Recovery and Resilience: How Humpback Whales Navigate Antarctic Waters
The humpback whales active in Antarctic waters present breathtaking displays. Whether these magnificent creatures are launching from the deep in an aerial act or slapping their fins on the ocean’s surface to create arcs of dancing seawater, they’re a powerful symbol of resiliency. Hunted to the brink of extinction before the International Whaling Commission intervention in the 1960s, humpback whales have slowly started to recover and recolonize some of their traditional Southern Hemisphere habitats.
“Humpbacks were once hunted to less than 10 percent of their initial abundance,” explains Silversea Expedition Expert Olive Andrews, who is also the Marine Program Manager at Conservation International and a researcher with the South Pacific Whale Research Consortium. “They are curious and graceful,” she adds. “We are super lucky that there are any left on our planet to see.”
Andrews recalls a standout moment on a recent cruise in Antarctica. While sailing through the Gerlache Strait in the late evening, dinner guests spotted humpback whales just feet from the ship. “There was a pink glow across the icy mountains around us, as the sun traversed the horizon,” she says. “All at once, diners leaped from their chairs and lined the windows to observe feeding humpbacks. We must have seen over 300 whales that evening.”
As she sails international waters with Silversea guests, Andrews explores the species’ Southern Hemisphere recovery and also describes how humpbacks engage with their sensitive surroundings. Here, she shares some of the captivating details.
Humpback Whales: Resilient from Birth
Though commercial fishing once contributed to a declining humpback whale population, the species has been bouncing back in recent decades. Hunting moratoriums and protective treaties signed in the late 20th century sparked the rebound. Biology also plays a role. “Humpback whales have recovered from past exploitation faster than some other large baleen whales, like right, fin and blue whales, due to their life history strategies,” says Andrews.
Humpbacks start reproducing at a younger age than other whales, she explains, and female humpbacks typically give birth every one to two years. That means they repopulate more quickly than species such as the Southern right whale, whose estimated age for first reproduction is eight. They produce a calf on average every three years. Humpback whales, meanwhile, reach sexual maturity as early as three and can reproduce every year, although most calve biannually. “Humpbacks are also opportunistic,” adds Andrews, citing how the whales have found new feeding areas opened by a reduction in polar sea ice.
The Art of the Bubble Net
On a typical summer day, mammoth humpbacks might eat up to 3,000 pounds (1360 kilograms) of fish and small crustaceans that will sustain them through the winter. These whales collect and confuse their prey through a unique “bubble net” feeding technique. Humpbacks form a circle, capture unsuspecting targets in a curtain of bubbles, and swim open-mouthed through the loop to collect the krill and fish.
Unlike killer whales and other toothed whales that form lasting social bonds from birth, a humpback calf typically stays with its mother for just one year. Later in life, some humpbacks then form long-term feeding aggregations that meet between annual migrations to and from the tropics.
After reconvening, one humpback in the group uses a high-pitch sound to guide teammates toward their prey. “On the acoustic signal, they swim in a cylindrical formation and blow bubbles from their blowholes. The whales encircle and trap herring and small fish into a ball, which they all lunge through to feed,” says Andrews. “By working together, as many as 11 whales are able to capture more fish than they would alone.”
The feeding behavior was first documented among humpbacks in Alaska, but lucky guests can view the phenomenon during Antarctic expeditions in the summer. “Look for signs that the water is ‘boiling’ or bubbling,” says Andrews. “In a short time, whales will lunge up with their jaws open.”
Despite growing to more than 50 feet (15 meters) in length, adult humpbacks remain surprisingly agile, energetic and acrobatic. When they breach, these bulky marine mammals can lift themselves entirely out of the sea. “Humpback whales breach, or launch, their entire 40-ton bodies out of the water, by two strokes of their peduncle,” explains Andrews. “That muscle in their tailstock is the largest in the animal kingdom. “Humpbacks might engage in this extraordinary performance to dislodge parasites or communicate with other whales. Some breach when excited or stressed, while others do so to play. The maneuver also enables humpbacks see above the water.
Whales also sometimes peek from the sea—behavior known as “spyhopping,” as well. “They raise their heads out of the water so that their eyes are just below the surface,” says Andrews, who often observes this behavior while exploring with guests by zodiac. “Humpbacks are very inquisitive creatures. They do this to look at something above the water, such as our ships and the people on them.”
Songs of the Sea
Humpbacks sing elegant and intricate melodies that carry for miles under the sea. A single song might last for up to 20 minutes. While the complex, continually evolving songs play a role in mate selection, they’re also a communication technique that can indicate the breeding area from which a whale originates.
“The male humpback’s song in the South Pacific is an example of the largest-scale documentation of cultural learning outside of humans,” says Andrews. “All the males at each breeding ground sing the same song, yet every year the song is different.”
Andrews is among the international researchers studying these tunes and using the findings to inform long-term humpback conservation efforts. Her teams work with specialized software, and an underwater microphone called a hydrophone to record and analyze how tunes and phrases vary by season.
“Guests who travel with me may have an opportunity to use the hydrophone to listen to whales live,” she says.
As she monitors elaborate whale songs, views the feeding patterns of these massive mammals, or simply sits back and watch the graceful motions of a pod on the move, Andrews regularly enjoys rare, up-close looks at the daily lives of humpbacks as part of her work. At the same time, she sees a striking example of how international conservation efforts can support a species’ natural strengths, creating a framework for long-term recovery.