Enigmatic megafauna: type D killer whale in the Southern Ocean

In 1955, 17 killer whales (Orcinus orca) stranded on a beach in Paraparaumu, New Zealand. From the grainy, black and white photographs (Fig. 1), it was clear that they were not typical killer whales: they were small, with narrow, pointy dorsal fins, a bulbous head, and the prominent white eyepatch normally found on killer whales was reduced to a tiny slip. Nothing like them had ever been reported, either before the stranding or for decades afterward. Fast forward, 50 years, to 2005. At a killer whale workshop in Seattle, Washington, a French researcher shared with one of us (R. L. Pittman) photographs of killer whales that were depredating Patagonian toothfish (Dissostichus eleginoides) from commercial longline vessels at Crozet Island, in the southern Indian Ocean. When the researcher pointed out a group of “odd‐looking” individuals, there was a flash of recognition and the kind of moment that field naturalists live for: it was the New Zealand killer whales, with their unmistakable round heads and tiny eyepatches. After a half century, they were no longer extinct mutants, but alive and harassing fishermen. Moreover, Crozet is one‐third of the way around the world from New Zealand, suggesting they were potentially widespread. Globally, killer whales display a surprising amount of phenotypic diversity, with numerous described “ecotypes”: forms that are morphologically, ecologically, and phylogenetically distinct but ostensibly all the same species. For example, in the Southern Ocean (i.e., south of 60°S), five different killer whale ecotypes are currently recognized: types A, B1, B2, C and D (Fig. 2; Pitman and Ensor 2003, Pitman et al. 2011, Durban et al. 2016). Even to laypeople, most of these are readily distinguishable in the field, in addition to having different habitat and prey preferences. Moreover, although their ranges are often sympatric, they do not mix socially, and genetic studies confirm that they rarely interbreed. Of these, type D is the most distinctive and, by far, the least well‐known killer whale ecotype. To document the distribution and relative abundance of killer whales in the Southern Ocean, 20 years ago we began collecting photographs of encounters, including many images taken by “citizen scientists” on tour vessels visiting Antarctica. Among the scores of encounters documented during the first five years after the Seattle workshop, were six more groups of the New Zealand whales. From these, we published a short paper with a field description of what we referred to as the “type D” killer whale, confirming that it was extant and