Dolphin swimming–a review

Abstract

Research into dolphin swimming has historically been guided by false assumptions of ‘effortless’, ‘high‐speed’ swimming. These assumptions have instigated the development of drag‐reduction hypotheses but tests of these hypotheses have generally had little success. The autecological approach has dominated recent efforts and has been more successful. In this review we summarize results of decades of research efforts to study these creatures. (1) Drag is minimized primarily by the streamlined shape of the body and appendages, with no known contributions from compliant dampening, dermal ridges, secretions, boundary layer heating, or skin folds. All indications are that the boundary layer is turbulent. (2) Muscles for the upstroke and downstroke of swimming dolphins provide approximately equal power. (3) Output force is enhanced by insertions occurring on the long processes of the vertebrae and on the subdermal connective tissue sheath. (4) Measured swimming speeds are lower than previously believed, with maximum reported routine speeds being approximately 3 m/s. (5) Porpoising behaviour appears to be the most energetically conservative manner in which to breathe when swimming at high speed. (6) Riding surf and wind waves involves the balance between the wave slope and the weight of the animal whereas riding the bow wave involves the interaction of the pressure wave in front of a ship and the drag of the dolphin.

Infant position in mother-calf dolphin pairs: formation locomotion with hydrodynamic benefits

“…1c,d). Because the morphology and swimming kinematics of dolphins are characteristic of the thunniform mode, which is typical of some of the fastest marine vertebrates (including scombrid fishes, laminid sharks, and cetaceans; Lighthill 1969), dolphins generate thrust exclusively with a high aspect-ratio caudal hydrofoil (tailflukes; Fish & Hui 1991). Thus, a qualitative assessment of swim effort was obtained by considering the quantitative measurements of tail movement amplitude and beat frequency; higher amplitudes and frequencies are associated with greater energy expenditure (Kooyman & Ponganis 1998).…”

Phenotypic variation in dorsal fin morphology of coastal bottlenose dolphins (Tursiops truncatus) off Mexico

“…(Aleyev, 1977; Pauly and 48 Palomares, 1989;Fish, 1998;Wright, 2000), and this is also widely accepted in 49 cetaceans (Fish and Hui, 1991; Berta and Sumich, 1999;Fish and Rohr, 1999; Reynolds et al, 50 2000;Morteo, 2003). Morphological variation of the dorsal fin, to some extent, has been used for 51 population and/or species identification (Lang and Pryor, 1966;Aleyev, 1977;Fish, 1998; 52 Weller, 1998;Morteo et al, 2005;Felix et al, 2017).…”

Advances in the visualization and analysis of boundary layer flow in swimming fish

“…In general, recent findings suggest that it is less incumbent upon fish and cetaceans to possess extraordinary drag reducing secrets (Lang, 1974;Fish and Hui, 1991). Still, the problem has not been unequivocally resolved.…”