An Eden orca, known as Old Tom, famous for helping whalers slaughter baleen whales, has been put under a microscope.
A team of Flinders University researchers analysed the killer whale’s DNA and believe its common ancestors are from New Zealand. Eden is on the south coast of New South Wales.
The researchers have published the report in the American Genetic Association’s Journal of Heredity.
Apparently cooperative hunting between orcas and humans was a well-known facet of whaling for a century, in the coastal town. Old Tom was a well-known local killer whale, until he suddenly turned up dead on a local beach.
The Flinders University team collected DNA from Tom’s skeleton, which is housed in a Museum at Eden, to explore the links between the Eden whales and other populations, and whether the orcas’ disappearance from Eden reflected a local extinction.
The researchers were able to sequence 11,464 base pairs (bp) out of the expected 16,386 to 16,392bp.
“A base pair consists of two complementary DNA nucleotide bases that pair together to form a ‘rung of the DNA ladder’,” says the National Genome Research Institute.
“Old Tom shared a most recent common ancestor with killer whales from Australasia, the North Atlantic, and the North Pacific, having the highest genetic similarity with contemporary New Zealand killer whales,” they conclude.
“However, much of the variation found in Old Tom’s genome was not shared with these widespread populations, suggesting ancestral rather than ongoing gene flow. Our genetic comparisons failed to find any clear descendants of Tom, raising the possibility of local extinction of this group.”
“The disappearance of the group may have resulted from losing either the suitable environment, the motivation from the animal or human partner, and/or their compatible interspecies knowledge of how to cooperate,” the Flinders’ report continues.
The rare relationship between whales and humans opened a dialogue between the local Indigenous people, the Thau, and the research team.
The report says “Steven Holmes [has] a direct bloodline descendant of Budginbro and his wife Char Ree Larra. Budginbro was the Indigenous guide… We incorporated Steven’s people’s oral history in an attempt to help decolonize the recorded history.”
Eden Killer Whale Museum recognised Tom as one of the pod’s leader, guiding one of the many pods passing by or into the Twofold Bay. He measured 6.7 metres (22 feet) in length and weighed around 6 tonnes.
The orca was distinguished by his “tall dorsal fin… [and] regularly swum to the mouth of the Kiah,” says the museum.
Old Tom aided the hunters by “flop-tailed” signalling when a whale was close by, “accompanied the boats during a chase, sometimes taking the rope in his teeth to tow the vessel. Evidence of this can be seen in the distinctive wear patterns on the teeth of his lower jaw.”
“Every June, records suggest that killer whales arrived in Turembulerrer (Twofold Bay) and would herd baleen whales into the bay or would alert whalers by tail slapping and splashing in front of the whaling station,” says the Flinders’ report.
This mutual understanding rewarded the orcas because the whale hunters fed the whales’ tongues and lips to the killer whales. This was known as the “Law of Tongue”.
“Killer whales, including those in Australian waters, have been recorded to favour the tongue in predations of baleen whales.”
On the 17 September 1930, Tom’s carcass floated into the bay. Eden has created a museum where Old Tom’s skeleton is on exhibition. The pods were remembered as the Killers of Eden.