As they say, a picture is worth a thousand words. With that in mind, I refer you to the maps and photos above. They pretty much say it all. Directly or indirectly, Europeans were responsible for slaughtering perhaps 99,000 grizzly bears over a 150 year period, resulting in the extirpation of grizzlies in roughly 98% of their western range within the contiguous United States. The four maps above offer snapshots of grizzly bear distributions at four different times. The distribution of extant bears is shown in green and the distribution of extirpated bears is denoted by yellow. The time periods illustrated in these maps correspond with the time of first sustained contact with Europeans (1800), fifty years later in the aftermath of the first wave of westward European migrants (1850), a time when numerous populations were winking out (1910), and at the culmination of extirpations, just prior to when grizzly bears were declared Threatened by the US government (1970). The map of distributions circa 1910 is thanks largely to the record-keeping of C. Hart Merriam, who was the head of the US Division of Biological Survey between 1886-1910, during which time he oversaw a number of surveys that documented the last grizzlies remaining in the West. In addition to documenting the demise of grizzlies, he also gifted us by naming 83 "species" of grizzlies in North America, none of which have stood the test of time (see Evolution). Note that grizzlies were extirpated first in the southern and central Great Plains, a topic that I return to below.
There is no mystery about why Europeans were so lethal (see The lethality factor). Killing grizzlies was both informal and formal policy. Essentially no bear survived contact with an armed European. Moreover, the federal government mounted a taxpayer supported campaign to exterminate grizzly bears (and other carnivores) in the West starting in 1914 with the formation of the Predatory Animal and Rodent Control (PARC) Branch of the Biological Survey. In addition to hounds, set-guns, and traps, PARC agents used lots of poison. The basic ethos was informed by Manifest Density and the derived imperative to cleanse the earth of any obstruction to the settlement and "civilization" of an ever-diminishing wild West. Grizzlies weren't the only victims. The rogues gallery above (below the maps) gives testimony to the widespread and enthusiastic slaughter. A couple of exemplars include George A. Custer (far left in the middle of the group) and Ben Lilly (second from right), who was a notorious (famous?) killer of bears in Arizona and New Mexico. David Brown and Tracy Storer and Lloyd Tevis provide detailed histories of the demise of grizzlies in their respective books covering the Southwest ("The Grizzly in the Southwest") and California ("California Grizzly").
The map at right provides a bit more detail on the timing of grizzly bear extinctions, with a focus on the period between 1850 and 1970. The locations of regional extirpations--or at least the last kown grizzlies--are given along with the year it occurred. I've summarized this information in the inset graph to the lower right which shows a smoothed frequency distribution (in red) for extirpations. You can see that there were two major peaks centered on roughly 1890 and 1920, and a late minor peak centered on 1950-1970, representing the last holdouts in particularly rugged and remote areas such as central Idaho. Most of the early extirpations were along the western edge of the Great Plains, immediately post-dating the demise of the bison.
You will also notice that I've shown trends in the size of European (i.e., "censused") populations in three regions of the West. All three trend lines tell much the same story of rapid increases between 1880 and 1900 (the Homestead era) coinciding with the first peak of grizzly bear extirpations. This was followed by a plateau in growth on the Plains (the circles with dashed line) and sustained population growth elsewhere.
Driver's of extirpation
Clearly, much of the dynamic that drove grizzlies to near extinction in the West had to do with what was going on between people's ears. Which had a lot to do with culture and up-bringing (i.e., The lethality factor). But aside from this perhaps dominant consideration, there were factors that either accelerated or slowed local extirpations. Several of these factors pertained either directly or indirectly to features that either attracted grizzlies to people or kept them (more-or-less) safely sequestered away.
The figures at left show relations between the likelihood that grizzlies would have persisted in a given area (the vertical or y-axis) and features of that area that either accelerated or slowed extirpation (the horizonatl or x-axis). Of all the factors that I considered, the extent of whitebark pine habitat, the extent of grizzly bear range in the surrounding area at the beginning of a transition, and densities of (European) people were most closely related to persistence of grizzly bears. These relationships are shown left to right, for two different time periods: 1850-1920 in the top panels, and 1920-1970 in the bottom panels.
The strong negative relationship between persistence of grizzlies and densities of people (the red dots) doesn't require explanation. The positive relationship of persistence to extent of local distributions at the beginning of a transition period (gray dots) relates in a straight-forward way to the idea that, if you start with more, you're more likely to end up with something. But the positive relationship between persistence and whitebark pine not only requires a bit of explanation, but also broaches an important topic when it comes to understanding the survival of bears anywhere in the world. Put simply, grizzlies were more likely to survive in areas where key food resources kept them out of harms way, that is, away from armed people with bad attitudes. Conversely, foods that tended to concentrate grizzlies near people and in ways that made them vulberable, tended to die out. So, back to whitebark pine. The tree is an important source of bear food. It also lives at high elevations in rugged mountains. Hence, bears that made substantial use of pine seeds found a safe haven and tended to survive. By contrast, grizzlies that fed on spawning salmon in the Pacific Northwest, or berries and bison carcasses on the Great Plains, all tended to concentrate along rivers and streams, which were precisely the areas that were settled earliest and used most heavily for transport by newly arrived Europeans. Hence, bears in these areas disappeared relatively quickly, and sometimes despite the prevalence of wilderness conditions in the surrounding uplands.
I conclude this section on the direct effects of Europeans by examining proximal, or fine-scale, drivers of risk for grizzly bears. The bar graph immediately above summarizes the results of combing through a large number of journals and other texts attributed to various European explorers or settlers. The horizontal length of each bar corresponds to the number of instances where one of these Europeans observed a grizzly engaged in a particular kind of feeding activity on or near the Great Plains. The most common was scavenging on a bison carcass, which is a reflection of the extent to which bison were a key food of grizzlies on the Great Plains (see The bison factor). Second to this was consumption of plum and chokecherry fruits in riparian areas. But notice the number of instances where the observed activity involved meat or other food associated with people--livestock, dirty camps, or the remains of animals killed by hunters. Here, we see a foreshadowing of current dynamics. Clearly, a non-trivial number of encounters beween grizzly bears and Europeans was organized around human-associated foods. No doubt these foods lured grizzlies near Europeans, almost invariably ending in the death of the bear. As is currently the case, human-related attractants were a huge problem for grizzly bears.
The First Peoples factor
In thinking through all of the factors that might have contributed to driving the 1800s-1900s extirpations of grizzlies, I ended up speculating on a possible role played by First Peoples. Before getting into the details of this possible effect, it is worth reiterating that the ultimate driver of all destructive dynamics was self-evidently the arrival and spread of Europeans and their markets and technologies. So, with that in mind, the maps immediately above show the spread and adoption of horses and guns by First Peoples. Horses were introduced by the Spanish conquerors, perhaps as some minimal compensation for the extent of their atrocities. Guns largely eminated from trade with the French, English, and successor American entrepeneurs--all greedy for profits and indifferent to harm. The delimiting lines mark the extent of the area within which First Peoples had adopted horses and guns as part of their lifeways. The map above left intersects the diffusion of horses with that of guns, and identifies areas where both had been integrated by 1750 and 1790. The timing and delineation of diffusions is thanks to Francis Haines, Frank Secoy, J.C. Ewers, and D.E. Worcester. The basic point is that guns were (more-or-less) diffusing from the east, and horses from the southwest. Both were adopted earliest by First Peoples in the central Great Plains, and by essentially all Tribes on the plains by 1790.
In the figure above right I overlay the areas within which guns and horses had been adopted by First Peoples with the distribution of grizzly bears around 1850, which is roughly when the earliest extirpations occurred on the Great Plains. I would argue that the less productive conditions of the southern plains predisposed grizzly bears to over-exploitation or harvest. It is easy (at least for me) to imagine First Peoples on newly acquired horses and, following that, with newly acquired guns, being more lethal to grizzly bears than they had ever been before. I don't show it here, but Comancheria, the domain of the dominant Comanche and their Kiowa allies, spatially coincides with the earliest demise of grizzlies--well before Europeans were around in any numbers. This is in the southern plains of New Mexico, Oklahoma, and Texas--also the least productive environment of the Great Plains for bison and grizzly bears (see The bison factor). Parenthetically, the first half of the 1800s predated major effects linked to the bison hide market, which I address immediately below.
As I elaborate in The bison factor, availability of bison was almost certainly a major factor driving population dynamics of grizzly bears on the Great Plains. Which is to say that the decline and extirpation of bison populations during the mid- to late-1800s undoubtedly also helped drive grizzly bears to local extinction.
The graphs at left summarize factors that were probable drivers of bison extirpations: drought, the adoption of horses and guns by First Peoples, the arrival of emigrant Europeans, and the emergence of the European-driven bison hide market. The latter three factors are denoted by horizontal bars in shades of burgundy at the top of each timeline at left. The blue trend lines show estimated levels of drought (or, the opposite) in three regions of the Great Plains, from north (top) to south (bottom) derived from the work of Zhihua Zhang and his colleagues. I've also demarked periods of more-or-less sustained drought in each region by vertical orange bars. Bison population fluctuations on the Great Plains during the Holocene have been conclusively tied to grassland productivity, which has been, in turn, linked to rainfall and the prevalence of less nutritious C4 verus C3 grasses.
There are some lines of evidence suggesting that major declines in regional bison herds began as early as the 1830s and 1840s. Andrew Isenberg has perhaps the most informative and compelling account of the demise of bison in his book "The Destruction of the Bison,' which contains themes that had been previously articulated by Dan Flores in his seminal paper "Bison ecology and bison diplomacy." There is solid evidence that a number of plains Tribes fully participated in the bison hide market established by Europeans several decades before European hide hunters arrived in any numbers to deliver the death blow to bison. There are suggestions of not only surplus killing of bison by First Peoples for hides, but also local declines of bison in areas where this surplus killing was most intense. One notable example is along the Missouri River in present-day South Dakota. Early declines of bison herds here have been implicated as one of several drivers that displaced some Siouan tribes west in the mid-1800s (see below).
There are a couple of noteworthy synergies evident in these graphs. Perhaps most intriguing is the coincidence of the heaviest bison hide-hunting with sustained periods of drought on the northern and southern plains--but most notably in the north. Given the link between bison population dynamics and moisture, it is likely that declines in productivity of female bison exacerbated the already catastrophic effects of hide-hunting during the 1860s and 1870s..
The map above highlights a final factor of potential relevance to understanding the fates of grizzly bears during the 1700s and 1800s--the long-range movements and considerable flux of Tribal boundaries. The European invasion of North America set in motion a myriad of dynamics that affected every living thing on the continent. As I've described above, these dynamics included the descimation and displacement of First Peoples. But there was an interesting dynamic behind this phenomenon: that of Tribes who benefitted from the early acquisition of either guns or horses being displaced by Europeans or other Tribes, moving, and then displacing other Tribes in turn. The end result of this progressive falling of dominos was an almost complete replacement of the original Tribes living within the eastern half of grizzly bear range by the 1700s and early 1800s.
So, getting back to the map. I've tried to summarize a lot of information, including: the European names and estimated boundaries of Tribes around 1850; whether the Tribes on the Great Plains were primarily sedentary (in green) or nomadic (in brown); the estimated migration routes taken by these Tribes primarily during the 1700s (by gray arrows); and settlements of the Apache and Padouca that predated the arrival of Tribes who had recently been mounted on horses. Just a note: the Tribal boundaries are probably well-accepted by most who are interested in such things. The migration routes are another matter. The lore of most Tribes represents each as living in a particular area since the creation of time--or since many generations before. On the European side, various scholars have various interpretations of where different Tribes originated and how they moved. I will not vouch for the final verdict of any account, but the evidence assembled by European scholars convinces me that a highly dynamic situation occurred during the 1700s and early 1800s. Whatever the migration route, Tribes were moving around a lot and displacing and even descimating other Tribes. And all of this was accompanied by heightened inter-Tribal conflict which probably began with population increases that predated the arrival of Europeans (see The human factor), but with the dynamics between 1700 and 1900 triggered by the onslaught of Europeans.
What does this mean for grizzly bears? The feature of most relevance to bears is probably the wide brown dashed lines in the map above. They denote what some scholars have called "war zones," which were presumably so contested that the only people venturing there were war parties. Andrea Laliberte and Bill Ripple popularized this notion based on their analysis of the spatial distribution of First Americans and wildlife documented by the Lewis & Clark expedition along the Missouri River. I've extracted the portion of their map (included above) that shows the First Peoples villages (dark brown dots) and wildlife sightings (proportional to the width of the red line) summarized from Lewis & Clark's journals. The basic point is: wildlife were more abundant in areas more sparsely occupied by First Peoples, especially those who were nomadic, as well as in areas that were violently contested by neighboring Tribes (i.e., War Zones). As it turns out, most of Lewis & Clark's sightings of grizzly bears also occurred in these relatively human-free zones. Riffing off of the Laliberte and Ripple thesis, it may have been the case that grizzlies benefitted, both directly and indirectly, by the heightened warfare among Tribes that occurred during the 1700s and early 1800s. The zones of particular relevance to grizzlies would have been those around the Blackfeet, Crow, Pawnee, and Arapaho Tribes. How much confidence do I place in this hypothesis? Well...it is largely speculative and supported only by circumstantial evidence. As the Eighteenth-Century English would say, I wouldn't stake my wig on it. But the hypothesis seems plausible.