Voyage of the seal: Foster Scholar Sarah Kienle identifies differences in elephant seal feeding patterns
By Yaamini Venkataraman
September 2018
It was almost an ordinary day in the field for Dr. Nancy Foster Scholar Sarah Kienle — except for the Jeff Corwin show camera crew. She was helping the crew with a routine procedure on an adult female northern elephant seal in Año Nuevo State Reserve, using a pulley attached to a sling and a tripod system to lift the seal so the team could weigh her. “This time, the carabiner attached to the sling breaks and smashes me in the forehead,” Kienle says. “I crumple and it’s all captured on film. The seal wasn’t off the ground so she was fine, but I staggered off to the side. It gave me a pretty spectacular bruise. When the episode was aired, the screen goes blank. Then you hear this ‘Ahh!’ and see me crumpled on the ground.”
Thankfully, Kienle sprang back up and leapt into her dissertation at the University of California, Santa Cruz. Along the West Coast, national marine sanctuaries like Channel Islands, Monterey Bay, and Greater Farallones play host to a majority of northern elephant seal breeding colonies. They also provide beaches for traveling seals and sea lions to rest. For her work, Kienle focuses on the feeding habits of northern elephant seals that breed within Monterey Bay National Marine Sanctuary.
“Elephant seals are extremes in everything they do: extreme divers and extreme navigators that migrate incredible distances and stay away from land for months at a time. There are also extreme differences between males and females,” Kienle says. While scientists know about elephant seals’ general habitats, they still don’t know some of the specifics, like where they feed or what they eat. Kienle is interested in digging into these specifics. With this baseline information, researchers can better understand how seals will fare in a changing ocean.
According to Kienle, most of what researchers know about elephant seals at sea comes from satellite tracking devices placed on female seals. They know female seals head into the open ocean, feed, and come back to beaches to give birth or molt. Male seals, however, stick to the coastline – but little else is known about their at-sea behavior. To tease out feeding differences between male and female northern elephant seals, Kienle needed to collect a variety of information: safely-collected blood and whiskers to figure out what seals eat; body measurements like mass, length, girth, and blubber thickness that give information about foraging success; and movement patterns and dive behavior from satellite tags.
Using all of these data, Kienle has found clear differences between male and female northern elephant seal feeding patterns. They feed in different areas, have distinct movement and diving patterns, and gain disparate amounts of mass and energy from feeding. According to Kienle, male seals are “consistent.” After breeding in the spring and molting in the summer in California, males beeline north to continental shelves off of Oregon and Washington, the Gulf of Alaska, or the Aleutian Islands for a few months. Once there, they dive to the bottom of the shelf to eat. Female seals, on the other hand, are “variable.” They often take long, meandering paths through the western North Pacific Ocean. Out in the open ocean, they take long, deep dives and feed for three to four days in one area before moving on to the next cluster of prey.
But there’s more. When females are feeding, Kienle has found that they are less likely to die than male seals, making the typical female feeding behavior less risky than the male behavior.
“The hypothesis I am exploring is that male seals appear to travel to areas that have an increased risk, potentially from predation, but better prey.” Fending off white sharks and orcas — the only known northern elephant seal predators — male seals risk their lives to eat food that allows them to gain mass and energy right before they need to compete for female mates during the breeding season.
Aside from figuring out why males engage in riskier foraging behavior, Kienle wants to compare foraging patterns across several northern elephant seal breeding colonies. Although these animals are found along the coast from Baja California to Oregon, most elephant seal information comes from the colony at Año Nuevo. Expanding elephant seal research to other colonies will help resource managers in Monterey Bay National Marine Sanctuary and beyond protect elephant seals and other large, migrating marine animals.
For example, the continental shelves used as feeding grounds by male seals lie right up against urbanized areas, making them more susceptible to negative human impacts like pollution or overfishing. If seals from different colonies feed in distinct open ocean and continental shelf habitats, they could fare differently under changing ocean conditions.
“[Continental shelves] are often more negatively affected by human activities, making national marine sanctuaries and other marine protected areas critical to protecting and preserving the habitats that so many marine predators, like northern elephant seals, need to survive,” Kienle says.
Though she never expected to study elephant seals, Kienle has wanted to be a marine biologist since she was in fifth grade. “I blame Ben Affleck,” Kienle says. “He was in this science TV program called Voyage of the Mimi that we watched in fifth grade. It was about these researchers studying humpback whales. That must have been when I first learned about marine biology as a career.” She even found her old diary, in which she lists “astronaut” and “marine biologist” as future careers. Kienle shared her love for ecology, evolution, and the ocean when she was a middle school and high school teacher through Teach for America for three years before graduate school.
When she finishes her degree, Kienle wants to keep spreading her love and interest in marine science with the sanctuaries.
“I love the fact [that sanctuaries] have tangible management and research goals, and they are specific to [individual] sanctuaries,” Kienle says. “It gives you a way to take your research and translate it to policy or management. I would love to keep working with the sanctuaries.”
Yaamini Venkataraman is a volunteer social media intern for NOAA’s Office of National Marine Sanctuaries and a graduate student at the University of Washington.
Graduate Student Spotlight: The Dr. Nancy Foster Scholars
NOAA's Dr. Nancy Foster Scholarship Program provides graduate students in oceanography, marine biology, maritime archaeology, and coastal and ocean resource management with financial support and tools for success inside and outside graduate school. The program seeks to increase the number of women and minorities in these scientific disciplines, particularly as they relate to the mission of the NOAA Office of National Marine Sanctuaries. In this series, we highlight the diverse perspectives on research and engagement held by our current scholars.