Deepening Understanding

pair of heavisides dolphins


When Morgan Martin ’14 (MS) arrived at USD to begin her graduate studies in marine science, she imagined herself in a SeaWorld-like setting, interacting with blubbery sea lions, San Diego’s iconic coastline as her picturesque backdrop. The reality could hardly have been less glamorous.

“I worked with sea lion poop,” she says, still laughing at the memory of countless hours in the lab at the National Oceanic and Atmosphere Administration’s Southwest Fisheries Science Center in La Jolla. “I had 600 individual sea lion scat samples I had to wash, then microscope the remains. I ended up counting more than 20,000 fish ear bones and squid beaks to analyze what the sea lions were eating.”

Martin, a native of Springfield, Illinois, had dreamed of working with marine mammals ever since a visit to Florida when she was seven. She’d never been to California before she applied to USD. The offer she received from Ron Kaufmann, the director of what’s now known as the Environmental and Ocean Sciences Graduate Program, seemed too good to turn down. He’d set her up with one of USD’s off-campus scientific research partners.

“I knew it involved sea lions, and I knew it involved dietary research on sea lions, but I didn’t know the nature of the samples she was going to be working with, and I didn’t know exactly what the project was going to be,” Kaufmann recalls. “Some people would’ve run screaming into the night, but Morgan actually handled it pretty well.”

Given what he knew about Martin’s character, attitude and aptitude, Kaufmann fully expected her to quickly move on from sea lion scat once she had completed her master’s. She did, in a big way, winning a Fulbright scholarship and a National Geographic Society Explorer’s grant to pursue her PhD in Namibia through the University of Pretoria. There, on the other side of the world, Martin finally came face to face with the creatures she’s coveted since she was a kid.

“Namibia is a global hotspot for whale and dolphin life,” she says from her home base of Walvis Bay. “There are 86 species in the world total, and 33 live here.” Among them is a resident species of smaller dolphin called Heaviside’s, who are quite common along the coast. Martin says she sees them on a regular basis. “They’re often swimming out in the bay.”

Which is how she made a discovery that landed her research on the cover of The Proceedings of the Royal Society B, a highly respected biological science journal. Equipped with underwater microphones called hydrophones that she dangled off her kayak, Martin began recording the sounds emitted by the Heaviside’s. She described the corresponding activities she witnessed into a Dictaphone slung around her neck. “No one has ever tried to do it with this species before,” she explained. “It was basically an unopened book.”

What she found when she opened that book surprised her, along with many underwater acoustics experts.

These little dolphins use two different types of sonar sound, known as clicks. One, used for navigating and hunting, is ultrasonic and can’t be heard by killer whales, which are the dolphins’ only ocean predators. But the second is lower in frequency and has a much wider bandwidth.

“The lower frequency and broader bandwidth of these clicks means they are less directional and travel further underwater, so they are much more effective for communication,” Martin explains. “What we put together was that they’re using the second type of click to communicate. So far, this seems to be the only species that selectively increases communication range by changing the structure of their clicks.” The tradeoff, she notes, is that their social chatter can be heard by killer whales, which puts them at higher risk of being hunted and caught.

What’s impressive about Martin’s discovery is that among more than 70 species of whales and dolphins whose underwater acoustics have been studied, the Heaviside’s are the only ones now reliably known to produce use both types of clicks.

“What Morgan has done is pretty terrific. I’ve already shared it with some colleagues who do marine mammal acoustic work,” said Kaufmann. “It’s a neat insight into how dolphins manage to communicate with each other and balance being eaten by a predator that can listen in on some of the frequencies they use.”

Professor Zhi-Yong Yin, who worked with Martin as her faculty thesis advisor at USD and has kept in touch with her since, expected nothing less.

“It’s not surprising that she’s been successful,” he says. “She’s willing to put in the effort. I think she’s going to be a very promising new scientist in her field.” But while Yin was quick to credit Martin’s talent and work ethic, he adds, “I think what we did here set her up with a good foundation.”

USD’s Environmental and Ocean Sciences Graduate Program enrolls between five and seven students per year. They work closely with not only faculty but also with more than 100 undergraduate majors — one distinctive feature of the curriculum. Another is its emphasis on lab and field work. “Instead of being in a classroom, we go to the ocean, to the mountains, to the deserts,” Kaufmann said. “We get our students out into the field, so they can see the systems they’re supposed to be learning about.”

Beyond the sea lion scat, those excursions are among what Martin remembers best. “We went to the Salton Sea, to Mexico, to Cabrillo, La Jolla and Mission Bay,” she said. “Being able to leave school and go on a field trip right outside the door was incredible. Everything was at your fingertips. It spurred my love of marine life and the oceans even more.” — Karen Gross

Leave a Reply

Your email address will not be published. Required fields are marked *