A modern-day elephant seal in South Georgia. Photo: 123RF
New research suggests a distinct lineage of elephant seals were well established in New Zealand at the time of human arrival.
Joint senior author Associate Professor Nic Rawlence, director of the Otago Paleogenetics Laboratory, said the story of the marine mammal's history in Aotearoa offered insight into how our ecosystem may react to future climate change and human impact.
Rawlence said southern elephant seals were the "canary in the coal mine" for the Southern Ocean and a great indicator of the region's environmental health.
Southern elephant seals are not a common sight on the mainland of New Zealand, but they certainly used to be "from Cape Reinga to Bluff" on our prehistoric beaches, according to the new research.
"They're an integral part of the Southern Ocean ecosystem - elephant seals respond rapidly to human impact and climate change. If they start responding detrimentally then they are acting as this canary, and we should heed the warning," Rawlence said.
"Apex predators like elephant seals keep the rest of the ecosystem in check, but if you're losing those then your ecosystem health is deteriorating.
"Southern elephant seals are at the top of the food chain. If we start losing them, it means whatever is affecting the elephant seals it means it's not just affecting them, it's not an isolated incident and will affect the food chain."
Southern elephant seals are the largest marine mammal that are not cetacean (whales, dolphins, and porpoises). Males, with their distinctive snouts, can weigh up to 3700kg, while females are usually around 1000kg.
They can be found throughout the Southern Ocean, parts of the Antarctic continent and sub-Antarctic islands.
Changes in Antarctic sea ice is impacting on the distance between breeding grounds and where southern elephants go to feed.
Rawlence said a unique lineage of Australasian elephant seals were likely pushed to prehistoric New Zealand by expanding sea ice during the ice age. However, this range expansion would not become permanent due to indigenous subsistence hunting and European industrial sealing.
But Rawlence said their existence points to a healthier moment in time for our prehistoric coastlines, which would have looked like "an alien world".
"At the time of human arrival, you would have seen elephant seals from Cape Reinga to Bluff. They would have been breeding here - we know this because we've found pup remains.
"The beaches would have been covered by elephant seals, sea lions and penguins… you would have tripped over a penguin or a pinniped (seals) within the first five minutes of arriving in New Zealand.
"We had a prehistoric New Zealand sea lion, very different genetically to seal lion that's here now, a lineage unique to mainland New Zealand and another lineage unique to the Chatham Islands.
"There was a penguin called the Waitaha penguin, a cousin of the Hoiho penguin or the yellow eyed penguin, living in New Zealand."
While the southern elephant seal species had shown to respond quickly to human exploitation and climate change, Rawlence said action to protect their habitat needed to be taken.
"They can only respond to a certain point, there's what you could call some ecosystem buffering and once they hit that cliff edge or point of no return, then they're off of it."
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