Attracting unwanted attention: generalization of behavioural adaptation to an invasive predator carries costs

Behavioural responses of animals to environmental cues are often governed by general ‘rules of thumb’. Animals that face novel conditions as a result of global environmental change may alter these behavioural rules to persist. However, adaptation of generalized rules to novel pressures may cause a species to be maladapted to original conditions (e.g. predators) that remain in its environment. Invasive red imported fire ants, Solenopsis invicta, are novel predators of eastern fence lizards, Sceloporus undulatus. Lizards from fire ant-invaded sites break crypsis to flee from fire ants at higher frequencies than fire ant-naïve lizards. This shift promotes survival of attacks by these invasive ants but could result in attacks by native visual predators. Generalization of this increase in antipredator behaviour to native species could further increase this cost. We tested whether lizards’ increased propensity to flee from fire ants is generalized to native ants and a predatory bird. We found that increased behavioural responsiveness to fire ants was generalized to two native ants but not to a perceived avian predator. We also found that lizards from populations invaded by fire ants had higher prevalence of injuries in the field, likely indicating greater attempted predation. We propose that generalized anti-ant behaviour may improve survival in the presence of fire ants but increase attacks by native visual predators. This study suggests that generalized rules can be maladaptive under novel conditions and highlights the challenges of assessing the costs and benefits of adaptations to rapid environmental change.