How Smooth Is A Dolphin?

July 17, 2019
Belugas in Water with Topography of Animals Ridges

Dolphin skin has long inspired research on drag reduction mechanisms due to the presence of skin ridges that could reduce fluid resistance. PhD candidate Dylan Wainwright and Prof. George Lauder collected in vivo three-dimensional surface data on the skin from five species of odontocetes (cetaceans that includes dolphins, porpoises, and all other whales possessing teeth) to quantitatively examine skin texture, including the presence and size of ridges.

Wainwright, Lauder and team molded the skin of live dolphins to study the texture of their skin and how it might relate to flow around dolphins during swimming. Scientists had previously found that dolphins have small ridges on their skin and there is some debate if these ridges might somehow help dolphins swim more efficiently by changing how water flows around their bodies. The study was published in Biology Letters found ridges on dolphins (mostly on their backs before their dorsal fins, as well as on the sides of their bodies). However, they found the ridges aren't present in all individuals and that the ridges are generally very small (5-10 microns high in most species, but as large as 30-80 microns high in killer whales and belugas). Simple fluid mechanics equations revealed the ridges are too small to be changing water flow around dolphin bodies in any appreciable way.

Note: The team applied molding compound to the skin that was pealed away in a minute and preserved an impression of any surface structure and roughness features on the skin. The procedure is completely harmless, leaving no impressions on the skin of any kind. Researchers even applied it to their own skin!