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| Photo Credit: © Olga Filatova/SDU |
When SDU whale researcher Olga Filatova set off on her first field trip in 2000, she spent five years looking for whales before she saw a humpback.
“It was incredibly rare to spot one back then. Today, we see them almost every day when we’re in the field,” she says. “We don’t know exactly how many humpbacks there are now, but definitely many more than when I started.”
A cautious estimate from the Endangered Species Coalition puts today’s population at around 80,000—up from just 10,000 at their lowest point. That makes humpbacks one of the great success stories of conservation.
Five summers in humpback waters
One major reason is that commercial whaling was banned in 1986. But according to Olga Filatova, their willingness to switch between different food sources also matters.
“Unlike several other whale species, humpback whales prefer to stay in an area, even if one food source runs out – as long as there is something else to eat. We’ve seen humpback whales hunt cod in an area, and when the cod disappeared, they switched to krill,” says Olga Filatova.
She and colleagues observed this between 2017 and 2021 during summers and autumns in the Senyavin Strait east of the Chukotka Peninsula in far eastern Russia, north of the Bering Sea. In 2017, they saw a group of about 100 humpback whales hunting polar cod. The following year, there was no cod, but the whales had stayed in the area and switched to hunting krill.
How to know what humpbacks eat
You might spot a humpback whale snatching a fish from the water’s surface if you’re lucky enough to be out on a boat. But most of their hunting takes place out of sight, below the surface. To figure out what they’re eating, researchers need different tools—and in this study, one of those tools was stable isotope analysis of whale skin samples. By analyzing nitrogen stable isotope in whale skin, scientists can tell what the whales had been eating. Lower values of 15N stable isotope indicate a diet rich in krill, while higher ratio of this isotope point to fish like cod. That’s because animals higher up the food chain tend to accumulate heavier nitrogen isotopes.
“This showed us that whales can change hunting behavior and food preference when conditions change. That’s a high degree of flexibility and likely one of the reasons for their evolutionary success,” explains Olga Filatova.
Other species of fin whales tend to burn more energy searching for their favorite foods and are more likely to leave an area when prey vanishes. Humpbacks, however, are not built for speed. In fact, they have a reputation for being the laziest hunters of all whales. They invent many methods to trick prey and capture it with as low energy expenditure as possible.
For example, one of their techniques called “trap feeding” involves simply floating on the surface with their mouths open in areas where sea gulls are catching fish. As the fish try to escape the gulls, they swim straight into the whale’s mouth, thinking that it is a good safe shelter.
Moving into new habitats
“They’re not fast, and they’ve got these big, clumsy flippers—but what they lack in speed, they make up for in creativity and willingness to eat whatever’s available,” Filatova says.
Filatova is optimistic about humpbacks’ future. Not only are they resourceful eaters with relatively low energy demands, but they’re also one of the few species actually benefiting from climate change. As sea ice melts, new habitats open up—and they’re already moving in.
“We are getting more and more reports of humpbacks in Arctic waters where they have never been seen before,” she says.
Humpback whales
Humpback whales are 11–19 meters long (females are the largest), weigh up to 35 tons, and can live 50–60 years. A female carries her calf for about 11.5 months and gives birth every two to three years. Humpbacks are found in oceans all over the world and travel up to 25,000 km each year. These two in the surface waters of the Senyavin Strait in far eastern Russia were photographed by Olga Filatova.
More worried about other whales
Humpback whales migrate yearly from tropical to polar seas, spending winter in warm waters and feeding in rich cold waters of high latitudes in summer.
“I’m not worried about them. I’m more worried about whales that can only live in Arctic waters – that’s the bowhead whale, the beluga whale, and the narwhal,” says Olga Filatova.
Funding: The field trips between 2017 and 2021 were supported by the Russian Science Foundation.
Published in journal: Marine Mammal Science
Authors: Olga V. Titova, Ivan D. Fedutin, Alexey V. Tiunov, Sergey M. Tsurikov, Alexander M. Burdin, Erich Hoyt, and Olga A. Filatova
Source/Credit: University of Southern Denmark | Birgitte Svennevig
Reference Number: mb112425_01