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When Ice Melts: Tipping the Scales in the Predator/Prey Arms Race in Antarctica

The Lindblad Expeditions-National Geographic (LEX-NG) Fund aims to protect the last wild places in the ocean while facilitating conservation, research, education, and community development programs in the places we explore. This blog entry spotlights some of the exciting work our grantees are doing with support from the LEX-NG Fund.

A man is poised with a crossbow on an inflatable Zodiac in the Weddell Sea, impressively keeping his balance as the tiny boat pitches in the Antarctic swells. He’s aiming at a killer whale that’s surfaced to breathe. Unlike his predecessors from long ago, he’s not trying to kill the whale. Rather, his crossbow is equipped with a satellite tracking device that he is attempting to attach to the whale’s dorsal fin.

The man is Dr. John Durban, and along with his partners Dr. Holly Fearnbach and Bob Pitman with the U.S. National Marine Fisheries Service, he is conducting research to understand the role of killer whales as top predators in the changing Antarctic ecosystem. With a grant from the Lindblad Expeditions-National Geographic (LEX-NG) Fund, this team of scientists makes annual expeditions to Antarctica to carry out their research.

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Drs. John Durban and Holly Fearnbach deploy a satellite tracking tag on the dorsal fin of a killer whale. Research Authorized by Permit No. 14097-06 authorized by U.S. National Marine Fisheries Service Permit No. 14097-06. Photo courtesy of Lindblad Expeditions.

While Antarctica tends to get a bad rap as a frozen wasteland, it’s actually a dazzling wilderness of ice and stone. Offshore, the Southern Ocean is chock full of marine life. Despite the frigid water temperatures—somewhere in the vicinity of 30℉…brrr!—an abundance of marine creatures exist as part of a robust food web.

At the bottom (of the web, not the ocean), is krill. This mini crustacean smaller than your pinky finger is the foundation of the Antarctic food chain. Species from minke whales to small fish, squid, and penguins dine on this shrimp-like creature. Bigger fish and seals eat the fish, squid, and penguins that eat the krill. And at the top of the web is the killer whale: a cunning and efficient predator.

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With a grant from the LEX-NG Fund, Dr. John Durban and Bob Pitman with the U.S. National Marine Fisheries Service conduct research on killer whales in Antarctica. Photo by Kathryn Jeffs.

So what has the intrepid research team discovered so far? To start, that not all killer whales in Antarctica are the same (if you’ve seen one, you haven’t seen ‘em all). They’ve learned that what scientists previously thought was one type of killer whale living in Antarctica is actually at least five separate types, possibly distinct species, each with their own diet preferences and habitats. This means that each type of killer whale will respond differently to changes in climate or prey availability.

Three of these types can be found regularly around the Antarctic Peninsula: Types A, B1, and B2. Type A killer whales are the ‘big game’ hunters of the bunch. They’ve been spotted taking down large prey such as minke whales and elephant seals. Type B1 killer whales hunt for seals deep in the pack ice and have developed the strategic technique of swimming in sync to create coordinated waves to knock the seals off ice floes. Meanwhile, Type B2’s prefer Chinstrap and Gentoo penguins and probably fish.

Using satellite tags, the researchers can study how far killer whales swim in search of prey, both in terms of range of movement and dive depths. By tracking prey as well, such as minke whales, they can compare the habitats of predator and prey.

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Type B1 killer whales work in concert to wave-wash a seal from an ice floe in Antarctica, a hunting technique that has evolved to help them access their prey. Photo by John Durban.

A poet might describe the interaction between predators and prey as a deadly dance—one creature hunts, the other evades, and so it goes. Not the best analogy though. A dance insinuates predictable steps and a steady tempo. In reality, it’s an arms race.

The smartest prey learn tactics to evade their hunters. For example, some seals haul out on larger ice floes, making it more difficult for B1 killer whales to create waves big enough to knock them off. Others learn to stick to only the thickest pack ice to avoid Antarctica’s top predator.

In response, the killer whales develop more effective hunting techniques to capture their prey. It’s a constant one-upmanship for survival.

In an ecosystem in stasis, there is equilibrium. There will always be young, naive seals that rest on small ice floes, making themselves an easy target for killer whales, and older, experienced seals that have the know-how to avoid them. Enough prey exist to sustain the killer whales, but not so many killer whales that they deplete their prey. There’s balance.

What happens when the balance is tipped?

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Killer whales and seals have been locked in a predator-prey arms race for countless generations. Who will win? Or will they both lose because of encroaching human activities and climate change? Photo by Robert Pitman.

It’s difficult to imagine Antarctica being affected by climate change, with 98% percent of its land covered by ice over a mile thick, but it is. According to scientists, the Antarctic Peninsula in particular is showing signs of rapid warming.

If climate change persists and prey begin to diminish or migrate, what will happen to killer whales? Similarly, if ice continues to melt, possibly giving killer whales easier access to prey, will this shift the balance of the predator-prey arms race that has evolved over generations?

With support from the LEX-NG Fund, John Durban and Holly Fearnbach are in Antarctica right now aboard the National Geographic Explorer attempting to answer these questions by filling in key gaps in our knowledge about killer whales and their marine ecosystem.

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Using an unmanned hexacopter hovering over 100 feet above the water, John Durban and Holly Fearnbach took this aerial photo of killer whales in Antarctica in January 2016 to measure their size and body condition. Research Authorized by Permit No. 14097-06 authorized by U.S. National Marine Fisheries Service Permit No. 14097-06.

For the first time ever in Antarctica, they are using a small, unmanned hexacopter, aka, a super-cool, high-tech drone, to take pictures of killer whales from over 100 feet above the water’s surface (don’t try this at home, kids). The hexacopter is equipped with an altimeter to record height, so they can properly scale the photos and use them to measure the growth and body condition of whales from year to year. From this novel perspective, they’re also hoping to catch a glimpse of whales hunting prey at the surface to help learn more about their prey preferences.

Using the knowledge gleaned from their work, we can begin to understand what the future holds for killer whales and their prey in Antarctica, and how we, as humans, can better protect them.

With climate change altering their habitat—as well as the impact of human activities such as commercial fishing and krill harvesting—how will the scales tip in this changing ecosystem? Who will win the arms race: killer whales or their prey? Or, sadly, will they all lose?

Only time, and research, will tell.

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If you would like to learn more about killer whale research in Antarctica, or other projects supported by the LEX-NG Fund worldwide, please contact the Fund by email. To contribute to the LEX-NG Fund, click here.