Telemetry
Four gray foxes, two males and two females, were captured. Each was fitted with a radio-
Figure 2.
Error polygons were computed by first calculating confidence limits (95%) for
bearing means (
intersection. Each fix was then expressed as the intersection of bearing means
(
polygon. The dimensions 2mx and 2my represent the 95% confidence range
associated with the fix along the X and Y axes respectively.
[4] Source listings of all Fortran IV computer programs are included in Hallberg (1974).
telemetry collar and monitored from 25 March through 27 July 1973. The effective telemetry range varied with atmospheric conditions, but the system usually performed well when within 0.16–0.8 km. (0.1–0.5 mi.) of the subject. Under ideal conditions signals were received from distances exceeding 1.6 km. (1 mi.).
Diurnal resting places were located with a three-element, hand-held yagi antenna and Davidson Model W portable receiver. All triangulation data were collected using a vehicle-mounted broadside array, consisting of two vertically polarized 3-element yagi antennas. The array pivoted from a television mast which also supported a Suunto compass from a projecting arm (Hallberg etal . 1974).
Each subject's location with respect to time was determined from field bearings, recorded to the nearest 0.5° of direction, being determined in the following manner:
1) two to five bearings were made in rapid succession and recorded from a predetermined station in the subject's vicinity;
2) the telemetry vehicle was quickly driven to an adjacent station where a second series of bearings was taken.
The entire procedure required two to five minutes to complete and was similar to the technique employed by Ables (1969) and Trapp (1978). During field observations, an attempt was made to locate two or three subjects every 30 minutes (mean = 34 minutes; range = 4 to 282 minutes; n = 1,094). It was not feasible to locate all subjects every 30 minutes because they were frequently too far apart.