With spring well underway, North Atlantic right whales, which wintered to Georgia to give birth, have migrated back north to their feeding grounds off New England and Canada. Researchers know from aerial photographs that at least 16 calves were born in the 2022/23 season.
But scientists aren’t just looking for whales, they’re also listening for them. And this year they added an underwater robot to the listening platforms in Georgia.
In late January, scientist Catherine Edwards of the Skidaway Institute of Oceanography used a torpedo-shaped glider called the Argus to eavesdrop on these endangered whales as they swam near Savannah Harbor. Edwards teamed up with University of South Carolina researcher Erin Meyer-Gutbrod, who led the team that listened to the recordings in near real-time.
“Catherine is sort of the genius that drives the glider around,” Meyer-Gutbrod said. “And we’re the ones actually trying to filter out the noise from whale detection.”
There are only about 340 North Atlantic right whales left. Beginning around November each year, adult females migrate north from their summer feeding grounds to reach their winter calving grounds off Georgia and Florida.
Right whales are also known as “city whales” due to their propensity to hug the coast of the East Coast, where much of the US population resides. On their migration, they traverse a dangerous gauntlet of shipping lanes, recreational boats, and heavily fished areas. At least 11 right whales have been killed by ship strikes in the last six years alone. Two others were seriously injured.
This is where the eavesdropping underwater robots come into play. Edwards and Meyer-Gutbrod listen for whales so they can alert shipowners and recreational boaters to their presence.
Vessels larger than 65 feet are already required to reach speeds of 10 knots in certain areas during calving season. There are also voluntary speed limits. But all are routinely ignored. Studies have shown that compliance rates for ships calling at the Port of Savannah are less than 10 percent.
And the same aerial photographs that identify newborn calves as they criss-cross Georgia’s offshore waters from about mid-November to April share whale sightings with sailors. However, producing this information is expensive and not comprehensive. Due to bad weather, planes and whales can only be spotted when they surface.
Ears in the water is a possible solution. Edwards used their robot from January 30th to February 13th this year. The yellow glider zigzagged up and down through the water, changing its buoyancy and center of gravity. Without a motor, it is relatively quiet and is therefore ideal for whale listening. Equipped with a satellite phone, the glider surfaced every four hours to transmit recorded data to base stations on land.
Archipeligo (Right Whale Catalog #3370) and her new calf swim off Little St Simons on December 8, 2022. (Florida Fish and Wildlife Conservation Commission taken with NOAA Permission 20556-01)
“During this mission, we spotted eight right whales that were screened by our shore based team, which is really, really, really cool,” Edwards said.
A hydrophone on the glider picks up the sounds and transmits them to a website called Robots 4 Whales at the Woods Hole Oceanographic Institute. A machine learning algorithm sorts what it identifies as whale sounds. Meyer-Gutbrod and three of her graduate students checked the whale calls.
In addition to the 15-day whale calls recorded by gliders, there are stationary hydrophones attached to buoys that collect data 24/7 for the past year.
The scientists compare the effectiveness of the mobile and fixed hydrophones and try to find out how far away from the robot a whale can be spotted. Eventually, they want to use these tools to alert ship captains in real time when whales are nearby.
“We hope that if we alert them in real time, ship captains will be more likely to maintain ship speed,” Meyer-Gutbrod said.
(A mobile app called WhaleAlert can already be used to alert ship captains that whales have recently been sighted or heard in an area.)
Challenges abound. One of them is that mother-calf pairs are probably pretty quiet.
“First of all, she communicates mainly with her calf, which is right next to her, like she’s touching the distance because she’s being suckled all the time,” Meyer-Gutbrod said. “So there is no reason to single out her voice. But I would also imagine, and we have no way of proving it, that the mother doesn’t really want to draw a lot of attention with this vulnerable newborn.”
There is also concern that seafarers could misinterpret the lack of detected whale calls to mean that the whales are not present. That is not necessarily the case.
“We can’t tell you if you’re not here,” Edwards said. “There is evidence that right whales are sometimes silent due to human activity.”
The calving season ended in April with the birth of 16 calves. It is already known that one of them died. Researchers estimate that more than 20 calves need to be born each year to keep the population alive.
“Unfortunately, they’re not reproducing fast enough to counteract the detrimental human impact on the population,” Edwards said. “So they keep decreasing every year.”
But the listener work has already proven useful, Meyer-Gutbrod said.
“We are conducting the analysis for a buoy just off the coast of Norfolk, Virginia. “We heard some right whales quite unexpectedly a couple of weeks ago because it’s usually assumed they’re back north by now,” she said in early May. “And so NOAA established a temporary slowdown zone in the area around this buoy.”
Researchers also want to study recent changes in whale migration patterns. A decline in food supplies during the summer months has resulted in a northward shift of feeding grounds for North Atlantic right whales from the Gulf of Maine to the Gulf of St. Lawrence. While surveys have documented this shift, scientists have not yet assessed its impact on winter migration patterns.
They expect their glider to be back in the water in December.
The project is funded by a $196,847 grant from the Broad Reach Fund. The researchers plan to use the glider again in December after the right whales return to Georgia for calving season.
This story was provided by WABE content partner The Current.
