According to Kelsall (1969), deer measure only 20 to 24 inches from hoof tip to chest, with legs extended.

It is true that wolves stand even shorter than deer and so might be expected to flounder even more. However, this is where another factor becomes important, the "weight-load-on-track" or total weight per area of track. As Kelsall (1969) has pointed out, the mean weight-load-on-track for deer is extremely difficult to measure directly, because the actual under-surface of the deer's foot slants vertically, and a much greater area may be used to support an animal in snow than on a hard surface. This probably explains the discrepancy between Kelsall's measurements and work done by Verme (1968) in Michigan. According to Kelsall, deer weight-load-on-track (hoof only) varies between 431 and 1,124 gm./cm.^2. However, Verme stated that his compaction gauge (with a weight load of about 211 gm./cm.^2, described earlier in this paper) sank in virtually the same amount in snow as did deer. Under the snow conditions in our study area, we found that the same type of compaction gauge generally penetrated to a depth within a half inch of that to which deer were sinking. On this basis, it seems reasonable to suggest that a deer in snow is supported by more of its foot than just the hoof, and that the actual weight-load-on-track of deer in snow is about 211 gm./cm.^2.

For wolves, this measure varies from 89 to 103 gm./cm.^2 (Foromozov 1946). This means that for the same amount of force applied during running, a wolf would have twice as much support as a deer. It also means that in deep snow a walking wolf generally is much less restricted than a walking deer. Late in February 1969, for example, when deer were seriously limited in their ability to travel, wolves were able to travel widely (Mech _et al._, p. 1).

Even though wolves have much greater support than deer, when running they still sink into the snow almost as much as deer under most conditions, probably because both run with such force that snow usually offers little support. Nevertheless, with extremely deep snow, the difference in support factor between wolves and deer could become critical, and this is probably what happened during February and March 1969. With deer seriously restrained by the deep snow, even a slight advantage in favor of the wolf could increase hunting success. A high snow density during that period would accentuate this advantage. This is because until the snow becomes dense enough to hold a running deer, each increase in density would further the advantage of the wolf, which would require only half the density to support it, while it would hinder the deer.

One result of the extreme snow conditions of early 1969 was that deer tended to gravitate to lakes, where snow was shallow and footing was firm. Initially upon disturbance by human beings, and probably by wolves, these deer usually headed inland, but it is apparent from a number of kills examined that when pressed hard by wolves inland, deer headed out onto lakes where possible. Apparently they could run there with better footing. However, frozen lakes also provide wolves with good running conditions, and even seem to give them an advantage (Rutter and Pimlott 1968, Mech 1970), so many of these deer were killed (fig. 11).

Stenlund (1955, p. 44) reported as follows on years of low snowfall, the opposite condition, which demonstrated the same relationship between snow depth and kills on lakes: "The winters of 1951-52 and 1952-53 were abnormally mild with little early snow. As a result, few wolf-killed deer appeared on the lakes and most deer attempted to outrun wolves in the woods."

[Ill.u.s.tration: _Figure 11.--On frozen lakes, wolves often seem to have the advantage over deer, such as in this case where the wolf (center) has just killed a deer and is trying to discourage a raven from joining him in the feed. (Photo courtesy of L. D. Frenzel_.)]

Thus it appears that extreme snow conditions in our study area increase the vulnerability of deer to wolf predation in three ways: (1) by causing a decline in the health and nutritional state of some members of the deer population; (2) by hindering the escapability of the deer; and (3) by causing deer to congregate on frozen lakes where wolves have the advantage in running.

SUMMARY

During the winters of 1966-67, 1967-68, and 1968-69, the interactions of wolves (_Canis lupus_) and white-tailed deer (_Odocoileus virginia.n.u.s_) were observed in northeastern Minnesota from aircraft.

Snow depth and supporting ability were also measured during these winters, and the ability of wolves to capture deer was compared for a period of usual snow conditions versus a period of extreme snow conditions.

It was found that during February and March 1969, when snow remained from 2.5 to 3.9 feet deep and failed to support running deer, wolves were able to capture deer more easily. This was evidenced by kills that were left partly or completely uneaten, and by a higher rate of predation by radiotagged wolves and their a.s.sociates.

Although both wolves and deer floundered in the extremely deep snow, the relatively lighter weight-load-on-track of wolves evidently gave them a greater advantage than under the usual snow conditions, when wolves were observed floundering more than deer. This factor, plus a decline in the health and vigor of some segments of the deer population and a tendency for deer to congregate on frozen lakes, where wolves have an advantage, help explain the increased vulnerability of deer to wolf predation during the winters of deep snow.

ACKNOWLEDGMENTS

This study was supported by Macalester College, the Minnesota Department of Conservation, the USDA Forest Service, the U.S. Bureau of Sport Fisheries and Wildlife, and the New York Zoological Society.

Pilots John Winship, Pat Magie, Jack Burgess, and Don Murray flew the observation planes during radiotracking. Miss Elizabeth Dayton, Mr.

Wallace C. Dayton, and the Quetico-Superior Foundation, all of Minneapolis, financed Mech during the writing of this report.

Thanks are also due L. J. Verme, J. P. Kelsall, and J. M. Peek for their helpful reviews.

LITERATURE CITED

Foromozov, A. N. 1946. The snow cover as an environment factor and its importance in the life of mammals and birds. (Moskovskoe obshchestvo ispytatelei priroda) Materialy k poznaniyu fauny i flory SSSR, Otdel.

Zool. n. 5 (XX). (Translation from Russian published by Boreal Inst.i.tute, Univ. Alberta, Edmonton, Alberta.)

Kelsall, J. P. 1968. The caribou. Can. Wildl. Serv. Monog. 3, 340 p.

Kelsall, J. P. 1969. Structural adaptations of moose and deer for snow.

J. Mammal. 50: 302-310.

Mech, L. D. 1966. Hunting behavior of wolves in Minnesota. J. Mammal.

47: 347-348.

Mech, L. D. 1970. The wolf: the ecology and behavior of an endangered species. 389 p. New York: Natural History Press, Doubleday.

Nasimovich, A. A. 1955. The role of the regime of snow cover in the life of ungulates in the U.S.S.R. Moskva, Akademiya Nauk SSSR. 403 p.

Pimlott, D. H., Shannon, J. A., and Kolenosky, G. B. 1969. The ecology of the timber wolf in Algonquin Provincial Park. Out. Dep. Lands and Forests Res. Rep. (Wildl.) 87, 92 p.

Rutter, R. J., and Pimlott, D. H. 1968. The world of the wolf. 202 p.

Philadelphia and New York: J. B. Lippincott Co.

Stenlund, M. H. 1955. A field study of the timber wolf (_Canis lupus_) on the Superior National Forest, Minnesota. Minn. Conserv. Dep. Tech.

Bull. 4, 55 p.

Verme, L. J. 1968. An index of winter severity for northern deer. J.

Wildl. Manage. 32: 566-574.

THE POSSIBLE OCCURRENCE OF THE GREAT PLAINS WOLF IN NORTHEASTERN MINNESOTA

L. David Mech and L. D. Frenzel, Jr.

The timber wolf (_Canis lupus_) of northeastern Minnesota occupies an area within the range given by Goldman (1944) for the eastern timber wolf (_C. l. lycaon_ Schreber). However, this area is within 150 miles of the eastern edge of the former range of the Great Plains wolf (_C.

l. nubilus_ Say), and there is some question as to whether the Minnesota wolf is really an intergrade between these two subspecies.

Writing of _nubilus_, Goldman (1944, p. 444) stated: "Specimens from eastern Minnesota and Michigan seem more properly referable to _lycaon_, but relationship to _nubilus_ is shown in somewhat intermediate characters."

In describing _lycaon_ as basically a gray wolf, Goldman made no mention of the occurrence of black or white color phases in that subspecies. However, in discussing _nubilus_, Goldman (1944, p. 442) wrote the following: "Many color variations are presented. Individuals may be nearly white at any season, except for a sprinkling of black hairs over the back, a small, narrow, but conspicuous, black patch over the tail gland, and a more or less distinctly black tip. Black individuals may occur in the same litter with those normally colored."

Goldman also referred to _nubilus_ as "now probably extinct."

[Ill.u.s.tration: _Figure 1.--A few wolves observed in the study area were jet black. (Photo courtesy of L. D. Mech.)_]

In the eastern part of the range of _lycaon_, color phases other than gray appear to be rare as Rutter and Pimlott (1969, p. 188) attest: "The uniformity of the color of timber wolves in many areas is evidenced by the work in Algonquin Park, in Ontario. There, over the past eight years, dozens of packs have been observed from the air.

However, we have never been able to discriminate between any of them on the basis of the color variation of individual animals."

Thus it seems significant to report on incidences of black and white color phases in wolves that we have observed in northeastern Minnesota during some 480 hours of flying a.s.sociated with wolf research (Mech _et al._, p. 1). The observations took place in the Superior National Forest, in northern Cook, Lake, and St. Louis Counties during the winters of 1966-67, 1967-68, and 1968-69. A total of 309 sightings were made of wolves that could be cla.s.sified by color; of these, 11 (3.6 percent) were jet black (fig. 1) and two (0.6 percent) were creamish white, with the cream color the most intense on the back. No doubt some of the grays, and perhaps the blacks and whites, were repeated observations, but the figures should provide a reasonable approximation of the incidence of these color phases in this area. All black or white animals except one were observed with gray wolves (table 1 and fig. 2).

A number of black wolves, and a few white wolves, have been seen by other observers, all in the three counties listed earlier. To gain some idea of the past incidence of these color phases in the same general area, we asked Conservation Officers Robert Hodge, Robert Jacobsen, and Frank Baltich of the Ely, Minnesota, area about the numbers of each phase that they took before 1960. They reported killing an approximate total of 580 wolves, of which four were black and three were white or creamish white.

_Table 1.--Observations of wolves of black and white color phases_

+--------------+-------------------------+--------------------------+

Date

Location

Color combinations

within each pack

+--------------+-------------------------+--------------------------+

Feb. 24, 1967 T64N-R8W-S1 Vera Lake 3 grays; 1 black; 1 white

Mar. 4, 1967 T63N-R9W-S27 Lake Two 3 grays; 2 blacks

Dec. 18, 1968 T63N-R8W-S35 Lake Insula 2 grays; 2 blacks[37]

Jan. 17, 1969 T65N-R8W-S27 Carp Lake 1 gray; 1 white

Feb. 1, 1969 T63N-R8W-S13 Lake Insula 4 blacks; 2 grays[38]

Feb. 5, 1969 T63N-R8W-S8 Benezie Lake 1 black

Feb. 6, 1969 T63N-R10W-S33 Clear Lake 3 grays; 1 black

+--------------+-------------------------+--------------------------+ FOOTNOTES:

[37] These animals were near the sh.o.r.e of the lake, so others may have been inland where they could not be seen.

[38] This group might well have been the same as that seen on Dec. 18, 1968.

[Ill.u.s.tration: _Figure 2.--A pack of four blacks with two grays (first and third). (Photo courtesy of John Winship.)_]

Because black and white color phases have rarely if ever been reported for _lycaon_, yet were well known for _nubilus_, it is not unreasonable to conclude that the race of wolves now occupying northeastern Minnesota does show strong _nubilus_ influence. Goldman examined the skulls only of 10 Minnesota specimens a.s.signable to _lycaon_ and only one referable to _nubilus_. Because wolves in the known range of _nubilus_ are thought to be extinct, and because the animals in northeastern Minnesota are legally unprotected and subject to a control program, it seems highly desirable that the question of their taxonomy be studied intensively while specimens are still available.