How far do whales swim for lunch?

Just off Brazil’s central coast, an inflatable speedboat follows a pod of humpback whales. In the bow, harnessed against the ocean chop, a marine scientist waits, eyes fixed on the water. A towering vapour cloud signals one of the 40-tonne beasts has surfaced. The great black arch of its back glides past and the scientist sees his chance. Using compressed air, he launches a transmitter dart, aiming just ahead of the small fin that gives the humpback its name. The tiny device buries, unnoticed, in the thick blubber with just a small antenna visible.

For the next eight months or so, whenever the whale surfaces, the transmitter will report its position and how deep it dived to an orbiting relay satellite.

The scientist is part of a team in the whale-monitoring programme run by Brazilian science non-profit Instituto Aqualie and supported by Shell Brasil to learn more about humpback whales.

Safety in numbers

Along with many other whale species, South Atlantic humpbacks were hunted to near extinction in the 19th and early 20th centuries. Their numbers have slowly recovered since gaining international treaty protection in the mid-1960s. Still, through the end of the last century, very little was known about the Brazil population – other than that they were seen off the coast every winter.

Over the last decade the team has tagged, tracked and studied more than 120 Brazilian humpbacks. This is the longest-running humpback whale tracking project anywhere, according to Dr. Alex Zerbini, Instituto Aqualie’s science director.

”The programme has not only revealed important information about their movement, migration, breeding and feeding behaviour,” says Alex. “It’s also developed satellite tagging methods now used by scientists throughout the world.”

The transmitters have shown, for example, that the whales are able to navigate more than 3,700 kilometres (2,000 nautical miles) of open ocean between Brazil and their summer feeding grounds in Antarctic waters of the south Atlantic. They do this in a nearly straight line with no visible reference points, apparently following the same route every year.