Department of Biological Sciences, Simon Fraser University, Burnaby, British Columbia, Canada.
Department of Biodiversity, Earth & Environmental Science, Drexel University, Philadelphia, Pennsylvania, United States of America.
PLoS One. 2013 Dec 26;8(12):e84114. doi: 10.1371/journal.pone.0084114. eCollection 2013.
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. The "hit-and-run" predation tactic of caracaras when they attacked nests of large and aggressive wasps reduced the risk of getting stung. 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.
红头美洲鹫 Ibycter americanus（隼形目）是新热带地区社会性黄蜂的专业捕食者。有人提出，这些美洲鹫具有化学驱避剂，可以让它们在不被工蜂攻击的情况下取走黄蜂巢的幼虫。为了确定美洲鹫如何利用黄蜂巢，以及化学驱避剂是否有助于捕食，我们：（1） 视频记录了鸟类攻击黄蜂巢的情况；（2） 分析了鸟类面部、脚部和羽毛的表面提取物，以寻找潜在的化学驱避剂；（3） 对黄蜂巢进行机械损伤，以确定黄蜂对不同程度干扰的防御行为。在美洲鹫捕食事件中，两种大型黄蜂对美洲鹫进行了刺击攻击，而三种体型较小的黄蜂则没有。美洲鹫在攻击大型和攻击性黄蜂巢时采用的“打了就跑”的捕食策略降低了被蛰的风险。我们的数据表明，美洲鹫的捕食策略基于对目标黄蜂巢的机械干扰和破坏。美洲鹫的攻击行为和对巢穴的严重实验性干扰总是会导致黄蜂逃跑（放弃它们的巢穴）。美洲鹫足部提取物中的两种化合物[ sulcatone 和 iridodial] 引起了黄蜂触角的电生理反应，并且也存在于同种栖息的树栖筑巢的 Azteca 蚂蚁的防御分泌物中。这些化合物似乎不是黄蜂驱避剂，而是美洲鹫在栖息有 Azteca 蚂蚁的树上停留时偶然获得的。我们得出结论，美洲鹫的捕食成功并不依赖于黄蜂驱避剂，而是依赖于典型的群体筑巢 Polistine 黄蜂的逃跑反应。我们的研究强调了脊椎动物捕食者在社会性黄蜂的生态学和进化中的潜在重要性。
