An extremely rare humpback whale with a double dorsal fin has been filmed swimming in Australia.
The video, posted by John Natoli to Facebook group Cetal Fauna, shows the whale breaching the surface of the water off Brunswick Heads, Byron Bay. Its two dorsal fins are clearly visible.
In a caption to the video, Natoli said the phenomenon was spotted by Blue Bay Whale Watching skipper Mark Wraight.
Around 99.9 percent of whales spotted off the coast of Byron Bay are humpback whales. The whale watching season in the area usually ends in late October, when the humpbacks migrate onwards.
The phenomenon cannot be easily explained.
Vadim Pavlov, a research scientist at the Hopkins Marine Station at Stanford University, told Newsweek that he has not seen this before.
"Usually, the various types of the unusual dorsal fin shape are associated with trauma due to collision with a boat. You can find a number of photos of this online. What I can see on the video you sent me doesn't seem like an old wound but rather a duplication of the dorsal fin," Pavlov said.
"It appears as an atavism that was previously described in whales and dolphins. But this case has one clear distinction: All known cases are the rudimentary fin-shaped hind appendages. The uniqueness of this case is that the dorsal fin (as well as the tail flukes) is the de-novo structure of cetaceans which is not related with the appendages.
"So, the appearance of a second dorsal fin is not associated with the evolution of cetaceans and their terrestrial ancestors. It could be associated with the abnormal prenatal development."
Amanda L. Bradford, a research ecologist at the NOAA Cetacean Research Program, told Newsweek that it is difficult to know what caused this, "other than it being a physical anomaly caused by a genetic mutation."
Bradford said environmental factors may also be at play.
Although rare, it appears this phenomenon has been seen before in other whales.
Other Facebook users commented on the post, believing that this was actually a well-known whale in the area, known as "Spiky."
One user posted a picture of a very similar looking whale, pictured swimming in Tonga in 2017. Natoli replied to the comment, and said it definitely appeared to be the same whale.
Another user posted a picture of Spiky as a calf in 2001. It is not clear how many times Spiky has been sighted over the past 21 years.
The Facebook user said there have even been sightings of triple dorsal finned whales.
Uncommon Knowledge
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Newsweek is committed to challenging conventional wisdom and finding connections in the search for common ground.
About the writer
Robyn White is a Newsweek Nature Reporter based in London, UK. Her focus is reporting on wildlife, science and the ... Read more
