A couple years back, during a day cruise around the Channel Islands, we found ourselves surrounded by a sizable school of common dolphins. (Not a mega-pod, alas, but even a few dozen dolphins is a pretty awe-inspiring sight.) Common dolphins are, as their name suggests, among the most abundant marine mammals in the world; it’s probably easier to name the coastlines where they don’t occur than where they do. (Here’s a range map, for the curious.) They’re famously social, energetic, and playful, and the pair above, along with their comrades, weaved around our vessel for a good 15 minutes, flying through the Pacific in graceful synchrony.
Despite their ubiquity, common dolphins are still a bit of a mystery. In 1994, Delphinus delphis, long considered a single species, was split into two, the long-beaked common dolphin (D. capensis) and the short-beaked common dolphin. The primary difference was — guess what? — the snout, which, in the long-beakers, “can be up to 10% of the total body size.” In 2015, though, the dolphin’s taxonomic story twisted again: Researchers declared Delphins capensis “invalid” on the basis of DNA evidence. All the world’s common dolphins allegedly belonged to Delphinus delphis, though the researchers did acknowledge the existence of a few subspecies, including D. d. bairdii, the eastern North Pacific long-beaked common dolphin, whose name is as long as its rostrum.
Got all that?
I’m reasonably certain the animals we saw in the Channel Islands were long-beakers (they tend to spend more time around coastlines rather than the open ocean, and are apparently more, well, common around the islands than the short-beakers), but I’ve been staring at dolphin photos for the last twenty minutes and feel no closer to a definitive diagnosis. If you’re a confident cetologist, get at me in the comments.
Photo: Ben Goldfarb