Ecological Studies of the Timber Wolf in Northeastern Minnesota Part 2

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_

#: _Number_ %: _Percent_

---------------------------------------------------:---------------------------- : : Net weekly : Net daily distances : distances :----------------------------------------------:---------------------------- : : : : :Mean net : : : : : : : : :distance : : : : : Days :Days no : Days :Mean net:per day : :Weeks:Mean net: Wolf: data : net :movement:distance:excluding :Range:data :distance: Range # :obtained:movement: :per day :days of no: : :per week: : : : : :movement : : : : :--------:--------:--------:--------:----------:-----:-----:--------:------- : # : # % : # % : Miles : Miles :Miles: # : 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 0.0-5.0 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 0.0-4.5 15 4.6 0.0-31.0 1059 26 1 4 25 96 2.5 2.6 0.0-5.6 18 2.9 0.0-4.6 ----:--------:--------:--------:--------:----------:-----:-----:--------:-------

Nevertheless, one major piece of information is obvious from the figures: 1059's pack of five wolves had a much smaller range than any of the other uninjured animals--approximately 43 square miles when figured by the minimum-area method (Mohr 1947). The next smallest range was that of 1051 (excluding the area of his later dispersal--see below), which was some seven times the size of the pack's range.

_Table 4.--Straight line distances (miles) traveled between consecutive days ("net daily distance") by radiotagged wolves in northeastern Minnesota during February 1969_

+-------+-------------------------+-------------------------+ Mean net Greatest net Wolf daily distance daily distance number +------------+------------+------------+------------+ Feb. 1-23 Feb. 23-28 Feb. 1-23 Feb. 23-28 +-------+------------+------------+------------+------------+ 1051 1.1 3.5 2.3 4.8 1053 0.7 2.5 3.0 5.0 1055 2.7 6.2 8.0 12.8 1057 1.0 1.5 4.0 4.5 1059 2.2 3.1 4.0 5.6 +-------+------------+------------+------------+------------+

There is little published information on the movements and ranges of lone wolves with which to compare our data. Mech (1970) summarized information regarding ranges of packs. Reported ranges varied from 36 square miles for a pack of two wolves in Minnesota (Stenlund 1955) to 5,000 square miles for a pack of 10 in Alaska (Burkholder 1959).

Considering only data based on intensive study in the same general region (Minnesota, Isle Royale, and Ontario) as our study area, the largest range reported was 210 square miles for a pack of 15 to 21 wolves on Isle Royale (Mech 1966, Jordan _et al._ 1967). On a per-wolf basis, the ranges in this region varied from 6 to 28 square miles per wolf. Our pack of five with its range of 43 square miles would have about 9 square miles per wolf.

A more accurate a.s.sessment of the ranges of the radiotagged wolves requires an individual discussion for each.

_No. 1051._--The range of 1051 was composed basically of three distinct areas (fig. 19). Within 10 days after being released, the wolf left the general area of his capture (Area A near Isabella Lake) and traveled to Area B along Highway 1, some 17 miles to the southwest. From December 9 to January 4 wolf 1051 remained in Area B, which covers about 45 square miles. Between January 4 and 6 he returned to Area A and stayed in 13 square miles until February 3. Between February 3 and 5 he s.h.i.+fted to Area C east of s...o...b..nk Lake, 11 miles northwest of Area A. He remained in that 16-square-mile area until February 25, then suddenly left and headed 8 miles to the northeast.

_Table 5.--Extent of ranges used by radiotagged wolves_

+--------+----------+----------+--------------+----------------------+ Wolf Greatest Greatest Total area[9] Area[9] of intense use number length width (before late Feb.) +--------+----------+----------+--------------+----------------------+ _Miles_ _Miles_ _Sq. miles_ _Sq. miles_ 1051[10] 28.5 13.6 318 13 (Location A[11]) 45 (Location B) 16 (Location C) 1053 31.1 22.0 392 31 1055 55.4 24.9 997 40 1057 32.3 3.8 77 14 1059[12] 8.4 8.0 43 39 +--------+----------+----------+--------------+----------------------+

FOOTNOTES:

[9] Minimum area method (Mohr 1947).

[10] Before dispersal.

[11] See text and figure 19.

[12] Pack of five.

[Ill.u.s.tration: _Figure 19.--Locations and range of wolf 1051. Lines are NOT travel routes; rather they merely indicate sequence of locations.

Only selected lakes are shown._]

From February 26 until April 24 the movements of 1051 were strongly indicative of dispersal (fig. 20). His average weekly straight line move during that period was 25 miles (compared with 6 miles per week before this period), and until March 14 he maintained an almost straight south-southwest heading to a location west of the town of Castle Danger. After that the animal traveled a series of northwest-southwest alternations that on April 3 took him east of Big Sandy Lake to a point 129 miles southwest of where he had begun the dispersal. There he remained for about 2 weeks, but between April 17 and 24 he traveled 26 miles northwest. We last saw him at 3:30 p.m. on April 24 heading northwest through a swamp 15 miles southeast of Grand Rapids, approximately 122 miles from where he had started. The total of straight line distances between 16 consecutive pairs of locations taken at intervals of from 1 to 8 days was 226 miles, which is the minimum distance the wolf traveled during his dispersal.

[Ill.u.s.tration: _Figure 20.--Dispersal of wolf 1051. Lines merely indicate sequence of locations. Only selected lakes are shown._]

We observed 1051 for distances of up to 5 miles during these travels; he maintained a steady trot that seemed faster than usual, and he appeared intent on heading in a straight line. He did chase deer during his travels, and twice was seen feeding on carca.s.ses. In the area where he remained for about 2 weeks, he was twice seen closely a.s.sociated with another wolf. This relations.h.i.+p will be discussed later.

An extensive search was made for 1051's signals on May 2 in an area of at least 50 miles radius from his last known location, but it was unsuccessful. On each subsequent tracking flight, the wolf's frequency was also monitored with no success. Possible explanations for the loss of the signal from this wolf include the following: (1) premature expiration of the transmitter, (2) capture of the wolf and breakage of the transmitter, (3) loss of the exposed antenna and consequent reduction of range, and (4) travel of the wolf out of range of the tracking aircraft.

During 1051's travels a number of interesting events took place:

Nov. 27, 1968--Captured and radiotagged

Dec. 4, 1968--Crossed road in front of tracking truck

Dec. 8, 1968--Moved to Area B

Dec. 9, 1968--Surprised on the ground at distance of 35 feet

Dec. 18, 1968--Chased by loggers with axes

Dec. 25, 1968--Almost shot by trapper who saw collar and withheld fire

Jan. 5, 1969--Returned to Area A

Jan. 13, 1969--"b.u.mped" twice on logging road by loggers in auto but no apparent injury

Feb. 4, 1969--Moved to Area C

Feb. 26, 1969--Began long-range southwest movement considered to be dispersal

Mar. 14, 1969--Seen feeding on old carca.s.s within 200 yards of houses, dogs, and a man walking

Mar. 27, 1969--Chased two deer across 4-lane State highway 53

Apr. 3, 1969--Found with another wolf at point farthest south in his range

Apr. 24, 1969--Last contact with this animal; was seen traveling NW

_Wolf 1053._--This wolf was basically a scavenger who subsisted for long periods on the remains of old carca.s.ses. She was known to have visited the remains of at least four deer and three moose, and she stayed near one moose carca.s.s from February 8 to 20, at least during the day. Between her date of capture, December 10, and February 28, 1053 traveled about in an area of 31 square miles in the Arrow Lake-Maniwaki Lake region (fig. 21).