New Study Finds Blue Whale Hybrids in the Atlantic Ocean

Newly sequenced genomes of Atlantic blue whales show high levels of fin whale DNA

Blue whale skeleton in the Natural History Museum/ credit: Just Pics

A 2024 study published by Sushma Jossey et al. in the Conservation Genetics journal has shown high levels of fin whale DNA in Atlantic blue whales. The study, which was published last month, was carried out as part of a conservation strategy for the endangered species, which was hunted to near extinction in the mid-20th century. Researchers generated a new genome assembly, which was analysed against historical samples dating back to 1876 to assess the impact of whaling on the blue whale’s genetic diversity.  

Although blue whale numbers have been increasing since whaling was banned in 1985, their growth is reported to be ‘spotty and equivocal’. This is thought to be due to various other factors, like fishing gear entanglement, marine noise, pollutants and climate change. It is thought that only 3-11% of the global species estimate from 1926 still remain, which brings worries about the blue whale’s genetic diversity and therefore the strength of the species. The results of the study showed a low but statistically significant population, and a higher-than-expected genetic diversity. This came as a surprise, when inbreeding was the concern. On analysis it was discovered that around 3.5% of the DNA in the sampled group actually came from fin whales.

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The knowledge of crossover between blue whales and fin whales isn’t new. It was first proven in the 1990s, but during this time it was thought that the hybrids were infertile. Now, new evidence suggests that not only are the hybrids living into adulthood, they are also able to reproduce with one of the parent species. The evidence from this new study has built on findings from a study in 2020 by Pampoulie et al., which used genetic tools to analyse samples from eight suspected fin-blue hybrids. Not only were the hybrid suspicions proved correct, but it was also discovered that one of the individuals had been born to a male fin whale and a female hybrid – the first second-generation hybrid ever recorded. Interestingly, second-generation hybrids have usually been found to have a fin whale father and a hybrid mother. The reasons for this are still unknown, but could simply be physical.