An examination of blue whale genetics has revealed that the world’s largest animals have been breeding with fin whales. Not only that, but the resulting hybrids are fertile.
During a study published in Conservation Genetics, researchers analysed the genomes of the North Atlantic blue whale subspecies, a group that is still in recovery following extensive whaling in the past, discovering relatively high levels of fin whale DNA.
Although it has been known that the two species could create hybrids, often called flue whales, it was only recently found that these hybrids were fertile.
By mating with blue whales, fin whale DNA is introduced into the blue whale population in a process known as introgression.
Strangely, this introgression only seems to be going one way, from fin whales to blue whales, as the hybrids don’t appear to be mating with fin whales.
“We don’t know why introgression appears unidirectional,” says Mark Engstrom, co-author on the study, “but it may be related to reproductive behaviour and mating activities of the two species, and also possibly with the much larger numbers of fin whale individuals (and in this case specifically males) compared to the smaller population size of blues.”
Engstrom adds that this hybridisation and introgression isn’t currently a cause for alarm but should be monitored going forward.
“As well as concerns that an endangered species could become extinct, there is also the associated issue of one species being highly protected and the other not,” says Danny Groves, head of communications at Whale and Dolphin Conservation, who was not involved in the study. “For example, the cruel whale hunts in Iceland have led to hybrid blue and fin whales being killed.”
