Cryptic Beaked whales make supersonic sounds
The operating area for the recent Beaked whale survey in U.S. and Canadian waters is shown in the orange box. The black line from the far eastern coast of Maine out to sea is the U.S.-Canada maritime boundary known as the Hague Line. The lighter curved lines from lower left to top right mark depth
— Map by Danielle Cholewiak/NOAA Fisheries)
A True’s beaked whale on the surface. These deep-diving marine mammals are difficult to study.
— Photo by Robert Pitman/NOAA Fisheries)
From ecoRI News (ecori.org)
A month-long survey of the deep waters from Georges Bank to the continental shelf south of Rhode Island has turned up an unexpectedly large number of a little-known whale, and scientists are excited that they were able to tag one of the animals for the first time.
True’s beaked whales were first identified in 1913 by Frederick W. True and have seldom been observed anywhere in the world since then. But researchers from the Northeast Fisheries Science Center in Woods Hole, Mass., saw and heard several of the elusive animals almost daily during their expedition from July 20 to Aug. 19.
“Deep-diving cetaceans such as beaked whales are difficult to study due to their cryptic nature and their offshore distribution. But they are an important part of the deep-water marine ecosystem,” said Danielle Cholewiak, the chief scientist on the project. “Beaked whales are an extraordinary group of species, adapted for an extreme lifestyle. They dive to incredible depths to forage and spend long periods of time deep underwater.”
Portsmouth native Annamaria Izzi, one of the biologists participating in the expedition, jokingly described True’s beaked whales as looking “like ugly upside-down dolphins” with no teeth inside their mouth but two teeth sticking outside their mouth that males use to fight with each other.
Every day during the research cruise, Izzi and her colleagues deployed an array of hydrophones — underwater microphones — that were dragged behind the ship to listen for whales.
“We went from knowing nothing about them to having interesting clicks on the hydrophone and a couple visual approaches that cued us in to what they look like and sound like,” Izzi said. The clicking sounds were created by the whales using their echolocation abilities to navigate in the darkness of the deep water. “Beaked whales are similar to bats in their use of echolocation,” she added.
This year’s expedition was a follow-up to similar efforts in 2016 and 2017 that resulted in the discovery of what Izzi called “hot spots of acoustic detection of beaked whales,” mostly near the Northeast Canyons and Seamounts Marine National Monument south of Cape Cod. (Two years ago this month, this area became the first marine national monument off the Atlantic Coast, but Interior Secretary Ryan Zinke is considering opening the Northeast Canyons and Seamounts to commercial fishing.)
“The noise they make is supersonic; you can’t hear it, so you have to see it,” Izzi explained. “A computer program takes in the sounds detected by the hydrophone and gives a visual representation of it.”
One of the main accomplishments of the expedition was the tagging of one True’s beaked whale using what scientists call a digital acoustic recording tag attached to the whale with a suction-cup. The device recorded the movements and acoustic behavior of the whale for about 12 hours before it came off and was recovered.
“The data from this tag gives us the first detailed glimpse into the underwater behavior of True’s baked whales,” Cholewiak said. “We are excited about the new insights we can glean about this species.”
The scientists will soon compare the diving behavior they recorded of the True’s beaked whales to the behavior of other species of beaked whales.
Izzi said the expedition raised a lot of new questions.
“I’m focused on the acoustic aspect of these whales, so I’m really interested in learning more about what we’re recording with the towed array,” she said. “The hydrophones are at the surface while the whales are diving deep, and they’re only clicking when they’re down deep. I know I’m not getting all the clicks they’re emitting, so I wonder what part of the diving sequence I’m picking up. What am I hearing and how is that different from what they’re actually producing?”
The scientists also collected water samples in the immediate vicinity of where the beaked whales swam in an effort to collect bits of whale DNA.
“Environmental DNA, or eDNA, is DNA left in the environment when an animal passes through it,” Cholewiak said. “It’s an exciting tool that may provide a better understanding of species identity and population structure, just from sampling water.”
A dozen eDNA samples were collected by the scientists and paired with biopsy samples and whale photographs to match the DNA samples to specific animals.
Why are True’s beaked whales being found in good numbers in the waters off southern New England? Izzi said it’s because the whales prefer the habitat around small island chains or underwater mountains, and the edge of the continental shelf and the seamounts in the new marine monument provide that unusual habitat.
“A lot of previous studies have been around the Canary Islands, the Bahamas, or around San Clemente Island off Southern California,” she said. “We don’t have any deep-sea islands around here, but we do have deep-sea seamounts, which are a good place for upwelling and primary productivity, where there’s more prey availability that can support large populations of whales.”
Izzi said the next step in studying True’s beaked whales in the region is to place more tags on the marine mammals.
“We have information that gives us a first look at the species, but it’s only based on one tag for 12 hours. Every whale is different,” she said. “We really need to get more tags on more whales. Our chief scientist is interested in looking at group structure and creating a photo ID catalog of individual whales based on their unique scar patterns. And we want to keep working with this eDNA approach to see if it works for beaked whales.”
The research is being conducted as part of the Atlantic Marine Assessment Program for Protected Species, an annual survey sponsored by the National Oceanic and Atmospheric Administration to assess the populations of marine mammals in area waters. The program focuses on the collection of seasonal data on the abundance, distribution, and behavior of marine mammals, sea turtles, and seabirds in the Atlantic Exclusive Economic Zone.
Rhode Island resident and author Todd McLeish runs a wildlife blog.