Humpback health in the crosshairs: UCSC scientists used pandemic calm to compare, contrast whale stress
Collecting whale blubber and studying the levels of stress hormones the giant mammals are facing now, compared to this time last year, gives scientists a clearer picture of how noise in the bay affects their well-being.
It’s 7:45 a.m. on a bitter-cold May morning on the Monterey Bay, and recreational fishers on small craft are everywhere, commercial fishing vessels dot the horizon, and beyond them, massive shipping containers make their way past the mouth of the bay, crawling toward the Port of Oakland.
Ari Friedlaender skims the choppy waves in a small, inflatable Zodiac, but he’s out on the water for a different reason — whales. He’s no whale-watching captain, though; he’s a marine ecologist at UC Santa Cruz and today is the final day of his whale-sampling season.
For the previous month, Friedlaender and his lab collected tiny cores of blubber, or body fat, from just below the dorsal fins of over 30 humpback whales. Their blubber contains a suite of hormones that reflect how stressed out they are — a topic that became especially interesting when the human world came to a complete halt last spring.
When COVID-19 surged in March of 2020, people stayed home. Tourism dwindled. Commerce paused and boat ramps closed. While our ways of life were turned upside-down, marine life got a months-long vacation from humans for the first time in recent history.
“We just can’t conduct studies that can replicate this experimentally,” says Jillian Wisse, a conservation physiologist who studies whale stress at Duke University. “It’s exciting to see that a group was able to jump on that opportunity and pull this off.”
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As expected, the pandemic didn’t stop the whales from migrating into the bay. By April of last year, the humpbacks began to arrive in Monterey Bay for the summer foraging season. Before they even had funding or a formalized plan, Friedlaender’s team set out to collect bits of blubber from the whales, using the Marine Mammal Center’s boats and essential-business designation to seize this rare moment.
“It was just a quiet environment, everything looked different, everything sounded different,” says Friedlaender. “We were just like ‘We’ve got to get out there because we’re not going to get this time back.’”
How to poke a whale
This spring, the whales are back in the bay again and, as evidenced by the dozens of vessels chugging around during the final whale-sampling trip, the humans are back, too.
After a half-hour of scanning the horizon and steering the boat southward, Friedlaender spots a 10-foot plume of mist in the distance. He veers toward it while Ryan Reisinger, a postdoctoral researcher in Friedlaender’s lab, loads a camouflage crossbow.
The arrow-like darts used for collecting the blubber are custom made, he explains, and they won’t go more than an inch into the animals’ tissue. The tip of the dart is like a long, skinny cookie cutter, about the width of a pencil. “It’s like being poked in the side,” adds Friedlaender. “It’s jolting, but it doesn’t do any serious harm.”
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As Friedlaender homes in on the last place he saw the whale, Reisinger steps up onto a metal pulpit hanging over the front of the boat. For several minutes, they idle, waiting for the next burst of breath to breach the surface. The whales are busy, likely feeding, and their breaths are few and far between.
Then, behind the boat, two enormous exhales break the silence. Friedlaender repositions to give Reisinger a clear shot, about 40 feet from a pair of adult humpbacks. The best moment to shoot is right before a whale dives — when its back arches highest above the water. But everything is in motion, and the resting whales occasionally dip behind the five-foot swells. Reisinger misses his chance when the first whale goes down, but stays focused on the second, patiently holding the crosshairs to his eye.
As the trailing whale arches up, Reisinger lets out a quick yell, and pulls the trigger. The crossbow twangs and an instant later, the dart bounces off the whale’s back. It flinches a little, flicking its tail, but because whales are huge, the small flinch makes a big splash.
Friedlaender maneuvers toward the dart, which is wrapped in yellow foam to keep it afloat, and plucks it from the water before transferring the tube of fat into a vial. The blubber is pinkish-white, the texture of raw meat, and smells sweet and fishy, like scallops.
Back in the lab, a suite of hormones including cortisol, testosterone and progesterone will be extracted to determine the animal’s sex, reproductive state, and stress levels during the previous few weeks.
As soon as they finish taking notes and putting the blubber on ice, the researchers resume positions in search of more whales. Reisinger successfully darts two more during the trip, wrapping up the sampling season until October.
Living with sound
So why exactly is anthropogenic — or human-produced — noise a problem for whales? As far as we know, it’s probably for a lot of the same reasons that screeching trains, blaring sirens and low-flying planes are a problem for people.
Noise drowns out other important sounds, it damages our hearing and, “in most cases, in a noisy environment, animals have to literally increase the energy of their calls, which means talking louder for us,” says Friedlaender.
Research from the past 10-15 years suggests that chronic exposure to traffic noise harms human cardiovascular health by activating our fight-or-flight response — whether we realize it or not. The verdict for the heart health of whales, however, is still unclear.
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There is plenty of research detailing how anthropogenic noise impacts marine mammal behavior. But until last year, the only data on the effects of boat noise on chronic whale stress came from a study conducted after the 9/11 attacks, which linked lower shipping traffic to reduced stress in North Atlantic right whales.
“Having more data points for [chronic whale stress] will be super helpful,” says Wisse. “Right now that 9/11 study is the only direct link we have … physiological research, especially in free-swimming individuals, is severely lacking.”
For those free-swimming whales at sea, there is another layer to the problem: The ocean is relatively opaque. On a good day, it’s tough to see beyond 30 feet from below the surface in Monterey Bay and visibility goes down the deeper you dive. (Compare that to the 20-mile view Santa Cruzans have of the Monterey Peninsula.) Because of this, whales and other marine creatures have evolved to rely heavily on sound to find prey, communicate over long distances, and navigate the sea.
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Boat noise can jam the signals whales are sending to each other, prevent them from hearing a shoal of tasty anchovies or krill, and even drive them out of the area — all resulting in extra energy expenditure. That’s energy they can’t afford to waste, especially females with newborn calves in tow.
Wisse, who isn’t involved in the study, says she’s especially interested to see Friedlaender’s results on reproductive hormones, “because there’s so much we still don’t understand about how chronic stress impacts reproduction in these animals.”
(Click through the images below to see the relative boat traffic in three humpback whale study areas.)
Coexisting with whales
Once Friedlaender’s lab members analyze the blubber, they will connect the chronic stress levels with ambient underwater sound recordings from hydrophones around the bay. The Monterey Bay Aquarium Research Institute and the National Marine Sanctuary have been collecting the sounds of Monterey Bay every hour of every day for the past several years, making the bay a “really nice natural laboratory,” says Friedlaender.
While this study is focused on the population of whales that forages in the Monterey Bay each summer, Friedlaender is collaborating with folks from the Stellwagen Bank National Marine Sanctuary near the busy Boston Harbor and the Palmer Research Station in Antarctica to compare noise-induced chronic stress among their respective humpback populations, too.
What will happen with the results of this comprehensive study is the next big question. Wisse says that depending on what the study’s results are, she’d like to see them “moved into a regulatory context,” such as putting pressure on the United Nations’ International Maritime Organization.
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“There are noise-quieting technologies out there that the shipping industry could use today if they put the money there. There are tools available, but the political will has not been there.”
Friedlaender is quick to say his goal is not to indict the people who recreate, fish, and make their living out on the water. Instead, he advocates for increased awareness, so people can make more informed decisions.
If this study shows that humpback whales are significantly stressed out by our noise, but can quickly return to a relaxed state in our absence, he says, “I hope that it would then provide a roadmap for how we can be better stewards and caretakers of the places and animals that are precious to us.”
Listen to Cypress Hansen’s podcast on her oceanic adventure here via KSQD.