Ecological Studies of the Timber Wolf in Northeastern Minnesota.
by L. David Mech and L. D. Frenzel and Robert R. Ream and John W. Winship and P. D. Karns.
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
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 lat.i.tude), 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 encompa.s.ses 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 alt.i.tudes 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 acc.u.mulated 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).
[Ill.u.s.tration: _Figure 1 (left half)--Map of the study area._]
[Ill.u.s.tration: _Figure 1 (right half)--Map of the study area._ BOUNDARY WATERS CANOE AREA SUPERIOR NATIONAL FOREST]
[Ill.u.s.tration: _Figure 2.--Lakes are common throughout most of the study area. (Photo courtesy of L. D. Mech.)_]
[Ill.u.s.tration: _Figure 3.--Ridges, islands, swamps, and bays are part of the variable topography in the Superior National Forest. (Photo courtesy of L. D. Mech.)_]
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.
[Ill.u.s.tration: _Figure 4.--An important technique used in the study involved aerial tracking and observing of wolf packs. (Photo courtesy of L. D. Frenzel.)_]
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).
[Ill.u.s.tration: _Figure 5.--A wolf caught in a trap. (Photo courtesy of D. L. Breneman.)_]
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.
[Ill.u.s.tration: _Figure 6.--A choker was used to restrain wolves caught in traps. (Photo courtesy of D. L. Breneman.)_]
[Ill.u.s.tration: _Figure 7.--A. A small hypodermic syringe is loaded with drugs. B. The loaded syringe is used on the end of a pole. (Photos courtesy of D. L. Breneman.)_]
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.
[Ill.u.s.tration: _Figure 8.--Once pinned by the forked stick, the wolf ceased struggling. (Photo courtesy of Richard Bend.)_]
[Ill.u.s.tration: _Figure 9.--After release, the wolf lay still for 1-1/2 hours before jumping up and running off. (Photo courtesy of L. D.
Mech.)_]
Each wolf was examined, outfitted with a radio transmitter collar 15 inches inside circ.u.mference (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.
[Ill.u.s.tration: _Figure 10.--A radio transmitter collar was placed around the neck of each trapped wolf. (Photo courtesy of D. L.
Breneman.)_]
[Ill.u.s.tration: _Figure 11.--Each ear of the wolf was tagged with identifying numbers. (Photo courtesy of Richard Bend.)_]
[Ill.u.s.tration: _Figure 12.--Each radio collar had a different frequency tuned to special receivers, which allowed each wolf to be identified.
(Photo courtesy of D. L. Breneman.)_]
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 alt.i.tude 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 alt.i.tude 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.
[Ill.u.s.tration: _Figure 13.--Directional yagi antennas fastened to the wing struts of the aircraft were necessary to "home in" on the wolves.
(Photo courtesy of U.S. Bureau of Sport Fisheries and Wildlife.)_]
[Ill.u.s.tration: _Figure 14.--The tracking aircraft was usually flown at alt.i.tudes of 1,500 to 3,000 feet.
(Photo courtesy of d.i.c.k Shank.)_]
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 alt.i.tude 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 alt.i.tude 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 alt.i.tudes of 500 feet and less without disturbance (fig. 15).