The BBC notes that before Migaloo was seen in 1991, no other all-white humpback whaleshad ever been spotted.
According to The White Whale Research Centre, Migaloo was believed to be the only all-white humpback until last September, when a white calf was spotted near the Great Barrier Reef.
Migaloo is believed to be albino, which means that his skin lacks pigment, according researchers. But since scientists cannot confirm his condition, he's referred to as a "hypo-pigmented" whale, the White Whale Research Centre notes.
In April, a team of scientists from Russia announced that it would search for Iceberg, an all-white killer whale that was seen in August 2010.