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Satellite Tagging Humpbacks In The South Pacific: Windows On The Whales' World

Page - November 14, 2007
Humpback whales are among the widest-ranging animals on Earth. Each year, they leave productive summer feeding grounds in high latitudes to undertake a migration that will take them anywhere from 1,500 to 5,000 miles (2,400 to 8,000 kilometres), into the warm tropical waters where they mate and give birth to their young.

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

During this time, they do not eat for weeks or months, subsisting instead on the thick layers of fat (blubber) which have been steadily built up over the summer feeding season. While on their breeding grounds, the males sing their long, haunting songs and compete sometimes quite aggressively over mating access to females.

Pregnant females give birth to their calves in the warm tropical water, and diligently nurse them with a fat-rich milk that promotes rapid growth. Then, at winter's end, all the whales make the long journey back to polar waters, and the annual cycle begins once more.

Ancient cycle

It is a cycle that has been repeated for thousands of generations of whales, over what may well have been millions of years. It is strange to think of how long the world's oceans have resonated with the songs of humpback whales, and even stranger to consider that, through uncontrolled whaling, humans came close to permanently silencing this ancient chorus, and barely half a century ago.

In the Southern Hemisphere, humpback whales feed in the frigid waters off Antarctica, and they breed and calve in coastal or island waters that stretch in a global band between the equator and the Tropic of Capricorn. A particular whale's particular feeding and breeding grounds are determined largely by where that whale's mother comes from.

If your mom was a whale who fed in the waters south of Australia, then that's where you yourself will return each spring to eat.

If your mom was a whale who migrated to Fiji to give birth to you, then Fiji is probably where you will head when it is your turn to breed. Except that Fiji no longer hosts very many whales.

Today, a handful of humpbacks return there, and one can wait a long time between sightings, even during the supposed peak of the season in August. Yet it was not always so.

In the 1950's, the late Dr William Dawbin conducted annual surveys for humpback whales at various places in Fiji, and recorded several hundred whales a week at the peak.

However, this was before 1959, when the USSR - which at that point had already been engaged in a secret campaign of illegal whaling for more than ten years - began a slaughter of humpback whales that was excessive even by the unrestrained standards of 20th century whaling.

Population crash

Over the course of just two winters, Soviet factory ships slaughtered almost 25,000 humpbacks; most met their end in the portion of the Antarctic that lies south of Australia and New Zealand.

The result was an instant crash of the population - so rapid that coastal whaling stations operating to the north, in New Zealand and eastern Australia, almost immediately went out of business for lack of whales.

We do not know how small the surviving humpback whale population was, but it was likely just a few hundred animals. In the four decades since those dark days, humpback whales have recovered remarkably well - in some areas.

Off eastern Australia, for example, the population is now on the order of several thousand animals, and continues to grow at a healthy rate. But in other places, including Fiji, New Zealand and New Caledonia, there is little or no sign of such recovery.

Whether this is because the cultural memory of the existence of these formerly populous habitats died with the slaughtered whales is not clear. And today, after almost half a century of protection, humpback whales will once again be hunted in the Antarctic.

Discredited science

Later this month, the Japanese whaling fleet will leave its home port and head for the Antarctic, where it intends to kill up to 935 minke whales as well as 50 fin whales and 50 humpbacks.

These catches will continue each year, indefinitely, in the latest phase of Japan's "scientific" whaling program - a program which has been widely discredited by numerous scientists, and which is seen as a convenient way for Japan to circumvent the global moratorium on commercial whaling enacted by the International Whaling Commission (IWC) in 1986.

Under the terms of the 1946 International Convention for the Regulation of Whaling (which established the IWC), any nation may issue its nationals a permit to kill whales for the purpose of studying them. Such a provision made perfect sense sixty years ago when the Convention was signed; in those days, there was no other way to study whales except by killing them.

The provision (known as Article VIII) was intended to allow scientists to kill small numbers of animals for study; it never included a limit to the number of whales that can be killed, because in 1946 no one imagined that Article VIII would ever be used as a way of getting around a ban on whaling.

Endangered populations

One of the big problems with Japan's intended catch of humpback whales is that it is impossible for a harpooner to tell whether the whale in his sights comes from the relatively healthy population off Australia, or from one of the small, unrecovered stocks in places like Fiji and New Caledonia.

Although 50 whales a year may not seem like a huge number when set against the massive totals racked up by the USSR and other whaling nations in the 1950's and 60's, such catches have the potential to threaten the remnant populations that are struggling to make a comeback.

Key to all of this is a knowledge of population structure. Specifically, in order to properly manage any whale species, one needs to know how many populations exist, and their size and relationship to one another.

The importance of this can be illustrated with a simple example. Imagine that there are a thousand humpback whales in a single population -that these animals mix freely with each other, and that they all breed together.

Now imagine that each year a certain number of these whales are killed by "unnatural" causes - whaling, entanglement in fishing gear, ship strikes, et cetera. The impact of these mortalities on a single stock of a thousand whales will be far less than if the thousand animals actually make up two separate populations, with one being 900 and the other only 100 animals.

The impact of any number of deaths on a population of a hundred will obviously be a lot greater than if that same number of mortalities is taken from a single, mixed stock of a thousand animals.

In other words, you need to know how many populations you're dealing with before you can make sensible decisions about how to manage them. For the purpose of management, scientists and the IWC usually define populations by drawing lines on a map; this is inevitable and convenient, but of course the whales themselves don't recognize such neat boundaries.

Currently, the IWC recognizes seven Southern Hemisphere populations of humpback whales. Each of these populations feeds in a particular portion of the Antarctic, and these feeding areas are linked to specific breeding grounds in tropical waters.

For example, humpbacks that feed in what is known as "Area V" - broadly, the area of the Southern Ocean south of Australia and New Zealand - are thought to breed off the eastern coast of Australia and in western Oceania.

Management of these animals - an activity which could cover everything from conservation measures to setting future catch quotas - is all based on the assumption that this population is largely separate from others (which in turn are managed according to our knowledge of their particular size and structure).

How do we study population structure?

There are various methods, most of which involve somehow tracking whales from one place to another, and in the process testing whether our notions of the structure and boundaries of their populations are accurate.

For example, if a whale from eastern Australia suddenly showed up in the Antarctic south of Africa, this would challenge the current idea that the Australian population is linked to feeding grounds in the polar waters south of that continent.

How serious a challenge this would represent would depend upon whether such movements turned out to be fairly common, or looked instead like a one-shot case of an "aberrant" wandering whale.

To date, incidentally, no such movement has been detected, although scientists working in the Indian Ocean did recently record a whale going from the east coast of Africa to the west!

How to track whales

The principal means of tracking whales from place to place are threefold. The first is photo-identification, which involves photographing the unique markings on the underside of a humpback whale's tail.

These markings are like a fingerprint in that no two whales have exactly the same tail pattern, and this feature has been used to identify many thousands of individual humpback whales all over the world.

Photo-id has allowed scientists to follow individual whales over periods of literally decades in some areas, and also to document the reproductive success of females and their offspring over several generations.

A second method is similar but more high-tech. By taking a tiny sample of skin from a humpback whale through a biopsy - a dart is fired at a whale from a crossbow, and harmlessly takes a small sample before bouncing off into the water - scientists can examine the whale's DNA and conduct many sophisticated and highly informative analyses.

These including determining the animal's sex (which usually cannot be done visually), as well as assessing its maternal lineage, and constructing a genetic profile that allows the whale to be individually identified.

As with photo-id - where two photographs of the same whale in different areas can be matched - a humpback biopsy-sampled in two different places can be unequivocally identified as the same individual through genotyping.

All of these tests and many more can be conducted with a single tiny piece of skin - rather different from the "whole-animal" sampling employed by Japanese whalers.

With either of these methods, an individual whale can be resighted or resampled again and again, giving us ever-more information about its movements over the course of years or even its entire life (something which, needless to say, is not possible when a whale is killed - you get one data point, and that's that).

Using these methods, thousands of whales have been documented traveling over sometimes huge distances. For example, in the North Atlantic, some humpback whales have been followed for more than thirty years, and observed at migratory endpoints as far apart as Norway and the Caribbean.

However, what photo-id and genetics cannot do is tell us the daily movements of animals, or to track their wanderings through the large areas of ocean in which human observers aren't present.

We may photograph a whale in the Cook Islands or New Caledonia and then see it again off Tonga (in fact, many such matches have been made with both photographs and genetics); however, we don't know the many details of where it goes in between these brief snapshots of its life. This is where the third technique comes in.

Satellite tagging

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.

Photo-id and genetic sampling requires scientists to be next to the animal, and it is impossible to follow the whale in rough weather, or at night, or far from the safety of coastal waters. In contrast, a tagged whale can be followed anywhere on Earth, at any time.

Not only do scientists get to see the end points, but they learn every detail of the whales movements without ever having to relocate the animal in the vastness of its huge migratory range (traditional methods require you to find the whale to photograph or biopsy it - and that is as much a matter of luck as anything else).

This year, a group of scientists working in the South Pacific were funded by Greenpeace International to conduct a collaborative satellite tagging project in two locations: New Caledonia and the Cook Islands. New Caledonia was chosen because this is one of the small, unrecovered populations about which we have considerable concern relative to the imminent Japanese whaling effort.

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 Area V feeding grounds which will be one focus of Japan's scientific whaling in the coming years.

Indeed, a recent genetic match of a whale moving between these two areas has confirmed this. Whales from the Cook Islands likely migrate further to the east than the New Caledonia animals, and the population there is even smaller.

Nan Hauser, who directs Cook Islands Whale Research, typically photo-identifies only 60 or 70 whales a season. Again, tagging fills in the gaps.

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.

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.

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.

Last year, Hauser's project placed a single satellite tag on a whale - a mother observed off the main island of Rarotonga -and watched over four months as the animal migrated from the Cooks into the Southern Ocean.

By the time the tag ceased transmitting in late January 2007, the whale had traveled almost 4000 km to the Antarctic Circle, and was close to the boundary between two IWC management areas - which came as a surprise to many.

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.

Although all the tags ceased transmission before any of the whales reached the Antarctic, the information they yielded was spectacular. Because by necessity we usually work close to our own coasts, we tend to fall into the trap of seeing humpback whales as coastal animals, yet they are not.

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 then, 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. We 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.

In the Cooks, 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 the 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?

We 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 was that - 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.

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.

With just these twenty animals, we have already learned more about movements and connections of whales in the South Pacific than was known before. Satellite tagging of course cannot tell us everything; rather, it is used to address some specific areas of research, and not others.

But in combination with other non-lethal approaches such as photo identification, genetic analysis and other techniques, it can provide far better information for the conservation and management of these animals than "scientific" whaling ever will.

This information was provided by the scientists researching humpback whales in the South Pacific who are collaborating with Greenpeace on the Great Whale Trail.