“Despite seasonal migrations of more than 16,000 km return, humpback whale populations are actually more isolated from one another than we thought. Their populations appear separated by warm equatorial waters that they rarely cross,” said Dr Jennifer Jackson, lead author in a Press Release.
“The colour of the bodies and undersides of the tail (the ‘flukes’) of humpback whales in the northern oceans tend to be much darker than those in the Southern Hemisphere. Until this study we didn’t realise that these kinds of subtle differences are actually a sign of long-term isolation between humpback populations in the three global ocean basins.
“Using genetic samples, collected from free-swimming whales with a small biopsy dart, we’ve been able to look at two types of humpback DNA; the ‘mitochondrial’ DNA which is inherited from the mother, and the nuclear DNA which is inherited from both parents. The mitochondrial DNA allows us to build up a picture of how female humpbacks have moved across the globe over the last million years. The nuclear DNA, which evolves more slowly, provides us with a general pattern of species movements as a whole.
“We found that although female whales have crossed from one hemisphere to another at certain times in the last few thousand years, they generally stay in their ocean of birth. This genetically isolates populations, and it appears to have created a separate subspecies.”
These findings reveal a little bit more about these massive and intriguing whales that have the longest migrations. The findings are published in the journal Proceedings of the Royal Society B.
There are just 9 to15 records of humpback whales in Sri Lankan waters. Humpbacks seen in Sri Lankan waters may be from as far away as the Southern Ocean or as near as the Gulf of Oman, where a population of humpbacks is thought to be resident. The last recorded sighting was a pair off Mirissa in January this year.