For years, biologists studying the deep Pacific had been listening for a mysterious underwater signal: a beaked whale call labeled BW43. The signature appeared in hydrophone data beginning in 2020, but no one had ever seen the animal that produced it. That changed on a June morning in 2024, off Baja California, Mexico, aboard Oregon State University’s research vessel Pacific Storm.
Scientists on deck were preparing for another day of searching when a call came from the bridge — whales surfacing on the starboard side. For hours, two small beaked whales appeared and vanished in the distance, long enough for brief looks but not long enough to identify them with certainty.
Then researcher Robert Pitman, a now-retired scientist from Oregon State University, managed to take a small biopsy using a crossbow fitted with a sampling arrow. The fragment of skin — about the size of a pencil eraser — would later confirm what the team suspected: the whales were ginkgo-toothed beaked whales, a species never before documented alive in the wild.
The confirmation, published later in Marine Mammal Science and led by Elizabeth Henderson of the US Naval Information Warfare Center, marked the end of a five-year search. Henderson and colleagues from Mexico and the United States had been tracking the BW43 call since 2020, originally believing it might belong to Perrin’s beaked whale, another species never seen alive.
The team returned to the same area for three seasons, first with a sailboat and later a Mexican fishing vessel, without success. In 2024, working with Oregon State University and its more advanced equipment, they were finally able to pair the acoustic signal with a live animal. The Pacific Storm towed an array of hydrophones capable of identifying specific beaked whale calls and carried high-powered binoculars suited for long-distance visual searches.
Beaked whales are among the least understood mammals on Earth. There are 24 known species, most of them rarely seen because they dive deeper and stay underwater longer than any other marine mammal. Many species have only been described from stranded carcasses, and new species continue to be identified, including one as recently as 2021.
Their sensitivity to sonar is well-documented; exposure in certain circumstances can disrupt foraging or cause rapid ascents that lead to fatal injuries similar to decompression sickness. Understanding where these species live is essential for reducing the risk from naval activities and other noise disturbances.
The biopsy itself was almost lost. Before the researchers could retrieve it from the water, an albatross attempted to take it, forcing the crew to scare the bird off before recovering the sample.
The find also shifted assumptions about the whales’ range. Ginkgo-toothed beaked whales were previously known mostly from strandings across the Pacific, particularly Japan. The team’s analysis of acoustic databases suggests they live year-round off California and northern Baja California. Two previous strandings on the west coast of North America, once considered rare anomalies, now appear consistent with this distribution.
Many beaked whale calls remain unmatched to species, and several species still have no confirmed call at all. Researchers are now working to link additional acoustic signatures with specific animals so that long-term monitoring can rely on underwater listening rather than visual sightings — often the only viable method for such elusive species.
