*Department of Organismic and Evolutionary Biology, Harvard University, Concord Field Station, 100 Old Causeway Road, Bedford, MA 01730, USA; Department of Biology, Indiana University, Bloomington; Department of Botany, University of Otago, PO Box 56, Dunedin 9054, New Zealand.
Integr Comp Biol. 2013 Nov;53(5):787-98. doi: 10.1093/icb/ict072. Epub 2013 Jun 19.
The dynamics of predator-prey interactions vary enormously, due both to the heterogeneity of natural environments and to wide variability in the sensorimotor systems of predator and prey. In addition, most predators pursue a range of different types of prey, and most organisms are preyed upon by a variety of predators. We do not yet know whether predators employ a general kinematic and behavioral strategy, or whether they tailor their pursuits to each type of prey; nor do we know how widely prey differ in their survival strategies and sensorimotor capabilities. To gain insight into these questions, we compared aerial predation in 4 species of libelluid dragonflies pursuing 4 types of dipteran prey, spanning a range of sizes. We quantified the proportion of predation attempts that were successful (capture success), as well as the total time spent and the distance flown in pursuit of prey (capture efficiency). Our results show that dragonfly prey-capture success and efficiency both decrease with increasing size of prey, and that average prey velocity generally increases with size. However, it is not clear that the greater distances and times required for capturing larger prey are due solely to the flight performance (e.g., speed or evasiveness) of the prey, as predicted. Dragonflies initiated pursuits of large prey when they were located farther away, on average, as compared to small prey, and the total distance flown in pursuit was correlated with initial distance to the prey. The greater initial distances observed during pursuits of larger prey may arise from constraints on dragonflies' visual perception; dragonflies typically pursued prey subtending a visual angle of 1°, and rarely pursued prey at visual angles greater than 3°. Thus, dragonflies may be unable to perceive large prey flying very close to their perch (subtending a visual angle greater than 3-4°) as a distinct target. In comparing the performance of different dragonfly species that co-occur in the same habitat, we found significant differences that are not explained by body size, suggesting that some dragonflies may be specialized for pursuing particular types of prey. Our results underscore the importance of performing comparative studies of predator-prey interactions with freely behaving subjects in natural settings, to provide insight into how the behavior of both participants influences the dynamics of the interaction. In addition, it is clear that gaining a full understanding of predator-prey interactions requires detailed knowledge not only of locomotory mechanics and behavior, but also of the sensory capabilities and constraints of both predator and prey.
捕食者-猎物相互作用的动力学变化极大，这既源于自然环境的异质性，也源于捕食者和猎物感觉运动系统的广泛可变性。此外，大多数捕食者会追捕多种不同类型的猎物，而大多数生物都会受到多种捕食者的捕食。我们还不知道捕食者是否采用了通用的运动学和行为策略，或者它们是否根据每种猎物的特点来调整自己的追捕策略；我们也不知道猎物在生存策略和感觉运动能力上的差异有多大。为了深入了解这些问题，我们比较了 4 种蜻蜓在追捕 4 种不同类型的双翅目猎物时的空中捕食行为，这些猎物的体型大小跨度很大。我们量化了捕食尝试的成功率（捕获成功率），以及追捕猎物所花费的总时间和飞行距离（捕获效率）。研究结果表明，蜻蜓的猎物捕获成功率和效率都随猎物体型的增大而降低，而猎物的平均速度通常随体型的增大而增大。然而，尚不清楚捕捉较大猎物所需的更大距离和时间是否仅仅是由于猎物的飞行性能（例如速度或逃避能力）所致，这与预测结果并不相符。与追捕小型猎物相比，蜻蜓在平均情况下会更远地启动对大型猎物的追捕，而且追捕过程中的总飞行距离与最初与猎物的距离有关。在追捕较大猎物时观察到的较大初始距离可能源于对蜻蜓视觉感知的限制；蜻蜓通常追捕视角为 1°的猎物，很少追捕视角大于 3°的猎物。因此，蜻蜓可能无法将在其栖息处附近飞行的大型猎物（视角大于 3-4°）视为一个清晰的目标。在比较同一栖息地中共同出现的不同蜻蜓物种的表现时，我们发现了显著的差异，这些差异无法用体型大小来解释，这表明一些蜻蜓可能专门用于追捕特定类型的猎物。研究结果强调了在自然环境中对自由活动的捕食者-猎物相互作用进行比较研究的重要性，以便深入了解双方行为如何影响相互作用的动态。此外，很明显，要全面了解捕食者-猎物相互作用，不仅需要详细了解运动力学和行为，还需要了解捕食者和猎物的感觉能力和限制。
