With the southern migration of humpback whales along Australia's east coast now in full swing, new research has found the journey is an intriguing one.
The story starts a decade ago. After spending the winter in Queensland’s Hervey Bay birthing and feeding her calf, humpback whale matriarch Rama, with newborn alongside, joined the southern migration to feeding grounds in the Antarctic.
But in an unexpected move at the southern end of the Australian mainland, Rama and calf separated from the main group. Instead of passing by the eastern side of Tasmania to get to Antarctica, the pair went around the Victorian coast, across Bass Strait and passed the northwest corner of Tasmania before continuing in a south-westerly direction.
Why she would take her calf so far west of what is considered the primary feeding area for eastern Australian humpback whales has researchers Drs Trish and Wally Franklin from Southern Cross University’s Marine Ecology Research Centre intrigued.
The mysterious journey, observed a decade ago, is described in a paper published earlier this year by the Franklins and a team of researchers in the Journal of Cetacean Research and Management (JCRM). That study and an inter-related whale fluke study , also in JCRM, provide insight into the migratory movements of humpback whales between their tropical breeding grounds off east Africa, west Australia and east Australia and their feeding areas in Antarctica.
“But the findings also deepen the mystery of where the whales feed and how and why they mix in Antarctica,” Dr Wally Franklin said.
Clue 1: the Greenpeace fluke photos
To discover how the researchers observed Rama and her offspring taking a different route, we begin with the Franklins’ whale fluke paper.
The research team matched photographs of the underside tails (flukes) of 30 individual humpback whales obtained in Antarctica against large catalogues of humpback whale tail-flukes held by researchers from east Africa, west Australia and east Australia.
“Photographs of the underside tail-fluke of a humpback whale are like ‘fingerprints’ which enable us to recognise and identify individual whales,” said Dr Trish Franklin.
The Antarctic tail-fluke photographs were obtained by a small team of scientists, led by one of the paper’s co-authors Leandra Gonçalves who was aboard the Greenpeace International vessel Esperanza during November 2007 and February 2008.
At the time, Greenpeace were monitoring the Japanese commercial whaling fleet in waters off the Antarctic coast between east Africa and Western Australia, south of the Indian Ocean.
“Previously only a single humpback tail-fluke from this part of Antarctica had been available for research so the Greenpeace flukes were a vital contribution towards studying the origin of the humpback whales feeding in this area of the Antarctic,” Dr Wally Franklin said.
The results of the study concluded that the humpback whales photographed in Antarctica were from a different population to the east African and east Australian populations.
“It’s likely the Antarctic humpbacks, photographed by Greenpeace, were most likely from the west Australian humpback whale population,” said Dr Trish Franklin.
Now back to Rama and her link with the Greenpeace photos.
Clue 2: satellite radio tags
Almost a decade ago in late October 2008, scientists from the Australian Marine Mammal Centre attached 16 satellite-linked radio tags to southbound humpback whales off Eden on the NSW south coast. The tags remained active from three to 156 days, providing a full description of the transit tracks of some whales from Eden to Antarctic feeding areas.
All whales, except one (later identified as Rama), followed the coast of NSW and Tasmania south and/or travelled east through the southern waters of New Zealand, to feeding areas around or east and west of the Balleny Islands (2000 km south of NZ).
This was consistent with earlier research published by the Franklins in 2008 which reported for the first time that east Australian humpback whales travel through the southern waters of New Zealand en route to and from Antarctic feeding areas and that the waters around the Balleny Islands, off the Antarctic coast south of New Zealand, are a primary feeding area for east Australian humpback whales.
“The other whale, accompanied by a calf, travelled down the NSW coast, around the Victorian coast, across Bass Strait and passing the northwest corner of Tasmania continued in a south westerly direction towards the coast of Antarctica into the feeding area where the Greenpeace flukes had been photographed earlier that year,” Dr Wally Franklin said.
Dr Trish Franklin examined photographs taken of the 16 whales off Eden and was able to match two to her Hervey Bay catalogue using dorsal fin and lateral body photographs.
One was a younger male, which she had photographed in Hervey Bay in September the same year. It was among the whales that turned towards the southern waters of New Zealand after leaving Eden.
“The other whale was a mature female, known as Rama, which I had photographed and observed with new calves for several years in Hervey Bay during the late 90s,” Dr Trish Franklin said.
“Surprisingly she was the whale that travelled through Bass Strait down into the Antarctic area where the Greenpeace flukes were obtained.
“The results of this study indicate that eastern Australian whales may have more diverse Antarctic feeding locations than previously thought. Moreover, the migratory movement of Rama raises intriguing questions of why she would take her calf so far west of what is considered the primary feeding area for eastern Australian humpback whales, around the Balleny Islands.
“Answers to this mystery may only be obtained as we gather much more data on the migratory movement over many years, of known individual female and male humpback whales.”
Additional information about photographs of Rama:
Rama was also was photographed by Dr Trish Franklin in Hervey Bay, Qld:
- in 1998 from 27 September to 1 October;
- in 1999 on 10 August;
- in 2000 from 6 to 25 September;
- in 2001 on 3 October;
- in 2002 on 11 October; and
- in 2005 from 4 to 7 September.
A calf accompanied the female Rama in each year it was sighted in Hervey Bay, except 1999.
The research papers are available for download from: https://archive.iwc.int/?r=6886
Franklin, W., Franklin, T., Cerchio, S., Rosenbaum, H., Jenner, C., Jenner, M., Gonçalves, L., Leaper, R., Brooks, L., and Clapham, P. 2017a. Photo-identification comparison of humpback whale (Megaptera novaeangliae) flukes from Antarctic Area IV with fluke catalogues from East Africa, Western Australia and Eastern Australia. J. CETACEAN RES. MANAGE (17): 1-7.
Franklin, W., Franklin, T., Andrews-Goff, V., Paton, D.A., and Double, M. 2017b. Movement of two Humpback whales (Megaptera novaeangliae) satellite-radio tagged off Eden, NSW and matched by photo-identification with the Hervey Bay catalogue. J. CETACEAN RES. MANAGE (17): 29-33.
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