Singing the blues
A population of rare blue whales has been found using sensors built to detect illegal nuclear weapons testing.
It is not clear how many of the pygmy blue whales there are but scientists think it is a large group given the number of songs they have recorded.
They have been named the “Chagos” group after the archipelago in the Indian Ocean where they were detected.
Pygmy whales can grow to about 24m in length and weigh up to 100 tonnes. They rarely breach, which makes them hard to spot, and their songs are very low frequency, barely audible to the human ear, and have a signature style.