The Herculean task of sedentary predators in disturbed habitats: the response of antlion larvae

Habitat disturbance can significantly affect the ecological dynamics and behaviour of organisms, particularly those that are sedentary. This study investigates the responses of larvae of two antlion species, Euroleon nostras and Myrmeleon formicarius to a disturbance, namely stones of different mass, dropped into the pitfall traps. Additionally, we investigated the interaction between disturbance and different feeding conditions, providing insights into the ecological flexibility of these predators. Our findings revealed that removing the stone and maintaining the pit afterwards by the antlion larvae affected the larval mass, especially for the starved larvae, which lost more mass during the experiment. Fed E. nostras larvae were the only group to gain mass, whereas M. formicarius lost mass, indicating that M. formicarius might be more sensitive to disturbance. The changes in pit diameter paralleled the changes in mass; only fed E. nostras constructed larger pits at the end of the experiment. Different responses of the species to disturbance were also evident in relocation behaviour: M. formicarius relocated more frequently, particularly when larger stones were present, likely prioritizing relocation over energy-intensive stone removal. Stone removal behaviour did not differ between species but only according to the stone size relative to the larval size. Larvae threw out stones from the pit mostly if the stones were not larger than themselves. Heavier stones were either pushed to the pit wall or out of the pit. Our results suggest that the availability of prey, behavioural plasticity and adaptation to the natural habitat are crucial factors in the response of sedentary predators to disturbance.