Geoscience Reference
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kitchen 10 percent (table 4.2). Manly-Chesson selection indices for these
rooms would be 0.51 and 0.40, respectively. Now suppose the person feels
cramped in the kitchen and moves a wall, making it twice as big, at the expense
of a room other than the bedroom. Afterwards the kitchen makes up 20 per-
cent of the area of the house, the same as the bedroom, but use of the kitchen
does not increase because it still takes the same amount of time to prepare and
consume meals there. The selection index for the kitchen thus drops to 0.25,
despite the fact that it is now more comfortable and better serves its purpose.
Moreover, although no changes were made to the bedroom, its selection index
improved to 0.63 as a result of the renovations to the kitchen. Superficially, it
would appear that the expense for remodeling was not worth it.
Analogously, one might imagine a situation in which an animal used a
habitat substantially more than its availability, but used it only for sleeping. If
that habitat became more available, the animal would not be expected to sleep
more, so its selection for it would appear to decline. A management agency
that produced more of this habitat because results of a habitat selection study
showed it to be used disproportionate to its availability would be disappointed
to find that these efforts made the animal's selection for it drop.
Table 4.2
Effect of Altered Availability (Floor Space) on Perceived Selection
of Rooms in a House
Manly-Chesson
Selectivity
Index
a
Manly-Chesson
Standardized
Index
b
%
Available
%
Used
Rooms
Before renovation
Kitchen
10
20
2.00
0.40
Bedroom
20
50
2.50
0.51
Others
70
30
0.43
0.09
After renovation
Kitchen
20
20
1.00
0.25
Bedroom
20
50
2.50
0.63
Others
60
30
0.50
0.12
This hypothetical example shows the nonintuitive result of diminished apparent selection for a
kitchen after it was renovated to create more room. Neither use nor availability of the bedroom was
changed, yet its standardized index increased after the kitchen was enlarged.
a
% Used /% available.
b
Selectivity indices standardized so that they sum to 1 (selectivity index divided by sum of selectivity
indices).
