Super Bowl Sunday was a quiet day for wildlife disease expert Mourad Gabriel. He and his wife, Greta Wengert, an ecologist, planned to watch the game, then peel off to do some work.
Their house, on the crest of a wooded knoll near the Northern California coastal town of Arcata, is open and sunlit. From the kitchen table where Gabriel often works, he can see the sloping backyard where the family's two boisterous Labrador retrievers loved to play.
One of the dogs, Nyxo, was rescued from a local shelter. The dog frequently kept the 39-year-old PhD company during his fieldwork, which includes studying the decline of the Pacific fisher — a forest predator, related to the weasel, that is a candidate for inclusion on the federal endangered species list later this year.
After the football game, the couple turned in. The next morning, Greta found Nyxo on the floor writhing in pain. Hours later, he was dead.
Gabriel drove the body to UC Davis to help perform a necropsy in a lab where he often worked. Pathologists opened Nyxo's chest and found it filled with blood — a clear indication that the dog had died from a particularly nasty "super-toxic" rat poison that Gabriel and colleagues had written about in 2012.
Their scientific paper had linked the toxin to the deaths of Pacific fishers. The creatures had eaten rodents poisoned by illegal marijuana growers across California, including those hidden in Humboldt County's lushly forested mountains.
In a county whose economy is driven by the marijuana trade, the findings made Gabriel a target. Comments on websites warned that "snitches wind up in ditches." An email inquiring about where he lived was traced by federal authorities to Mexico, suggesting that he had enemies among drug cartels.
Gabriel reported his dog's death to Humboldt County Sheriff Mike Downey. In the 13 weeks since, his department's investigation has yielded no leads. Despite a $20,000 reward, his deputies have gotten almost no cooperation from the public.
"We have an old-time saying in Humboldt County," Downey said. "'Our hills contain a lot of things we don't know about.'"
Gabriel's troubles have roots in a 2009 necropsy he performed on a Pacific fisher.
Beady-eyed and hatchet-headed, the animals have shortish brown fur with tufts of white. They are long and slender, the adults measuring up to 4 feet and weighing 5 to 13 pounds. Their hind legs can rotate nearly 180 degrees, allowing them to scamper down trees head first.
The necropsy was on an outwardly healthy young male, known as M05, whose carcass had been found high in the Sierra near Yosemite National Park. Gabriel and pathologists at UC Davis' California Animal Health and Food Safety Lab could see that it was not killed by a mountain lion or bobcat, responsible for most fisher deaths. And there was no sign of disease.
But when the team cut into the body, they found the chest and abdominal cavity brimming with blood. The fisher had lost nearly 80% of its blood.
The wildlife experts were mystified. Whatever led to this savage hemorrhagic response was like nothing they had ever seen.
Weeks later, lab results isolated the cause: a super-toxic rat poison banned for sale to the public.
Finding the poison in that first fisher set off alarm bells because the animals are in decline. The Pacific fisher population has dwindled to below 2,000 in two population clusters in the Sierra Nevada. How had the rodenticide found its way into a rare animal living in the middle of nowhere?
Feverishly working backward, Gabriel and the other pathologists retested tissue samples from every fisher they had collected since 2005. To their horror, nearly 80% tested positive for rodenticides. Some fishers had four or five types of poison in their systems.
Gabriel said pathologists did not find rat bait in the animals' stomachs. Rather, they had been exposed to the poison by preying on rodents that had eaten the bait.
Further, the scientists noticed a pattern of high mortality in early spring, when marijuana seedlings sprout and growers spread bait to kill deer mice and other rodents. Under federal Environmental Protection Agency restrictions, the super-toxics can be sold only to professional exterminators and employees of farms, warehouses and other commercial operations. However, the banned rat bait is readily available to anyone online.