Movements and Range
Wolf movement is greatly hindered by deep, soft snow, so during winter travel, wolves frequently use areas where they sink into the snow the least. In our study area, frozen waterways are used extensively where possible, just as reported by Stenlund (1955). Where few lakes or rivers exist, wolves follow railroad beds and logging roads, often soon after a plow or other vehicle has driven on them. In cutting cross country through deep snow, wolves travel single file and tend to stick to windblown ridges and to trails of deer and moose. Wolves that have ranges small enough to cover in a few days form a network of their own trails, which they can maintain merely by traveling regularly over them. Packs on Isle Royale depended a great deal on such a system of trails (Mech 1966a), and so did Pack No. 1059 in our study area.
Wolf packs can travel up to 45 miles in a day but it is usually larger packs that do so (Stenlund 1955, Burkholder 1959, Mech 1966a, Pimlott et al. 1969). In our study area we sometimes saw evidence of long moves by large packs along strings of lakes and waterways. However, most of our movement data pertain to lone wolves and a pack of five. The daily travel of these animals was usually much less than that reported for large packs.
Our radiotracking data provide an index to the extent of travel for each wolf rather than the actual amount of travel, for it is based on straight line distances between consecutive points at which an animal was found. This measure will be referred to as the "net daily distance."
Much variation was found in the net daily distances of wolves, with the longest ranging from 4.5 miles for 1057 to 12.8 for 1055 ([table 3]). The mean net daily distance for each animal, excluding days with no net movement, varied from 1.5 to 3.6 miles. The movements of these wolves may have been affected by the snow depth and penetrability, for mean and maximum net daily distances suddenly increased for all animals between February 23 and 28, when snow penetrability had decreased to a point where walking wolves would be expected to sink in only about 6 inches ([table 4]). Other possible explanations for the wolves' sudden increase in movements will be discussed below.
The straight line distances traveled between consecutive weekly locations (called the "net weekly distances") showed a similar variation ([table 3]). The maximum net weekly distance for each wolf varied from 4.6 miles for 1059 to 49.0 for 1055, with means ranging from 2.9 to 15.6 miles for the same wolves. No doubt 1059's net weekly distances were relatively short because her total range and that of her pack were much smaller than those of the other wolves.
It is difficult to obtain comparable measures of the extent of the ranges covered by each of the radiotagged wolves because their patterns of travel varied so much. Thus the figures given in [table 5] should be regarded only as gross indicators of the minimum range of each animal. The area figures are especially deceiving in the case of 1055, for she had a horseshoe-shaped range, much of which apparently was not used.
Table 3.—Straight line distances (miles) between consecutive locations of radiotagged wolves
| Wolf number | Net daily distances | Net weekly distances | |||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|
| Days data obtained | Days no net movement | Days movement | Mean net distance per day | Mean net distance per day excluding days of no movement | Range | Weeks data | Mean net distance per week | Range | |||
| Number | Number | Percent | Number | Percent | Miles | Miles | Miles | Number | Miles | Miles | |
| 1051 | 54 | 13 | 24 | 41 | 76 | 2.0 | 2.6 | 0.0-12.0 | 22 | 12.7 | 1.0-46.0 |
| 1053 | 37 | 20 | 54 | 17 | 46 | 1.0 | 2.1 | 0.0-05.0 | 23 | 6.3 | 0.0-23.6 |
| 1055 | 46 | 7 | 15 | 39 | 85 | 2.9 | 3.6 | 0.0-12.8 | 21 | 15.6 | 1.7-49.0 |
| 1057 | 29 | 11 | 38 | 18 | 62 | 1.0 | 1.5 | 0.0-04.5 | 15 | 4.6 | 0.0-31.0 |
| 1059 | 26 | 1 | 4 | 25 | 96 | 2.5 | 2.6 | 0.0-05.6 | 18 | 2.9 | 0.0-04.6 |