KINGSTON, R.I. – June 24, 2025 – While leopard seals might be easily recognized for their ominous portrayals as villains in movies — think Happy Feet or Eight Below — they largely remain a mystery to humans. Sarah Kienle, an assistant professor of natural resources science at the University of Rhode Island, is working to fix that by contributing to our scientific understanding of these marine apex predators. 

Largely an Antarctic species, leopard seals can also be found in Argentina, Chile, New Zealand, and Australia. They are notoriously hard to research: they aren’t in human care, they are solitary creatures who spend most of their lives underwater, and they live in relatively inaccessible places. Little is known about these top predators’ mating and birthing behaviors, population estimates, migration patterns, or whether they can survive in environments without ice.

“It’s very hard to get data on them,” Kienle says. “You have to be creative with your data sources and the questions you’re asking to be able to get answers.” The difficulty also makes it fun, she adds, and has led to important collaborations across researchers and governments worldwide.

Dietary revelations

Funded by two National Science Foundation grants, Kienle is collaborating on a variety of research projects shaping the baseline knowledge of leopard seals. In one case, she and a team of researchers have utilized an unexpected source to transform humans’ entire understanding of leopard seals. The source: whiskers.

Using tactics such as whisker analysis, Kienle and her collaborators are making significant discoveries about this mysterious species — including how their surprising feeding habits might be reshaping ecosystems.

“Whiskers are an amazing tissue that can represent up to a year’s worth of data,” Kienle says. “When you cut them into tiny segments, you can look at changes in the animals’ trophic level — meaning, what level of the food chain they’re feeding at across a year — from a single whisker.”

For this study, Emily Sperou, a new URI postdoctoral researcher in Kienle’s lab, meticulously cut up leopard seal whiskers — some procured during their field work, others donated by the National Oceanic and Atmospheric Administration — into tiny pieces and then analyzed them for carbon and nitrogen. The latter is what indicates the animals’ trophic position.

“Leopard seals have a huge dietary range,” Kienle says. “They are described as generalists, and at the population level that’s true, but the population is made up of a lot of individualized specialists.”

The researchers determined that specialization — individual leopard seals consistently targeting specific prey, habits that are largely driven by seals’ body size and sex — may be impacting declines in prey populations such as Antarctic fur seals.

Whisker analysis sampled across multiple years has allowed scientists to investigate consistency through time, relationship between body size and stress level, and diet specialization patterns. At URI, Sperou will now compare the whiskers of leopard seals from Antarctica to other regions — specifically Chile and New Zealand — to get a more global sense of their trophic level and specialization patterns.

The first reference genome

Kienle and her lab have also collaborated with researchers in the Marine Mammal Molecular Ecology Laboratory at Hampton University in Virginia, as well as with researchers across the globe to publish the first reference genome of a leopard seal. 

“You need a reference before you can start making comparisons, and this genome provides a starting point to begin answering complicated questions,” Kienle says. “How genetically diverse are leopard seals? Do we see population structure in their genome, suggesting that they have been isolated? Are they going on long migrations?”

Kienle has contributed to the sample collection for this study. The group now plans to start a comparative project looking at relatedness among individuals from Antarctica, Chile, and New Zealand, as well as whether there is genetic variation among sampled populations or molecular adaptations associated with different characteristics and traits. 

As a comparative biologist, Kienle says she’s interested in discovering new and different patterns and determining how representative they are, as well as how the information gained can be used moving forward. 

While leopard seals are not currently listed as a threatened species, environmental change is likely driving some of the feeding and migration patterns scientists are beginning to identify. “We need to figure out how to best protect them in a world that is undoubtedly changing,” Kienle says. 

Working hard, hardly working

Kienle recently was with a team of researchers conducting fieldwork in Parry Fjord, an isolated part of Patagonia, Chile, to study the ecology of leopard seals and their genetic connection to Antarctic populations. Renato Borras-Chavez, a postdoctoral researcher, was recently awarded first place in URI’s Research and Scholarship Photo Contest for an image he took capturing a critical moment from the expedition. Kienle is pictured in blue, Borras-Chavez in brown, and Sperou to the far right in the orange life vest.

After hours of patrolling the freezing waters looking for animals, the team came across a female leopard seal resting on an iceberg. “We were focused, pressured — piloting a drone, collecting data, and preparing to take a sample — but she was undisturbed, basking in the icy stillness. The contrast was clear: We were working hard, while she was hardly working,” says Borras-Chavez.

This story was written by Anna Gray in the College of the Environment and Life Sciences.