A single blue whale named Isabela may have helped marine biologists solve one of the largest questions in animal migration: Where do South Pacific blue whales give birth?
One might expect that as the largest species in Earth's history, blue whales (Balaenoptera musculus) would be easy to spot, but it is a big ocean out there. While blue whales are thought to give birth in tropical waters like their humpback relatives, confirmation has been hard to come by. Even the identification of their feeding and possible breeding grounds off southern Chile only happened in 2004, despite this probably being the largest population center south of the equator.
The answer, at least in Isabela's case, resonates for those who love evolutionary history. She migrated from the blue whale feeding grounds of the Corcovado Gulf in southern Chile to the waters around the Galapagos, where Darwin's theories first stirred.
At 5,000 kilometers (3,100 miles), the migration is well short of that achieved by some whale species, but the longest recorded for a Southern Hemisphere blue whale.
"Efforts to protect blue whales and other ocean-going species will always fall short without full knowledge of a species' migratory range,” said Juan Pablo Torres-Florez, lead author of the paper in Marine Mammal Science that documents the epic voyage. "Moreover, with this kind of finding we encourage eastern south Pacific governments to think about the creation of a marine protected areas network for the conservation of this and other migratory species.”
Torres-Florez, of the Universidad Austral de Chile, collaborated with researchers from NOAA and the Wildlife Conservation Society. "The movement of this one whale provides important information that will enable us to look further at these important areas for blue whales with goal to ensure their long-term protection,” said Dr. Howard Rosenbaum of the WCS's Ocean Giants Program.
The discovery was made not by attaching a tracking device to Isabela, but from separate teams collecting skin samples from whales in different parts of the world. When the data was shared, the teams studying whales in Corcovado and those working off the Galapagos realized they had tested the same whale, a conclusion confirmed through photographs of Isabela's distinctive dorsal fin and back patterns.
Since the two samples were taken eight years apart, the authors do not know when Isabela made the journey, and whether it was a one-off event or part of a regular cycle.
Little is known about Isabela's age or breeding history, but she is 25 meters (82 feet) long and probably weighs close to 100 tonnes, although no one has been game to ask her to try out some scales.