Scientists say New Zealand's great white sharks migrate to tropical waters off Australia and islands in the Pacific to feed on baby humpback whales.

New Zealand fisheries scientists have tracked tagged sharks using GPS and have concluded the giant ocean hunters appear to be regular winter visitors to tropical waters.

One of nine great white sharks to have GPS-linked tags attached this year, a 3.5-metre specimen nicknamed Thomas, migrated to Australia's Great Barrier Reef.

He turned up within 100 kilometres of where a 4.4-metre female great white, nicknamed Kerri, arrived last summer, setting a distance record for a New Zealand shark.

Both swam more than 3000 kilometres o the reef after being fitted with tags which record location depth and temperatures.

"We think they may be searching for newborn humpback whale calves, because all tags have surfaced in or near known humpback calving sites," National Institute of Water and Atmospheric Research fisheries scientist Malcolm Francis said.

AAP