Scientists have sighted two humpback whales that separately made record crossings between Australia and Brazil.
The whales were identified by distinctive tail markings at the two locations about 9,000 miles (14,500 kilometers) apart. They traveled in opposite directions and farther than any other humpback whale known so far.
“This is a very rare event, but it is a magnificent demonstration of the great variety of these animals”said Phillip Clapham, former director of a NOAA whale research program who was not involved in the new discoveries.
Humpback whales are known to travel long distances across major oceans in predictable patterns, usually following migratory routes learned from their mothers. They feed on krill and small fish in the warmer months and breed in tropical waters during the winter.
It is difficult to follow the movements of creatures that spend most of their lives underwater. In the new study, scientists analyzed more than 19,000 images of whales taken over the past four decades by research groups and citizen scientists.
A computer recognition program helped identify the whales based on the color patterns and serrated edges of their tails. Researchers located two different whales at breeding grounds in eastern Australia and Brazil over the years, suggesting they had crossed from one location to another.
A whale traveled just over 15,000 kilometers, thus surpassing other previous records, such as that of a whale humpback that swam from Colombia to Zanzibar.
The results were published Tuesday in the journal Royal Society Open Science.
Because the photos only show the whales at the beginning and end of their journeys, researchers don’t know the exact route they took.
Whales don’t typically travel between mating grounds, so it’s still unclear why these two embarked on their journeys separately. They may have encountered other whales at shared feeding grounds and separated rather than returning to where they came from, Stephanie Stack, a co-author of the study and a member of the Pacific Whale Foundation, said in an email.
“Finding not one, but two specimens that have crossed between Australia and Brazil calls into question what we thought we knew about how separated these populations really are,” Stack says.
These odysseys are more difficult for whales in the northern hemisphere, where large continents make it difficult to cross the oceans.
Scientists say this record-breaking voyage demonstrates how far humpback whales can travel. These methods can also help keep track of them as the climate change It warms the oceans, possibly changing where krill live and where humpback whales might go to feed and breed.