Peter Tyack: Marine Mammal Communications

“Right whales have moved from being basses to being tenors to avoid all of the low-frequency noise from shipping.”

That summer job was fortuitous because it led Tyack to study marine mammal communication. Next door to the house where Walcott and his students worked, Roger Payne—who in 1967, along with his then wife Katharine, had famously discovered that humpback whales sing songs—was analyzing whale-song recordings. Tyack would go over to Payne’s house every few weeks to sing madrigals. One evening, Payne answered a phone call from the New York Zoological Society, where he worked during the rest of the year. The staff member on the other end told Payne that they needed to hire a caretaker for their whale field site in Patagonia. Tyack enthusiastically volunteered.

Taking a year off from Harvard, he flew to Patagonia and traveled to the Peninsula Valdez in Argentina. “It’s 42° south latitude. As a comparison, Boston is 42° north latitude. There were only a few hundred people living there, and there was this incredible richness of marine wildlife,” he says. Using a hydrophone he installed a kilometer offshore, Tyack recorded the sounds of bottlenose dolphins as they swam past the research camp. He assembled the electronics for the underwater recorders himself, learning on the go. “There were just bits and pieces from disposable buoys donated by the US Navy. I pirated them to make the equipment I needed. That’s field biology—you have to learn how to solve whatever problem comes at you.” When he returned to Boston, Tyack wrote his senior thesis about how the pattern of the animals’ calls changed depending on other nearby dolphins, people, or boats. The experience made Tyack realize he wanted to do fieldwork as a career.

Here, Tyack discusses the whale equivalent of “the cocktail party effect,” how studying whales has shown him the limits of humans’ imagination, and the excitement a day in the field can bring.

TYACK TRAINS

Hands on learning. Tyack was part of the Sputnik  generation, a time when there was an emphasis on the creative process in science. “In elementary school, what grabbed my attention was the hour a day we spent doing a science study project. It was very much capturing the experience first and then working out what was going on,” says Tyack. “We collected water from a puddle, looked under a lens, and saw protozoans; we explored how the volume of a gas changes its temperature.”

Sparking an interest. Tyack’s father was a historian, and his mother was a psycholinguist who studied language learning disabilities. His parents met through singing, and Tyack says he grew up with a love of acoustics and music. His family lived in Boston until he was 5 years old, and his parents, avid sailors, frequently took the young Tyack ocean sailing. He encountered his first whale at age 5, while sailing with his parents and a family friend who was blind. “The man could hear the whale at sea before anyone could see anything. Within a few minutes we sighted the whale, which is the first time I ever saw one.” The family moved to Portland, Oregon, where Tyack hiked and did mountain climbing. “Living on the West Coast lodged my initial interest in field biology,” he says.

In good company. Tyack entered Harvard University as a freshman in 1972. He was initially interested in neuroscience, but after taking  a freshman course with E.O. Wilson, who was studying sociobiology and evolution at the time, he decided to major in biological anthropology. In his sophomore year, Tyack read a New Yorker article that featured William Schevill, a founder of the field of marine mammal acoustics and the first to record and study underwater sounds of marine mammals. The article noted that Schevill’s office, in the attic of Harvard’s Museum of Comparative Zoology, was impossible to find. “It took me three trips of exploring the attic to find it, but I finally found the office. I took a reading course with him on marine mammal behavior and very quickly focused on bioacoustics.”

A research vision. After his senior year, Tyack continued to work with Payne and went to Hawaii to capture recordings of humpback whales. Because humpbacks usually sing only when alone, it was easier to study their vocal communication than those of dolphins. “Dolphins travel in a group, and you can capture the group sound, but it’s very difficult to identify which individual is making a sound and which one is responding. I’ve spent my career trying to solve that problem,” says Tyack. Land animals give visual cues when making a sound, and our ears can locate where a sound is coming from in air. But underwater, cetaceans provide no visual cues, and our ears do not sense the direction of a sound. Tyack observed that a humpback would continue to sing when it surfaced, but the sound would lose its low-frequency energy. Then the whale would take a breath through its blowhole and dive back down, continuing to sing. This disruption resulted in a change in frequency that could identify the singer.

TYACK TACKLES

Whale serenade. While in Hawaii, Tyack applied to graduate programs and chose to study animal behavior at Rockefeller University, entering grad school in 1977. He wanted to continue the humpback whale work and chose two advisors: Donald Griffin, who was among the first to study cognitive awareness in animals, and Peter Marler, who studied the singing behavior and patterns of birds. Tyack also continued to work with Payne, an adjunct professor at Rockefeller. “Roger was my practical field advisor, while Griffin never went into the field, but he explored a set of intellectual questions. That was helpful in pulling me to think broadly and to not get caught up in the minutiae of a single field project.”

Tyack would spend January to May in Maui, Hawaii, following the movements and recording the songs of humpback whales. He observed that lone whales (it was difficult to determine their sex) do most of the singing, and only during breeding season, and proposed that the males sing to females to communicate their readiness to mate and to other males to communicate a readiness to compete. Along with Roger and Katharine Payne, Tyack also found that the whales sang different variations of songs and that the songs changed throughout the breeding season, providing some of the first examples of complex changes in animal vocalization. “The animals are constantly changing the song while singing, and the only way that can happen is by vocal learning, which is rare among mammals,” says Tyack.

Sound engineer. In 1982, Tyack began a postdoctoral fellowship at the Woods Hole Oceanographic Institution with William Watkins, which lasted three years, and then transitioned into a permanent research position there. “The field then was limited in methodology, and it was helpful to be in a place that was centered on solving measurement problems at sea, even though I had very few colleagues in animal behavior there,” he says. He designed a device—an underwater microphone, circuitry, and light-emitting diodes that lit up depending on the strength of the animal call—that could be attached to captive dolphins’ heads to identify which dolphin in a group is vocalizing. Working at an aquarium on Cape Cod, Tyack showed that each animal produces a signature whistle and can precisely mimic other animals’ whistles. More recently Tyack, along with acoustical engineer Mark Johnson, built a recording device that can attach to large marine mammals in the wild and record their sounds. “Mark was a very creative engineer and added accelerometers and magnetometers to the device to record the animal’s orientation, which gives us a much richer view of how the animal is moving along with its sounds,” says Tyack. Over the course of 15 years, he developed smaller versions of the tags that can be used to track dolphins. The tags last up to 24 hours, recording tens of gigabytes of data. “The tags are tools to understand how these animals communicate with one another, a phenomenon I’m still exploring to this day,” says Tyack.
    
Unintended consequences. Those devices, it turned out, could also be used as an acoustic dosimeter to study the impact of man-made noises in the ocean. “As we developed these tags, evidence emerged that sounds of naval sonars could cause massive numbers of deep-diving beaked whales to strand and die in Greece and the Bahamas. It seemed that there was something causing the animals to respond to the sonar in a way that caused them to strand,” says Tyack. Using the tags, Tyack and his team studied beaked whales in the Bahamas, finding that the whales use echolocation to forage for prey at a depth of a kilometer or more, a “crazy place for a mammal to make a living.” After experiments studying how beaked whales respond to sonar, the National Marine Fisheries Service and the Navy reached an agreement to lower the threshold at which sonar was predicted to disrupt the behavior of the animals.

Not-so-white noise.  In 2011, after 29 years at Woods Hole, Tyack moved to the University of St Andrews in Scotland. He continues to study the effect of man-made noises on the ocean’s marine mammals. “The beaked whale problem was a canary in the coal mine—an unexpected and dramatic problem that does not seem to be true for all marine mammals, but that has alerted us to the potential impact of chronic noise on these animals. But chronic noise is very difficult to study. How can you tell that a whale a hundred miles from another whale is not responding because of another noise?” Tyack, along with his then graduate student Susan Parks, has used the acoustic recording tags to show that the animals can compensate for the interfering noise. “It turns out that right whales have their own version of the cocktail party effect. The louder the interfering noise, the louder the whales begin to call to compensate for the noise. The animals don’t just live with a reduced range; they must have an effective range to which they want to communicate, but they will modify their signals to do that,” says Tyack. The animals also compensate by changing the wave frequency of their call or by repeating their message. “These whales have increased the frequency of their calls in the 20th century by significant amounts. They have moved from being basses to being tenors to avoid all of the low-frequency noise from shipping.” Tyack is now trying to understand the impact of these behavioral and physiological responses to noise. “What does this do to reproduction and survival? We don’t know the answer to this difficult question.”

Tyack Thrives

Good old days. “Originally, to capture whale sounds, we used analog electronics that showed the amount of energy at different frequencies by burning marks onto special paper. In the original humpback song analysis, Katharine [Payne] had to analyze the 10-minute songs by stitching together pieces of paper with 1.2-second data increments. It was a nightmare. By the time I worked on my PhD, there were digital machines that converted the audio into the energy at different frequencies that were captured on 35-mm photographic paper. Now, any student with a laptop can download a program and do this analysis instantly with almost no effort.”

Thrill of the unknown. “What I’ve always loved about fieldwork is that you have no idea what the day will bring, what you will discover. In Argentina, it was much more contemplative; I was alone much of the time. But in Hawaii, for example, it was a team of 15 to 20 to man the boats and the shore station. I like peace and quiet, but it taught me how much you can do with a team that functions well.”

Risky business. “I was always comfortable in the water and on boats. I always loved swimming and became certified to dive as an undergraduate. The water and boats can be big hurdles for people wanting to get into marine biology. I remember discussions with primate evolutionary biologists at a time in the 1970s when Stanford students were held hostage by an African rebel group, and researchers risked infection with tropical disease. And they would say to me, ‘Oh my god, you have to get out on a boat?’ I was just incredulous. Here they were the ones taking real risks. Meanwhile, getting on a boat was no risk at all.”

A problem of scale. “The problem with studying whales is that they live on a much larger scale than we do. The animals can be separated by kilometers, and sitting in a boat your field of view is way too small. When we look from the boat, the scope over which our senses are operating [is] so much smaller that it takes a leap of the imagination to [comprehend] that another whale can hear a whale’s call a hundred kilometers away. These are ocean basin–scale animals that are swimming from Hawaii to Alaska, solving orientation and navigation problems over the whole North Pacific. But that is hard to grasp, an impoverishment of our imagination.” 

Greatest Hits

• Provided evidence that, similar to those of songbirds, humpback whale songs play a role in mating
• Found that humpback whales have a wide range of songs and are able to make complex and rapid changes to their songs—evidence that the marine mammal is capable of vocal learning
• Demonstrated that individual dolphins produce a signature whistle and showed that the animals can readily imitate the whistles of other dolphins
• Pioneered a sound-orientation tag that, when attached to a dolphin, is able to identify the animal producing vocalization in a group of captive animals, and a digital acoustic-recording tag to measure the vocal responses of wild cetaceans
• Raised awareness of how oil rigs, boats, and sonar disturb marine mammals