Efforts to save a rare olive ridley turtle that was found on 90 Mile Beach on election day were unsuccessful.
Department of Conservation staff collected the turtle on the Saturday evening and dispatched it by air to Auckland the following day. It was still alive when it reached Kelly Tarlton's Sea Life Aquarium, but died on the Monday.
DOC staff in Kaitaia suspected it had ingested plastic, but that had not been confirmed by Kelly Tarlton's staff yesterday afternoon.
Olive ridley turtles were not often seen in the Far North, a DOC spokesperson said, but the discovery of two - the other was found on a beach near Dargaville - within a few days of each other could be a sign the species was extending its range south as waters warmed.
"Once they were really, really rare; now they're just not common," she said.
"And plastic is killing them."
The Dargaville turtle, which also died, had ingested a significant quantity of plastic, which conservationists have long been warning they mistake for food.