Ecology alumna Jennifer Tennessen brings acoustics to killer whale conservation

UNIVERSITY PARK, Pa. — Jennifer Tennessen is a research associate at Western Washington University, working to understand the foraging behavior of an endangered population of killer whales in the Pacific Northwest. A 2015 graduate of the Penn State Huck Institutes of the Life Sciences' ecology graduate program, she's bringing the interdisciplinary approach of the Huck Institutes to her work, and is the first author on a paper published in February 2019 in the Journal of Experimental Biology.

Because killer whales hunt in vast areas under the ocean's surface — sometimes very deep under the surface — visual survey is impractical. Sensors must be designed, deployed, and have their data interpreted.

"Prey pursuit and capture occurs out of sight, up to about 300 meters below the surface," Tennessen explained. "Using multi-sensor, bio-logging tags suction cupped to the back of the whales, we are able to record sound and three-dimensional movement associated with foraging behavior, to understand when and how killer whales forage. We use this information to understand the impact on foraging behavior of underwater noise from commercial shipping vessels and a growing whale-watching fleet. Because a scarcity of salmon prey is one of the primary threats to population recovery, identifying how foraging occurs and the factors that may interfere with it are critical to determining how to protect and recover the population. We also use the tags to collect overnight data to understand whether diurnal and nocturnal foraging behavior differs."

Tennessen's work builds on the scientific training she received as a doctoral candidate at Penn State. While a graduate student at the Huck Institutes, Tennessen worked with faculty members specializing in a variety of disciplines, who helped shape her approach to research and stock her box of scientific tools.

"I was in a unique situation in which I benefited from having two supportive faculty advisers," said Tennessen. "My first adviser, Dr. Susan Parks, offered me incredible opportunities for growth as a field ecologist, arranging for me to play a significant role assisting field teams studying North Atlantic right whales in their summer feeding habitat at a remote research station in Lubec, Maine, and on their calving grounds in Fernandina Beach, Florida. When she eventually took another position elsewhere, Tracy Langkilde agreed to take me on as her student and warmly welcomed me into her lab family. Over the next few years, she compassionately and steadily supported me as I navigated field research with an entirely unfamiliar taxon (frogs) in a foreign setting (terrestrial).

"Additionally, I was mentored by Thomas Gabrielson, a faculty member in the Acoustics Program. His patience, methodological expertise, and teaching emphasis on hands-on experience provided me with a necessary and superb foundation for designing my field experiments in acoustic ecology. To this day, I continue to find my notes from his course in field methods and data analysis incredibly useful."

This experience with broad, multiparty collaboration has prepared Tennessen for the realities of her role as a public scientist. Her expertise better informs a conservation effort coordinated across two countries.

"My training in acoustics is an integral component of the work I am broadly interested in and engaged in," said Tennessen. "I am collaborating with colleagues at NOAA Fisheries and Canada's Department of Fisheries and Oceans to understand how anthropogenic sounds affect foraging behavior, and whether populations differ in their responses to noise.

"My colleagues and I work closely with policymakers at the state and federal levels, to provide science that can inform conservation management. Understanding how foraging occurs, and in what behavioral contexts, and the factors that may impair foraging success, can inform effective management of threats to reduce negative impacts of human disturbance."

Studying these animals has raised new questions about their behaviors. Tennessen's team learned that about half of the whales' dives past depths of 50 meters fail to produce a catch — so why do they expend precious energy on these unsuccessful deep dives? And why do they hunt upside down? The answer to that particular mystery might call for Tennessen's unique background.

"There are several possible explanations for this — it may be that this allows them to focus their acoustic beam (during echolocation) in a way that maximizes the area being searched," she said. "Alternatively, upside-down swimming at depth might be more kinematically efficient given their large bodies and particularly large dorsal fins. Another possibility is that upside down hunting might position their mouths to more effectively grab prey."

"When you're on the water with these animals for several hours, you get to observe many cycles of behavior," Tennessen added. "They seem to go through a lot of pretty normal activities, not much different from humans — eat, sleep, have sex, repeat. I think observing animals in their natural environment is quite humbling, and is a good reminder that we're all just animals trying to figure it out on this big rock."