Lonely whale's song remains a mystery

From NewScientist.com:

"A lone whale with a voice unlike any other has been wandering the Pacific for the past 12 years.

Marine biologist Mary Ann Daher of Woods Hole Oceanographic Institution in Massachusetts, US, and her colleagues used signals recorded by the US navy’s submarine-tracking hydrophones to trace the movements of whales in the north Pacific.

The partially declassified records show that a lone whale singing at around 52 hertz has cruised the ocean every autumn and winter since 1992. Its calls do not match those of any known species, although they are clearly those of a baleen whale, a group that includes blue, fin and humpback whales.

Blue whales typically call at frequencies between 15 and 20 hertz. They use some higher frequencies, but not 52 hertz, Daher says. Fin whales make pulsed sounds at around 20 hertz, while humpbacks sing at much higher frequencies. The tracks of the lone whale do not match the migration patterns of any other species, either.

Over the years the calls have deepened slightly, perhaps because the whale has aged, but its voice is still recognisable. Daher doubts that the whale belongs to a new species, although no similar call has been found anywhere else, despite careful monitoring."