Novel predator-prey interactions: Is resistance futile?

Premise: Prey species may possess inappropriate behavioural, morphological, and/or physiological responses to introduced, novel predators. Thus, introduced predators may exert strong selection on prey species. Organisms: Black-capped vireo, Vireo atricapilla, and the fire ant, Solenopsis invicta. Data: Behavioural response of and time-energy budget for parental vireo defence against nest predation by fire ants. Field site: Fort Hood, Texas, an 88,500-hectare US military installation. Results: Fire ants usually attacked vireo nests near midnight as parents slept. All attacked nests - whether with eggs or nestlings - failed. However, adults defended their nests vigorously. Nest defence was prolonged, with a mean duration of 7.7 ± 1.5 hours (25 times longer than that against native snake predators). Compared with brooding or incubation, nest defence is energetically expensive, depleting an estimated 59% of fat stores. Conclusions: Fire ants are effective nest predators on this low-nesting bird species. The behavioural response of vireos to this novel predator is wholly inappropriate, with no benefits and considerable costs. Besides the energetic costs, defence results in numerous bites and venomous stings. Vireos ought to abandon their nests when first attacked by fire ants.