Blue whales, the world’s largest mammals, are returning to Spain’s Atlantic coast after an absence of more than four decades.

The first one was spotted off the coast of Galicia in north-west Spain in 2017 by Bruno Díaz, a marine biologist who is head of the Bottlenose Dolphin Research Institute in O Grove, Galicia.

Another was spotted in 2018, another the following year, and then in 2020 they both returned. Just over a week ago a different specimen was sited off the Islas Cíes, near O Grove.

There was a centuries-old whaling industry and a dozen whaling ports in Galicia. Spain did not ban whaling until 1986, by which time the blue whale was all but extinct in the region.

Díaz said it was not yet clear whether the climate crisis was leading the creatures to change their habits and return to the area out of a form of homesickness, or ancestral memory. Researchers believe this type of folk memory, or cultural knowledge, exists in many species and is key to their survival. However, not everyone sees the whales’ return as good news.

“I’m pessimistic because there’s a high possibility that climate change is having a major impact on the blue whale’s habitat,” Alfredo López, a marine biologist at a Galician NGO that studies marine mammals, told the newspaper La Voz de Galicia.

A typical blue whale is 20-24 metres long and weighs 120 tonnes – equivalent to 16 elephants – but specimens of up to 30 metres and 170 tonnes have been found.

Video courtesy of the Bottlenose Dolphin Research Institute.