Suffused: baleen fringe mat porosity and hydrodynamics in balaenid and balaenopterid whales

• Published in: Biological Journal of the Linnean Society
• Main Authors: Potvin, Jean, Werth, Alexander J
• Format: Article in Journal/Newspaper
• Language: English
• Published: Oxford University Press (OUP) 2024
• Subjects: Balaena mysticetus; Balaenoptera physalus; bowhead whale; Fin whale
• Online Access: http://dx.doi.org/10.1093/biolinnean/blae030; https://academic.oup.com/biolinnean/advance-article-pdf/doi/10.1093/biolinnean/blae030/57272947/blae030.pdf

Abstract Baleen plates of filter-feeding whales are longitudinally fibrous, separating where eroded medially into mats of fringes due to friction from water, prey, and the tongue. The fringes end up spreading-out, in other words suffusing, over the comb-like structure of the baleen assemblage. This study examined the relationships between mat morphology and the hydrodynamics it generates. Samples collected from nine rack locations on a bowhead whale (Balaena mysticetus) and fin whale (Balaenoptera physalus) were investigated with a new technique of mat porosity determination in a flume setting. Porosity was measured in the range of 5–20% and 8–37% in the bowhead and fin whale samples respectively. These were largest ventrally in both species, while remaining somewhat insensitive to the flume’s water speed. A new hydrodynamical model of the through-mat currents was used to estimate speeds of 0.15–3.0 cm/s and mat permeabilities of the order of 10−13 m2, depending on the applied pressure. Finally, and relative to samples collected near the entrance of the mouth, these trends were quantitatively similar in both species. With tongue- and flow-based erosion as the main mechanism for mat creation in all extant mysticetes, our analysis suggests baleen-generated filtration as having emerged early in their evolution.