Blue whale–fin whale hybrid

A hybrid between the blue whale (Balaenoptera musculus) and the fin whale (Balaenoptera physalus), the two largest whale species. Hybrids have been noted in commercial whaling records since the late 1800s, and genetic analyses suggest that most have a blue whale mother and a fin whale father. A 2026 review by Iceland's Marine and Freshwater Research Institute counted 46 possible hybrids, 17 of them genetically confirmed: 15 from the North Atlantic, one from the Mediterranean and one from the northeast Pacific. A pregnant hybrid caught off Iceland in 1986 carried a fetus fathered by a blue whale, showing that some hybrids are fertile, and a 2024 genomic study found that North Atlantic blue whales carry on average about 3.5 percent fin whale DNA. A living hybrid off southern California and Mexico was photographed repeatedly between 2004 and 2020.

Text from OyList