A lone humpback whale travelled more than 9,800 kilometers from breeding areas in Brazil to those in Madagascar, setting a record for the longest mammal migration even documented.
Humpback whales are known to have some of the longest migration distances of all mammals, and this huge journey is about 400 kilometers father than the previous humpback record. The finding was made by Peter Stevick, a biologist at the College of the Atlantic in Bar Harbor, Maine.
The whale's journey was unusual not only for its length, but also because it travelled across about 90 degrees of longitude from west to east. Typically, humpbacks move in a north-south direction between cold feeding areas and warm breeding grounds.
The whale, a female, was first spotted off the coast of Brazil, where researches photographed its tail fluke and took skin samples to determine the animal's sex. Two years later, a tourist on a whale-watching boat snapped a photo of the humpback near Madagascar.
To match the two sightings, Stevick's team used an extensive international catalogue of photographs of the undersides of tail flukes, which have distinctive markings. Researchers routinely compare the markings in each new photograph to those in the archive.
The scientists then estimated the animal's shortest possible route: an are skirting the southern tip of South Africa and heading north-east towards Madagascar. The minimum distance is 9,800 kilometers, says Stevick, but this is likely to be an underestimate, because the whale probably took a roundabout way to feed on frill in the Southern Ocean near Antarctica before reaching its destination.
Most humpback-whale researches focus on their efforts on the Northern Hemisphere because the Southern Ocean near the Antarctica is a tough environment and it is hard to get to, explaining Rochelle Constantine, who studies the ecology of humpback whales at the University of Auckland in New Zealand. But, for whales, oceans in the Southern Hemisphere are wider and easier to travel across, says Constantine. Scientists will probably observe more long-distance migrations in the Southern Hemisphere as satellite tracking becomes increasingly common, she adds.
Daniel Palacios, an oceanographer at the University of Hawaii at Monoa, says that record-breaking journey could indicate that migration patterns are shifting as populations begin to recover from near-extinction and the population increases. But the reasons why whale did not follow the usual migration routes remain a mystery. She could have been exploring new habitats, or simply have lost her way. “We generally think of humpback whales as very well studied, but then they surprise us with things like this,” Palacios says. “Undoubtedly there are a lot of things we still don't know about whale migration.”
43. In what way was the whale's journey considered unusual?
A.It covered a long distance from west to east. |
B.A female whale rather than a male one completed it. |
C.The whale moved from its breeding ground to its feeding area. |
D.No one had ever spotted the whale other than at its destination. |
44. Why did the researchers compare the markings on tail flukes?
A.There is a vast collection of such markings. | B.The markings there last by far the longest. |
C.No two whales share the same markings. | D.The markings are easiest to photograph. |
45. What can be inferred from the passage?
A.More evidence should have been provided that the whale had even arrived at Madagascar. |
B.South Hemisphere can provide more information about humpback whales' migration. |
C.The whale's actual route might well have been shorter than the scientists had estimated. |
D.North Hemisphere's environment is becoming tougher for whales to survive. |
46. What is the passage mainly about?
A.A female whale was spotted twice in the Southern Ocean. |
B.Research on whales is a breakthrough. |
C.Whales' migration routes vary with the climate change. |
D.A whale surprises researchers with her journey. |