Long haul

Birds do it, fish do it and even some insects do it: seasonal, continent-scale migrations. Mammals appear much less adapted to move over such great distances, although whales undertake substantial annual journeys. Now new research suggests that the humpback whale of the Eastern Pacific travels further than any previously documented mammal — moving up and down the south-east Pacific. Researchers have shown that humpback whales travelling between grounds off the west coast of central America and feeding grounds in Antarctica clocked up more than 8,000 kilometres on one leg of the journey — the longest recorded for any individual mammal. Researchers have tracked the world’s longest mammalian migration from Antarctica to the tropics. Nigel Williams reports. Long haul The researchers believe the whales are heading for warmer waters in which to give birth to their calves. Mark Simmonds, director of science at the Whale and Dolphin Conservation Society, who was not involved in the work, said: “It has this extraordinary lifestyle with its breeding grounds in one place and its feeding grounds far away.” Kristin Rasmussen at the Cascadia Research Collective in Olympia, Washington, and her colleagues made daily excursions in small boats off the coast of Central America to observe the whales between June and October. They took photographs of the underside of the animals’ tails so that they could be identified at the other end of their journey. “Just like humans have unique fingerprints, whales have unique tail markings,” said Rasmussen. During the Antarctic summer, the team made similar observations and looked for whales which had been spotted in the tropical waters. Seven animals were photographed in both locations and a mother and calf pair were seen in Antarctic waters after they had earlier been spotted off Costa Rica, having travelled 8,000 kilometres. Another individual was seen in different locations also 8,000 kilometres apart. The study is reported in Biology Letters (published online). The study ends the controversy over which whale species travels the furthest. The grey whale’s migration from Mexico to the Arctic is also an impressive voyage. Blue whales — the largest animals on the planet — also migrate thousands of miles, with the North Atlantic population moving from Arctic feeding grounds to waters off the eastern coast of the US. But none of these animals has been shown to travel as far as humpbacks. The humpback whales studied cross the equator on their journey from the Antarctic to reach their preferred breeding grounds. To work out why they go so far, the