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Grizzly Bear Extirpations

Extirpations final figures with captions

This series of maps shows extirpations of grizzly bears in the western United States between 1800 and 1960. Grizzly bear distribution at each time step is shown in green along with the cumulative area of extirpations in yellow. An estimate of total grizzly bear population size (plus or minus one standard deviation) and distribution (in square km) is also given, along with the cumulative percent loss of both bear numbers and distributions as percentages of the 1800 total. The thermometer graphs at the outside margin of each map provide a visual snapshot of how much of the 1800s population had been lost at the end of each time step. Parenthetically, the gray in each map shows areas that are probably too hot and dry to support grizzlies. The reddish-brown area in (B) shows the area dominated by the Comanche, who probably contributed to the early demise of grizzlies on the southern Great Plains.

Extirpations in the Contiguous United States
Extirpations final figures with captions

This series of maps shows extirpations of grizzly bears in the Northern U.S. Rocky Mountains between 1900 and 1970. The areas occupied by grizzlies at each time step are shown in green. Estimated numbers of bears within each population are also provided for each time step, with estimates for the 1930s coming from Game Reports published by the US Forest Service during this time period. 

Areas in orange within maps (A) and (B) are shaded proportional to human densities at each time step estimated from US Bureau of Census reports. The dashed lines in (A) and (B) delineate a wild remote area with very low human densities in central Idaho where grizzly bears were extirpated at an anomalously rapid rate. The reason for this anomaly probably has something to do with spawning salmon (see the map at right). The distribution in the 1910s is taken from a contemporary map published by C. H. Merriam and from accounts in William Wright’s 1909 book “The Grizzly.”

Extirpations in the Northern Rockies
The Salmon Factor
Extirpations final figures with captions

The map immediately above shows the distribution of grizzly bears in the US Northern Rockies circa 1930 (in green) relative to the distribution of surviving salmon and steelhead spawning runs (in pink). The distribution of spawning salmonids coincides with the area in central Idaho where grizzlies were extirpated in a wild and remote area—depsite low human densities. The explanation for this juxtapose probably has to do with the fact that spawning salmon attracted bears to specific places at specific times along lower-elevation riparian corridors, which is also where most humans were active during the late 1800s and early 1900s. This anomalous juxtaposition exposed grizzlies to highly lethal people who clearly took full advantage of the opportunity to kill bears. For more on this see William Wright’s 1909 book “The Grizzly.”

Figures (A) and (B) show the pace and cumulative toll of grizzly bear extirpations in Mexico and the western United States between 1800 and 1980. Graph (A) shows estimated numbers of grizzlies over time in the western U.S., with median estimates shown by the dark green line and bounds of uncertainty by the lighter green band. Graph (B) shows the number of local extirpations by decade as pink dots, with the trend shown as a light red line. The period of greatest local extirpations was clearly between 1880 and 1940—a brief 60 year period. The white and gray dots in (B) show total numbers of resident people in different regions of the West, suggesting that extirpations accelerated hard on the heals of rapid increases in populations of European settlers. The map in (C) shows dates and locations of known local extirpations, with the circa-1800 distribution of grizzlies shown in lighter green and the circa-1910 distribution shown in dark green. The area dominated by the Comanche during the early 1800s (Comancheria) is shown in light orange, coincident with where grizzlies had been extirpated by 1850 on the southern Great Plains.

The Last Grizzlies
Extirpations final figures with captions
Extirpations final figures with captions

The map above shows in green the total current distribution of the phylogenetically unique Clade 4 grizzly bears in North America relative to, in yellow,  the distribution of this Clade  circa 1800. Roughly 95% of these genetically distinct bears were extirpated by European settlers in Canada, the United States, and Mexico between 1800 and the 1970s. The only other place on Earth where Clade 4 bears survive is as a small population on the Japanese island of Hokkaido.

The Lost Clade
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