Analyzed the data: RG SM. Red-throated Caracaras Ibycter americanus Falconidae are specialist predators of social wasps in the Neotropics. It had been proposed that these caracaras possess chemical repellents that allow them to take the brood of wasp nests without being attacked by worker wasps. To determine how caracaras exploit nests of social wasps and whether chemical repellents facilitate predation, we: 1 video recorded the birds attacking wasp nests; 2 analyzed surface extracts of the birds' faces, feet, and feathers for potential chemical repellents; and 3 inflicted mechanical damage on wasp nests to determine the defensive behavior of wasps in response to varying levels of disturbance.
During caracara predation events, two species of large-bodied wasps mounted stinging attacks on caracaras, whereas three smaller-bodied wasp species did not. Our data reveal that the predation strategy of caracaras is based on mechanical disturbance of, and damage to, target wasp nests.
Caracara attacks and severe experimental disturbance of nests invariably caused wasps to abscond abandon their nests. Two compounds in caracara foot extracts [sulcatone and iridodial] elicited electrophysiological responses from wasp antennae, and were also present in defensive secretions of sympatric arboreal-nesting Azteca ants.
These compounds appear not to be wasp repellents but to be acquired coincidentally by caracaras when they perch on trees inhabited with Azteca ants. We conclude that caracara predation success does not depend on wasp repellents but relies on the absconding response that is typical of swarm-founding polistine wasps. Our study highlights the potential importance of vertebrate predators in the ecology and evolution of social wasps.
It is well recognized that ants are important predators of social wasps, and that wasps exhibit ant-specific defensive adaptations [1] — [3] , but until recently little attention has been paid to the role of vertebrate predators in social wasp evolution. Few vertebrate predators are known to specialize on the brood larvae and pupae of social wasps as their primary food source, but behaviors such as stinging, venom spraying [4] , biting [5] , [6] , and physical fortification or camouflage of wasp nests [7] — [9] suggest selection for specific anti-vertebrate defensive tactics.
