52-hertz whale

The 52-hertz whale, colloquially referred to as 52 Blue, is an individual whale of unidentified species that calls at the unusual frequency of 52 hertz. This pitch is at a higher frequency than that of the other whale species with migration patterns most closely resembling the 52-hertz whale's[1] – the blue whale (10 to 39 Hz)[2] and the fin whale (20 Hz).[1] Its call has been detected regularly in many locations since the late 1980s, and appears to be the only individual emitting a whale call at this frequency. However, the whale itself has never been sighted; it has only been heard via hydrophones. It has been described as the "world's loneliest whale", though potential recordings of a second 52-hertz whale, heard elsewhere at the same time, have been sporadically found since 2010.[3][4]