Collective swimming kinematics of Carcharhinus limbatus to Sphyrna mokarran during wild predation events


SOCIETY FOR INTEGRATIVE AND COMPARATIVE BIOLOGY
2021 VIRTUAL ANNUAL MEETING (VAM)
January 3 – Febuary 28, 2021

Meeting Abstract


18-1  Sat Jan 2  Collective swimming kinematics of Carcharhinus limbatus to Sphyrna mokarran during wild predation events Ruddy, BT*; Kirwan, DJ; Kajiura, SM; Porter, ME; Florida Atlantic University; Florida Atlantic University; Florida Atlantic University; Florida Atlantic University bruddy2018@fau.edu

Schooling, or polarized collective movement, is hypothesized to provide increased predator awareness to individual fish. From lab experiments, swimming kinematics of prey are influenced by predator distance and neighbor interactions. Our goal was to examine distances among animals, excitation wave initiation, and swimming kinematics during wild predation events using the great hammerhead (Sphyrna mokarran; predator) and blacktip shark (Carcharhinus limbatus; prey). We predicted that individual blacktip sharks would initiate escape kinematic outputs in an excitation wave, or Trafalgar effect, that would propagate throughout the group starting nearest to the predator, and result in delayed initiation and decreased kinematic variables for individuals further. We used an aerial drone to capture footage of wild predation events (N=10) between blacktips and great hammerheads. Using Loggerpro motion tracking software, we calculated kinematic variables (peak to peak amplitude, tailbeat frequency, velocity, and whole-body curvature) of hammerheads and blacktips. ImageJ was used to quantify nearest-neighbor and prey-predator distances. Distance from the hammerhead was a significant effect in initiation of escape. When blacktips were within three body lengths of the hammerhead predator, we found increases in their body curvature, velocity, tailbeat frequency, and initiation of the Trafalgar effect. Within the excitation wave, blacktip sharks positioned closer to the hammerhead demonstrated increased values for body curvature, tailbeat frequency, and velocity compared to sharks further from the predator. These data show the Trafalfar effect is paired with changes in swimming kinematics that vary depending on distance from the predator in wild sharks.

the Society for
Integrative &
Comparative
Biology