312 
tually reported. The oral survey data, 
as explained in the Brown & Yeager re- 
port, represent two seasons, cover 7 per 
cent of the area of the state and include 
within the strips actually surveyed all 
trappers, licensed and unlicensed, those 
who reported and those who did not. 
Despite numerical differences, correla- 
tions between the monthly report index 
figures and the oral report data, for both 
average catch per fur-taker and percentage 
of fur-takers catching a given furbearer, 
is such as to provide valuable information 
regarding trends in catch. 
The differences between the two sets 
of data are found to be largely in level, 
and similarities to consist chiefly of paral- 
lelisms. In other words, though differ- 
ences exist, positive correlations are found 
in figures from the two studies. 
Distribution Patterns of Furbear- 
ers.—In general, it is true that the size 
of the average catch per fur-taker of a 
given furbearer correlates closely with 
the size of the population of that furbear- 
er. After calculating for any furbearer 
species the average catch per fur-taker, 
we can transfer the resulting data to: a 
map in such a way as to give us a logical 
and useful graphic representation that is 
a good clue to combined dispersion and 
abundance of the animal. 
Such a map has been made for each of 
the common furbearers discussed in this 
study. hese maps are the best clues we 
have to the distribution pattern of fur-, 
bearers in all Illinois counties. On these 
maps, the calculated figures are converted 
into dots in such a way that the county 
having the largest average catch in a given 
species is most heavily dotted, and other 
counties are dotted proportionately. Each 
species is considered separately, and the 
maps do not indicate relative abundance 
as among species; for instance, although 
the distribution map for minks is about 
as heavily stippled as that for muskrats, 
these maps are not intended to suggest 
that the catch of minks is as large as that 
of muskrats. Eight seasons of fur-takers’ 
records are summarized on the maps, the 
first of which is shown in fig. 4. 
These distribution maps indicate to what 
extent one set of data (from the oral sur- 
vey showing average catch per square 
mile for two seasons) parallels or cor- 
relates with another set of data (from the 
Inuinois NaturAL History SURVEY BULLETIN 
V ol. 22, Aree 
fur-takers’ monthly reports showing aver- 
age catch per fur-taker for eight seasons). 
On these maps, oral report data are shown 
as numerals; as stated above, fur-takers’ 
written report data are represented by 
dots. Comparison of the two sets of data 
reveals a close correlation. 
It will be seen that the distribution pat- 
tern of no two species is exactly alike and 
in most cases is not even similar. Each 
species is a law unto itself in this matter. 
Its distribution does not conform com- 
pletely to any easily apparent physical or 
agricultural characteristic of the land, and 
management must take into account this 
lack of conformity. 
The scope of this study did not permit 
construction of separate dispersion and 
localized abundance maps, which would 
show facts that the distribution, or com- 
bined dispersion-abundance, maps do not 
portray: whether the furbearer popula- 
tions are widely dispersed and small, nar- 
rowly dispersed and small, widely dis- 
persed and large, or narrowly dispersed 
and large. From a management point of 
view, each of these cases is important. 
In constructing a dispersion map, we 
first calculate the percentage of fur-takers 
who trapped a given species in each coun- 
ty, or other relatively small geographical 
unit; then we transfer the data to a map 
by use of dots and find a logical and useful 
pattern showing what proportion of fur- 
takers in any given area caught that par- 
ticular species. Such a map furnishes a 
good clue to the dispersion of the fur- 
bearer. If, in a given area, only a small 
proportion of the fur-takers caught the 
species, there is every likelihood that this 
species was not so widely distributed as 
in some area in which a large proportion 
of fur-takers caught it. 
In constructing a localized abundance 
map, we first calculate for any given 
species of furbearer the average catch per 
effective fur-taker, transfer these data to 
a map by use of dots and again find a 
logical and useful pattern. A map of 
this kind will be somewhat different from 
the dispersion map because it will show 
not the proportion of fur-takers who 
caught the furbearer but the size of the 
average catch. Such a map furnishes a 
useful clue to the abundance of any fur- 
bearer in small, localized areas where it is 
present. If the average catch of a given 
