Whale-watchers in Australia were treated to a special sighting on Monday when a rare white humpback was spotted swimming off the country’s eastern coast. Originally thought to be legendary albino whale, ‘Migaloo’, a lack of distinctive markings and the animal’s smaller size have led experts to since conclude that it is more likely to be ‘Migaloo Junior’, a calf first seen in 2011 and thought to be the offspring of the famous white whale.

Migaloo - whose name means “white fella” - made quite a splash when he was first spotted off Byron Bay in 1991. At the time he was believed to be the word’s first known albino humpback and has since become an ambassador for his species with locals reporting their sightings from all around Australia. He even has a Twitter account dedicated to tracking his migratory movements.

However, evidence from this latest sighting suggests that it is not the beloved albino humpback who was last seen in Sydney and Cairns in 2014. According to Oskar Peterson, founder of the White Whale Research Centre, Migaloo makes an annual 8,000-kilometre (5,000-mile) round-trip from his Antarctic feeding grounds in the Southern Ocean to the tropical waters around Queensland. The journey usually begins in April; Migaloo will swim past the Gold Coast in late June and will pass by again on the way back in October or November. The location of the latest sighting puts Migaloo six weeks behind schedule. So unless he became distracted by a female on the way, it’s more likely that this whale is actually 'Migaloo Junior'. The Migaloo Twitter account confirms this:

"This could well be Migaloo, but at this moment in time I am leaning towards that it is not. Due to his size and lack of photos at the moment, but also the timing of the year. It is very unusual," Peterson told Mashable.

However, Southern Cross University (SCU) academic Wally Franklin, who first spotted Migaloo in 1992 argues otherwise, claiming that the distinctive protrusions on the whale's backbone indicate that this is Migaloo.

Australia is home to at least three other white whales. "We know there were two white whales born the size of Migaloo on the east coast in the last four or five years. We also believe there is one that cruises up the west coast of Australia but we don't have photographic evidence of it," Peterson points out. Norway is also home to an albino humpback that could possibly be the father of the two white whales (although it’s thought to be unlikely).

Migaloo or not, this rare sighting has whale-watchers pretty excited!