We know that leopard seals are large, formidable predators, but exactly what they’re doing below the waterline has long remained a mystery. But now, thanks to National Geographic grantee Douglas Krause, we’re getting an underwater glimpse into leopard seals’ carnivorous lives—and the seal-on-seal battles are a sight to behold.
Krause, a National Oceanic and Atmospheric Administration (NOAA) wildlife biologist, teamed up with National Geographic to attach Crittercams to leopard seals at Cape Shirreff, Antarctica. “The footage can help us learn what the leopard seals are eating and how they’re interacting with their ecosystem. We can use that information to develop scientific advice for conservation efforts, to keep the environment healthy for leopard seals and all Antarctic animals,” Krause explains.
With discovery and conservation as their inspiration, Krause and the rest of the NOAA team took on the imposing task of attaching Crittercams to seven adult female leopard seals. “The leopard seals are frequently over 11 feet long and can weigh 1,100 to 1,200 pounds—basically the same size as a grizzly bear, or even a horse. Their size and capabilities as apex predators with very large mouths full of sharp teeth can be intimidating,” Krause says. “The idea is to very stealthily approach a sleeping animal so as not to disturb it. In most cases, we are able to dart her with a sedative while she’s still asleep. Then we move off the beach and get out of her line of sight so she can calm down, and typically she’ll just go back to sleep.”
Once the sedatives were in full effect, some team members attached the Crittercam to the leopard seal, while others monitored her vitals and ensured she didn’t reenter the water before the sedatives completely wore off. Then the team cleared the beach and watched the seal from afar to make sure she fully recovered. “Limiting disturbance and getting accurate data on their behavior—that’s the name of the game,” says Krause.
The leopard seals wore the Crittercams for five to seven days before the NOAA team collected the devices. And what they saw on the 50-plus hours of footage was unprecedented, says Krause. “We were extremely excited to see for the first time on video ever an act of kleptoparasitism—where one leopard seal will come up, fight with, and then steal the food of another leopard seal. That had been suggested by some people in the past but had never been confirmed on video.”
Watching the epic confrontations in action is not only remarkable, but as Krause explains, “now that we know that kleptoparasitism is happening, we have a much better understanding of the different ways that leopard seals can impact the ecosystem around them. The impact is potentially much greater.”
The footage showed one of the leopard seals, referred to as 397G, catching and losing six different fur seal pups as other leopard seals attack her to steal her prey. Hardly deterred, 397G generally “swims off very quickly, and almost immediately begins patrolling the shoreline for new prey. Within 10 minutes she has ambushed and caught another fur seal pup, which she does get to eat—one of the few. Interestingly, 397G was one of the most efficient hunters that I’ve ever seen,” Krause says.
The footage revealed other significant behavior too, including leopard seals engaging in food caching (hiding prey on the seafloor to eat later), dragging fur seal pups from the beach, and hunting bottom-dwelling fish. The NOAA team literally cheered, gasped, and yelled in excitement when they watched the Crittercam footage for the first time.
“There were many instances of me and the rest of the team putting in extremely long hours to deploy and then recover the Crittercams, but it was worth it, both scientifically and personally.” Krause says. “I have been going to the Antarctic for over 10 years now, and almost that whole time I’ve been watching leopard seals because I find them fascinating, but I was always restricted to only viewing what they were doing above the waterline, and usually during the day. I was extremely excited to finally get that view below the waterline.”
To see more of Krause and the NOAA team’s work in Antarctica, check out their interactions with some adorable and mischievous animals in Seal Pups: Ferociously Cute and Worth Protecting and Tagging Adorable, Nasty Little Penguins: #BestJobEver. Watch the entire Expedition Raw series, too.
This research was supported by The National Geographic Society/Waitt Grants Program. Learn more about the science and exploration supported by the nonprofit National Geographic Society at natgeo.org/grants.
All research conducted in accordance with MMPA Permit #16472-03.