Blue whales are the largest animals to have ever lived but they were once hunted to the brink of extinction. The international community only agreed to stop hunting them in 1965 when they numbered fewer than 200. Now scientists are using new methods to learn whether the number of blue whales in the wild is increasing – and they are seeing and hearing promising signs. Reporter Luca Ittimani speaks to marine mammal acoustician Brian Miller about the whale’s Antarctic resurgence You can support the Guardian at theguardian.com/fullstorysupport