BEIJING, Nov. 4 (Xinhua) -- A study led by Stanford University in the United States shows that as the largest known animal in the world today, blue whales can eat an average of 16 tons per day during the feeding period, exceeding previous estimates. Its "close relatives" baleen whales also eat a lot of food, such as the North Pacific humpback whale can eat 9 tons of eclipses, and the fin whales can eat 8 tons.
This 2017 profile photo shows researchers at the University of New South Wales in Australia working on a humpback whale off the coast of Queensland, Australia. (Xinhua News Agency, courtesy of the University of New South Wales)
To accurately calculate the amount of food eaten by the seven species of baleen whales, the researchers tracked 321 baleen whales living in the Atlantic, Pacific and Southern Oceans from 2010 to 2019 using electronic tag devices attached to the cetaceans' backs, cameras, microphones, GPS-based locators and motion trackers. Study subjects include blue whales, humpback whales, fin whales, bowhead whales, right whales, Antarctic minke whales and Brinell whales. The researchers used drones to assess the size of whales' mouths and the amount of food they could swallow at one time, and acoustically assessed the number of prey near the whales.
The researchers found that the food species of these marine mammals include crustaceans such as krill and fish, larger baleen whales such as blue whales prefer krill, and smaller baleen whales such as humpback whales, Brinell whales and minke whales feed mainly on krill and fish stocks. In addition, most of the study subjects did not eat all year round, but about 100 days a year, mainly during the summer breeding season, and rarely at other times. In the case of blue whales, for example, the average daily eclipse is 16 tons during the feeding period, and the annual feeding volume is about 1600 tons.
A Brinell whale preys on Weizhou Island in the Northwest Sea of Guangxi, China, on January 13. (Photo by Xinhua news agency reporter Liu Jinhai)
The amount of food these whales eats is related to their species, where they eat, and the type of food they eat. Taking the three humpback whale populations involved in the study as an example, whales that feed on North Pacific krill eat an average of 9 tons a day, whales that feed on fish in the North Pacific eat an average of 3.5 tons a day, and whales that feed on Antarctic krill eat an average of 3 tons a day. Arctic bowhead whales can eat 6 tons of crustaceans a day, North Atlantic right whales eat an average of 5 tons of crustaceans a day, South Atlantic Bruces whales eat an average of 1 ton of fish per day, and Southern Ocean minke whales eat an average of 0.69 tons of krill per day.
Studies have shown that the subjects ate more than previously estimated, and some even 4 times more than previously estimated. Researchers previously estimated the amount of food they ate from the stomach contents of the whales they were caught, or estimated the amount of baleen whales ate based on the amount of food eaten by smaller marine mammals.
A mother of an adult southern right whale plays with her cubs in the sea off Hermanus, South Africa's Western Cape, on Sept. 28 (drone photo). (Photo by Xinhua news agency reporter Chen Cheng)
The research report was published by the British journal Nature published on the 3rd. According to the report, this is the first time researchers have systematically calculated the amount of food eaten by baleen whales. Matthew Savoca, a marine biologist at Stanford University, the report's first author, said: "The amount of food eaten is unimaginable. But large cetaceans (in size) are inherently unimaginable. A blue whale is the size and weight of a Boeing 737. ”
One of the report's authors, Nick Pinson from the National Museum of Natural History, said that the baleen whales studied ate far more food than previously known and therefore produced more excrement than previously estimated, and that these excrements are important sources of nutrients for marine ecosystems and have an important "contribution" to marine ecosystems. Given that baleen whale populations have declined significantly as a result of commercial whaling in the 20th century, promoting a rebound in whale populations today has helped restore marine ecosystem functioning. (Qiao Ying)