Timber wolf (Canus lupus) colonization trends in the Central Forest of Wisconsin

Wayne H. Hall Jr., Richard P. Thiel, Wayne H. Hall, Wisconsin Department of Natural Resources, Sandhill Wildlife Area, PO Box 156, Babcock, WI 54413, USA

Wisconsin's 11,655 km2 Central Forest region is 216 km southeast of Minneapolis and 184 km northwest of Madison, WI. This region consists of sphagnum bogs, marshes, and ridges of oak, jackpine and white pine. Logging depleted forests between 1885 and 1910. Settlers farmed the cut over lands between 1900 and 1935, but sterile, sandy soils and summer frosts forced most to abandon their efforts. Today county, state and federal land management agencies primarily own this region. Cranberry agriculture predominates on private land. Logging is the major industry in this region, and dairy farming regions virtually surround the Central Forest.

Over-wintering white-tailed deer (Odocoileus virginianus) densities average 11.6/km2. Beaver (Castor canadensis) are abundant, although a population decline occurred in 1991-92. Wild turkey (Meleagris gallopavo), ruffed grouse (Bonasa umbellus), raccoon (Procyon lotor), legomorphs, coyote (Canis latrans), black bear (Ursus americanus), fisher (Martes pennanti) red fox (Vulpes vulpes), gray fox (Urocyon cinereoargenteus), and muskrat (Ondatra zibethicus) are also present.

Wolves were exterminated from central Wisconsin by 1920 and from the state by 1958. Wolf recolonization of Wisconsin began around 1975. By 1990, 34 wolves in 11 packs were counted; all confined to northern Wisconsin approximately 200 km north of the Central Forest region.

Citizen reports of wolf sightings in the Central Forest began in 1992. DNR surveys were initiated in December 1994, after 3 car-killed wolves were found in central Wisconsin, including a radioed wolf from northern Wisconsin and another from northern Minnesota. Two wolf packs were detected by DNR in winter 1994-95.

Winter wolf track surveys were conducted annually since 1994-95 to identify new packs, and census wolves. Summer howl surveys have been run annually to assess productivity. Wolves were captured, radio-tagged, and aerially monitored to ascertain territory sizes, boundaries, and the number of wolves existing in radioed packs annually since 1995. Wolf prey was determined by field inspecting scats and identifying remains by percent occurrence.

The arrival of wolves in the Central Forest coincided with an upturn in wolf numbers in northern Wisconsin and Michigan's Upper Peninsula. A pair of wolves established the Wildcat pack in the Central Forest in 1992. By 1997-98, 25-30 wolves were found in 7 packs for a mean finite rate of increase of 1.6. This is similar to the rate (2) observed in a proliferating population in northwest Minnesota between 1972-77 (Fritts and Mech 1981), and contrasts with a population (1.05) studied in northern Wisconsin between 1979 and 1988 (Wydeven et al. 1995).

Initial colonization occurred in portions of the Central Forest with the lowest road and resident human densities. The rate of pack colonization averaged = 1.6 between 1992 and winter 1998-99 when 7 packs were present in the region.

Four wolves have been radioed since 1995. Three wolves were from the Wildcat pack, and one was from the Bear Bluff pack. Mean territory size of the two packs was 129.5 km2, smaller than the 179 km2 average territory size reported in northern Wisconsin. Smaller territory size may be a function of higher deer densities in the Central Forest. Deer constitute over 90 percent of prey remains found in scats.

Radioed yearling male 274 dispersed 45 km from the Wildcat pack in October 1996 and settled into an area devoid of other wolves near the city limits of Wisconsin Rapids. He returned to his natal pack on 3 occasions between October and February. In March he returned and remained in his natal pack territory until the following October. By December, wolf 274 localized his movements along the edge of the neighboring Bear Bluff territory, and by January he was seen with another wolf. Wolf 274 and the uncollared wolf had pups in 1998 and colonized the Dead Creek pack. None of the wolves radioed in the Central Forest have died. Five wolves have been killed on roads within or near the Central Forest since 1994.