| Summary: | Vertebrate evolution has resulted in a diversity of feeding mechanisms.
Cetaceans are secondarily derived tetrapods that have returned to a marine habitat. As a
result, they display feeding modes that have converged with more basal aquatic
vertebrates, but display a diversity of new solutions and adaptations. To begin to
explore the diversity of feeding adaptations among odontocetes, kinematics of feeding
modes and feeding adaptations for belugas (Delphinapterus leucas), Pacific white-sided
dolphins (Lagenorhynchus obliquidens), and long-finned pilot whales (Globicephala
melas) were characterized. In addition, direct measurements of intraoral pressure were
collected to determine maximum suction performance. Characters from these analyses
were combined with data for other odontocetes, and were mapped onto a phylogeny of
Odontoceti to begin to explore where changes in feeding modes took place. Feeding
modes were diverse in belugas, Pacific white-sided dolphins, and pilot whales and
included suction, ram, and a combination of both. In general, four phases were
observed: (I) preparatory, (II) jaw opening, (III) gular depression, and (IV) jaw closing.
Suction was a large component of the prey capture method in belugas and subambient
pressures in excess of 100 kPa were generated. Belugas were also capable of lateral lip
gape occlusion and anterior lip pursing to form a small anterior aperture. Pacific whitesided
dolphins relied on ram to capture prey. However, some degree of pursing and
resultant subambient pressure was observed that was likely used to compensate for high
ram speeds or for prey manipulation and transport to the esophagus. Pilot whales were
more similar to belugas in kinematics, but maintained high approach velocities and did not generate significant suction pressures; suction and ram were used in combination.
Belugas and pilot whales appeared to employ hyolingual depression as a primary suction
generation mechanism, whereas Pacific white-sided dolphins relied on fast jaw opening.
Ancestral state reconstructions indicated that suction feeding capability evolved
independently at least six times within Odontoceti. These results indicate the diversity
of feeding behaviors in odontocetes and provide directives for future studies on the
diversity of feeding in secondarily aquatic mammals.
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