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The Bear Truth: Grizzlies' Snagged Hair Samples Reveal Dependence on Salmon

Poor salmon runs along British Columbia's central coast rain forest since 2003 have spurred scientists to gauge the fish's nutritional impact on grizzly bears



Dean Azim

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Editor's note: This story is part of a four-part series that Anne Casselman, a freelance writer and regular contributor to Scientific American, reported in early June during a rare opportunity to conduct field reporting on grizzly bears in Heiltsuk First Nation traditional territory in British Columbia. For a first-person acocunt of her experience there, click here.

HEILTSUK TRADITIONAL TERRITORY, British Columbia—"Remember, if she charges, don't run," Doug Brown, researcher and field station manager for Raincoast Conservation Foundation and member of the Heiltsuk First Nation, tells me as we climb out of the boat at the head of one of the countless inlets found in Heiltsuk Traditional Territory along British Columbia's central coast. It's June and the early morning summer sun rapidly scales over the steep slopes flanking the inlet. Several hundred meters away a grizzly mother is grazing along the edge of the estuary with her two and a half-year old cubs. "Cub," however, is a misnomer in this instance. These are three-year-olds, large beasts in their own right. Through my binoculars I see the mother lift her broad head to sniff the wind. The muscles powering her lumbering 135-kilogram-plus body ripple still. "So how far away does the bear need to be for the bear spray to work?" I ask Doug. "Ten feet," he replies. I picture just how large this grizzly would be that close—and how fast she would close that distance. "Wow," I mutter. Doug replies: "Yeah, that's why I carry two canisters."

This mother's triplets are likely the fruit of a banner salmon run four years ago, a rarity, given the poor runs seen here since 2003. Like so many marine and terrestrial animals of the Great Bear Rainforest—roughly defined as the north-central coast of British Columbia—the grizzlies here rely on salmon in their diet to sustain their life cycles, which may be a problem because the salmon aren't doing so well. "All of us are governed by the same ecological currencies, and the currency here is salmon," Chris Darimont, chief scientist with the Raincoast Conservation Foundation (RCF) and conservation ecologist at University of California, Santa Cruz, says. "When the wealth of salmon goes away there's poverty for the people here, and also ecological poverty."

The Heiltsuk First Nation is well aware of the ecological toll that a diminishing salmon biomass will exact on terrestrial and marine systems alike. "The land and the bears and the sea, our people have always said it goes hand in hand," says William Gladstone, chief negotiator of the Gladstone Reconciliation and community elder. "We've been really fortunate that we do have enough salmon going up our [river] systems but there is a point where the balance is going to be upset, where you're going to start losing them, too." With salmon on the decline, the animals supported by the system are endangered, Gladstone says. "We're very concerned about that."

Anecdotes of grizzlies starving to death or becoming scarce are increasingly common along the central coast, but just how big a threat diminishing salmon stocks are to grizzlies remains unknown. Research has shown that salmon availability determines how big a bear will grow as well as the reproductive output of a female bear. Beyond that, the details of the relationship between grizzlies and the fish are unclear. "It would be nice to have a mechanistic and quantitative understanding of how bear populations respond to the variation in salmon population," Darimont explains. Such research could forecast grizzly populations into the future and help fisheries managers optimize the salmon needs of the bears with those of fisheries. For example, Darimont has recently co-authored a study (recently submitted for publication) that models and estimates how reducing salmon catch by fisheries would boost flagging grizzly numbers in interior British Columbian watersheds.

Fisheries and Oceans Canada's Policy for Conservation of Wild Pacific Salmon  (as of yet unimplemented) adopts an ecosystem-based management plan for coastal salmon, and Darimont hopes that the results his study will help inform how much of the species should be allocated to natural ecosystems in order to safeguard the biodiversity of the "salmon forests."

"Well, I think all living beings have a right to use the resources and I have watched the bears, wolves in the spawning time use salmon," says Gary Housty, Heiltsuk hereditary chief. "So, you know, everybody is a user and when this is taken away from us by poor management it denies this great food that all users need."

Grizzly bears across the province of British Columbia have already been extirpated in 12 larger provincial parks and their numbers are severely reduced in seven more. Across the province, the population is declining in primarily due to habitat loss and habitat fragmentation. How much grizzlies are affected by salmon stocks remains unknown. The RCF study has identified 29 individual grizzlies in their study area, but Darimont has yet to crunch the numbers and project the population size.

Remote and vast study sites
To that end, the RCF is funding a long-term study that examines how intertwined grizzly bears are with their chief food source, salmon. The Raincoast researchers conduct noninvasive DNA, isotope and hormone analysis on grizzly bear hair samples collected from 72 sites, of which this one inlet is one. Roughly half the sites set up across this 5,000-square-kilometer remote study area are accessible by small helicopter. The rest by boat.

Since the study began a couple years ago, the researchers have expanded their study area by 2,000 square kilometers—at the same time that salmon numbers remain severely diminished.

The RCF's bear study follows the lead a similar study in the Koeye River watershed led by Coastwatch, the science arm of the Qqs Projects Society (pronounced kuks). Based in the tribal territory's coastal community of Bella Bella, Qqs is a Heiltsuk nongovernmental organization dedicated to promoting the nation's cultural and environmental values in local youth. The Coastwatch study, which reports to the Heiltsuk Integrated Resource Management Department, began as part of a drive to tally grizzly numbers in the vicinity of a Qqs youth science camp. William Housty is the director of Coastwatch and is leading the five-year study, which surveys grizzly bears in the Koeye watershed using hair-snagging stations. "We were able to paint a really good picture of the bears and their movement," says Housty, who is co-author on an upcoming research paper that outlines their results.

Stink sauce
I ask Housty why the bears matter so much, why they warrant such dedicated research. "Just by knowing that there's grizzlies in that territory tells us that that land is pristine—it has salmon, it has grass, it has spring habitats," he explains. "We know that our land is thriving because the bears are thriving."

One year Coastwatch collected hair from 65 individual grizzlies, all in just one river watershed. The scenery hugging the inlet head where the mother and her three cubs live is epic in its grandeur. We're at the water's edge of the Coast Mountain range, which is broader and higher than the Rockies in the U.S. Mountain peaks, softened by glacial retreat millennia ago and cloaked in inky green coastal western hemlock and red cedar forest, careen into the sea. Even from the water, the wintry and spicy smells of the forest meet our nostrils. A flock of goldeneyes take flight, trembling en masse as they rise. Beneath the hull of our boat, the kelp and eelgrass beds are a nursery for salmon fry, the start of a life cycle that ends with adult fish returning to the river system, feeding a whole forest with the nutrients locked in their reddened flesh.

"Those very same bears we saw this morning have visited our snagging station," Darimont says. "We have their hair; we have their genetic code." I recall the four baited hair-snagging stations that I visited by boat with the field crew yesterday, as they dismantled the sites after completing the last sampling round of the field season. At each site, 25 meters of barbed wire stretches taught between trees at a level of 50 centimeters (the magic elevation apparently for getting snags from both little creatures that scooch under the wire and bigger beasts that step over it) forming a perimeter around a one-meter-high pile of brush drenched with a non-reward bait, a thick oily puree of rotted fish. Stand in the wrong place and the cloying smell of the bait decks your senses. I can only imagine how potent the aroma is when the stuff is freshly applied.

"Twelve days ago exactly we poured four liters of liquified fish, we call it our stink sauce, here," Darimont explained as the team got to work collecting the hair samples and dismantling the site. "Fun juice," Doug interjected, as he squatted on the forest floor to collect the hairs caught on the barbed wire. One hair on barb B7 was a bit thicker than the softer tufts of hair on the other barbs. "One nice guard hair," Doug said as he used his pliers to insert the hair into a tiny manila envelope.

Bear-hair bonanza
The guard hairs (coarse, outer protective hairs) are a bonanza of information. Not only can genetic work on them be used to identify individual bears, but the researchers can also run isotope analyses to determine how much of the bear's diet in the previous year came from salmon. One of the Raincoast biologists and graduate student at the University of Calgary, Heather Bryan, has worked out a way to collect trace amounts of hormones from the hair, which will determine how stressed the bears were in the previous year, for example.

"It always amazes me," Darimont remarked as Doug Brown brought out his micro-jet blowtorch to sterilize the barb for next year's field season. "These can be 200- to 300-kilogram animals and from less than a milligram of material we can get species, sex, individual, establish what they've eaten, and if they might be stressed. It's like CSI in the rainforest." Darimont hopes to continue the study for years and even decades to come, citing some of ecology's iconic studies that link predator and prey such as Charles Elton's hare–lynx study or the ongoing moose and wolf study on Michigan's Isle Royale, the longest running continuous study of a predator–prey relationship.

So far the "stink sauce" has lured in 29 individual grizzlies and 68 black bears over two years. Darimont and his crew also know, from isotopic analyses, that between 65 to 95 percent of their grizzly bears' diet is derived from salmon—a remarkable percentage considering that the salmon are around for a mere two to three months of the year. "It shows you how important that resource is and it gives you a hint of how much bloody salmon they eat!" he says.

Another really interesting early story emerging from RCF's bear hair study is how black bears and grizzlies compete and cordon off their own dietary niches. When black bears co-habit an area with grizzlies, they are largely vegetarian,  presumably deferring to the grizzlies' appetite for salmon. But black bears living on the inner islands, which are largely grizzly-free, eat far more salmon.

Pristine land
We've finally left the grizzly mother and her cubs behind. "These sort of experiences that we have had this morning carry us through, when it's a lot less sunny than this...or, worse, in the winter when we're in front of our computers," Darimont tells me over the roar of the wind on Wyatt, Raincoast's trusty 17-foot Olympic motorboat as we return to the RCF field station, located just across the water from Bella Bella, located on Campbell Island. "It's spell-binding to be in front of these animals in their home."

In a mere four days on the ground in the central coast, the wildlife tally includes many humpback whales (one of whose gaping maw rose out of the water, forming a shiny dark blue bath tub with water overflowing the sides), four grizzly bears, seals, sea otters and a pod of Pacific white-sided dolphins. It's a remarkable showing, but perhaps to be expected from one of the few remaining areas in the world with largely intact tracts of coastal temperate rainforest. As Coastwatch's Housty says: "The bears are telling us that we have pristine land and we need to keep it that way."

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