Alive and whale: a missing cetacean resurfaces in the Tropics

Natural History, Sept, 2002 by Robert L. Pitman

It had to be out there somewhere. It wasn't just a set of car keys that had gone missing--somehow an entire species of whale had been lost for more than a century.

The story picks up in 1882 with a worn skull found on a beach in Queensland, Australia. The specimen ended up in the Queensland Museum, but it was not until 1926 that Heber Albert Longman, the museum's director, recognized it as a new species of beaked whale. From the family Ziphiidae, these whales are so named because they have mouths like beaks, as dolphins do. But these would be large dolphins: members of some species range up to almost forty-two feet, although most individuals are only half that size. Longman named the new whale Mesoplodon pacificus. The genus name, derived from the Greek, means "armed with a middle tooth"; males of most species of Mesoplodon have a single large tooth that erupts from each side of the lower jawbone, halfway along its length. (Because heavy scarring is frequently found on adult males but never on females, scientists assume that males use these teeth as tusks to fight with other males for breeding privileges.) The name pacificus merely underscores the fact that the original specimen--the holotype--came from the Pacific coast of Australia.

For decades afterward, various authorities questioned the status of M. pacificus as a separate species, based as this was on a single specimen. Some suggested that the specimen could be a subspecies of True's beaked whale, M. mirus (a species with distinct populations in the North Atlantic and the southern oceans), or possibly a female southern bottlenose whale, Hyperoodon planifrons. It is a scientific truism that less data will always support more hypotheses.

Another seventy-three years elapsed before anyone found a second specimen. In 1955, another well-worn skull turned up, this time on the east coast of Africa, where Somalian fishermen found it on a beach. Although the find convinced even the skeptics that M. pacificus was indeed a different beast, it provided almost no new information about the animal. Beaked whales are probably the most poorly known group of large mammals alive today. They are shy and swim in deep waters, far offshore. If a vessel approaches within half a mile, they usually slip under the waves, diving for half an hour or more, and are typically never seen again. Even a researcher like me, who has spent his life counting and identifying whales and dolphins while traveling the oceans of the world, sees beaked whales only occasionally. I can rarely identify members of this family with certainty and can almost never photograph them. Several species of beaked whales have never been identified alive in the wild; practically everything known about most of them is based on stranded animals. And among these, M. pacificus was the rarest of the rare--just two skulls found on two beaches.

In 1968 Joseph C. Moore, then a curator at the Field Museum in Chicago, published a preliminary taxonomic review of the five living genera of beaked whales known at that time. He considered M. pacificus not only a valid species but one distinct enough from the other eleven species of Mesoplodon to deserve its own genus, for which he coined the name Indopacetus, to reflect the fact that the species was now known to occur in the Indian Ocean as well as in the Pacific. (I can only hope a different subspecies doesn't show up in the Atlantic--Indopacetus pacificus atlanticus?) However, many cetologists did not accept Moore's assessment, and several suggested that until more specimens became available, the whale was probably best left in the genus Mesoplodon.

And so, nearly a hundred years had passed since the holotype specimen had been dragged off an Australian beach, and Longman's beaked whale, as it had become known, had revealed itself to science only twice, offering up just two damaged skulls. This left plenty of room for questions: Was the animal extinct or just exceedingly rare? How was it related to other whales? Where did it live, and what did it look like? Based on skull size, it was estimated to be about twenty-three feet long. For those seeking the whale, the ocean was an immense haystack, but this was still an awfully big needle.

At some point during a search for a whale, the story must shift offshore. In 1966, while conducting biological surveys at sea in the central Pacific for the Smithsonian Institution, Ken Balcomb, now at the Center for Whale Research on San Juan Island (off the north coast of Washington State), photographed a herd of twenty-five to thirty-five unidentified beaked whales near the equator. They were grayish brown in color, and some had a conspicuous tan forehead, known as a melon. Between the prominent melon and the beak was a crease, which placed the species within a distinct subset of beaked whales--the bottlenoses. The animals that Balcomb photographed were also larger than most species of beaked whales; researchers estimated them to be between twenty-three and thirty feet long. Exactly which species they were, however, was unknown. Balcomb had taken remarkably good photos, but the experts who examined them in order to identify the whales could only shrug their shoulders.