by females—and higher dominant frequency. Low‐density males won more aggressive contests and sang the aggressive song more. Initiation of aggressive behaviours or song and singing more aggressive song were the only other significant predictors of contest outcome. These results suggest that males may plastically adjust calling song characteristics and aggressive behaviour, but not physiology, based on perceived density during development. We hypothesize that alternative mating tactics—that is, territory guarding versus attractive song production—may underlie these observed patterns. Overall, our study highlights the significant influence of early‐life biotic environments on adult behavioural decisions to enhance success in diverse environments.