- Researchers looking for elusive beaked whales in the South China Sea believe they spotted a pair of either the ginkgo-toothed or Deraniyagala’s beaked whale.
- Although they collected extensive observational data, they could not confirm the whales’ species without DNA samples.
- The sighting is nevertheless important: Knowledge of both beaked whale species has been limited to what researchers have learned from a handful of stranded whale carcasses and unconfirmed sightings.
- The encounter likely represents either the first ever live sighting of the ginkgo-toothed beaked whale (Mesoplodon ginkgodens), or the first live sighting of the nearly identical Deraniyagala’s beaked whale (Mesoplodon hotaula) in the western Pacific Ocean.
On a calm, cloudy morning in May 2019, a lookout on a research vessel lowered his binoculars and shouted, “Beaked whales! Beaked whales!” As Massimiliano Rosso, one of the scientists aboard, recalls it, the research crew sprang into action, focusing nervously on their assigned tasks of photographing the whales, recording video, scribbling observations, and timing the animals’ breaths and dives.
“You know you have very little time and probably won’t have any other chances to get the data,” said Rosso, a marine biologist at the Chinese Academy of Sciences in Sanya, China.
Rosso and a team of researchers from the academy were looking for rare beaked whales in the South China Sea, 300 kilometers (nearly 200 miles) from the island of Hainan. After reviewing their photos, they realized they had possibly recorded the first ever live sighting of the ginkgo-toothed beaked whale (Mesoplodon ginkgodens), or the first live sighting of the nearly identical Deraniyagala’s beaked whale (Mesoplodon hotaula) in the western Pacific Ocean.
“I have spent the last 20 years carrying out research on beaked whales,” Rosso said. “But I still get excited every time I spot one.”
Beaked whales make up around 25% of known cetaceans, which include all whales, dolphins and porpoises, yet their lifestyles preclude people from easily studying them. Only 4 to 5 meters (13 to 16 feet) long, beaked whales often forage hundreds to thousands of miles from coastlines, and one species, the Cuvier’s beaked whale (Ziphius cavirostris), is the world’s deepest diver, with a record of 2,992 meters (9,816 feet). Looking for these animals with binoculars from a boat requires careful strategy and a bit of luck, as the whales spend little time at the sea surface.
Nevertheless, these mysterious cetaceans made headlines in recent months: the Cuvier’s beaked whale broke another world record, for the longest dive on a single breath (nearly four hours); several rare species washed ashore in Northern Europe; and scientists may have discovered a new species off the Pacific coast of Mexico. In December, the IUCN updated nearly all beaked whale listings, moving some species from “data deficient” to “endangered” or “least concern.”
The IUCN still lists M. ginkgodens and M. hotaula as data deficient because researchers have learned about them mainly by studying dead specimens stranded on beaches. In their report, the researchers noted one previous, unconfirmed sighting of a mother and calf, believed to be M. hotaula, swimming near Palmyra Atoll in the middle of the Pacific in 2007. M. ginkgodens has yet to be seen alive, they added.
Rosso and the other scientists on the boat initially spotted three beaked whales, but only two lingered for them to observe, for about 50 minutes. The pair took multiple shallow dives in sync before filling their lungs to make one final deep dive, disappearing below the waves. The team identified the whales as a male and a female of different ages, based on their teeth and the number of circular scars on their bodies created by cookie-cutter sharks (Isistius spp.). The scientists also collected data on the animals’ body measurements, diving behavior and coloration, they reported last month in Integrative Zoology.
“It’s really, really rare to have a sighting as good as this of any beaked whale species,” said Jay Barlow, a senior scientist and beaked whale expert at the U.S. National Oceanic and Atmospheric Administration (NOAA) in California, who was not involved in the report. “It’s more detail than I’m used to seeing in a sighting report,” he added.
The scientists also observed that both whales had a dent in different spots on their upper “lips,” a feature previously reported on live whales injured by fishing gear. According to the report, four out of the last five stranded ginkgo-toothed and Deraniyagala’s beaked whale carcasses that scientists examined showed evidence of interaction with fishing gear or marine debris. “Urgent ecological info like baseline data on their distribution, stock size and population structure are urgently needed in order to assess their conservation status,” Rosso said.
To strengthen their identification of the two beaked whales they observed, the researchers compared their data to photographs of a handful of individuals of the two species that have washed ashore in the past. Their detailed descriptions of the dorsal fin, beak and head will help future identifications of these animals at sea. But because the scientists could not collect DNA samples from the whales, they concede that their species identification isn’t ironclad.
Barlow said he wished the authors had been able to deploy acoustic recorders in the water to get a sample of the whales’ echolocations. “That might have been diagnostic,” he said, noting that other scientists have already recorded Deraniyagala’s beaked whale songs in the wild. “They spend a lot more time vocalizing than they spend at the surface,” he said. Barlow, a member of the team that recently discovered the probable new beaked whale species off Mexico, said recordings of those whales played a large role in their identification.
Despite the uncertain identification, Rosso said he was delighted at the experience. “Often beaked whales are described as very shy animals,” he told Mongabay, “but I find such a description to be wrong.” Unperturbed by boats and people, the beaked whales in the South China Sea were “just focused on their business,” he said. This gives Rosso hope that future research cruises will succeed in spotting beaked whales in the region, provided their populations remain stable under the growing pressures of marine debris, ship traffic and climate change.
“Some would say that you shouldn’t be publishing on an unidentified species if it can’t be identified to the species level,” Barlow said. “But that’s how we learn — by little bits and pieces, so I applaud them for publishing this work.”
Cypress Hansen is a science writer based in Central California. Find her at Cypresswritesscience.com and on Twitter @pollenplankton.
Correction 1/15/21: We have updated this story to refer to Massimiliano Rosso as one of the scientists involved in the research described. A previous version of this story referred to Rosso incorrectly as the lead scientist; while Rosso was the first author on the paper reporting this research, Songhai Li, also of the Chinese Academy of Sciences in Sanya, China, held the role of lead scientist. We regret the error.
Correction 1/18/21: We have updated this story to define “cetaceans” as including porpoises in addition to whales and dolphins. A previous version of this story omitted porpoises from the definition. We regret the error.
Citation:
Rosso, M., Lin, M., Caruso, F., Liu, M., Dong, L., Borroni, A., … Li, S. (2020). First live sighting of Deraniyagala’s beaked whale (Mesoplodon hotaula) or ginkgo‐toothed beaked whale (Mesoplodon ginkgodens) in the western Pacific (South China Sea) with preliminary data on coloration, natural markings, and surfacing patterns. Integrative Zoology. doi:10.1111/1749-4877.12507
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