WALKER: HABITAT USE BY RACCOONS


 To obtain the requisite sample sizes necessary for habitat-use analysis, radio-
tracking effort was designed to ensure that a minimum of 50 locations was
obtained on each of at least 20 radio-collared animals (Allredge and Ratti 1986).
Raccoons were located during the daytime one or more times a week. During
nighttime tracking sessions, one to four individuals were located every two hours
throughout the night. Each raccoon was followed all night at least once every two
months. Approximately 40% of locations on each animal were collected at night
and 60% were daytime locations. Data for nine radio-tagged animals with fewer
than 50 locations were excluded from the habitat-use analysis.


 Habitat Availability


 A habitat map of the area was created by digitizing habitat contours from
1":200' aerial photos (Florida Department of Transportation, 1989) using the
ERDAS (Version 7.5, ERDAS, Inc., Atlanta, GA) geographic information system.
 The digitized maps were converted into the ARC/INFO (Version 3.4D,
Environmental Systems Research Institute, Redlands, CA) geographic information
system format for editing and manipulation. Universal transverse mercator (UTM)
reference points were obtained at the Ordway using a Magellan Global Positioning
System (GPS) to get UTM coordinates of known locations visible on the aerial
photos. The ARC/INFO map was transformed to UTM coordinates with a root
mean square (RMS) error of 0.015 with six reference points. This indicates that
the coordinates calculated for any given point should be within 15 m of the true
coordinates.
 Habitat-type composition of individual home ranges of the 20 raccoons
located 250 times was determined by overlaying the minimum convex polygon
(Mohr 1947) of each raccoon with the ARC/INFO habitat map. Minimum convex
polygons (MCP) were calculated with program HOME RANGE (Ackerman et al.
1990), converted into ERDAS format using HOME22 (S. Breneman unpubl.
program), and then into ARC/INFO format using ERDAS's conversion program.
Lake areas were subtracted from the MCPs and proportions of different habitats
available were based on non-lake land area. The boundaries of the study area were
defined by an MCP calculated from all locations of the 20 raccoons combined.
Habitat-type composition of the study area was determined by converting this
polygon into ARC/INFO format in the manner described above, and overlaying it
with the habitat map (Fig. 1).


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