Meeting Abstract
With the commercial availability of aerial drones, we are able to document animal interactions in the wild, including predator – prey interactions, leading to in-depth analyses of swimming kinematics. We quantified swimming kinematics of Sphyrna mokarran (great Hammerhead) and Carcharhinus limbatus (blacktip shark), a common prey item for the great hammerhead, prior to and at the point of attempted predation. We predicted that great hammerheads would have reduced average velocity relative to the blacktip sharks, as stalking behavior is documented in the literature as a common predatory tactic during attempts on larger groups. Based on documented escape behavior from laboratory experiments, we hypothesized that after interacting with a nearby hammerhead (within 4 body lengths), blacktip shark tailbeat frequency, velocity, and whole body curvature will increase. We used a DJI Phantom 4 Advanced aerial drone to capture footage of wild predation events between blacktips and great hammerheads nearshore (N = 10 distinct predation events). Using Loggerpro motion tracking software, we derived swimming kinematic variables (amplitude, tailbeat frequency, velocity, and whole body curvature) of individual blacktips and great hammerheads. ImageJ was used to quantify distance of each blacktip to the hammerhead to determine the point of interaction. We found that overall great hammerheads swam with a reduced average velocity when compared to the blacktips prior to interaction, indicative of a stalking behavior. Additionally, blacktips increased their body curvature, velocity, and tailbeat frequency in response to interacting with the great hammerhead. These data validate responses in lab settings and quantify modulations in fish swimming kinematics in response to a predatory stimulus.
