Whale migration - the first scientific results are in

Feature story - 13 November, 2007
Whales shouldn't have to die for research so we started the Great Whale Trail to prove it. Satellite tagging humpback whales isn't easy, the whales weigh in at over 30 tons and travel thousands of kilometres across the wildest oceans. Despite the difficulties, scientists working in the South Pacific managed to tag 20 humpbacks and begin tracking their epic migration. Now after two months, the first results are in, and they are amazing.

Humpback whales migrate from the Cook Islands in the South Pacific.

The Great Whale Trail is a collaboration between Greenpeace and scientists working on humpback whales in the South Pacific. With financial support from Greenpeace, humpback whales have been tagged by the Cook Islands Whale Research and Opération Cétacés (New Caledonia).

New Caledonia was chosen because the humpbacks which breed there are members of one of the small, unrecovered populations we're most worried about.

Dr Claire Garrigue of Operation Cétacés, who directs the study of humpback whales there, estimates that the population is in the low hundreds, with little sign of recovery from whaling. Given its location, we had strong suspicions that the New Caledonia humpbacks migrate into the feeding grounds which will be one focus of Japan's scientific whaling in the coming years.

Nan Hauser, who directs Cook Islands Whale Research, typically photo-identifies only 60 or 70 whales a season. Claire Garrigue may photograph a whale in the large lagoon off southern New Caledonia where she works; and a few weeks or years later Nan Hauser may see that same whale a mile off the coast of Rarotonga (Cook Islands).

These matches are very important scientifically; but the whale's movements in between these two farflung points in time and space are largely a mystery.

In August and September this year, Garrigue and Hauser, working with Brazilian scientist Ygor Geyer, succeeded in deploying 20 satellite tags on humpbacks - twelve in New Caledonia and a further eight in the Cooks. All of the scientists working on humpbacks in the South Pacific eagerly awaited the streams of data that came from the tags, and they were not disappointed.

By attaching a transmitter to a whale, its movements can be remotely followed on a daily basis by a satellite. The transmitter sends a signal to an Argos satellite, which in turn transmits the data to a ground station - and a scientist with a laptop can access this information from the comfort of an easy chair anywhere in the world.

Do New Caledonia whales travel to New Zealand? Do whales in the Cook Islands travel east or west when they leave, or are their movements all over the map?

Satellite tagging can address exactly these kinds of questions, and in doing so can provide critical information about population structure and behavior for use in management.

Although all the tags ceased transmission before any of the whales reached the Antarctic, the information they yielded was spectacular.

Of the 12 New Caledonia tags, several traveled from the southern lagoon by the coast offshore to a remote reef system to the southeast, and some of the whales remained there for an extended period.

Until the Great Whale Trail project, no one had any idea of the apparent importance of this offshore habitat to the animals. Garrigue is already planning photo-id and genetic sampling in the area next year, and the tagging results may well set in motion future efforts to protect this previously unknown habitat.

One whale surprised everyone by leaving the southern lagoon and moving up the entire length of the western coast of New Caledonia, and then traveling hundreds of miles west to the area of reefs and islands known as the Chesterfields.

This provided an interesting historical insight, because in Herman Melville's day the Chesterfields had been one site of American "yankee" whaling in the19th century. And then there were the long-distance migrants.

Some of the whales tagged off New Caledonia moved to Norfolk Island and/or to the northern coast of New Zealand, thus filling a key gap in our knowledge of their population structure. The scientists had always wondered where New Zealand whales went (there were a few photo-id matches prior to this project).

The movements between these two areas are important, because whales in neither area have shown signs of recovery from whaling, and thus the link is a logical one that has significant implications for conservation.

In this regard, the fact that none of the whales tagged in New Caledonia moved to Australia provides further support for the idea that the former is a largely separate stock whose recovery is not being accelerated by any influx of animals from the much larger Australian population.

Heading west

In the Cook Islands, the behavior of the eight tagged whales was characterized by one huge surprise: rather than spreading out and traveling in different directions, they all moved west.

One animal traveled all the way to American Samoa, while others moved through the many islands and reef systems that make up the Tonga group. Does this indicate that whales enter the Cooks in a kind of "wave" that sweeps through the islands from the east?

The scientists don't yet know, although such movements have been observed among humpbacks tracked by photo-id in another breeding area, the West Indies. Another surprise: even though some tags continued transmitting well into October, which is quite late in the season - none of the Cooks whales showed any signs of turning south towards the Antarctic.

This is in contrast to some of the New Caledonia whales, some of whom began moving south shortly after being tagged. The variability in these movements, and the consistency with which the Cooks animals all traveled west, have important implications for a variety of issues ranging from population structure to how these animals navigate.

In future months, scientists will be looking in more detail at the tracks of these animals, assessing whether their movements can be linked to discernable features in the ocean, the sea floor or perhaps even the Earth's magnetic field - all of which are possible mechanisms used by humpback whales to find their way across the vastness of the ocean.

Valuable information

Although this project was the first of is kind in this region, and therefore something of an experiment, it has already yielded far more information about these once-large populations than will be learned from the upcoming Japanese hunt. Over the next few months, fifty humpback whales will die in the Antarctic, killed in the name of scientific research that will tell us little that we do not already know.

Indeed, virtually nothing in the Japanese lethal studies program will address the major research recommendations formulated by the IWC for Southern Hemisphere humpbacks. In other words, the scientific recommendations of the body that manages whaling are being largely ignored - and still Japan claims that its science is useful.

The Great Whale Trail continues.

We may see one or more of our tags spring back to life, and all of our whales are in a visual database available to researchers worldwide. You can help ensure they all have names by voting for the best whale names submitted by whale defenders all over the world, beginning on the 19th of November.

In the meantime, you can sign up for Whale Mail and keep up to date on the ongoing developments in the Great Whale Trail adventure.

The above article is an edit of a longer, more detailed article about the science behind the Great Whale Trail.

Read the full version here.

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