The Wonderful Wizard and His Dancing Grizzly Bear Numbers
The Wizard of Oz is a great story full of the classic characters and elements of a good fantasy. A hardy troupe of protagonists, aided by a self-proclaimed powerful wizard, embarks on quest beset by an evil witch. The 1930’s Hollywood derivative of this story was one of my favorite movies as a kid. CBS aired the show annually during 1959-1967, which meant that each year my family gathered around our modest-sized black and white television with (of course) a tub of popcorn to watch Dorothy and her companions defeat the Wicked Witch of the West.
One interesting aspect of this story is the allegorical journey undertaken by Dorothy and her friends through which they arrive at a more empowered and confident sense of themselves. Tellingly, this evolution triangulates against, first, their dependency on and, then, their unmasking of the (mostly good-hearted) Great and Powerful Wizard of Oz, who turns out to be a charlatan, a salesman, and the owner of a useful hot air balloon. The climax comes when Toto, Dorothy’s dog, pulls back the curtain of the antechamber to the Wizard’s audience hall to reveal a very human man industriously pulling levers and chains to generate the intimidating façade of a great wizard.
Frank Baum wrote the Wizard of Oz stories partly for pure entertainment, but also partly as an instructive metaphor. Without delving into Baum’s metaphorical aspirations, I see some of my own.
Hopefully without stretching a point too far, The Wizard reminds us about the perennial plight of citizens in a democratic society. We frail humans are all too often seduced by the self-proclaimed and culturally-enshrined wizards of our day, to whom we look for wisdom, answers, and direction. At least in the U.S., these “wizards” include scientists, technocrats, and other experts who we ascribe privileged access to mystical insights and powers. But, of course, the moral is that a vibrant democracy requires that we empower ourselves through self-education and a healthy level of skepticism that includes periodically peeking behind the curtain to see who is pulling what levers and why.
Which brings me to my point. There are currently a number of government officials industriously pushing and pulling on levers and chains, veiled by their self-proclaimed expertise, shrouded in a cloud of bureaucratic smoke--preaching a seductively simple story about Yellowstone’s grizzly bears. And the story is clearly intended to support removal of federal Endangered Species Act protections and transfer management authority to the states of Wyoming, Montana, and Idaho.
A Just-So Bedtime Story
In a nutshell, this is their story.
The Yellowstone grizzly bear population has grown and grown until there isn’t any more room for any more bears. The population has reached carrying capacity. The hotel is fully booked, the sardine can is full. And, of course, this burgeoning of bears is almost wholly due to the efforts of the hero-protagonist technocrats—our figurative all-powerful wizards. Changes in the natural environment—changes in abundance of foods—had nothing to do with it. After all, grizzly bears are resilient omnivores that can just as easily subsist on salad greens as on steak.
As part of this story, the government’s ordained scientific experts assert that they assiduously looked at the potential effects of foods…well, actually, food. Which is to say, they looked at the effects of changes in abundance of a single food source—whitebark pine trees (a source of fat-rich seeds)—and found nothing. Trees were being decimated by bark beetles but the rates at which grizzly bears died didn’t change, barring that of young bears that were being killed by mean older bears that they were randomly bumping into more often because there were so many more bears running around on any given acre. In other words, if there were changes, they were solely because of increasing densities of bears.
As a corollary, the government’s technocrats claim that “carrying capacity” is fixed and unchanging for Yellowstone’s grizzly bears. The population has increased to this food-determined level and has been hovering there since; hence, the more-or-less static death rates that the scientists claim to have documented—even including a decrease in death rates for male bears. And, of course, the argument depends on accepting that grizzly bears are indifferent to changes in quality and quantity of foods—including the foods from which they historically obtained over 80% of their energy and nutrients. Yellowstone’s grizzlies were presumably unaffected by the virtual extirpation of cutthroat trout, loss of over 70% of seed-producing whitebark pines, and 50-90% declines in the ecosystem’s elk herds. Never mind that government scientists didn’t even bother to look for an effect of elk or trout losses—or a millennial drought, or major increases in bear consumption of army cutworm moths (another important food) for that matter. Grass and dandelions and mushrooms will presumably do just fine.
Well. Yes. Ahem. Probably not.
Now for the Rest of the Story
The just-so story being promulgated by government technocrats--most notable the Interagency Grizzly Bear Study Team (IGBST) and the US Fish & Wildlife Service's recently retired Chris Servheen--fails on just about every count. The government’s simple-minded and convoluted reckonings of carrying capacity and nutritional ecology are, well, simple-minded and convoluted. Carrying capacity—that is, the food-determined capacity of any given acre to support a bear—clearly varies enormously from one season or one year to the next. It fluctuates all over the place. Moreover, carrying capacity can exhibit long-term upward and downward trends.
There is good reason to believe that carrying capacity for grizzly bears within the confines of Yellowstone’s Primary Conservation Area has actually declined, probably substantially so. Grizzlies historically got most of their energy and nutrients from elk, bison, cutthroat trout, whitebark pine seeds, and army cutworm moths. As I mentioned immediately above, we lost a significant amount of all these foods—barring moths—and, as it turns out, livestock. If Yellowstone’s grizzlies are up against carrying capacity, it probably has more to do with them bumping their figurative heads against a ceiling that’s collapsing on them.
And then there’s the notion that one food is as good anther, sold under the rhetorical billing of “resilience” and “omnivory.” As one omnivore talking to another, it is patently ridiculous to claim that we can do just as well on salad as we can on steak, or even on rice and potatoes—or to claim the same for grizzly bears. Burke and Wills, the famous European explorers of the Australian outback, managed to starve to death while feasting on an aquatic fern called nardoo. Interestingly, there are some people who are willing to believe just about anything offered up by the technocrats.
Including a Look at the Data
But in addition to the intrinsic implausibility of the government’s story, there are publicly-available data by which one can independently judge the story’s veracity. These data include annual estimates of grizzly bear population size, reckonings of population distribution, tallies of grizzlies known to have died, and estimates of abundance for all of the important foods, whether direct measures or proxies. And when you look at these data, a radically different picture emerges.
Starting with the easiest point: The government does claim (mostly) that Yellowstone’s grizzly bear population hasn’t increased much or at all since the early 2000s. So we have nearly as many bears now as we did, say, 15 years ago. Of course, at times you will hear claims of 2% per annum increases, typically whenever convenient. But this doesn’t change the fact that the latest “official” claims are of no increase. Actually, the best available estimate of trend based on the best available estimates of population size show no change or, if there is change, a slight increase from 2002-2006 and then a slight decrease thereafter. I show these population trends based on what’s called the Mark-Resight method in figure 1 below.
Interestingly, during the same time that numbers of bears were static, the population’s distribution increased by 30-40%, mostly to the east and southeast into Wyoming. The key point here is that the same number of bears ended up being spread out over an ever-larger area beginning in the early 2000s. Axiomatically, population-level density declined (number of animals divided by the extent of their distribution). So density couldn’t have increased. Density as such, especially increasing density, doesn’t explain anything.
So let’s look at what’s been going on with known and probable deaths of grizzly bears in the Yellowstone ecosystem. Trends in these numbers are enlightening in their own right, but especially intriguing when compared to numbers of live bears. This kind of comparison gives you a direct indication of what’s been going on with death rates (death rate is essentially numbers of deaths divided by numbers of live bears for a given period of time).
I show these trends in figure 1 immediately below as well. The red wavy lines are a smoothed representation of deaths, with females shown at top and males at bottom. The black dashed and dotted line represents annual estimates of population size. Notice the stark increase in deaths of both males and females during the same time that population size remained more-or-less flat. Ergo, death rates of both males and females must have been increasing dramatically, especially from the mid-2000s on—which flatly contradicts the government’s assertion that death rates have remained the same, or, in the case of males, even improved. How can this be? I don’t know, but I’m inclined to believe some pretty straight-forward and robust data more than obscure and closely guarded complex models promulgated by a chosen few technocrats.
Figure 1. These graphs show numbers of known and probable grizzly bear deaths in red, differentiating females (top) from males (bottom), this for bears 2+ years old. The light gray line shows annual values in contrast to the red lines which show a 3-year moving average. Total population estimates are shown by the black dots and dashed line fit to a trend indicated by the thick gray line. A trend line is also fit to numbers of deaths for the period 2002-2011, a period when the government claims that death rates were stable or improving.
It seems especially egregious that the government asserts stable or improving death rates at the same time that the grizzly bears deaths we know about were increasing at a rate of 9-11% per annum—during 2002-2011. This is an astounding rate of increase.
If you accept what seems obvious, that we’ve had major increases in grizzly bear death rates, at the same time that the surviving bears were spreading out over a larger area, then the question becomes: Why? If density is not the explanation, what is?
I think the answer emphatically has to do with foods—and the extent to which consumption of those foods exposes bears to people. And exposure to humans matters because roughly 80% of all adult bears that die do so because a human kills it—especially humans with bad attitudes and guns.
I put together the trends relevant to this point in figure 2. There are three graphs, each showing trends in total numbers of dead bears (the top red lines) superimposed on trends in an important food; elk on the left, cutthroat trout in the middle, and drought (as a proxy for a number of other vegetal foods) on the right. I don’t show abundance of whitebark pine seeds, but I’ll get around to that shortly. Parenthetically, the lower red line tracks numbers of bears dying from natural causes, with the remainder attributable to humans.
Figure 2. This triptych of graphs each repeat the same trend lines for total grizzly bear deaths (the top red line), differentiating those from natural causes (bottom red line). The gray lines show trends in numbers of elk in the ecosystem (left), numbers of cutthroat trout in Yellowstone Lake (middle), and levels of drought (according to the Palmer Drought Index, inverted).
The trends are striking. Deaths started to increase at about the same time as we began to see major declines in trout and elk numbers. The sharp uptick in deaths starting around 2007 further correlates with major declines in availability of pine seeds (you can see trends in availability of pine seeds as dotted lines in figure 3 below). We can explain over 70% of the annual variation in numbers of grizzly bear deaths in Yellowstone simply on the basis of food availability. As simple as that, and in stark contradiction to the government’s assertion that food has played no role.
A Plot Twist Related to Whitebark Pine
There is an another key point to be made about the effect of whitebark pine losses in all of this. Grizzly bears made a major shift to eating more meat as compensation for losing pine seeds—and meat is an energy-rich nutritious food. But there are two big problems with meat. First, wild meat on the hoof has declined substantially (e.g., elk), which leaves bears scrambling for other sources. Second, meat is a particularly hazardous food for bears when it brings them into contact with hostile and well-armed people…which is precisely what’s happened since roughly 2007.
Figure 3 shows trends in numbers of grizzly bears killed by humans because of conflicts associated with meat (the red dots), with numbers killed by big game hunters in the top graph and numbers killed because of conflicts over livestock in the bottom. Parenthetically, hunter kills have increased at the same time that numbers of hunters afield have declined (the gray dots), with lethal encounters often arising from surprise encounters or because bears are contesting possession of an hunter-killed elk. So there is no particular mystery about where bears are increasingly turning to find meat; its livestock, largely on the ecosystem’s periphery, in areas only recently colonized by bears. Because they are looking for food? Probably. And do the government technocrats even acknowledge a connection between loss of pine seeds and the hazardous consequences of eating more meat? Of course not. It doesn’t fit the just-so story.
Figure 3. This graph shows trends in numbers of grizzly bears killed (the red dots) in conflicts with hunters (top) and over livestock (bottom). The gray dots at top further illustrate the declining numbers of hunters afield in Yellowstone and the pink dots at bottom, numbers of livestock-related conflicts, as such. The black dotted lines illustrate the terminal decline in abundance of whitebark pine seeds that began around 2007.
So I have one final and important point to make about whitebark pine. The government’s anointed researchers in the IGBST claim to have accounted for availability of whitebark pine seeds in the science they’ve been pumping out during the last 5 years or so. They haven’t. In fact, they messed up their representation of whitebark pine seed availability so badly that it renders their analyses nonsense.
The problem is simply this, and it consists of two parts. First, the most straight-forward part: Their map of whitebark pine distribution misses roughly 60% of the places where we know for a fact that grizzly bears ate pine seeds. The map was generated from satellite data whereas the information on where bears ate pine seeds was collected by people standing on the ground. I know which I would believe.
But the second fatal problem is that the government’s scientists confused pine trees with pine seeds. Or, put another way, grizzly bears don’t eat trees, or leaves, or bark, they eat pine seeds. This distinction is hugely important because pine cone (and seed) crops vary enormously from one year to the next—even with the same number of trees out there. The government failed to account for this simple fact and, instead, represented availability of “whitebark pine” as a satellite-reckoned estimate of the extent of whitebark pine forests in the ecosystem, declining as a presumed function of the massive kills by bark beetles that commenced in the early 2000s. They didn’t account for size of the cone crop and, as it turns out, we had a pine cone drought during a period of maximum whitebark pine forest extent, and a relative abundance of pine seeds during a period of major bark beetle kills. The surviving trees were producing roughly twice as many cones. Why? Who knows, but the fact remains.
The point of this is that the government got their reckonings of pine seed abundance ass backwards in pretty much all of their analyses simply because they conflated the aerial extent of whitebark forests with annual abundance of seeds. In other words, aside from all of the other paradoxes, contradictions, and problems I describe, the government failed to actually accomplish the single task they set themselves.
A Story for Thinking Adults
So, here is a more plausible and alarming story…
Carrying capacity in the Yellowstone ecosystem is declining, and has declined since the mid-1990s, triggering a spread of the grizzly bear population out over an ever-larger area in search of food. Declines in carrying capacity, largely in the core of the ecosystem, commenced with losses of elk and cutthroat trout, were amplified by a period of drought during 1999-2009, and further escalated by declines in availability of whitebark pine seeds beginning around 2006. These losses triggered an increase in death rates that has been amplified in recent years by an increasing reliance of bears on meat in situations that bring them into contact with intolerant and well-armed people. As a consequence, the population has reached a tipping point. Future prospects are not good.
This is a population of grizzly bears that’s in trouble. Now is not the time to lessen protections and contemplate any increases in mortality—certainly not to accommodate the crass motivations of those who want to trophy hunt Yellowstone’s grizzly bears. And, in case you missed it, our state wildlife management agencies are pretty much slaved to the purposes of such people.
It is time to draw back the curtain...