Part 9

That lone wolves had more of a food surplus than those in the pack is confirmed by the figures on the average number of days that the various wolves fed on kills (table 7). Wolf 1051 spent an average of only 2.2 to 2.4 days feeding at each of his kills, whereas 1059's pack of five spent an average of 5.8 to 7.5 wolf-days at each kill. Further confirmation is found in the fact that even when most wolves were leaving their kills partly uneaten, a pack of 8 to 10 wolves (probably that to which 1057 belonged) was seen completely devouring a kill.

Table 7.--Kill rate of deer by radiotagged wolves and their associates

#: Number

-------------------------------------------------------------------------- Wolf-days Wolf Wolf-days Wolf-days Wolf-days feeding # Wolves Dates of data Kills per kill feeding per kill -------------------------------------------------------------------------- # # # Mean # # Mean #

1051 1 Nov. 26 to 101 14-16 6.3-7.2 33-40 2.2-2.4 Apr. 3

1053 1 Dec. 14 to 75 2-3 25.0-37.5 9-18 4.5-6.0 Mar. 27

1055 1-2 Jan. 9 to 61 4-9 6.7-15.0 13-25 2.8-3.3 Mar. 14

1057 1-13 Jan. 24 to 51 5-7 7.3-10.2 25-33 4.7-5.0 Feb. 28

1059 5 Jan. 25 to 180 10-13 14.0-18.0 75 5.8-7.5 Mar. 14 -------------------------------------------------------------------------- Summary 22 Nov. 27 to 468 35-48 9.8-13.4 145-181 3.8-4.1 Apr. 3

Before 142 7-9 15.7-20.3 39-56 5.1-5.6 Feb. 1

After 326 28-39 8.4-11.6 106-125 3.2-3.8 Jan. 31 --------------------------------------------------------------------------

FOOTNOTES:

Kill rate per wolf.

Figures for this animal are so low because she was basically a scavenger.

Average kill rate per wolf for all radiotagged wolves and their associates, derived by dividing total number of wolf-days by total number of kills.

Average number of days that each wolf spent at each kill, derived by dividing total number of wolf-days spent feeding by the total number of kills.

This figure probably is the closest to the actual kill rate during most winters.

Therefore it is probable that the kill rate per wolf for members of the pack of five is much closer to the usual average winter kill rate. It can still be considered higher than the usual winter rate, however, because this pack also was leaving some of its kills partly uneaten.

A reasonable approximation of the average kill rate during most winters would be the rate found for our radiotagged wolves before February 1, because the relations among the wolves, the deer, and the snow during that period were not unlike those of most winters. The average kill rate per wolf before February 1 was estimated at one deer per 15.7 to 20.3 days.

After this period, the rate increased to about one deer per 8.4 to 11.6 days, and an estimated 50 percent of the available food was left uneaten (see Mech et al., page 51). This implies that the kill rate during February and March was about twice as high as usual. On this basis, the usual kill rate would be estimated at one deer per 16.8 to 23.2 days, which checks well with the rate found before February (one deer per 15.7 to 20.3 days). Thus we feel that an estimated kill rate of about one deer per 18 days per wolf is a close approximation of the average kill rate for most winters. This is about 50 percent less than the kill rate of one deer per 4 days estimated by Stenlund (1955) for two packs of three wolves (one deer per 12 days per wolf). However, it compares favorably with the actual kill rate of one deer per wolf per 17.6 days found for a pack of eight wolves in Ontario.

Once the average rate of kill is known, the average food consumption per wolf can be calculated. The average deer (considering both fawns and adults) from the Superior National Forest during winter weighs about 113 pounds (calculated from Erickson et al. 1961), and an arbitrary 13 pounds can be deducted from this for inedible portions. This leaves 100 pounds of deer per wolf per 18 days, or 5.6 pounds per wolf per day. This figure is much less than the 10 to 14 pounds estimated consumption rate for wolves feeding on moose on Isle Royale (Mech 1966a). However, much variation can be expected in an animal whose physiology must be adapted to a feast-or-famine existence.

Wolves can be maintained in captivity on 2.5 pounds of meat per day, and large active dogs (Canis familiaris) require 3.7 pounds per day, so it is likely that the minimum daily requirement for wolves in the wild is about 4.0 pounds per day (Mech 1970). This figure agrees well with the estimated consumption rate for our study area.

FOOTNOTES:

Kolenosky, G. B. Wolf movements, activities and predation impact on a wintering deer population in East-Central Ontario. (Manuscript in preparation for publication.)

Relative Population Density

Censusing wolves in a 1.5-million-acre study area is a difficult task, and we have no direct information on which to base a population estimate. However, some deductions can be made about the relative population densities in our study area between the period 1948 to 1953 and the period of the present study, 1967 to 1969.

R. A. Rausch (1967a) hypothesized that the frequency of large packs is higher when population density is high, and presented evidence supporting this idea. On this assumption, a comparison of pack-size distributions between various periods can indicate relative population densities between periods. The advantage of this method is that it eliminates the usual type of year-to-year biases in wolf censuses such as might result from differences in precise census route, type of aircraft, skill of observers, and other conditions. Only a difference that would cause a bias in the size of the packs seen would be of importance.

Therefore, we tested the difference in size distributions of population units between the 1948-53 study period and the present period (table 1), using a Kolmogorov-Smirnov two-sample test (Siegel 1956). The average "pack" size in the earlier years was 2.8, compared with 4.2 at present; thus pack sizes are significantly larger at present (95 percent level). This indicates that the population density from 1967 to 1969 may have been higher than from 1948 to 1953. This apparent change may be attributable to a reduction in snaring, trapping, and aerial hunting that took place between the two periods as a result of changes in State game regulations.