We can’t support any more bears. We’ve got bears coming out of our ears. We’ve reached carrying capacity. Such is the purported state of grizzly bears in Yellowstone.
Sound familiar? It should. For those of you who have been paying attention to the rhetoric relentlessly voiced by agency spokespeople for the last 6 years, you will have heard the refrain about too many bears in too little space over and over again. In fact, this claim undergirds much of the argument made by the US Fish & Wildlife Service (FWS) and state wildlife managers for removing ESA protections from Yellowstone’s grizzlies (which is to say, “delist” them).
This rhetoric emerged with a vengeance during 2015 when, in a conversation with environmentalists, then-FWS Director Dan Ashe emphasized that “the Yellowstone ecosystem just can’t hold any more bears.” Frank van Manen, leader of the Interagency Grizzly Bear Study Team (IGBST) soon followed with the quip: “we are packing more sardines in the sardine can.” The monotonous refrain has continued since then, most recently voiced (again) by van Manen at an April 2019 meeting of bear managers: “…I think we might have now reached the point where 100 percent [of suitable habitat] is occupied.”
If you were inclined to defer to the agency experts, you would probably heave a sigh and say, “well, I guess we just need to move ahead with delisting Yellowstone’s grizzly bears. We’ve reached carrying capacity.” In fact, that is the outcome that the agency experts probably hope for and expect.
But I would argue that there is cause to question the experts. In fact, there is an increasing and, to my mind, wholly justified tendency for the public to question experts, especially when there is reason to suspect that they are politically motivated. And there is ample evidence for political motivations behind what we are hearing from spokespeople for all of the agencies involved in managing Yellowstone’s grizzly bears, including the government’s scientists (for more see this webpage, this blog, and its sequel).
Unpacking the Sardine Can
To start, it is worth unpacking the concept of “carrying capacity” given that this term is being bandied about with such abandon by government scientists and managers. To listen to van Manen you would think that the number of grizzlies able to live in the Yellowstone ecosystem (i.e., “carrying capacity”) is a static food-related attribute of the land contained within a fixed box. In fact, this notion was codified in the since-overturned rule issued by the FWS during 2018 that removed ESA protections for Yellowstone grizzlies. In this document you can find a simple-minded figure showing a theoretical population of bears reaching a flat fixed line denoting “carrying capacity”—the kind of figure that would only pass muster during an introductory lecture of Wildlife Management 101 or with an impressionable public audience. Hence the sardine metaphor.
The truth could hardly be more different. Even accepting the notion of fixed boundaries, within those bounds the food-related capacity of any given acre varies from month to month and year to year. In fact, we’ve seen a long-term and sustained decline in the availability of high-quality foods that has almost certainly caused a decline in the intrinsic food-related capacity of Yellowstone’s core habitat to sustain grizzlies. Cutthroat trout have nearly disappeared; whitebark pine has been substantially reduced; and elk herds have declined, some dramatically. That’s three of the four legs of the food stool that has supported Yellowstone’s grizzly bears (the fourth leg is army cutworm moths). All of the evidence belies any claims, implicit or otherwise, that food-related carrying capacity is static. If anything, the sardine can has shrunk in size.
More importantly, carrying capacity is determined not only by the food-driven rate at which females produce cubs, but also by the rate at which grizzly bears of all description die. So, mortality is a major part of the equation. And guess what causes most deaths of adult grizzlies in Yellowstone? People do. So our lethality to bears is a big part of the carrying capacity equation, which comes down to our collective attitudes and behaviors and the extent to which they translate into dead bears. More on this a little later.
And the rate at which young bears (i.e., cubs and yearlings) die also matters. As it turns out, death rates of cubs and yearlings have increased substantially of late, primarily due to “natural” causes—including bears killing bears. Again, to listening to van Manen you would think that young bears in Yellowstone are dying in increasing numbers simply because of increasing densities of adult grizzlies, likening these adults to a bunch of equally lethal pinballs bouncing around according to some random Brownian motion in a fixed space. Too many damn sardines. More on this a little later as well.
The notion of fixed boundaries to an immutable box is a final major fallacy in the government’s “carrying capacity” argument. The capacity of Yellowstone’s ecosystem to support grizzlies is determined not only by the per acre abundance of foods and the unit area lethality of the landscape, but also by the extent of the area within which bears can live and contribute to the larger population. And clearly, this extent has increased substantially over time. We have grizzlies living in roughly twice the area we had them in the 1970s. Moreover, there have been multiple analyses, by government and independent scientists alike, showing that there is ample habitat with natural foods sufficient to support grizzly bears in places where grizzlies have not yet established themselves: the southern Wind River Range, the Palisades area, the Centennials, and more.
A Social Sardine Can?
And, yet, the FWS and its allies and minions claim that the box is fixed, invoking yet another pseudo-idea, that of “social carrying capacity.” More to the point, the FWS claims that there is no more space for grizzlies in Yellowstone because “people” will not accept them anywhere else. So now we have gone from the simplistic static, food-based, box of van Manen’s to a concept fielded by the FWS that begins to grapple, at least on the face of it, with the aspect of carrying capacity that relates to human attitudes and lethality.
But who are these “people” anyway, and who queried them, how? As it turns out, “people” amount to ranchers, outfitters, and others with enough political clout to bully not only state wildlife managers, but also the FWS. As a result, “social carrying capacity” has been defined by a few regressive energy executives as well as some sheep and cattle ranchers who don’t want to live with grizzlies, not by the people whom the agencies are supposed to be serving under the rubric of the public trust. “Social carrying capacity” turns out to be a convenient political ruse, not any sort of on-the-ground reality determined by the attitudes, choices, and behaviors of a wide range of relevant people. In fact, the sardine can could be a whole lot bigger.
The Density Ruse
So, let’s return briefly to the density issue, which is closely tied to the notion of carrying capacity and blithely invoked to explain rising deaths of young bears. Have grizzly bear densities actually increased, as van Manen claims? And, if so, are high densities the reason for increasing death rates among young bears? Well, the answers are No, and Probably Not.
As it turns out, the Yellowstone grizzly bear population has not increased to any extent during the last 17 years. It may have even been declining since 2007 (see some info on all of this here and here). At the same time, the distribution of this population has increased by over 40%. Ergo, density axiomatically decreased, not increased, which debars a connection between deaths of cubs and yearlings and densities of adults, as such. More likely, cubs and yearlings are dying in greater numbers because their moms have turned increasingly to eating meat (including livestock) to compensate for losses of whitebark pine and cutthroat trout. And meat-eating is an incredibly hazardous undertaking for any bear, especially those with vulnerable young (for more information, see this blog).
Putting this all together, we have a narrative being promoted by our government officials that is based on a simple-minded, poorly conceived, and highly-politicized notion of this thing called carrying capacity. Moreover, the government narrative is at odds with the best available evidence. All of this politicized spin being billed under the rubric of “science” is clearly designed to support the agenda of delisting Yellowstone’s grizzly bears.
Interestingly, this tradition of scientized politics and politicized science dates back decades among IGBST scientists. Richard Knight, then-Leader of the IGBST, co-authored a paper published during 1996 in which he claimed that the mid-1990s population of 350 grizzly bears “…may be approaching carrying capacity.” Notice that this is half the current estimated population size. Not coincidentally, this 1996 paper was published during the first attempted run-up to removing ESA protections for Yellowstone grizzly bears. There is a clear political logic behind the history of claims regarding carrying capacity—but not a scientific one. Scientifically, there is no more reason now to think that we’ve reached “carrying capacity” with roughly 700 grizzlies than there was when we had nearer 350 bears.
Out of the Sardine Can
In fact, what we have is a picture altogether different from that being painted by government managers and scientists. We have a box with highly fungible and potentially much expandable boundaries within which we have experienced major declines in food-related carrying capacity, but within which, also, we’ve increased carrying capacity due to major beneficial changes in human attitudes and behaviors—related to increased law enforcement, increased sanitation, other controls on human foods, and reductions in livestock, especially sheep. Bear densities have declined, at the same time that distributions have expanded and grizzlies have turned to eating alternative foods, many of which are concentrated on the peripheries of the current ecosystem. This is not a sardine can being crowded by ever greater numbers of sardines.
But perhaps the most important point is one that features us—and what goes on between our ears. History has shown that perhaps the most important determinant of the numbers of grizzly bears that can live in any given area is our behaviors, in turn rooted in our worldviews—how we see ourselves in relation to the world and to the creatures in it. There is no doubt that our European ancestors saw no place for grizzlies in the world. And they proved it by killing 99% of all grizzlies in 98% of all the places they once lived. But we are not our ancestors.
We have the chance to create a world where grizzlies and people coexist in places where we probably can’t even imagine it is possible. But, it is possible. Grizzlies have proven that they can tolerate us and live among humans with few problems. The famous mother grizzly of Pilgrim Creek, bear #399, is one among many that has proven the point (for some more information on her, see this web page). It comes down to us, and the grace and compassion we can bring to coexisting with grizzly bears.
Dr. van Manen, ex-Director Ashe, and all who invoke the over-tired metaphors of sardine cans and other hard-edged boxes and boundaries are wrong. We can have more grizzly bears in the Yellowstone ecosystem—and beyond. And we should have.