Two humpback whales have been spotted in separate breeding grounds in Australia and Brazil, the first time scientists have seen this species travel such large distances in the Southern Ocean during its lifetime.
An article published in the Royal Society Open Science journal Wednesday’s work is the result of using thousands of images of the unique tails (or flukes) of sea-dwelling mammals to identify the creatures and their activity habits.
Where and when were both the whales seen?
A whale was spotted in Queensland on the east coast of Australia in 2007 and again in 2013. It then appeared near Sao Paulo, Brazil in 2019 – the two points separated by about 14,200 kilometers (8,823 miles).
The second whale was first spotted off the coast of Bahia, Brazil, in 2003, and then 22 years later, 15,100 kilometers away, near Hervey Bay in Queensland.
The study said it was not possible to record how far the whales actually traveled during their journeys, as their data “reflected the separation between sightings rather than the actual distance traveled, as photo-identification records only the end points of each individual’s journey.”
The researchers said the findings extended the known spatial limits of inter-basin connectivity for Southern Hemisphere humpbacks, supporting the “Southern Ocean exchange hypothesis” – that species may meet on shared Antarctic feeding grounds and then in exceptional cases follow a different route back to the breeding site.
Whales feed on krill and small fish in cooler waters during the hot summer months, and then migrate to cooler tropical waters such as Brazil and Australia to breed during the winter.
“Respecting intervals of 6 and 22 years suggests that these are rare, possibly single-lifetime events, rather than regular migratory changes,” the authors wrote.
Preliminary data suggests such trips are very rare
Of the thousands of identified whales studied, only 0.01% of specimens were able to complete such a journey. But the researchers called for continued global collaboration on photo-ID platforms to try to better understand how common this may be.
“Despite their rarity, these exchanges matter for the long-term health of whale populations,” Griffith University PhD researcher and report co-author Stephanie Stack Said.
“Individuals sometimes moving between distant breeding grounds can help maintain genetic diversity in a population,” he said, adding that they may also bring new songs to new pods in the process.
Scientists suspect that climate change and warming oceans may make this phenomenon more common.
“Climate-induced changes in the Southern Ocean, including changes in sea ice and the distribution of Antarctic krill, may further increase the likelihood of such crossings over time,” Griffith University wrote.
Dr. Christina Castro of the Pacific Whale Foundation thanked amateur whale spotters for their photographs, which served as a database for the study and allowed activities to be identified.
“Research like this highlights the value of citizen science,” he said. “Each photo contributes to our understanding of whale biology and, in this case, helps illuminate one of the most extreme activities ever recorded.”
Edited by: Shawn Sinico