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Keywords:

  • cetaceans;
  • echelon position;
  • hydrodynamics;
  • stroke and glide propulsion;
  • swimming kinematics

Summary

  • 1
    Formation locomotion theoretically provides energy savings and it is evident across diverse taxa. Echelon position, described in cetacean (dolphin and whale) mother–infant dyads as calf in very close proximity of its mother's mid-lateral flank, may be a type of formation locomotion that provides hydrodynamic benefits for the calf. Until now, the difficulties associated with assessing the swimming energetics of marine mammals have precluded empirical quantifications of these benefits.
  • 2
    Through kinematic analyses, this study demonstrates empirically that 0–1 month-old dolphin (Tursiops truncatus) calves in echelon position are afforded locomotor advantages as evident by increased swim performance with concurrent reductions in effort.
  • 3
    Compared to periods of independent swimming, calves in echelon position showed a 28% increase in average swim speed with reduced effort during stroke phases, as evident by a 22% reduction in fluke stroke amplitude and 19% increase in distance per stroke.
  • 4
    In addition, calves in echelon position spent over a third of their time gliding while no glide phases were observed for independently swimming calves.
  • 5
    The hydrodynamic benefits of echelon position enable cetacean calves, which have extremely limited locomotor performance, to maintain proximity of their mothers during travel, which is vital to infant survival.
  • 6
    This study adds to the limited empirical data regarding the energy economy of formation locomotion in animals.