Satellite Tags on Humpback Whales Expose Unknown Migration Routes
An international group of scientists is learning new things about the migration routes and daily habits of South Pacific humpback whales from satellite tags the group recently placed in the thick blubber of 20 whales. Tagged off New Caledonia and the Cook Islands, data show individual whales taking divergent and circuitous routes to the austral summer feeding grounds of the Antarctic.
“The tagged whales almost immediately provided fascinating surprises for the research team,” said Dr. Phil Clapham of NOAA Fisheries Service’s Alaska Fisheries Science Center. “The whales are telling us where they go, and we have already learned new things about their preferred habitats and migratory routes.”
“Right now, 10 tags are still operating – five each from New Caledonia and the Cook Islands. We hope that they will continue to transmit for weeks or months, showing the final destinations of these animals as they undertake their long migration from the tropics to the cold waters of the Southern Ocean.”
Tag data show that several of the New Caledonia whales traveled to a seamount system southeast of the island. It is clear, Clapham said, judging by the time the whales spent there, that the habitat is important to them. Another whale migrated to the northern end of New Caledonia, and then traveled west to the Chesterfield Islands (a United States whaling ground in the 19th century). Others began their migration south, stopping off at Norfolk Island or hanging out off the North Island of New Zealand before continuing on towards the Antarctic. In the Cook Islands, most of the tagged whales moved west, heading towards or north of Tonga – facts prized by the scientists, since so little is known about the movements of Cook Islands humpback whales.
The 10 functioning tags transmit signals to scientists daily over an Argos satellite. Scientists are gaining a more detailed picture of the whales’ population structure and movements. The information may also serve to demonstrate the vulnerability of whales from small, un-recovered populations to the upcoming Japanese whale hunt in the South Pacific.
Last year, a pilot project placed a satellite tag on a mature female humpback in the Cook Islands. The tag stopped working after two weeks, but amazingly came to life again after three months of silence, when the whale was 3,000 km to the south of Tahiti and well on her way to the Antarctic. The tag provided the first documented connection between the Cook Islands and an Antarctic feeding area.
Tagging whales is a difficult business. Unlike tagging attaching a neck harness on wolves or bears, there is no simple way of attaching external tags. Tags for whales have to be implanted in the animal’s thick layer of blubber. Many work themselves free of the blubber after days or weeks, but some stay affixed and operate for months displaying the movements of the animal over long periods and sometimes vast distances.
The current conservation status of humpback whales in the Southern Hemisphere varies considerably. Some populations – such as those off the coasts of Australia – are recovering well from intensive 20th century whaling, and number in the thousands of whales. In contrast, there are several small and apparently struggling humpback populations in parts of Oceania, including New Caledonia, the Cook Islands, Fiji and New Zealand. These populations were hit very heavily by commercial whaling in the 1950’s and 60’s, including huge illegal catches by the former USSR.
The project is a collaboration between NOAA’s National Marine Mammal Lab, Operation Cetaces in New Caledonia, Cook Islands Whale Research and Instituto Aqualie. The work was primarily financed by Greenpeace International as part of a scientific collaboration to carry out critical non-lethal research on specific populations of South Pacific humpback whales at risk from a range of threats, including whaling.
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