SOME days when Joel Berger gets dressed for work he puts on a pair of jeans.
On other days, it鈥檚 a moose suit. That鈥檚 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鈥檚 front end sounds humiliating, imagine
having to impersonate a moose鈥檚 backside. That irksome task falls to Berger鈥檚
long-suffering collaborator, Carol Cunningham.
鈥淲e do it to get data. It鈥檚 that simple,鈥� he says pre-emptively. 鈥淲e have to
get close to unhabituated animals.鈥�
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鈥檚 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鈥檚 nose and then
measure how they reacted. But moose tend to live in remote forests and don鈥檛
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鈥檛 work very well,
says Berger. It can take weeks for the moose to run across the samples. 鈥淏y that
time the odour is diffuse,鈥� 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鈥檛 exactly keep
them toasty鈥攁nd the fur and foam have some major disadvantages when it
comes to outdoor pursuit.
鈥淚t鈥檚 a hassle to use,鈥� complains Berger. 鈥淚t鈥檚 big and bulky. But it does
work.鈥� 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. 鈥淚t鈥檚 a high-pitched `moo鈥欌�攁 `mew鈥�,鈥� says Berger.
Like a loud cat. He points out that it鈥檚 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鈥攁nd, er,
research samples. 鈥淵eah, we鈥檙e carrying bags of shit with us, too,鈥� 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鈥攁lways a
female, since they are less likely to have been hunted by people鈥攖he two
biologists have to keep their cool. Acting like any other moose, they 鈥渂rowse鈥�,
zigzagging aimlessly through the sage brush and spruce. It can take 20 minutes
to cover 200 metres. 鈥淵ou have to look pensive,鈥� advises special agent Berger,
鈥渁s though you don鈥檛 have this particular moose in mind.鈥�
When they get to within about 25 metres of the moose, the real research can
begin. Berger makes a 鈥渟cented鈥� 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. 鈥淲e dropped the moose suit and ran,鈥� says Berger. 鈥淲e had to go back to
get it.鈥�
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鈥檒l sniff the control ball only briefly鈥攁 faint human odour
rarely elicits a strong response鈥攁nd 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. 鈥淲e鈥檒l continue as long as the
moose will.鈥�
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鈥檛 surprising,
given that more than two-thirds of juvenile moose in those regions won鈥檛 make it
through their first summer.
In a paper in November鈥檚 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鈥攁nd 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鈥� 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鈥檚 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鈥檝e
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鈥檙e quick: both wolves and grizzlies are already being
reintroduced into the area. Besides, he says, 鈥渨e鈥檝e got funding for only three
more years鈥�.
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鈥檚 no longer enough food to go around. 鈥淭hey are really
hammering the vegetation,鈥� 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鈥攁 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鈥檇 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鈥檚 off to
Greenland and it won鈥檛 be moose he鈥檚 seeking. 鈥淚 would really like a caribou
suit,鈥� he mumbles. Is Santa listening?