SOME days when Joel Berger gets dressed for work he puts on a pair of jeans.
On other days, it’s a moose suit. That’s right: a big, moulded styrofoam head
covered in synthetic moose fur on top of a long moosey cape that reaches down to
his ankles. And if being the moose’s front end sounds humiliating, imagine
having to impersonate a moose’s backside. That irksome task falls to Berger’s
long-suffering collaborator, Carol Cunningham.
“We do it to get data. It’s that simple,” he says pre-emptively. “We have to
get close to unhabituated animals.”
Both Berger and Cunningham are biologists at the University of Nevada, in
Reno. They want to know if animals behave differently when their predators
disappear. Moose in Wyoming, for instance, are at the top of the food chain.
Over the past seven decades, all their predators have died out, mostly through
human interference. But it’s a different story in Alaska, where wolves and
grizzly bears still hunt the gentle beasts for supper.
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So Berger and Cunningham were wondering: how do the two populations differ?
Do moose in Wyoming still react to the scents of their erstwhile predators? Or
have they simply stopped bothering?
The question is not as easy to answer as you might imagine. Berger and
Cunningham had to devise a way to put scents under a moose’s nose and then
measure how they reacted. But moose tend to live in remote forests and don’t
mingle casually with humans.
First the researchers tried leaving dung and scent marks in the woods, going
back later to see if the moose had approached them. That didn’t work very well,
says Berger. It can take weeks for the moose to run across the samples. “By that
time the odour is diffuse,” he says. He and Cunningham tried hurling the stuff
in with masterful baseball pitches. They even catapulted it in with
slingshots.
But in the end, going undercover as a moose seemed to be the only solution.
So they commissioned a costume designer who had worked on the first Star
Wars film to fashion their suit.
By this time they had already worked out that the best way to deliver the
scent to the unsuspecting moose was inside a snowball. That meant tramping the
countryside in the depths of winter. Their unusual outfit doesn’t exactly keep
them toasty—and the fur and foam have some major disadvantages when it
comes to outdoor pursuit.
“It’s a hassle to use,” complains Berger. “It’s big and bulky. But it does
work.” Berger and Cunningham often have to hike into moose territory, pulling
all their gear behind them on a sled. Then, concealed in the woods, they don
their disguise.
Thus camouflaged, the two amble along slowly, pretending to be a moose. They
even make moose sounds. “It’s a high-pitched `moo’—a `mew’,” says Berger.
Like a loud cat. He points out that it’s not exactly easy to navigate with the
suit on, since they can barely see. The two have been known to fall over.
And a cumbersome moose suit is not their only distraction. Dangling round
their necks are stopwatches, a pad of paper, pencils, a camera—and, er,
research samples. “Yeah, we’re carrying bags of shit with us, too,” says Berger.
Not just any old stuff, but Siberian tiger, grizzly bear, black bear and cat,
not to mention an assortment of fine urines, including wolf, coyote and human.
All in individual bags.
Acting cool
When Berger and Cunningham spot a potential research subject—always a
female, since they are less likely to have been hunted by people—the two
biologists have to keep their cool. Acting like any other moose, they “browse”,
zigzagging aimlessly through the sage brush and spruce. It can take 20 minutes
to cover 200 metres. “You have to look pensive,” advises special agent Berger,
“as though you don’t have this particular moose in mind.”
When they get to within about 25 metres of the moose, the real research can
begin. Berger makes a “scented” snowball and lobs it near the moose subject.
Sometimes she ignores it, says Berger. Other times, she runs away. A couple of
times, moose have got downright furious and looked as if they were about to
charge. “We dropped the moose suit and ran,” says Berger. “We had to go back to
get it.”
But if the moose does go over and sniff at the snowball, Berger and
Cunningham are ready to time how long it takes her to get back to foraging.
Usually, she’ll sniff the control ball only briefly—a faint human odour
rarely elicits a strong response—and goes back to feeding within 20 to 40
seconds. In which case, Berger lobs a new snowball, this one made with, say,
coyote urine. The moose might be a bit more interested in this scent. But if she
goes back to grazing, Berger tosses another. “We’ll continue as long as the
moose will.”
They have found that moose from regions where there are no predators take
significantly less time to return to their feeding and are pretty uninterested,
even when sniffing the faeces of ancient enemies. Moose who still live
flank-by-flank with wolves and bears, on the other hand, become vigilant and
agitated, and sometimes stop feeding altogether. Perhaps this isn’t surprising,
given that more than two-thirds of juvenile moose in those regions won’t make it
through their first summer.
In a paper in November’s Proceedings of the Royal Society: B (vol
266, p 2261), Berger looks at how moose from different areas respond to another
potential warning signal: raven calls. As scavengers, ravens hang out near
carcasses—and carcasses are often found near wolves or grizzlies.
Berger visited four sites in Alaska and two in Wyoming: all had raven
populations, but only three had predators. Dressed normally this time, he lurked
near his moose targets and played recordings of raven calls. Then he compared
the animals’ responses in the three predator-haunted Alaskan sites with those of
their relatives in the three safe locations: Kalgin Island in Alaska, and two
spots in the Jackson Hole region of Wyoming’s Rocky Mountains, where predators
died out up to 75 years ago.
There are reports in the literature of birds and mammals that have stayed
wary of their traditional predators thousands of years after they’ve
disappeared. But Berger says his moose have lost their fear of old foes in fewer
than ten generations.
Berger is now keen to see how quickly the Wyoming moose can relearn old
tricks. He hopes they’re quick: both wolves and grizzlies are already being
reintroduced into the area. Besides, he says, “we’ve got funding for only three
more years”.
And even without predators, survival is still tough for the moose. Whereas
predators once kept the population fighting fit, now environment seems to be the
limiting factor, says Berger.
The moose population around Yellowstone has increased ten-fold since 1900,
says Berger. There’s no longer enough food to go around. “They are really
hammering the vegetation,” he says. And pregnancy rates have plummeted as a
result.
Berger took samples of moose faeces and analysed them for pregnancy hormones.
Only 75 per cent of the females in the Yellowstone area were pregnant. This
compares to a rate of 90 per cent thirty years ago—a rate still found in
moose up north where predation is high. The predator-free groups are
malnourished, he concludes in a paper out in October in the journal
Conservation Biology (vol 13, p 1980).
Berger is already planning several costumed outings for the new year. This
will include a trip to take close-up snapshots of moose orphans, which should
give him an idea of their weight and survival prospects.
You’d think one large game suit would be enough to satisfy any man. But even
as he savours dressing up as a moose, and hurling smelly snowballs at his
buddies, his thoughts are turning to other animals. Next March he’s off to
Greenland and it won’t be moose he’s seeking. “I would really like a caribou
suit,” he mumbles. Is Santa listening?