What’s black and white and eating stuff all over? Hypotheses for the evolution of killer whale coloration and similar coloration patterns in prey species
The greatest diversity of killer whale forms–or possible (sub)species – is in the Antarctic. One reason may be because killer whales originated in, or near, the Antarctic, which would also explain their large size - an example of Bergmann’s rule [http://en.wikipedia.org/wiki/Bergmann%27s_rule], i.e. species that evolve in higher latitudes are larger.
If killer whales did evolve in the Southern Ocean, penguins would have been an abundant prey source. There was a great diversity of penguin species when toothed whales arose [http://rsbl.royalsocietypublishing.org/content/9/6/20130748]. The distinctive black and white coloration of killer whales could have been aggressive mimicry [http://en.wikipedia.org/wiki/Aggressive_mimicry], allowing them to approach penguins - Gerlache killer whales (small type B) appear feed preferentially on penguins today [https://swfsc.noaa.gov/uploadedFiles/2010_Pitman%20and%20Durban_Polar%20Biology_Penguin%20predation.pdf]. Killer whales may then have diversified to fill other niches and eat other prey beyond the Southern Ocean. Many species of porpoises/ delphinids upon which killer whales prey also share their predators’ black and white coloration. This may again be mimicry, but defensive mimicry [http://en.wikipedia.org/wiki/Mimicry] – prey species resembling their chief predator gain a few precious seconds of confusion when they approach. These hypotheses might explain the ubiquitous and convergent black and white coloration in the cetacean prey of killer whales, and their unusual black and white color pattern.