Most seen dolphin off California should be it’s own species, new study argues

There’s been a 140-year debate about whether two dolphin types most commonly seen in the waters off Southern California are related.

Now, researchers affiliated with the National Oceanic and Atmospheric Administration believe they have the evidence to put to rest the question of whether the long-beaked common dolphin – most often observed in shallower waters – is its own species and completely separate from the short-beaked common dolphin, which swims in deeper waters off the coast.

The long-beaked common dolphin is larger, has different coloration and gets its name from an obviously longer snout.

With the two varieties swimming between Central California and Baja, Southern California has the world’s largest population of common dolphins and they are a popular sighting for the boat charters that cruise out of local harbors.

Experts say that while their ranges overlap, there has rarely been any interbreeding between the two populations of dolphins, based on at-sea observations and genetics, and that’s the most convincing evidence that the long-beaked dolphin should have its own species designation.

Being declared a species, not a sub-species, would give the long-beaked common dolphins greater protection. Their numbers and relative health would be more carefully tracked, and researchers could raise the red flag if there were a sudden die-off of the species that might not be noticeable when they are lumped in with the other common dolphins.

“They are two different-looking animals that come across each other and have the opportunity to interbreed,” said Tom Jefferson, an independent researcher at NOAA’s Southwest Fisheries Science Center. “The fact that they don’t is an indication to us that they view each other as something different. That’s what we see when they’re different species and should be reclassified.”

After examining more than 350 skulls – many are kept at The Natural History Museums of Los Angeles County – and DNA from almost 400 dolphins, Jefferson said he can prove that the long-beaked dolphins found predominantly off the West Coast evolved here as its own species.

Jefferson’s effort is the most recent in a series of back-and-forths on how to classify the long-beaked dolphins, first discovered in 1873.

At first, the larger dolphins were classified as their own species, but in 1884 they were demoted to a sub-species. And since then, their designations have changed four or five times, Jefferson said.

In 1994, they were again made species status. That lasted for about 20 years until the discovery of an error in how the scientific name was applied, and the study was thrown out. With the dolphins downgraded again to a sub-species, Jefferson set out to find definitive evidence that the long-beaked commons were their own species.

“We thought it was important to resolve the controversy,” he said.

Doing the work

The study to prove their species status, which included two other researchers and took six years to complete, was recently reviewed by the Taxonomy Committee of the Society of Marine Mammology. It maintains the official list of all marine species and meets once a year to review proposed changes – which require a two-thirds majority vote.

“Everyone agrees they’re different, but some wonder if they are different enough to say that they should be called separate species,” Jefferson said.  “We felt all the evidence was consistent.”

But when the committee considered Jefferson’s evidence in June, enough members disagreed and wanted more studies to confirm his team’s findings it delayed an official change, Jefferson said, adding that the committee wants him to review more common dolphins worldwide.

“It’s frustrating to me,” he said, hoping that he would have, for once and for all, closed the door of the discussion. “We’re a lot closer, but there is still more work to do to convince the doubters.”

But that will take more time and funding — Jefferson and his fellow authors have already spent so many years painstakingly gathering evidence, including hundreds of hours looking at dusty skulls in museums in Southern California and the Smithsonian in Washington, D.C.

Most of the skulls reviewed were housed at The Natural History Museums of Los Angeles County – known for having the world’s largest collection of marine mammal and cetacean remains.

The collection is housed in a giant warehouse in Vernon and tended to by Dave Janiger, who runs the warehouse and works and catalogs remains found on local beaches or received from the National Marine Fisheries, a department of NOAA.

The museum has 13,883 common dolphin specimens, 519 of which are long-beaked dolphins. The oldest dolphin skull is from 1907.

Measuring and sorting the skulls was tedious work. A big skylight lets in light, but the warehouse — especially in the summer — can reach 100 degrees; along with that comes the smell of decaying carcasses being prepared for necropsy and then later processed for their skeletal remains.

Jefferson spent hours upon hours climbing ladders and combing through large cabinets filled with rows and rows of dolphin skulls and skeletons.

“You need to handle them very carefully, as they are fragile and can be easily damaged,” Jefferson said. “Most of them were collected in the last few decades, but some of the skulls I have measured were collected in the late 1800s, so they are very precious — almost like antique furniture or jewelry.”

But the difficulty was worth it, Jefferson said.

“It is satisfying to be able to collect this important data that will help to clarify the taxonomy and hopefully help the species’ conservation,” he said.

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