Team Provides New Benchmark Data on Leopard Seals, Antarctica’s Mysterious Apex Predators | Media and public relations
Baylor researchers seek answers to how leopard seals survive in extreme polar environment in first-of-its-kind study
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WACO, Texas (August 24, 2022) – Baylor University Marine Biologist Sarah Kienle, Ph.D., has always been fascinated by leopard seals. These reptilian-looking prehistoric seals are often portrayed as creepy villains in films such as “Happy Feet” and “Eight Below,” but little is known about them. things about their basic biology. The combination of Antarctica’s extreme climate, the species’ solitary habits, and its deadly reputation make the leopard seal one of the most difficult top predators on Earth to study.
In a first-of-its-kind National Science Foundation-funded study attributed to Professor Daniel Costa (Senior Principal Investigator; UCSC), Associate Professor Stephen Trumble, Ph.D. (Baylor), Professor Shane Kanatous, Ph.D. (Colorado State University), Wildlife Biologist Mike Goebel, Ph.D. (NOAA), and Professor Daniel Crocker, Ph.D. (Sonoma State University), the IPs and Kienle (a graduate student and postdoctoral researcher at the time) embarked on a common goal: to learn more about leopard seals. For two years, the research group studied 22 leopard seals off the coast of the Western Antarctic Peninsula, a rapidly warming and changing area. They weighed and measured each seal and tracked each seal’s activities and dive patterns using satellite/GPS beacons.
In the study published in Marine Science Frontiers – “Plasticity in the morphometrics and movements of an Antarctic apex predator, the leopard seal” – Kienle (first author) and team have documented the flexible behaviors and traits that may provide leopard seals with the resilience needed to survive the extreme climatic and environmental disturbances occurring around Antarctica.
“This study greatly improves our understanding of the life history, spatial patterns and diving behavior of leopard seals,” Kienle said. “We show that these leopard seals have great variability (or flexibility) in these different traits. Throughout the animal kingdom, variability is vital for animals to adapt and respond to changes in their environment, so we’re thrilled to see great variability in this Antarctic predator.
Among the findings of the research team detailed in the journal article:
- Adult female leopard seals are a lot larger than adult males; in fact, females are 1.5 times larger and longer.
- The team measured one of the largest leopard seals of all time, an adult female nicknamed “Bigonia”, which weighed 540 kg (1,190 lbs).
- Sexual dimorphism in favor of females (where females are larger) is unusual among marine mammals, a diverse group that includes polar bears, whales, dolphins, seals, and sea lions, but leopard seals are the most extreme example of dimorphism in favor of females among the 130+ species of marine mammals.
- It’s unclear why females are larger than males, although Kienle explained that other studies show that larger females are better at defending feeding areas, as well as stealing prey from smaller seals. . Larger females also eat larger, energy-rich prey, including fur seals and penguins, while smaller males and females often eat smaller prey like krill and fish. This suggests that larger body size in adult females is beneficial and provides a selective advantage that Kienle and her team will continue to explore.
- Based on movement data, female leopard seals spent more time “walking out” — or getting out of the water to rest on ice or land — than males.
- Two adult female leopard seals in this study spent two weeks in a row on the ice in the middle of the ocean, without eating or entering the water. Kienle and her colleagues suggest that this two-week stranding period is when female leopard seals give birth and nurse their young.
- At the end of the two weeks, the females return to the water and begin to dive again for food and, at the same time, they probably wean their young. That’s a short time to spend with their cubs because the leopard seal does all of these energy-demanding things without any food.
- Both male and female leopard seals swim short and long distances in coastal and open ocean habitats.
- One seal only traveled 46km from where the team worked with the seal, staying in and around the islands off the Antarctic Peninsula.
- Another seal, however, traveled 1,700 km during the same period from the tagging location, swimming to an island over a thousand kilometers away.
- Leopard seals of both sexes are small, shallow divers, diving an average of 30 meters and performing three-minute dives.
- Other seals can dive thousands of feet deep and hold their breath for over 40 minutes. However, the research team recorded the longest and deepest dive on record for leopard seals made by a man nicknamed “Deadpool”, who dived 1,256 meters for 25 minutes.
“It’s interesting to see such a variation [in movements and dive behavior] in a relatively small number of animals. To me, that means leopard seals are very flexible in their movements, and that’s a really good thing for adapting to changes in your environment,” Kienle said.
What’s next for this team of leopard seal biologists? Kienle said the team continues to analyze additional data from those same 22 leopard seals for publication. Kienle is also excited to compare how the leopard seals in this study compare to other leopard seal populations in the Southern Ocean.
“I have so many more questions, and I’m excited to continue learning more about leopard seals for years to come. There’s so much more to discover about this incredible Antarctic predator,” said Kienle, who runs the Laboratory of Comparative Ecophysiology of Animals at Baylor which focuses on understanding how different animals function in the context of their environment.
ABOUT THE AUTHORS
In addition to Kienle and Trumble, the research team included Michael E. Goebel, Antarctic Ecosystems Research Division, Southwest Fisheries Science Center, National Oceanic and Atmospheric Administration (NOAA) Fisheries, La Jolla , California, and Department of Ecology and Evolutionary Biology, University of California Santa Cruz, Santa Cruz, California; Erin LaBrecque, Marine Mammal Commission, Bethesda, MD; Renato Borras-Chavez, Center for Applied Ecology and Sustainability (CAPES), Department of Ecology, Pontificia Universidad Cato´ lica de Chile, Santiago, Chile, and Instituto Antartico Chileno (INACH), Punta Arenas, Chile; Shane B. Kanatous, Department of Biology, Colorado State University, Fort Collins, CO; Daniel E. Crocker, Department of Biology, Colorado State University, Fort Collins, CO; and Daniel P. Costa, Department of Ecology and Evolutionary Biology, University of California, Santa Cruz, Santa Cruz, CA.
This work was supported by National Science Foundation grant #1644256.
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