of an obsession, this passion for these large animals, and as i grew up and understood how whale populations had been decimated through centuries of commercial whaling, it just became unbearable not to do something to help. >> susanna has been visiting patagonia since 2007, studying whale acoustics using underwater microphones. she's recorded tens of thousands of hours of blue whale song and has made an extraordinary discovery. >> we found out that the blue whales here produce a unique song dialect. >> in fact, these are a distinct sub-species of blue whale, one of just five on the planet.