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USDA FOREST SERVICE RESEARCH PAPER NC-52 1971

Ecological Studies of the TIMBER WOLF in Northeastern Minnesota

NORTH CENTRAL FOREST EXPERIMENT STATION FOREST SERVICE U. S. DEPARTMENT OF AGRICULTURE

FOREWORD

The largest population of timber wolves remaining in the United States (excluding Alaska) lives in northern Minnesota. Many of these wolves inhabit the Superior National Forest, so protecting the habitat of this endangered species is largely a Forest Service responsibility.

As the "Age of Ecology" broadens into the 1970's, wolves and wolf habitat will become a subject of concerted research. Forest land managers will have to know more about how the timber wolf fits into a forest system. Building on nearly 50 years of research in northern forests, we at the North Central Station intend to expand our studies of wildlife habitat. We are happy to publish the enclosed papers as one step in this direction.

D. B. King, Director

North Central Forest Experiment Station D. B. King, Director Forest Service--U.S. Department of Agriculture Folwell Avenue St. Paul, Minnesota 55101

ECOLOGICAL STUDIES OF THE TIMBER WOLF IN NORTHEASTERN MINNESOTA

L. David Mech and L. D. Frenzel, Jr. (Editors)

CONTENTS

Movements, Behavior, and Ecology of Timber Wolves in Northeastern Minnesota L. David Mech, L. D. Frenzel, Jr., Robert R. Ream, and John W. Winship 1

An Analysis of the Age, Sex, and Condition of Deer Killed by Wolves in Northeastern Minnesota L. David Mech and L. D. Frenzel, Jr. 35

The Effect of Snow Conditions on the Vulnerability of White-Tailed Deer to Wolf Predation L. David Mech, L. D. Frenzel, Jr., and P. D. Karns 51

The Possible Occurrence of the Great Plains Wolf in Northeastern Minnesota L. David Mech and L. D. Frenzel, Jr. 60

THE AUTHORS

Dr. Mech, formerly with the Department of Biology, Macalester College, St. Paul, Minnesota, is now employed by the U.S. Bureau of Sport Fisheries and Wildlife, Twin Cities, Minnesota.

Dr. Frenzel, formerly with the Department of Biology, Macalester College, St. Paul, Minnesota, is now employed by the Department of Entomology, Fisheries, and Wildlife, University of Minnesota, St. Paul, Minnesota.

Dr. Ream, formerly with the North Central Forest Experiment Station (maintained in cooperation with the University of Minnesota), Forest Service, U.S. Department of Agriculture, is now employed by the School of Forestry, University of Montana, Missoula, Montana.

Mr. Winship is with the U.S. Bureau of Sport Fisheries and Wildlife, Twin Cities, Minnesota.

Mr. Karns is with the Minnesota Department of Conservation, Forest Lake, Minnesota.

For sale by the Superintendent of Documents, U.S. Government Printing Office, Washington, D.C. 20402

MOVEMENTS, BEHAVIOR, AND ECOLOGY OF TIMBER WOLVES IN NORTHEASTERN MINNESOTA

L. David Mech, L. D. Frenzel, Jr., Robert R. Ream, and John W. Winship

The largest population of wolves (_Canis lupus_) remaining today in the continental United States outside of Alaska is in northern Minnesota. As of mid-1970 this population was not legally protected, and the species, which once ranged over almost all of North America, is now considered by the U.S. Department of the Interior to be in danger of extinction in the contiguous 48 States. Until the present research, the only field studies of Minnesota wolves were those of Olson (1938 a, b) and Stenlund (1955). Those investigations provided much useful general information about Minnesota wolves and gave the present authors an excellent background with which to begin more detailed investigations.

This paper reports on the basic aspects of a series of studies that began in 1964, and concentrates primarily on wolf movements and activity, social behavior, hunting behavior, and population organization. Most of the data were collected during January, February, and March 1967; February, November, and December 1968; and January through August 1969. A total of 192 days was spent in the field.

According to a distribution map of wolf subspecies (Goldman 1944), the race of wolves in our study area is _Canis lupus lycaon_. However, evidence presented by Mech and Frenzel (see page 60) suggests that there may be strong influence by _C. l. nubilus_, a more western race of wolf formerly thought to be extinct (Goldman 1944).

Between 1965 and the present, wolves in the study area were neither protected nor bountied, and the influence of trapping and hunting is thought to have been negligible.

THE STUDY AREA

This study was conducted in the Superior National Forest (fig. 1) in northern St. Louis, Lake, and Cook Counties of northeastern Minnesota (92° west longitude, 48° north latitude), an area well described by Stenlund (1955). Most of the data were collected from within and immediately south of the Boundary Waters Canoe Area, a special wilderness region in which travel by motorized vehicles is restricted. The total study area encompasses approximately 1.5 million acres, and numerous lakes and rivers comprise about 15 percent of this area (fig. 2). The topography varies from large stretches of swamps to rocky ridges, with altitudes ranging from 1,000 to 2,300 feet above sea level (fig. 3). Winter temperatures lower than -30° F. are not unusual, and snow depths generally range from 20 to 30 inches on the level. However, an important exception occurred in early 1969 when depths of 45 inches and more accumulated in much of the area. Further details on snow conditions in the study area during the period of this investigation are given by Mech _et al._ (see page 51). Conifers predominate in the forest overstory, with the following species present: jack pine (_Pinus banksiana_ Lamb.), white pine (_P. strobus_ L.), red pine (_P. resinosa_ Ait.), black spruce (_Picea_ mariana (Mill.) B.S.P.), white spruce (_P. glauca_ (Moench) Voss), balsam fir (_Abies balsamea_ (L.) Mill.), white cedar (_Thuja occidentalis_ L.), and tamarack (_Larix laricina_ (DuRoi) K. Koch). However, as a result of extensive cutting and fires much of the conifer cover is interspersed with large stands of white birch (_Betula papyrifera_ Marsh.) and aspen (_Populus tremuloides_ Michx.). Detailed descriptions of the forest vegetation were presented by Ohmann and Ream (1969).

METHODS

The observations discussed in this paper were all made from aircraft, the method of flying being that reported by Burkholder (1959) and Mech (1966a). The following aircraft were used (in order of size): Aeronca Champ,[1] Supercub, Cessna 172, Cessna 180, and Cessna 206. The smaller aircraft were excellent for holding in tight circles during observations but had the disadvantage of being slow and cold; the larger planes could cover the study area much more quickly and were more comfortable, but were not as maneuverable during observations. For radiotracking, to be discussed below, the best compromise seemed to be a Cessna 172.

To make observations of wolves, we flew over frozen waterways until tracks were found, and then followed the tracks until we lost them or saw the wolves (fig. 4). Several times we located wolves directly just by scanning the lakes. However, because there seemed to be a number of packs in the area, and because most wolves were the same color (with the exception of a few black or white individuals) (see Mech and Frenzel, page 60), it usually was not possible to follow packs from one day to the next and be certain of identification. Moreover, it was impossible to locate any pack at will because most wolves also spent much time inland.

Therefore, to facilitate our observations and to obtain data on wolf movements and extent of range, we began a radiotracking program in 1968-69. A professional trapper, Robert Himes, was employed to capture the wolves. Using Newhouse No. 4 and 14 steel traps at scent-post sets, he caught two wolves, and captured another with a live-snare similar to that used by Nellis (1968); the senior author trapped two additional wolves (fig. 5).

The four wolves held in steel traps were restrained by a choker (fig. 6), and then anesthetized by intramuscular injections (fig. 7A, B) of a combination of 30 mg. of phencyclidine hydrochloride (Sernylan, Parke-Davis Co.) and 25 mg. promazine hydrochloride (Sparine, Wyeth Laboratories) as prescribed by Seal and Erickson (1969); these drugs proved most satisfactory.

The fifth wolf (a female), which was captured around the chest by the live-snare, was handled without drugs. A forked stick was used to hold down her head (Kolenosky and Johnston 1967), and she offered no resistance (fig. 8). Evidently she went into shock or some other psychophysiological state of unconsciousness, for after her release she remained on her side and did not move for 1.5 hours, despite our prodding during the first few minutes (fig. 9). Then suddenly she leaped up and ran off.

Each wolf was examined, outfitted with a radio transmitter collar 15 inches inside circumference (fig. 10) and tagged with identification numbers in both ears (fig. 11). Each transmitter was of a different frequency in the 150 MH_z range, emitted a pulsed signal ranging from 75 to 350 pulses per minute, and had a calculated life of at least 300 days (fig. 12). Two types of 12-inch whip antennas were used on the transmitters: one type extended up the side of the collar and then stuck out above for 6 inches; the other was fully attached inside the collar and extended up one side, around the top, and partly down the other side. The transmitter, batteries, and antenna were molded into a collar of acrylic weighing 11 ounces (Mech _et al._ 1965).[2] All radio equipment functioned flawlessly for at least 5 months, and one transmitter continued operating for at least 9 months.

For tracking radio-equipped wolves, a directional yagi antenna (fig. 13) was attached to each of the wing struts of an aircraft and connected inside to a portable receiver. The usual tracking technique was to fly at 1,500 to 3,000 feet elevation to the last known location of the wolf being sought (fig. 14). If a signal was not obtained at that point, the aircraft spiraled upward until the signal was found or until 10,000 feet altitude had been reached. If the signal still was not heard, a search pattern was flown at 10,000 feet. The range of the signal from this altitude was 15 to 35 miles; at 3,000 feet it was 10 to 15 miles. Collars with antennas molded fully inside gave only about two-thirds the range of those protruding partly, but could be expected to last longer because the antennas could not break off. It is unknown whether any protruding antennas did break during the study, but on January 5, 1970, one wolf was recaptured, and its antenna had broken.

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.

FOOTNOTES:

[1] _Mention of trade names does not constitute endorsement by the USDA Forest Service._

[2] _The acrylic collar was fashioned by the Davidson Co., Minneapolis, Minnesota, which also produced some of the transmitters. Other transmitters and two radio receivers were manufactured by the AVM Instrument Co., Champaign, Illinois._

RESULTS AND OBSERVATIONS

Aerial observations made during this study involved 490 hours distributed as follows: January, February, March 1967--124 hours; February 1968--10 hours; December 1968 through August 1969--356 hours. Seventy-seven observations involving a total of 323 wolves were made (table 1), excluding animals located through radiotracking.

One male and four female wolves were radiotagged, and they and their associates were followed intermittently for periods of 5 to 8 months (table 2). All except one initially suffered some injury to a foot. Three of these animals were seen limping, but only in one case was the limp judged extreme enough to have significantly affected the movements or behavior of the animal. In that one case, the wolf (No. 1057) was caught in a steel trap on an extremely cold night, and her foot froze. After that she was often seen hopping on three legs. She was not able to keep up with her pack, which consisted of 10 to 13 members, and her movements were much restricted compared with those of other wolves. However, she was frequently observed feeding on fresh kills, and may even have made them herself.

_Table 1.--Sizes of wolf population units observed in northeastern Minnesota_

#: _Number_ %: _Percent_

+------------------+-------------------------------------------+ | | Wolf observations | |Population unit[3]+----------+----------+----------+----------+ |(number of wolves)| Winter | Winter | Total |Winters[4]| | | 1966-67 | 1968-69 | | 1948-53 | +------------------+----------+----------+----------+----------+ | # % # % # % # % | | 1 8 31 17 33 25 32 48 43 | | 2 3 12 6 12 9 12 24 22 | | 3 3 12 2 4 5 6 7 6 | | 4 -- -- 7 14 7 9 7 6 | | 5 2 7 4 8 6 8 8 7 | | 6 3 12 4 8 7 9 7 6 | | 7 2 7 1 2 3 4 4 4 | | 8 3 12 3 6 6 8 3 3 | | 9 -- -- 2 4 2 3 3 3 | | 10 2 7 2 4 4 5 -- -- | | 11 -- -- -- -- -- -- -- -- | | 12 -- -- 1 2 1 1 1 1 | | 13 -- -- 2 4 2 3 -- -- | | --------------------------------------------+ |Total number | | of wolves 109 -- 214 -- 323 -- 318 -- | |Total number | | of observations 26 -- 51 -- 77 -- 112 -- | |Mean population | | unit size 4.2 -- 4.2 -- 4.2 -- 2.8 -- | +--------------------------------------------------------------+

FOOTNOTES:

[3] Because wolf packs sometimes split temporarily, these figures may not strictly represent actual pack sizes; nevertheless they should provide reasonably accurate approximations.

[4] From Stenlund (1955).

_Table 2.--Background information on five radiotagged wolves studied in northeastern Minnesota_

#: _Number_

:---------:-------:--------:--------:-------:-------:----------- Wolf :Estimated: Usual :Location: Date : Last : Days : General --------:weight[5]:associ-:captured:captured: date :located: condition # :Sex:(pounds) :ations : : :located: : ----:---:---------:-------:--------:--------:-------:-------:----------- #

1051 M 75 None[6] T62N-R7W Nov. Apr. 84 Good, but two -S18 27/68 24/69 toes frozen in trap; animal limped lightly for 5-6 wks.

1053 F 60 None T62N-R8W Dec. Aug. 72 Thin; top of -S13 10/68 29/69 foot cut in trap but no broken bones or frozen toes; limped for at least 10 wks.

1055 F 60 Another T61N-R10W Jan. May 65 Thin; two toes wolf -S26 5/69 30/69 lightly frozen; intermit- no limp ever tently noticed.

1057 F 60 Pack of T66N-R5W Jan. Apr. 47 Thin; front 13[7] -S33 8/69 24/69 foot frozen in trap; lost use of foot and could not stay with pack.

1059 F 65 Pack T62N-R11W Jan. Aug. 51 Good but thin; of 5 -S26 22/69 29/69 captured in snare; no apparent injury. ----:---:---------:-------:--------:--------:-------:-------:-------------

FOOTNOTES:

[5] Wolf 1059, when killed by a trapper on January 10, 1970, appeared to be of the same size and condition as when radiotagged; she only weighed 53 pounds, however, indicating that probably all the weights are overestimated.

[6] Tracks of a pack of at least two other wolves came by trap where 1051 was caught; however, there was never any other indication that 1051 may have been a member of a pack.

[7] A frozen foot prevented 1057 from staying with her pack; but she did associate with other wolves intermittently and with the whole pack when it came by her restricted area.

The precise ages of the radiotagged wolves were unknown. All individuals, however, had sharp unworn teeth, indicating that they were all relatively young. No. 1051, the only male studied, had testes 2.0 cm. long and 1.5 cm. wide; their volume therefore would be less than 4.5 cc. The small size of these testes, compared with the 7 to 28 cc. reported by Fuller and Novakowski (1955) as the volume of the testes from wolves taken during fall, would indicate that 1051 had not yet matured. Since the animal's testes and canine lengths were considerably greater than those of pups caught in a later study, we presume 1051 was 18 or 30 months old.

Two of the females, No. 1055 and No. 1059, both captured in January, had vulvas that seemed to be beginning to swell. No. 1059 was killed by a trapper about a year later, on January 10, 1970, and an examination revealed that she had bred in 1969 and carried five fetuses. Sectioning her incisors and reading the apparent annulations indicated that she probably was 3+ or 4+ years old.[8]

Three of the wolves were basically lone individuals. One of these, No. 1051, was captured on a night when tracks of at least two other wolves came by the trap, and this could mean that he had been part of a pack. However, it is also possible that these were merely tracks of non-associated wolves that were also traveling through the area. In any case, 1051 was not seen associating with any other wolf until 4 months after he was caught, and even then the association seemed to be temporary and casual. It could be argued that capture, handling by humans, or wearing a collar prevented him from regaining old associations or making new ones. However, the wolves radiotagged by Kolenosky and Johnston (1967) were quickly accepted back into their packs, and so were two of ours. Thus we conclude that 1051 probably was a lone wolf when captured.

When 1053 was trapped, her tracks were the only ones in the area, and she was never seen closely associating with another wolf. No. 1055 probably was with another wolf when captured, as evidenced by tracks. About a month after she was radiotagged she associated with another wolf intermittently for about 2 weeks, after which she was only seen alone.