Will we ever run out of Beaked Whales?

 The beaked whales are fascinating enough to make cetologists drool. Not only are they distinctive in themselves, and sometimes weird, like the strap-toothed whales, they seem to be innumerable. In October 2021, scientists announced the finding of the 23d species (depending how you count: there are some questions here) of this enigmatic group. This Southern Hemisphere cetacean, one of many species identified from stranded specimens, was christened Ramari's beaked whale, Mesoplodon eueu,

A 19th-century vision of a beaked whale

The newest discovery complements a long list of 21st century surprises and appearances.  

Until 2002, the Indopacific beaked whale (Mesoplodon  pacificus or Indopacetus pacificus) was known only from two skulls washed ashore thousands of miles and 73  years apart. Dr. Lyall Watson, in his Sea Guide to Whales of the World, suggested a large pod of beaked whales photographed near Christmas Island might belong to this species, which is also called Longman’s beaked whale. He made the same suggestion concerning brown whales reported in the Gulf of Aden by Captain Willem F.  J. Morzer-Bruyuns, although that witness was certain he was seeing an unknown type of killer whale. Numerous other possible sightings of Longman’s beaked whale, such as a report of two unidentified grayish whales seen near the Seychelles in 1980, were recorded, but no one was certain which ones –if any – referred to this enigma of the seas.

All that changed in 2002.  An odd beaked whale beached on July 26 in Japan, but no one thought much of it initially.  The carcass was photographed, then buried.  When a cetologist saw the pictures, he scrambled to get the thing disinterred as quickly as possible.  It was the first example of Longman’s beaked whale ever recovered intact.  In an odd coincidence, a second specimen identified as I. pacificus drifted ashore in South Africa the following month, although Japanese experts questioned this identification.   (Two old South African specimens, which had been identified as other species, were then re-examined and were reported to be Longman’s whale as well. By now you should be getting an inkling of how complex distinguishing beaked whales in.)  Until this point, cetologists knew nothing of the animal’s appearance (it’s predominantly grayish brown, with the head often appearing darker and sporting some small white side markings) and were unsure of the size (about twenty feet).

            The smallest beaked whale is the Peruvian, or Lesser, beaked whale.  Scientists had no inkling of its existence until 1976, when Dr. James Mead found its decaying skull on a beach in Peru.   By the time Mead formally published his description of Mesoplodon peruvianus in 1991, Peruvian scientists and fishermen had helped him assemble a total of eleven specimens.  All were found either washed up on shore or trapped in fishing nets. 

            The adult Peruvian beaked whale is normally about eleven feet long.  It is mainly dark gray, with a paler gray underside.  It has a small dorsal fin set well back on the body.  While all known mesoplodonts have such dorsal fins, there are differences in shape which help distinguish the different species.  In some beaked whales, like the Peruvian, the fin is a near-perfect equilateral triangle with a straight trailing edge.  In others, such as True’s beaked whale (M. mirus), the trailing edge is concave, so the fin is more falcate or sickle-shaped. 

            It turned out this whale has a wider distribution than originally thought.  Other specimens have since been found stranded in Mexico near Baja California and on the island of Espiritu Santo in the eastern tropical Pacific. There are still few recorded observations of the living animal, although pods of two or three have been seen.

            In 1995, four cetologists published the results of their study of a single calvarium (the portion of the skull housing the brain) found on the beach of Robinson Crusoe Island off Chile in 1986.  Julio Reyes and his colleagues proclaimed they had identified another new species of beaked whale.  Bahamonde’s beaked whale (Mesoplodon bahamondi) was distinguished principally by an unusually short and broad rostrum (snout).  

            The discoverers suggested Bahamonde’s whale could represent the mysterious Mesoplodon “Species A,” an unidentified beaked whale reported and photographed in the Eastern Tropical Pacific region.  The overall length of M. bahamondi is estimated at sixteen to eighteen  feet, which is an approximate match to these sightings.  British paleobiologist Darren Naish, who makes a specialty of studying unusual cetaceans,  cautioned that, “Glimpses of the head of Species A do not reveal the very abrupt rostrum that seems to be diagnostic for M. bahamondi, so they are probably not the same.” 

            As things turned out, Naish was right.  Bahamonde’s beaked whale was not Species A – but it was identical to another mystery species.  In a paper published in 2002, a group of cetologists demonstrated that M. bahamondi, while a valid species, was a resurrection of a species described in 1874 but generally forgotten.  Mesoplodon traversii was restored to its rightful place in the genus after 128 years, while M. bahamondi was reduced, in taxonomic parlance, to the status of a junior synonym.  This does not diminish the importance of the work by Reyes and company.  It’s significant any time a genuine new whale goes into the books – whether it’s brand new or just a case of science saying hello to a long-forgotten discovery.

            The beaked whales still had some surprises in store for science.  One of the peculiarities of this group of cetaceans is that, while experts like Dr. Merel Dalebout of Dalhousie University in Halifax, Nova Scotia estimate they have been reproductively separated for perhaps three million years, their morphology hasn’t changed nearly as much as their genetics.  It’s common for genetic change to lead morphological change, resulting in species that are distinct but still look similar, but the beaked whales have taken this principle to an extreme.  Not only do many of the twenty-one  known species look similar in life, requiring an expert to distinguish them, but even when an animal is beached it can be mistaken for another species.

That was the case with Perrin’s beaked whale, Mesoplodon perrini.  There have been many sightings of beaked whales which puzzled observers.  For example, Dr. Karin Forney of the Southwest Fisheries Science Center spotted one off the coast of Oregon in 1996.  The animal was brownish-gray and bore some resemblance to Hector’s beaked whale (M. hectori.)  However, some important details failed to match up.  Most adult male beaked whales have two or more teeth in the lower jaw, which in many species are erupted (that is, are visible even when the jaw is closed.)  The shape and placement of these teeth is a major criterion for classifying these enigmatic cetaceans.  In Forney’s whale, the visible teeth were not close to the beak tip as is normal in M. hectori. 

As it turned out, the similarity to M. hectori was significant. Between 1975 and 1997, four beaked whales stranded on the coast of California were initially identified as Hector's beaked whales.   Dr. Dalebout and her associates, in surveying DNA samples from numerous mesoplodonts, found these four didn’t fit well with M. hectori.  Neither did a fifth California specimen, which had been identified as Cuvier’s beaked whale.  In 2002, Dalebout, along with four of her colleagues, published the discovery of Mesoplodon perrini.  When Karin Forney saw the description, she knew what she had observed in 1996.  It was indeed, at the time she’d seen it, an undescribed whale.

In 2016, A new species of whale was discovered based on a body, 7.3m long, that floated ashore on the Pribilof Islands.  This is just marvelous. I follow news of new and unidentified whales all the time, and I never heard a word about this, although it's apparently known to Japanese fishers, so it has a  range that spreads far west. Indeed, Japanese scientists were already investigating the reports. This isn't a case where someone had it in hand and decided that its features or DNA warranted a split of a known species, as was the case with Balaenoptera omurai in 2003. This species was confirmed by DNA work, which resulted in reordering of its genus, but it began with a brand-new discovery from the field, when a biology teacher called in a seal researcher he knew who said, "This is weird," and then she called in a cetologist. Other previously collected (misidentified) skeletons have been located. 

Here's the published abstract from Marine Mammal Science:

Philip A. Morin, et. al.

There are two recognized species in the genus Berardius, Baird's and Arnoux's beaked whales. In Japan, whalers have traditionally recognized two forms of Baird's beaked whales, the common “slate-gray” form and a smaller, rare “black” form. Previous comparison of mtDNA control region sequences from three black specimens to gray specimens around Japan indicated that the two forms comprise different stocks and potentially different species. We have expanded sampling to include control region haplotypes of 178 Baird's beaked whales from across their range in the North Pacific. We identified five additional specimens of the black form from the Aleutian Islands and Bering Sea, for a total of eight “black” specimens. The divergence between mtDNA haplotypes of the black and gray forms of Baird's beaked whale was greater than their divergence from the congeneric Arnoux's beaked whale found in the Southern Ocean, and similar to that observed among other congeneric beaked whale species. Taken together, genetic evidence from specimens in Japan and across the North Pacific, combined with evidence of smaller adult body size, indicate presence of an unnamed species of Berardius in the North Pacific. It was named in this paper. 

Readers of this blog know of Dr. Robert Pitman, who's done so much work with orcas and beaked whales. Of this find, he said, "It boggles my mind to think that a large, very different-looking whale has gone unnoticed by the scientific community for so long. It sends a clear message about how little we know about what is in the ocean around us."

It does indeed. 

What is still out there? Well, there are these odd vocalizations from the Antarctic. There's this apparent species, still being investigated. Who knows what else?