A recently discovered species of whale that lives in U.S. waters is already on the brink of extinction, according to an open letter signed by more than 100 marine scientists. The international group of researchers is calling for the Biden administration to take "significant action" to save the newfound species, which was only identified last year and currently has around 50 individuals remaining.

Rice's whale, also known as the Gulf of Mexico whale (Balaenoptera ricei), is a baleen whale endemic to the northeast region of the Gulf of Mexico, making it the only cetacean species that lives exclusively in U.S. waters. The species was previously misidentified as an isolated population of Bryde's whale (Balaenoptera brydei), which can be found across the globe. But in January 2021, a study published in the journal Marine Mammal Science analyzed an individual that washed up dead on a beach and found that Rice's whales are both morphologically and genetically distinct from Bryde's whales. The newfound species can grow up to 40 feet (12 meters) long and has one of the most complex vocal repertoires of all known whale species.

Researchers estimate that there are only 51 Rice's whales remaining. The tiny population is under threat from the oil and gas industry, as well as excessive boat traffic and abandoned fishing gear. The species is listed as critically endangered by the International Union for Conservation of Nature (IUCN) Red List of Threatened Species, and is also protected by the U.S. Endangered Species Act, as well as the Marine Mammal Protection Act.

Now, in an open letter to the Biden administration published Oct. 13, a group of 101 whale experts from around the world have called on the U.S. government to do more to protect the whales before they are wiped out forever.

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"Unless significant conservation actions are taken, the United States is likely to cause the first anthropogenic extinction of a great whale species," the researchers wrote. "With abundance so low, the loss of even a single whale threatens the survival of the species."

In the letter, the researchers explain that the main threats to Rice's whales are linked to drilling and exploration for fossil fuels in the Gulf of Mexico.

Researchers estimate that in 2010, the Deepwater Horizon disaster — the largest marine oil spill in human history, which released around 416,000 tons (377,000 metric tons) of oil into the Gulf of Mexico — was responsible for killing around 20% of the Rice's whale population.

"Another oil spill of the same size could wipe them out almost right away," Erich Hoyt, a research fellow at Whale and Dolphin Conservation (WDC) in the U.K. and author of the "Encyclopedia of Whales, Dolphins and Porpoises," (Firefly Books, 2017) told Live Science in an email.

Scientists believe that the whales are extremely susceptible to noise pollution created during seismic surveys, when fossil fuel companies blast the water column with powerful sound waves to detect potential oil and gas deposits beneath the seafloor. These sound waves can disrupt the communication, navigation and feeding behaviors of cetaceans and even permanently deafen some individuals, the researchers wrote.

In the letter, the researchers highlight that the Biden administration is "presently considering a new five-year program for offshore oil and gas leasing," which could include permits to continue damaging seismic surveys during this time. The scientists urged the government to abandon this program immediately and ban all seismic surveys in the area.

"Continuing with seismic exploration or drilling in the northern Gulf is antithetical to basic principles of conservation and would jeopardize the species' survival and recovery," the researchers wrote.

The researchers also highlighted the threat posed by vessel strikes. The whales spend the night resting within the upper 50 feet (15 m) of the water column, which leaves them "acutely vulnerable to ship strikes," researchers wrote. A number of major shipping routes traverse the whales' habitat, and vessel-strike injuries have been observed in a dead beached whale, as well as a living individual with a significant spinal deformity resulting from a vessel strike, which will likely greatly reduce its lifespan, according to the letter.

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Rice's whales are also potentially susceptible to entanglement in ghost fishing gear and to becoming unintended bycatch from large-scale fisheries, Hoyt said.

The hazards listed in the letter are an issue for most other cetacean species, but they are particularly problematic for a dwindling species like Rice's whales.

"These threats apply to all whale species to various degrees in other parts of the ocean," Hoyt said. "But especially when a species is greatly reduced in number."

In addition to ending oil and gas exploration in the area, researchers have called for speed limits and redirected routes for shipping companies, and the relocation of fish farms, offshore wind farms and other new developments to outside of the whales’ habitat. The scientists say that if these actions are taken swiftly the species has a chance of surviving.

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"Gulf of Mexico whales can recover," the researchers wrote. "Our experience with other baleen whales shows that populations can rebound as conditions improve."

However, even if the Biden administration does implement the sweeping reforms suggested by scientists, the species still faces a "very long road to recovery," Hoyt said. It may also take decades to properly assess if they can or will recover, he added.

So far, the Biden administration has not commented on the new letter.