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Scat-Sniffing Dogs Nose Out Clues to Caribou Decline

22 June 2011 11:00 am
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Center for Conservation Biology

Picking up the scent. Conservation Canine, Marvin, and his handler search for caribou, moose, and wolf scat in Alberta.

Dogs trained to sniff out scat have helped researchers solve a mystery in western Canada: What's driving woodland caribou to the brink of extinction? Their findings reveal that human activities are the key reason for the caribous' troubles, not wolves, as some researchers had suspected. Moreover, the diligent dogs turned up enough scat to indicate that there are almost twice as many caribou in the region than previously reported.

"It doesn't mean the caribou aren't in trouble," says study leader Samuel Wasser, a conservation biologist at the University of Washington, Seattle. "But it does mean we have more time to come up with a solution, one that doesn't involve pulling out the wolves."

Normally, wildlife biologists radio-collar some animals in a caribou herd to track them and use aerial surveys to count their numbers. But Wasser, who has used detection dogs in other conservation studies (for example, to find the roosts of northern spotted owls and to monitor the population of grizzly bears in Jasper National Park), thought the canines could do a better job. Over three winters, four trained dogs and their handlers surveyed a variety of habitats in a 2500-square-kilometer area in western Alberta. The dogs were asked to alert their handlers by sitting next to the spot where they had sniffed out the scat of a caribou, moose, or wolf.

Altogether, the dogs identified 1914 caribou, 1175 moose, and 327 wolf scat samples, Wasser's team reports this week in Frontiers in Ecology and the Environment. The cold temperatures (at times as low as -10°C) meant that the samples were well-preserved. In the lab, Wasser and colleagues analyzed the caribou and moose scat for stress hormones. They also extracted DNA from the droppings of all three species, identifying individual animals—an analysis that led the researchers to conclude that in 2009 there were 330 caribou in this region, not the 90 to 150 animals previous studies estimated. The team also estimated that 387 moose and 113 wolves call this part of Canada home.

Most significantly, the scientists found that the wolves are not eating many caribou. "Eighty percent of their diet is deer," Wasser says. "Only 10% comes from caribou." The other 10% is from moose they kill.

As for the caribous' overall health, Wasser's study shows that the closer the herds are to actively used roads and oil-exploration crews, the higher their nutritional and psychological stress levels are. Because this region is rich in oil sands, caribou are encountering more vehicles and humans in the winter as oil-exploration and development activities surge. Stress levels decrease and the caribous' nutrition improves when humans leave the areas during the springtime thaw, when the soft, boggy ground makes work difficult, the study shows.

"The caribou prefer flat, open areas, where they can see and hear potential predators, although that isn't where their preferred food [lichen] is found," Wasser says. "Security is more important to them than food nutrition." The caribou would even bypass lichen-rich areas that are near active roads.

Wasser's report is scoring high marks for its innovative approach among conservation biologists. "Using the dogs is brilliant in terms of efficiency and expediency, and it's noninvasive," says Fiona Schmiegelow, a conservation biologist at the University of Alberta in Canada who is based in Whitehorse, Yukon. "It's intriguing how they've used this method to gather a whole range of data—identifying individuals, habitat selection, population size, stress, physical condition, and diet composition," adds James Estes, an ecologist at the University of California, Santa Cruz.

To try to stop the caribou decline, some researchers have proposed exterminating the region's gray wolves. But "since the wolves are eating deer primarily, and not caribou, [wildlife managers] may end up just substituting one problem for another" if the wolves are removed, because the deer population will likely explode, says William Ripple, an ecologist at Oregon State University in Corvallis.

Instead of killing the wolves, Wasser suggests that the oil-development companies consolidate their activities and build roads in areas that the caribou dislike, such as the upland areas where deer hang out. "He's absolutely nailed it," Schmiegelow says. "But sadly, the reason people advocate for predator control is that controlling humans is considered even more extreme." And with the oil sands in this area billed as the second-largest reservoir in the world, she says that it's likely that "dollars will swamp anything else."

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