When a signal was received, the aircraft was headed in the approximate direction of the source until the signal strength reached a peak; a 90° turn was then made in the direction the signal seemed the strongest. A series of these maneuvers soon narrowed the area to the point where visual search was possible. After practice and experience with this technique, we could locate the approximate source of the signal within 10 to 30 minutes after first receiving it.
Even though the radiotagged wolves spent most of their time inland, often in stands of conifers, they were frequently observed from the aircraft. The technique was to circle at 300 to 800 feet altitude around a radius of a quarter mile from the point where the strongest signal emanated. From December through April, 65 percent of the wolves located by radio were sighted; the rate was much higher for more experienced personnel. A pack of five wolves that was tracked was seen 31 times out of 33 attempts during February and March.
Whenever wolves were located, radiotagged or not, observations were made from an altitude that did not disturb them. Packs varied in the concern shown the aircraft, but only one or two ran from it. The radiotagged wolves, and a pack of 10 to 13 animals, were habituated to the aircraft and usually could be observed from altitudes of 500 feet and less without disturbance ([fig. 15]).
Almost all the radiotracking was done from aircraft, but when inclement weather prevented flying, some attempts from the ground succeeded when wolves were close enough to roads. The usual range on the ground was 0.75 to 1.50 miles. One wolf was approached to within 35 feet through radiotracking.
Figure 15.—The wolves studied soon became accustomed to the aircraft and could then be observed during their natural activity. (Photo courtesy of L. D. Mech.)
FOOTNOTES:
[1] Mention of trade names does not constitute endorsement by the USDA Forest Service.