EACH winter, humpback whales travel from the Antarctic to the northern tropics to find warm water in which to raise their young. The migration is the longest documented for any mammal.
Kristin Rasmussen of Cascadia Research Collective in Olympia, Washington, and her colleagues photographed the tails of humpbacks wintering off the Caribbean coast of Costa Rica. From their individual tail patterns they identified seven of the same animals after they had returned to the Antarctic. One mother and calf made the 8300-kilometre trip in 161 days (Biology Letters, DOI: 10.1098/rsbl.2007.0067).
Using satellite data, the team also recorded sea-surface temperatures for the sites where humpbacks spent the winter. 鈥淲intering areas occur where waters with temperatures between 21 掳C and 28 掳C are found,鈥� says Rasmussen. This supports the idea that the long migration saves the whales energy in the end.
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Rasmussen says that Japan鈥檚 proposed annual 鈥渟cientific鈥� catch of 50 humpbacks makes it important to understand whale migration. 鈥淜illing whales in one area could potentially impact their population halfway around the world,鈥� she says.
