WALKING out on the tundra with half a tonne of angry polar bear jogging
towards you is disconcerting. But after a minute or two the bear, still a couple
of hundred metres away, begins to slow, shakes himself, staggers, sways and
finally goes down with eyes blinking, tongue wagging and lips twitching. By the
time I reach him he is doing a plausible impersonation of a hearth rug.
Around Churchill on the shores of Hudson Bay in Canada, tourists pay
C$800 (拢326) an hour to watch polar bears from helicopters or
鈥渢undra buggies鈥濃�攖rains of slow-moving coaches complete with dining and
sleeping cars, that crawl on giant wheels over the frozen ground. But travelling
with Nick Lunn and Dennis Andriashek of the Canadian Wildlife Service, you get a
much closer encounter. Their helicopter pilot, Steve Miller, needs greater
manoeuvrability, so he has jettisoned me as excess baggage. It takes precision
flying, 10 millilitres of Telazol and a good aim to tranquillise a polar bear
from the air, but for these guys, it鈥檚 all in a day鈥檚 work.
For more than 30 years Lunn, Andriashek and their predecessors have been
carrying out one of the most detailed audits of any wild animal population
anywhere. Twice a year, in March and September, they go bear-tagging. In recent
years, however, their ever-expanding data set has started to reveal disturbing
signs that the bears are growing thinner and that new cubs are in increasingly
short supply. The researchers blame changes in the ice offshore for these
effects, and fear that a catastrophe could be near.
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Churchill calls itself the 鈥減olar bear capital of the world鈥�. The bears come
ashore each summer, on the southwest corner of the bay, because the sea ice,
their normal habitat, melts here last. From late July to early November they
laze around the tundra and along the coast, making the occasional foray into
Churchill itself before heading back out onto the reforming ice. The 1200 or so
animals now easily outnumber humans in an area whose population has shrunk from
10 000 to 600 in the past 20 years, with the closure of a military base and
rocket station.
鈥淲e have a file on about 80 per cent of the bears in this population,鈥� says
Andriashek. 鈥淲e know their age and size, we know many of their mothers and where
they were born. We have taken samples of their blood, fat and tissue, a tooth,
even a vial of their breath using a `bear breathalyser鈥�. Within a decade, we
hope that DNA work on the blood will allow us to write family trees for all
these bears. We鈥檒l know more about them than we do about the people of
颁丑耻谤肠丑颈濒濒.鈥�
Most cubs get tagged in their first or second summer with a plastic ear
marker and a tattoo on the inside of their upper lip. Adults are regularly
recaptured to check weight and growth. Some are fitted with a radio transmitting
collar so that they can be located from the helicopter or, for a select few and
at a cost of C$5000 each, from a satellite in orbit. Few animals escape
inspection. On the day I spent surveying the animals, every adult bear we found
had been tagged before. The nearest to an exception was identified by his lip
tattoo as 鈥淴9124鈥�. Now 18 years old, he had evaded capture since 3 November
1981, when he was a two-year-old cub.
Friend and foe
Some bears run when they see the helicopter. Many, especially mature males,
just stand and look鈥攁pparently more anxious to save energy than to escape.
The team tranquillises bears as they find them, though in very cold weather they
leave families alone for fear that the cubs will suffer before their mother
recovers. Another concern is that collapsing bears may drown in pools of water.
Miller, the regular pilot for the team, steers staggering bears away from
standing water.
No bear is typical. Bear 鈥�11875鈥� took 15 minutes to become unconscious. And
his eyelids continued to flicker as the researchers took a syringe of blood and
extracted a vestigial tooth to check his age, removed the barbed tranquilliser
from his flesh, and measured and breathalysed him. As we left half an hour
later, he was still flat out. But a young female showed a very different
metabolism. She went down in two minutes but was soon half awake, opening her
mouth and lifting her head as the team concluded their work.
Some bears reveal unexpected histories. DNA analysis of his blood showed that
鈥�12342鈥�, a two-year-old male, was a 鈥渓itter-switcher鈥濃�攁 cub who, for some
reason, had been abandoned by his mother and adopted by another female. Out of
the 13 animals we saw on my day with the team, the biggest was 鈥�10626鈥�, a
ten-year-old male measuring 248 centimetres from nose to tale, and the oldest, a
21-year-old female. Over the years, Lunn has given the once-over to about a
thousand bears. Andriashek reckons to have done more than two thousand, while
Miller had logged 4433 by the end of our trip.
Back at the Churchill Northern Studies Center, formerly the rocket launch
base, scientists mingle with pilots, tour leaders and adventure-seekers. The
talk is of close shaves on the tundra鈥攂ears nuzzling their way into tents
at night in search of food, or learning to open car doors. There is talk, too,
of the early days of research, when investigators went out on the ice to tag
bears, and had to use 鈥渁ngel dust鈥� (phencyclidine hydrochloride) and ketamine
hydrochloride to immobilise animals. It was a bit unpredictable: sometimes the
bears would jump up halfway through the investigation.
Churchill鈥檚 resident humans express a deep ambivalence towards their
four-legged visitors. Bears are one of the town鈥檚 biggest sources of income. But
not long ago, a Churchill resident was killed when he disturbed a bear rummaging
in the remains of a hotel that had recently burned down. Now the locals have got
tough. Bears entering the town or scavenging at the dump are put into solitary
confinement in a big, windowless, disused military warehouse out by the
airport.
鈥淭hey are given water but no food. And no sight of humans, until they are
shipped out onto the ice in the fall,鈥� says Lunn. 鈥淭hat way they seem to get the
message to stay away.鈥� Bears that relapse, and their cubs, tend to be shipped to
zoos鈥攁 policy that has been attacked by the animal welfare group Zoocheck
Canada. According to Zoocheck鈥檚 director, Rob Laidlaw, nobody checks to see what
becomes of these bears. One turned up in a Japanese bear park, another in a
Mexican circus. The authorities say the alternative is to kill the bears.
Despite the seeming brutality of these measures, polar bears are the only
species to have their own purpose-built international treaty. Signed in 1973 ,
the treaty has been a big success in its aims of conservation and research,
nursing the bear population back from a low of perhaps 5000 animals to some 25
000 worldwide today.
Norway and Russia forbid hunts altogether, but Canada licenses the native
residents of northern communities to harvest about 600 animals a year, out of a
national population of some 15 000. There is no hunting at Churchill, but it鈥檚
different up the coast of the bay at Arviat (formerly Eskimo Point). 鈥淭hey
usually fulfil their quota within a few weeks each fall as the bears from
Churchill return to the ice and head north along the coast,鈥� says Lunn. A large
hide will fetch up to C$2000, and the Canadian hunt is worth some
C$1 million a year.
Outside the arena of the hunt, however, the bears attract ongoing interest of
a more benevolent sort鈥攆rom researchers. Largest of all the bears, polar
bears evolved from grizzlies that lived along the Arctic coasts during the last
ice age, from about 100 000 to 10 000 years ago. In Canada, researchers have
identified 14 groups of polar bears that seem not to interbreed, and to have
largely separate territories. The Churchill population, for instance, winters on
its own patch of ice on the west side of Hudson Bay, and shuns its near
neighbours in James Bay.
Hard times
Out on the ice floes life is easy. Bears wait at breathing holes to catch
young ringed seals, their staple diet, socialise and mate in the spring. But as
the ice melts and they are forced onto land, things get tough. With very little
to eat, an adult may lose as much as a third of its body weight over the summer.
They can run at up to 40 kilometres per hour in short bursts鈥攆ast enough
to catch geese and possibly caribou. 鈥淏ut they don鈥檛 often do it,鈥� says Lunn,
鈥渂ecause they would use up more energy than they would get from the quarry.鈥�
Some bears resort to berries, but nobody is sure how important these are to
their diet. The bottled samples of exhaled air collected with the bear
breathalyser should resolve this issue. Keith Hobson at the Prairie and Northern
Wildlife Research Center in Saskatoon is analysing the isotopic composition of
the carbon dioxide in the breath, which should act as a marker for the animal鈥檚
last meal. Berries have a lower ratio of carbon-13 to carbon-12 than do seals
and other seafood.
Another active area of research is the denning habits of female bears. As the
other bears head out to the ice in November, pregnant mothers stay behind to
give birth inside earth dens. They stay with their newborn cubs until March,
when they emerge and head for the ice鈥攁 trek of up to 100 kilometres.
Satellite collars attached to pregnant bears in the summer should help confirm
preliminary findings that females choose different dens for each birth.
This behaviour seems odd, given the sophisticated structure of the dens,
which are carefully sited to incorporate the roots of black spruce bushes as
inner supports. But Peter Scott at Trent University in Peterborough, Ontario,
has found an explanation. By dating the damage to spruce roots caused when dens
were constructed, he has established that some sites have been in use for 200
years. So while a female may choose a new den each season, any one den will be
home to many different females.
While details of the bears鈥� lifestyle are intriguing, the main focus of the
Churchill team鈥檚 long-term monitoring programme is to track trends in the health
and reproduction of the bears鈥攙ital parameters for the survival of this,
one of the most southerly polar bear populations. And the signs are not good.
鈥淥ver the past 20 years, there has been a long-term decline in the condition and
reproduction of female bears especially,鈥� says Lunn. An index of body condition,
measured as body weight in kilograms divided by the square of the length in
metres, declined from 55 in the early 1980s to 49 a decade later. During the
same period average annual births per adult female declined from 0.99 to
0.84.
One theory about these trends is that the bears are being damaged by
pollutants such as PCBs, which travel to polar regions in the atmosphere and
then accumulate in the food chain (see 鈥淣orthern exposure鈥�, 31 May 1997, p 24).
Last year, Norwegian researchers discovered several hermaphrodite cubs showing
high levels of PCBs, suggesting that the chemicals had caused serious damage to
their hormone and reproductive systems. But PCB levels in Churchill鈥檚 bears are
lower than in bears further north, where extremely cold conditions seem to
distil the chemicals out of the atmosphere. According to Ian Stirling, head of
the Churchill research programme, who is based in Edmonton, Alberta, a more
likely explanation is warming in the region over the past two decades, which is
causing sea ice to melt earlier in spring.
The final weeks before the ice melts in Hudson Bay are a critical time for
the bears鈥攁nd possibly the key to their continued survival. Adult bears
out on the ice do most of their feeding at this time. There are rich pickings
after the birth of ringed seal pups during April. This is also the time when
emaciated females, who may lose half their body weight during their eight-month
fast on land, return to the ice with their young cubs. If their time on the ice
is reduced because it melts sooner, they won鈥檛 catch as many seal pups鈥攁nd
this may be devastating for the entire population.
The most intriguing evidence of the importance of this spring feeding
鈥渨indow鈥� is the sudden but temporary recovery in the bears鈥� health recorded in
1992. Stirling calls it the 鈥淧inatubo effect鈥�. During late 1991 and 1992 the
entire world cooled as the planet鈥檚 surface was veiled in dust from the eruption
of Mount Pinatubo in the Philippines in April 1991. That winter the Canadian
Arctic was cooler than in recent years, and in spring 1992 the Hudson Bay ice
melted three weeks later than normal. Bears fed on the ice until mid-August.
When they finally came ashore, they were fatter than in recent years, and
produced more and fitter cubs at the end of the year. The condition index for
adult females increased from 49 to 52 and the birth rate rose from 0.84 to 0.92.
Both indicators have subsequently slipped back to previous levels and continue
to fall.
The implications of this finding are depressing. Stirling estimates that if
the ice broke up even one week earlier than normal, typical female bears would
come ashore 10 kilograms lighter and return at the end of the summer 34
kilograms lighter. They would produce and wean fewer cubs. In the short term,
global warming could be good for bears further north, says Stirling, because the
break-up of permanent ice would provide a better habitat for seals. But round
Hudson Bay, he believes the bears could already be on a knife-edge. 鈥淭he first
impact [of warming] on polar bears will be felt at their southern limit, in
Hudson Bay,鈥� he says.
When Lunn and Andriashek go bear-tagging next month, they will find the
animals as usual, alone or with one or two cubs in tow, by creeks, at the edges
of lakes or mooching along the coast, biding their time, waiting for the ice to
return. But with the Arctic warming fast, the animals may become desperate.
Stirling fears that hungry, stressed and angry bears will wander into Churchill
in increasing numbers, desperate for food and willing to kill humans to get it.
A close encounter with one of these animals would be more than
disconcerting.