On Sept. 24, a U.S. District Court reinstated federal protections for grizzly bears in and around Yellowstone National Park, halting imminent hunts in Idaho and Wyoming in which up to 23 bears could have been shot. The decision not only highlighted the inherent difficulty in knowing how many bears roam the Greater Yellowstone Ecosystem, but also exposed the political pressures that may influence future counts.
Citing, in part, an increase in population, the U.S. Fish and Wildlife Service last summer declared the Greater Yellowstone grizzly population recovered. That announcement transferred management authority to state agencies in Idaho, Wyoming and Montana and paved the way for hunting outside Yellowstone National Park. Despite the boost in Yellowstone grizzly numbers (more than 700 today, up from as few as 136 in 1975), several tribal nations and environmental groups challenged the delisting in court.
Last week’s ruling, by Judge Dana Christensen of the District of Montana, restored the bears’ threatened status. Fish and Wildlife, he wrote, failed to consider how removing protections for Yellowstone grizzlies might harm other grizzly populations in the Lower 48 and misinterpreted scientific studies on the long-term genetic health of bear populations. Furthermore, he said, the agency erred by dropping a population provision from a plan developed with state and federal agencies in 2016, meant to guide management of Yellowstone area grizzlies after delisting. That provision would have required wildlife managers to “recalibrate” old population numbers were they to implement new estimation methods in the future.
The dropped provision represents an important tool for wildlife managers and biologists, who can’t simply count bears, but rely instead on estimates. That can produce misleading statistics when estimation techniques shift. For example, the method scientists use to monitor the Yellowstone grizzlies now tends to underestimate the population. So if state wildlife managers start using a new, more accurate method, it might appear as if there’s been a spike in the number of bears — unless the old estimates are recalibrated. Recalibration would help ensure that managers are comparing apples to apples: uncovering true trends in the population, not statistical glitches. Without it, critics say future hunts in Idaho, Wyoming and Montana could target hundreds of bears.
In his ruling, Christensen wrote that Fish and Wildlife appears to have omitted the recalibration provision from the 2016 plan because of political pressure from the states. Citing Fish and Wildlife employee emails, he wrote: “Because it was ‘the strongest agreement the service can get,’ the parties agreed that they would ignore recalibration and delete the ‘best available science’ requirement for changing the estimator.”
Christensen acknowledged agency claims that the emails were misconstrued and were evidence merely of debate over the provision. Fish and Wildlife has maintained that recalibration was dropped from the plan because the language surrounding its use was “too prescriptive” — so restrictive, in other words, that it might not be possible to do.
Meanwhile, although Yellowstone grizzlies are making a comeback, only an estimated 1,800 grizzly bears live in the Lower 48 today, just a fraction of the 50,000 or so that lived here before European colonization. How that estimate changes in the future depends on ecology, management and many other factors — including the way biologists take the tally.
If wildlife biologists switch the method they use to estimate how many grizzly bears live in and around Yellowstone but don’t recalibrate old estimates, it may look as though there’s been a surge in the population when in reality it hasn’t grown.