Who is that masked whale?
Every once in a while, a killer whale shows up, and we don’t know where it came from. Fifty years ago, nobody even would have wondered. Killer whales were considered a global species. From time to time, killer whales that seemed different would be found and be described as new species, but as recently as the early 1980’s, such proposals were not taken seriously by most taxonomists.
However, as work in the Pacific Northwest continued, it became apparent that residents and transients were distinct populations. By the late 1980’s, a few sightings of a third type that was rarely seen, but appeared different, had accumulated. In the 1990’s, genetic studies confirmed that residents and transients were genetically distinct, and had been so for a long time. Northern and Southern Residents were different as well, but their split was far more recent.
The recognition that Southern Residents were different than other killer whales led to a proposal to list them under the Endangered Species Act. NMFS declined, indicating that there were not sufficient data to justify the listing. Environmental groups filed suit, leading NMFS to initiate a global study of killer whales. While information gained from these global studies contributed nothing to how to recover Southern Residents, it did lead NMFS to inform the court that they would acknowledge that Southern Residents are listable, and then they proceeded to list them as Endangered.
These genetic and photographic studies indicated that there were numerous kinds of killer whales, and most significantly, that whales that were similar in appearance were similar genetically, in contrast to other whales in the same area that were morphologically distinct. That is, morphological variation was between species that were reproductively but not geographically isolated, it was not within population variation.
Transients were only found in the Pacific, and appeared to have split off from other known killer whales earlier than any other type. That allowed them time to split into many species or subspecies. The familiar transients seen in Bigg’s studies that ranged from California to Southeast Alaska became known as West Coast Transients.
Another branch on the transient lineage is known as AT1s. They’re found in Prince William Sound, but appear to be on an irreversible road to extinction, as no reproductive age or juvenile females remain. They are similar in appearance to WCTs, but eat fish in addition to marine mammals, and are genetically distinct.
Farther west in Alaska are Gulf of Alaska Transients, which differ in appearance, vocal behavior, and slightly in genetics, but they eat marine mammals.
Far to the south, there is at least one more branch of the transient family. Known as Eastern Tropical Pacific Transients, they have saddles that are very inconspicuous. There are likely to be other species and subspecies of transients, as little is known about killer whales on the Pacific Coast of South America.
Since the killer whale that stranded in California had a harbor seal in its stomach, it was likely a transient. Although well within West Coast Transient territory, the rounded dorsal fin was inconsistent with that population. The next closest population would be ETP transients, but the saddle was wrong for them. The dorsal fin was wrong for AT1s, but both the saddle and dorsal fin are appropriate for Gulf of Alaska Transients.
The little known killer whales from BC became known as offshores. Like GoA transients, they have saddles and dorsal fins similar in shape to the stranded whale. The stranding location is well within their range. However, it appears that offshores are a dwarf killer whale. As in the North Atlantic, where some killer whales are the same size as our residents, there is also a dwarf form, many of which were taken into captivity from Iceland. Likewise, the Antarctic has a dwarf form, which was described as a new species using data from Soviet whaling. The large size of the stranded whale made it unlikely it was an offshore. Further, offshores feed on sharks and turtles, and as a result, it looks like the tips of their teeth are taken off with a power sander, and their teeth have open pulp captivities, in contrast to the stranded whale whose teeth were in decent condition.
So how will we know for sure what type of killer whale stranded? Genetic testing will reveal the answer. Preliminary results suggest it is, in fact, part of the Gulf of Alaska transient population. More extensive sequencing will be needed to confirm this result.
By the way, the Southern Hemisphere has its share of killer whales, too. Species A is similar to our transients. Species B and C have pronounced dorsal capes, with C being the dwarf form. North Pacific killer whales only have a vestige of this cape—a fine line running from the saddle to the eye patch. Species D seems to have the head of a pilot whale but the fins and a color pattern more appropriate for killer whales. There is also a killer whale closely related to offshores. There may be other killer whales yet to be described as parts of the world have been poorly studied.
We don’t yet know enough about GoA Transients to say whether the stranded whale was outside of its normal range, or if some of them join migrating baleen whales to take advantage of vulnerable calves. We have seen individuals out of range before, with Luna the Southern Resident in the Northern Resident range, and Springer the Northern Resident in Southern Resident habitat before she was returned home. The ability to recognize out of range killer whales was an important element of the decision to list Lolita as an Endangered Southern Resident. While the circumstances of her capture made it likely she was a Southern Resident, it was important to rule out the possibility that she was a whale from another population that was just passing through, and to prove we would have been aware of it if that had happened.