Department of Biology, University of North Carolina, Chapel Hill, NC 27514, USA
Nicholas School of the Environment, Duke University Marine Laboratory, Beaufort, NC 28516, USA.
J Exp Biol. 2019 Jun 11;222(Pt 11):jeb190884. doi: 10.1242/jeb.190884.
Pursuit is a common behavior exhibited by animals chasing prey, competitors and potential mates. Because of their speed and maneuverability, dragonflies are frequently studied as a model system for biological pursuit. Most quantitative studies have focused on prey pursuits in captive environments. To determine whether a different pursuit strategy is used when chasing conspecifics of nearly equal speed and agility, we recorded 3D flight trajectories from nine territorial chases between male dragonflies in natural field conditions. During chases, dragonflies used an interception strategy with an unusually high-magnitude gain (=-10.03 s horizontal; -8.86 s vertical) and short time delay (τ=50 ms). The product τ determines how aggressively a pursuer corrects course to achieve interception. Previous studies of prey pursuit have found τ values close to -1/ (-0.37), the time-optimal value for achieving pursuit without overshooting. However, we found that dragonflies chasing conspecifics use more negative τ (-0.50 horizontal; -0.44 vertical), resulting in pursuits with a high degree of overshooting (i.e. moving past the target and alternating position from side to side). We confirmed via simulation that the observed gain and delay produce overshooting. We propose that overshooting is an adaptive feature of conspecific chases that can be achieved with only slight modification of the strategy used for intercepting prey. Overshooting might help avoid potentially damaging collisions while exhibiting the pursuing animal's flight performance and competitive ability. Repeated close approaches might also evoke evasive responses from the other dragonfly, effectively herding the competitor out of the territory.
追逐是动物追逐猎物、竞争对手和潜在配偶时表现出的一种常见行为。由于蜻蜓的速度和机动性，它们经常被作为生物追逐的模型系统进行研究。大多数定量研究都集中在圈养环境中的猎物追逐上。为了确定在追逐速度和敏捷性几乎相同的同种个体时是否使用了不同的追逐策略，我们在自然野外条件下记录了 9 次雄性蜻蜓的领地追逐的 3D 飞行轨迹。在追逐过程中，蜻蜓使用了一种拦截策略，具有异常高的幅度增益（=-10.03 s 水平；-8.86 s 垂直）和短时间延迟（τ=50 ms）。τ 决定了追逐者纠正路线以实现拦截的激进程度。以前对猎物追逐的研究发现，τ 值接近-1/(-0.37)，这是在不超过的情况下实现追逐的时间最优值。然而，我们发现追逐同种个体的蜻蜓使用更负的 τ（-0.50 水平；-0.44 垂直），导致追逐具有高度的过冲（即超过目标并从一侧到另一侧交替位置）。我们通过模拟确认了观察到的增益和延迟会产生过冲。我们提出，过冲是同种追逐的一种适应性特征，可以通过对拦截猎物的策略进行微小修改来实现。过冲可能有助于避免潜在的破坏性碰撞，同时展示追逐动物的飞行性能和竞争能力。反复的近距离接近也可能引发另一只蜻蜓的逃避反应，有效地将竞争者赶出领地。
