In the last five years alone, scientists have proposed six additions to the official list of whale species, and they show no signs of slowing down. Curated by the Society of Marine Mammalogy, the list of 94 recognized whale species and 50 subspecies has seen a number of shifts and changes over time as they are moved around and reorganized, but with recent trends of new additions since the turn of the millennium, it looks like we are in a new age of discovery for the world of cetaceans. Where are these whales coming from?
The Urban Dolphins
Eager eyes lean over the edge of the boat as the New York City skyline looms on the horizon — but they aren’t looking at distant skyscrapers. Instead, all eyes are drawn to bottlenose dolphins swimming in the water below. These are the animals you’ve probably seen on TV or at an aquarium, a frequent sight all the way from Long Island beaches down the East Coast to Florida. Even submerged up to their blowhole, they are instantly recognizable as icons of the sea. So it’s no small surprise that it was as recently as 2022 that these bottlenose dolphins living near the city and down the coast were announced to be a “new,” unrecognized species: Tursiops erebennus, or Tamanend’s bottlenose dolphin.
Though the species was recently recognized, the name Turisops erebennus isn’t new. Originally associated with a specimen described in 1865 by scientist Edward Cope, Tursiops erebennus was grouped into the larger Tursiops truncatus species along with another Atlantic coast specimen from the late nineteenth-century Tursiops subridens. These two specimen skeletons were either incomplete or immature — which alone were unfit to justify the status of distinct species. After this consolidation, the dolphins found along the US Atlantic shores were generally referred to as a coastal/inshore “ecotype” of the common bottlenose dolphin and those found in deeper water were known as an offshore ecotype.
“An ecotype avoids the whole question of taxonomy,” explained Dr. Phillip Morin, a population genetics expert in the National Oceanic and Atmospheric Administration’s Marine Mammal Genetics Group. Whereas modern taxonomy attempts to classify and categorize animals by evolutionary relationships, ecotypes are usually labels that describe groups of animals based on some other unifying characteristic. Scientists often use ecotypes to describe animals of the same species that fill different ecological roles or spaces, such as habitat or diet.
To all but the most trained eye, inshore and offshore bottlenose dolphins are nearly indiscernible at sea. With the most reliable indicator of ecotype being habitat distribution, the non-taxonomic distinction made sense. And until these animals caught the attention of Dr. Ana Costa, a scientist from the University of Miami’s Rosenstiel School of Marine, Atmospheric, and Earth Science who specializes in the setting of boundaries between species, there wasn’t enough information available to definitively address their evolutionary relationship.
During her previous studies, Costa helped establish the presence of a coastal bottlenose subspecies local to her home waters between southern Brazil and Argentina known as Lahille’s bottlenose dolphin (T. truncatus gephyreus). Using data from beached individuals, she was able to show that these coastal animals were larger than their widely distributed offshore counterparts, rarely interbred, and displayed some significant physical differences.
When her work moved focus toward US waters, she began comparing East Coast coastal bottlenose dolphins to offshore Tursiops truncatus and found significant physical and genetic differences between the two — and no sign of interbreeding. With the two Northwest Atlantic bottlenose ecotypes significantly different, she proposed the resurrection of the erebennus name to describe the smaller, coastal dolphins at a species level.
Tamanend’s bottlenose dolphins are not alone as recent “new” cetaceans. Far from it, in fact. In 2021, a former subspecies of Bryde’s whale (Balaenoptera brydei) living in the Gulf of Mexico was found to be a distinct, separate species dubbed Rice’s whale (Balaenoptera ricei). Similarly, Ramari’s beaked whale (Mesoplodon eueu) was split from True’s beaked whale (M. mirus) in a study from that same year. And as recently as March 2024, two new species are looking to join the fray…
The Salish Killer Whales
Of all the worldwide populations of killer whales, the most well-known come from the eastern North Pacific near the Salish Sea, a nutrient-rich marginal waterway nestled between British Columbia and Washington state. Tasked with creating a killer whale census for the region in the 1970s amidst population concerns, Canadian cetacean biologist Dr. Michael Bigg made history by describing the differing behaviors between two ecotypes, groups that became known as “resident” and “transient” killer whales.
Resident killer whales are salmon eaters, preferring to feast on the hefty Chinook salmon that migrate annually to spawn in places like Washington’s Snake River. Residents travel in large matrilineal pods with close social ties, moving around in search of calories. True to their social nature, they are known for their vocalizations — an array of peculiar whines, buzzes, and honks that fill the sea while swimming, hunting, and playing. The Southern Residents, the population found seasonally in the Salish Sea, are the subject of intense scientific scrutiny due to their limited numbers; as of the July 2023 census, they counted only 75 whales.
Transient, or Bigg’s killer whales have their own unique calls but tend to be less chatty, relying on stealth to feed on mammals like seals and young gray whales. A staple for whale watchers of the area, transients tend to be seen in smaller pods of only a few individuals. They were once more uncommon in the Salish Sea than their fish-eating counterparts, but after the Marine Mammal Protection Act of 1972 facilitated the historic recovery of their preferred seal prey — a now-consistent food source that requires less long-distance travel — they have seen significant increases in numbers and occurrence.
In short, these ecotypes have been well-defined and well-studied for nearly fifty years, with the longest-running comprehensive catalogues of individual whales in the entire world. When the news broke on the night of March 26, 2024 that both ecotypes were being proposed as new species, it was a development decades in the making.
In the early 2000s, scientists and activists alike argued for a formal distinction between the two ecotypes in order to better protect the critically endangered Southern Resident orcas — but the data was too limited to support separate species. In 2017, Dr. Barbara L. Taylor and a team of scientists published a revised set of standards that outlined the use of genetics in declaring new species of cetaceans.
“That’s what I’ve spent the last twenty years doing,” Dr. Morin said, calling in from Seattle. The new 2024 study that proposes the new species, of which Morin was the lead author, represents the progress inspired and enabled by decades of scientific reforms and technological advancements.
While we have known about the differences between the two former ecotypes for nearly fifty years, “genetics is the critical data type and will be moving forward,” Morin explained. As part of the study, scientists were able to gather samples from across the entire known ranges of North Pacific transients and residents, from California to Japan to Russia, and “identify them with 100% accuracy.” They were also able to separate the two from a third, lesser-known offshore ecotype known to feed largely on elasmobranchs, or sharks and rays. The scientists found no significant gene flow between the types, despite the fact that they often exist in the same places at the same time.
For hundreds of thousands of years, their cultures and genes have remained separate. “Body shape differences could be due to dietary differences. Vocalization can be learned,” Morin pointed out. “But these ‘ecotypes’ were genetically distinct.” Thus, Orcinus ater (Residents) and Orcinus rectipinnus (Bigg’s) were born. For now, the offshore killer whales remain known as Orcinus orca.
Though genetics are the cornerstone of the 2024 study’s findings, they were able to use analyses of physical specimens to support their conclusion. “We set out to do this not believing that we would ever get that [physical data],” Morin remarked. Most of the relevant museum skull specimens had to be genetically tested to figure out which population— Bigg’s or resident— they belonged to before co-author Charissa Fung could do the necessary measurements and analyses.
The Salish Sea orcas are the best-studied killer whales in the world. For other populations, figuring out species status may be more difficult. “Looking forward to other subspecies or species of killer whales that are possibly out there, we won’t have [those specimens],” Morin said. Including the two proposed to elevate to species status, there are about ten different known ecotypes of orca worldwide, some more strikingly unique than others. Because these other groups are not as well studied, there are far fewer collected skeletons housed in museum collections and genetic data is relatively scarce. The emphasis of Morin’s study and others on genetic data is key to further understanding the differences between whale populations and species.
The Subantarctic Type D orcas are of particular interest to whale experts. Visually distinct from all other types of killer whales, they sport tiny white eyepatches, more curvy, hooked dorsal fins, and are seldom seen. Recent studies report them as among the most inbred of all mammal species, and little to no information exists on their behavior, acoustics, or distribution. With more data, they could be identified as a separate species.
New species add considerable implications for conservation. Currently, orcas (Orcinus orca) are listed as Data Deficient by the IUCN, reflecting global uncertainty regarding their population numbers. As populations are designated as species or subspecies in future studies and are listed separately, we may be able to better manage each individual population according to their conservation needs and gain a better understanding of their ecology, distribution, and numbers. The same goes for other species that stand to be further divided.
Whales in the Future
With great science comes great responsibility. As exciting as it is to keep ‘discovering’ ‘new’ whales, there are some potential risks. “If you start creating more species than there actually are… Then you can start creating problems with conservation,” Dr. Costa explained, considering her work on bottlenose dolphins. “You could divert funding from an actually endangered species to something not that’s actually threatened.” The standards set forth by Taylor and co-authors in 2017 are designed to keep this in check. Exemplified in the studies by Costa and Morin, they demonstrate the power of genetics in species delimitation and the value of revisiting old species groupings with new perspectives and technologies. These “new” species aren’t new whales — they’re just being split up and redefined.
As technology advances, scientists gain the tools to put together the pieces necessary to pull the species apart. Drone footage and advances in genetic testing like eDNA, a way to sample fragments of DNA floating in the water, are enabling scientists to monitor the ocean in ways they could never imagine aboard a ship. “We might be able to start patching together more about distribution and even the presence of animals that we didn’t know were there,” said Morin.
The Society of Marine Mammalogy will soon meet to vote on the proposal for Orcinus ater and Orcinus rectipinnus, but Morin and others are confident. New tools in genetics stand to shake up the foundations of cetacean taxonomy, but central to conservation are knowledge and understanding — and we’re barely skimming the surface.