The widespread presence of melanin and the unexpectedly high number of melanophages may constitute a unique photoprotective trait of cetaceans and could reflect primitive adaptations to their environment and to their obligate marine-bound life.

The killer whale (KW, Orcinus orca) is the most cosmopolitan species among cetaceans (Bryun, Tosh, & Terauds, 2012;Heyning & Dahlheim, 1988), showing a unique global population genetic structure among nonhuman species (Foote et al., 2019). Its widespread distribution, along with its top predator status (Mehta et al., 2007), make it a good indicator of alterations in the marine trophic structure (Moore, 2008). Although the KW has been extensively studied over the past several decades, it is still classified as "Data deficient" in the Red List of the International Union for Conservation of Nature, as many populations are still scarcely known (Reeves, Pitman, & Ford, 2017).

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