A humpback whale that traveled at least 13,000 kilometers from the Pacific Ocean to the Indian Ocean has been discovered. This is the longest distance recorded for a humpback whale's migration to date. The attention of ecologists is likely to focus on this humpback whale that had to swim long distances while carrying its massive body.
Researchers at the Bazaruto Scientific Center in Tanzania reported on the 11th that they discovered a humpback whale that migrated the longest distance ever in the international journal Royal Society Open Science.
The humpback whale is a massive marine animal, measuring at least 12 meters in length. Not only is it known for its large size, but it is also famous for migrating the longest distances among all mammals on land and in the sea. Humpback whales travel long distances each year in search of breeding grounds. In the summer, they move to polar regions to hunt, and during winter, they breed near the equator. The distance the humpback whale migrates for breeding can reach 6,000 kilometers.
The researchers found a humpback whale that migrated 13,000 kilometers, exceeding the average migration distance by two times, through a citizen science project called Happy Whale, which collects humpback whale data from around the world. This minimum migration path stretches from the Pacific to the Indian Ocean, and the actual distance traveled by the humpback whale is expected to far exceed this.
Dr. Ekaterina Kalashnikova, the corresponding author of the paper, noted, "This seems to be the farthest migration distance recorded for a humpback whale." However, the reason why this humpback whale swam such a long distance remains unknown.
This humpback whale was first discovered in 2017 near the Pacific Ocean off Colombia. After five years, in 2022, it was rediscovered in the Indian Ocean near Zanzibar Island in Tanzania. The researchers were able to confidently identify that the humpback whale photographed in a completely different location after five years was the same individual due to its tail.
Humpback whales have unique pigments on the underside of their tails. By analyzing the distribution of these pigments, researchers can accurately identify which whale it is. It can be used to identify individuals much like a human fingerprint. The researchers are using artificial intelligence (AI) technology to analyze the patterns on the tails of humpback whales to study their migration routes.
The researchers are not only focused on the long migration distance of this humpback whale. There are two breeding grounds along the route where the humpback whale is presumed to have migrated. This suggests that there would be no reason for it to travel a long distance if it were looking for breeding grounds.
The researchers suggested that the humpback whale may have migrated in search of new hunting grounds due to climate change. As the appearance of krill, a staple in its diet, has changed, hunting has become more difficult, so it may have had to travel long distances in search of food. There is another possibility: the ban on whaling may have led to a rapid increase in the population, initiating an exploration for new breeding grounds.
Humpback whales were once on the brink of extinction due to indiscriminate fishing. During the 18th century, with the whaling industry booming, more than 300,000 were captured. In the South Atlantic, the primary habitat of humpback whales, the population plummeted from 27,000 in 1830 to just 450 by the mid-1950s.
Dr. Kalashnikova said, "We cannot know for certain why the humpback whale traveled such a long distance," but she noted, "The most likely reason is the impact of global climate change and the recovery of the population."
Reference material
Royal Society Open Science (2024), DOI: https://doi.org/10.1098/rsos.241361