September, 1943 Brown & YEAGER: 
velopment of extensive bottomlands. Scat- 
tered throughout are wooded limestone 
outcrops, frequently surrounded by blue- 
grass slopes. Although overgrazing is 
common, pasture management is fair in 
many instances. Cultivation is limited. 
Comparatively well vegetated soils release 
their waters slowly, giving rise to numer- 
ous small, clear streams. Deforestation 
has progressed somewhat less rapidly here 
than in most other places in Illinois, mak- 
ing for relatively good wildlife cover over 
much of the region. 
Western Prairie.—This is a fertile, 
rather low prairie area of 3,244 square 
miles, fig. 2. [he western border is the 
Mississippi River, along which there is 
local development of bluffs and bottom- 
land. Here, the prairie seemingly flows 
into the river at many points. Streams are 
small, and enough of them are intermit- 
tent to impair the quality of otherwise 
good muskrat and mink habitats. Woody 
cover is generally lacking. 
River Bluffs and Bottoms.—As a 
fur animal habitat this survey region, the 
only one not continuous, is perhaps the 
most interesting in the state, fig. 2. It 
contains 11,251 square miles, being ex- 
ceeded in size only by the black prairie 
and gray prairie areas. This region, figs. 
me ee 26, 27, 28; 29 and 30, deter- 
mined largely on the bases of drainage and 
topography, contains three main subtypes 
characterized, respectively, by (1) three 
large rivers, all fluctuating in nature; (2) ~ 
broken slopes or bluffs, which may be 
forested or partly cleared, and often pas- 
tured, leading down to bottomland; and 
(3) bottomland, timbered or cleared, often 
pastured and, in addition, often leveed. 
In all cases the bluffs are of limestone in 
varying stages of exposure and weather- 
ing. The region extends nearly the full 
north-south length of the state along the 
Mississippi River and through a number 
of counties along the southern half of the 
Illinois River. ‘The heaviest population of 
raccoons, opossums and gray foxes in the 
state occurs in this region, as would be 
expected in a forested area. This large 
region, as a whole, shows a comparatively 
low muskrat yield, although some of the 
better muskrat marshes in the state occur 
along the middle Illinois River. Deforest- 
ation, leveeing, turbid and polluted water, 
and severely fluctuating water levels tend 
SuRVEY OF FuR RESOURCE 44] 
to impair the quality of the river bluffs 
and bottoms for fur animal occupancy. 
Northwestern Sand Prairie—vThis 
region is a rolling sand prairie, rather 
well interspersed with marsh, fig. 2. The 
Fig. 3.—Relief map of Illinois showing main 
physical features of the state. (Print courtesy 
of the Illinois State Geological Survey.) 
area is 4,526 square miles. Numerous 
small rivers, creeks and drainage ditches, 
many of which run the year around, add 
to the quality of the aquatic habitat. Lack 
of uniformity in physical features charac- 
terizes the region; areas of fertile black 
soil, limestone outcrops, marsh and sand 
ridges are the most common formations. 
The irregularity is due to deposits left 
by different periods of glaciation, and to 
sheet wash from melting ice masses. Siz- 
able woodlands, chiefly of scrubby oak, 
supply some cover for raccoons. “The Rock 
River, the largest stream within the north- 
western part of the state, flows through 
the region. ‘The valley of this river and 
that of the Green River are the main 
