(Seychelles News Agency) - Two adult humpback whales died after beaching themselves on the Seychelles' Aldabra atoll, while a juvenile swam free, the Seychelles Islands Foundation said on Tuesday.

It was the first such beaching that the Foundation is aware of.

The Foundation said that rangers returning from a field camp came across the two stranded adult humpbacks and a juvenile swimming in the lagoon at Passe Hoareau, on the north coast of the atoll on Friday.

Despite attempts by the staff to save the two whales, the Foundation said that “the location and sheer size of the whales meant the team were not able to move or refloat the whales -- the adults died, and the current whereabouts of the juvenile is unknown.”

The humpback juvenile like the one in the picture swam free and whereabouts is still unknown. (Seychelles Islands Foundation) Photo License: All Rights Reserved

Humpback whales are enormous creatures and can grow to 18 metres long, and can weigh about 40 tonnes according to the  National Oceanic and Atmospheric Administration (NOAA). They do not have a hump on their backs --  the name comes from the large hump that forms when they arch their backs before making a deep dive into the ocean.

The cause of the whale beaching is unknown but according to the Foundation, “they appear to have come into the lagoon on the high spring tide and become stuck on the reef as the tide receded.”

“It is possible that after entering the lagoon at high tide, the humpbacks were unable to return to deep water via one of the channels before the tide became too low for them to navigate," the Foundation said  

One of the largest raised coral atolls in the world, Aldabra is 34 km long and 13 km wide. Its large and shallow lagoon, with an area of 196 kilometres square, is larger than the Seychelles' main island, Mahe. Located 1,120 kilometres southwest of the main island, the atoll is one of the Seychelles’ UNESCO World Heritage site and is managed by the Seychelles Islands Foundation (SIF).

Aldabra has a lagoon which is larger than the Seychelles' main island, Mahe. (Seychelles Islands Foundation) Photo License: All Rights Reserved

Aldabra has been experiencing record numbers of humpback sightings this year, particularly adults with calves, but these have been outside the atoll, not in the shallow water of the lagoon. 

The reasons why whale beach or are stranded in shallow water often remains unknown.  Whereas human impacts such as pollution, injuries from boat collisions or noise from ships have been implicated in some, the Foundation said: "Aldabra’s isolation makes this unlikely. It’s more likely that this was a sad, but natural event.”

Natural beaching in whales is said to occur due to factors such as rough weather, weakness due to old age or illness, difficulty giving birth, feeding too close to shore, or navigational errors.

Although whale deaths are tragic events, the beaching and deaths of two humpbacks at Aldabra atoll will provide a food for reef organisms for weeks, if not months to come. 

Tiger sharks feeding on one of the dead humpback whale. (Seychelles Islands Foundation) Photo License: All Rights Reserved