446 
a result, the region affords considerable 
upland game cover, but the limited and 
undependable water supply greatly impairs 
the aquatic habitat. During recent years 
the Gray Prairie region has been exploited 
for coal, and at present it is being appre- 
ciably disturbed by an oil boom. Mine 
and oil residues are polluting some of the 
streams. Woodlots and larger timbered 
areas are scattered throughout the region. 
Sampling Methods 
For each of the fur survey regions one 
or two typical counties were selected as 
samples. In all, 10 sample counties were 
surveyed, fig. 11. The River Bluffs and 
Bottoms and the Gray Prairie regions 
were represented by two counties each. 
Across each county from three to nine 
strips, each 1 mile wide, were laid out in 
Fig. 11—Map showing the counties sampled 
in the Illinois fur resource survey. Shown also 
are the main rivers and watersheds and di- 
vides (broken lines). 
ILLINoIs NATURAL History SURVEY BULLETIN 
Vol. 22, Art. 6 
an east-west direction, and every house- 
hold in this area was canvassed in gather- 
ing the sample data, fig. 12. From 11.23 
to 22.48 per cent of the counties made 
A -— FUR SURVEY REGION 
B — COUNTY SAMPLED 
C — SAMPLE STRIPS, 
EACH | MI. WIDE 
Fig. 12—Map showing the relation of three 
sample strips and county to fur survey region. 
The position of Lee County is outlined. 
up these samples, representing from 0.67 
to 9.68 per cent of the total area of the 
regions and 1.70 per cent of the total area 
of the state. These data are given in detail 
in table 1. 
‘The east-west direction of the strips 
tended to strike the streams at right angles, 
thus eliminating the error that would have 
resulted from following a stream or valley, 
comparatively productive of furs, for a 
long distance. In every case the strips 
extended the full east-west dimension of 
the county and insofar as physically possi- 
ble were straight. County road maps were 
used to good advantage in establishing the 
strips and in locating residences or in re- 
