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E x p e r i e n c e Y o u r A m e r i c a TM
ABOVE

A biologist inspects the teeth of 

an instrumented wolf.

NPS Photo

ON THE COVER

Gray wolf, northern Minnesota.

NPS photo by W. Route
Gray Wolves in and Adjacent to Voyageurs 

National Park, Minnesota

Research and Synthesis 1987–1991

Gray Wolves in and Adjacent to Voyageurs 

National Park, Minnesota

Research and Synthesis 1987–1991

Technical Report NPS / MWR / NRTR / 2004-01

Peter J. P. Gogan

USGS, Northern Rocky Mountain Science Center, Forestry Sciences Laboratory, Montana State 

University, Bozeman, MT 59717 USA

William T. Route 

National Park Service, Great Lakes Network Offi ce, 2800 Lake Shore Drive, Ashland, 

WI 54806 USA

Edward M. Olexa

USGS, Northern Rocky Mountain Science Center, Forestry Sciences Laboratory, Montana State 

University, Bozeman, MT 59717 USA

Nancy Thomas

USGS, National Wildlife Health Center, 6006 Schroeder Road, Madison, WI 53711 USA

David Kuehn

Forest Wildlife Populations and Research Group, Minnesota Department of Natural Resources, 

1201 East Highway 2, Grand Rapids, MN 55744 USA

Kevin M. Podruzny

Department of Ecology, Montana State University, Bozeman, MT 59717 USA

U.S. Department of the Interior

National Park Service

Midwest Regional Offi ce

Omaha, Nebraska
The National Park Service disseminates the results of biological, physical, and social science research; 

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the National Park Service. Mention of trade names or commercial products does not constitute endorsement or recommendation for use by the National Park Service.

A limited number of copies of this report is available from:

 Peter Gogan

 U.S. Geological Survey

 Northern Rocky Mountain Science Center

 Forestry Sciences Laboratory

 Montana State University

 Bozeman, MT 59717-2780

 peter_gogan@usgs.gov

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Suggested citation

Gogan, P. J. P., W. T. Route, E. M. Olexa, N. Thomas, D. Kuehn, and K. M. Podruzny. 2004. Gray wolves 

in and adjacent to Voyageurs National Park, Minnesota: Research and synthesis 1987–1991. Technical 

Report NPS/MWR/NRTR/2004-01. National Park Service, Omaha, Nebraska.

NPS D-146, September 2004
v

Abstract

We investigated the status of wolves (Canis lupus)

in and adjacent to Voyageurs National Park (VNP), 

Minnesota, from September 1987 through September 1991. Thirteen wolf packs were followed 

by radiotelemetry (13 males, 18 females were 

radio-marked) for 6 to 48 months. Six packs had 

territories exclusively or partially within VNP. Radiotelemetry data gathered during winter daylight 

hours indicated that wolves within VNP avoided 

the frozen surfaces and shorelines of larger lakes 

during that time period. In contrast, snow tracking revealed that wolves regularly traversed frozen 

surfaces and shorelines after dark. Our howling 

surveys averaged detection near 50% of the wolf 

packs known to exist in the study area. Pack territories ranged from 48 km2

 to 296 km2 with a 

mean of 152 km2

. Overall, mean mid-winter pack 

size was 5.5 wolves with a high of 6.3 in 1988 –

19 89 and a low of 4.5 in 1989–1990. Non-territorial wolves made up 9.5% of the population. 

Overall, mean wolf density was 33 / 1,000 km2

with an annual range of 24 to 42 / 1,000 km2

. We 

detected nine dispersals among 20 radio-marked 

wolves more than eight months old. All dispersals 

occurred in winter. Dispersing wolves averaged 

2.1 pre-dispersal movements beyond their home 

territory. Ages of dispersing wolves ranged from 

1.5 to 7.5 years. Natural causes of mortality 

among radio-marked wolves included intraspecifi c 

strife (n = 4) and starvation (n = 2). Confi rmed 

human-induced causes of mortality among radiomarked wolves included shooting (n = 2), trapping 

or snaring (n = 2), and unknown method (n = 2). 

Natural causes of mortality among non-radiomarked wolves included intraspecifi c strife (n = 1) 

and starvation (n = 1). Confi rmed human-induced 

causes of mortality among non-radio-marked 

wolves included automobile collisions (n = 3), 

shooting (n = 3), and trapping or snaring (n = 2). 

All mortalities within the boundaries of VNP were 

attributed to natural causes. Six of eight confi rmed mortalities among instrumented wolves 

and eight deaths of non-instrumented wolves beyond the boundaries of VNP were human caused. 

Two additional instrumented wolves disappeared 

at the onset of the Minnesota deer rifl e season, 

but their fate was not confi rmed. Twenty remains 

were necropsied, but no mortalities were attributable to diseases or parasites. The annual survival 

rate of adult wolves was 0.75. Season, and then 

age, were the most important parameters in 

explaining survival of all instrumented wolves. 

Instrumented wolves with territories exclusively 

within the boundaries of VNP had higher survival 

than those whose territories straddled or were 

beyond the park boundaries. The annual wolf diet 

consisted of 80% white-tailed deer (Odocoileus 

virginianus) and 15% beaver (Castor canadensis), 

as determined by scat analysis. Deer made up 

56% of the spring and 91% of the winter diet 

while beaver made up 35% of the spring and 7% 

of the winter diet. The overall sex ratio of adult 

deer killed by wolves in winter did not differ from 

50:50. However, the sex ratio of wolf-killed adult 

deer was skewed toward males in the winter of 

1987 – 1988 and toward females in 1988 – 1989. 

The median age of deer killed by wolves in winter 

was 6.5 and 7 years for females and males, respectively.

Key Words: Canis lupus, abundance, density, 

diseases and parasites, dispersal, feeding ecology, 

gray wolf, howling surveys, mortality, radiotelemetry, snow tracking, survival rates, pack size, territory size, Voyageurs National Park, Minnesota.

vii

Contents

Abstract v

List of fi gures viii

List of tables ix

Acknowledgments xi

Introduction 1

Study Area 3

Methods 7

Capture and radiotelemetry 7

Noninvasive population sampling 7

Snow tracking 7

Howling surveys 7

Incidental observations 8

Pack territory size 8

Pack size and density estimates 8

Dispersal events 8

Timing and causes of mortality 8

Survival rates 9

Diseases and parasites 9

Population genetics 9

Feeding ecology 9

Results and Discussion 11

Capture and radiotelemetry 11

Noninvasive population sampling 11

Snow tracking 11

Howling surveys 13

Snow tracking and howling as monitoring 

tools 14

Incidental observations 15

Pack numbers, territories, and wolf density 15

Dispersal 18

Cruiser Lake Pack split 19

Kohler Pit Pack split 21

Timing and causes of mortality 21

Survival rates 23

Survival by age 23

Survival by sex 24

Survival by territory location 24

Survival by time of year 24

Survival summary 25

Diseases and parasites 26

Population genetics 27

Feeding ecology 28

Conclusions 33

Management Implications 35

Appendixes

Appendix 1. Number of wolves harvested in the 

Fort Frances District, Ontario, 1948 – 1998. 37

Appendix 2. Accuracy of aerial-telemetry location 

estimates for gray wolves in and adjacent to Voyageurs National Park, Minnesota, 1989 – 1991. 38

Background 38

Methods 39

Results 39

Discussion and recommendations 44

Appendix 3. Examples of use of Program Mark in 

analysis of survival of instrumented wolves in and 

adjacent to Voyageurs National Park, Minnesota. 47

Example of Known Fates model data entry in 

program MARK 47

Survival by age and time of year 48

Adult survival by sex and time of year 50

Adult survival by home range location and time 

of year 52

Appendix 4. Number of track encounters, incidental observations, howling responses, radiotelemetry locations and counts during fl ights for 

wolf packs studied in and adjacent to Voyageurs 

National Park, Minnesota, 1987 – 1991. 54

Appendix 5. Histories of radio-marked wolves and 

wolf packs studied in and adjacent to Voyageurs 

National Park, Minnesota, 1987 – 1991. 55

Tom Cod Bay Pack (TCP) 55

Locator Lake Pack (LLP) 55

Middle Peninsula Pack (MPP) 56

Cruiser Lake Pack (CLP) 56

Moose River Grade Pack (MGP) 57

Browns Bay Pack (BBP) 58

Nebraska Bay Pack (NBP) 58

Kohler Pit (KPP) and Kohler Trio (KTP) Packs 58

Blue Moose Pack (BMP) 59

Dixon Creek Pack (DCP) 60

Moose Lake Pack (MLP) 60

Appendix 6. Calculations for estimating biomass 

and number of prey represented in 123 scats collected during summer 1987 and 1988 in and adjacent to Voyageurs National Park, Minnesota. 61

Appendix 7. Calculations for estimating biomass 

and number of prey represented in 97 scats collected during winter 1987 and 1988 in and adjacent to Voyageurs National Park, Minnesota. 62

Literature Cited 63
viii

Figures

Figure 1. Location of Voyageurs National Park, 

northern Minnesota. 3

Figure 2. Winter Severity Index (WSI) for International Falls, Minnesota, for winter 1984 – 1985 

through winter 1994 – 1995. The WSI is calculated 

as the number of days below −17.7° C or with 

more than 45.7 cm snow covering the ground. 

Winter Severity Index values greater than 100 are 

considered severe. Data provided by F. Swendsen, 

Minnesota Department of Natural Resources, International Falls, Minnesota. 4

Figure 3. Continuous distribution of wolves in 

Minnesota in 1988 – 1989 (left panel) (Fuller et al. 

1992) and wolf management zones in Minnesota 

identifi ed in the 1992 wolf recovery plan (right 

panel) (USFWS 1992). 5

Figure 4. Annual (upper panel) and monthly 

(lower panel) visitation patterns for Voyageurs National Park, Minnesota, 1985 – 1995. Vertical bars 

are 95% confi dence intervals. 6

Figure 5. History of radio contact with 31 radiomarked wolves in and adjacent to Voyageurs National Park, Minnesota. Black bars represent contact with wolves associated with packs or groups. 

Gray bars represent contact with wolves not 

associated with packs or groups or with wolves 

dispersing from packs or groups. Two wolves that 

dispersed from their original packs and joined 

other packs and one wolf that dispersed from a 

pack and joined a wandering group are represented twice. 12

Figure 6. Percent of encounters with different 

wolf group sizes during snow tracking in and 

adjacent to Voyageurs National Park, Minnesota, 

winter 1987 – 1988 and 1988 – 1989. 13

Figure 7. Location of tracks of all wolves encountered (upper left) and groups of two or 

more wolves encountered (upper right) in winter 

1987 – 1988 and all wolves encountered (lower 

left) and groups of two or more (lower right) encountered in winter 1988 – 1989 in and adjacent 

to Voyageurs National Park, Minnesota. 13

Figure 8. Location of howling survey sites with an 

estimated perimeter of audibility of 2.5 km (upper 

left) and responses by wolves to simulated howling for 1988 (upper right), 1989 (lower left), and 

1990 (lower right), Voyageurs National Park, Minnesota. 14

Figure 9. Locations of wolf packs within and adjacent to Voyageurs National Park, Minnesota, by 

year, 1987 through 1991. Three-letter abbreviations correspond with pack names in table 6. 

Stippled polygons indicate pack territories determined by 30 or more radiotelemetry locations. 

Other polygons were estimated from less than 30 

radiotelemetry locations, snow tracking, howling 

surveys, incidental observations, terrain, and human developments. Area estimates are for areas 

within the bold line. 17

Figure 10. Number of mortalities by month of instrumented wolves in and adjacent to Voyageurs 

National Park, Minnesota, 1987–1991. 22

Figure 11. Capture sites of wolves with a common 

wolf genome (W1) or with two distinct wolf-coyote genomes (W7, W9) in and adjacent to Voyageurs National Park, Minnesota, 1987–1991. 28

Figure 12. Percent occurrence of white-tailed deer 

and beaver in the wolf diet (upper panel) and relationship between occurrence and estimated biomass of prey species in the wolf diet (lower panel) 

in and adjacent to Voyageurs National Park, Minnesota, 1988 and 1989. 29

Figure 13. Number of deer found dead as a result of wolf predation and other causes in and 

adjacent to Voyageurs National Park, Minnesota, 

December 1987 through May 1990. 32

Figure 14. Age and sex structure of deer killed 

by wolves in and adjacent to Voyageurs National 

Park, Minnesota, December 1987 through May 

1990. 32
ix

Tables

Table 1. Weight by age class and sex of 30 wolves 

captured, radio-marked, and released for study in 

and adjacent to Voyageurs National Park, Minnesota, 1987–1991. 11

Table 2. Frequency of wolf group sizes encountered during snow tracking in and adjacent to 

Voyageurs National Park, Minnesota, winter 

1987 – 1988 and 1988 – 1989. 11

Table 3. Results of human-elicited wolf howling 

surveys at 24 sites in Voyageurs National Park, 

Minnesota, 1988 –1991. 15

Table 4. Detectability of known wolf packs by 

human-elicited howling surveys in Voyageurs National Park, Minnesota, 1988–1991. 16

Table 5. Minimum territory size for radio-marked 

wolf packs where 30 or more radiotelemetry locations were obtained in and adjacent to Voyageurs 

National Park, Minnesota, 1987–1991. 16

Table 6. Minimum estimates of pack size (E) and 

wolf density for nine packs, as estimated from 

track counts (T), incidental observations (I), and 

direct counts with the aid of radiotelemetry (R), in 

and adjacent to Voyageurs National Park, Minnesota, 1987–1991. 18

Table 7. Mean territory size and pack size for wolf 

populations on a white-tailed deer economy. 19

Table 8. Density of wolves that exist primarily on a 

white-tailed deer economy. 20

Table 9. Sex, pack affi liations, age, and dates of 

nine dispersals for eight different wolves radiomarked in and adjacent to Voyageurs National 

Park, Minnesota, 1987–1991. 20

Table 10. Estimated annual dispersal rates for 

wolves in and adjacent to Voyageurs National 

Park, Minnesota, 1987–1991. 21

Table 11. Mean straight-line distance between 

consecutive locations and number of pre-dispersal movements for dispersing wolves in and 

adjacent to Voyageurs National Park, Minnesota, 

1987–1991. 21

Table 12. Cause, residency, and location of death 

for known deaths of 14 radio-marked wolves in 

and adjacent to Voyageurs National Park, Minnesota, 1987–1991. 22

Table 13. Cause and location of death for 10 unmarked wolves found less than 10 km from study 

wolf pack territories in and adjacent to Voyageurs 

National Park, Minnesota, 1987–1991. 23

Table 14. Effects of age and time of year on 

Known Fates survival estimates from 30 radiomarked gray wolves in and adjacent to Voyageurs 

National Park, Minnesota, 1987–1991. 24

Table 15. Effects of sex and time of year on 

Known Fates survival estimates from 23 radiomarked adult gray wolves in and adjacent to 

Voyageurs National Park, Minnesota, 1987–1991. 

24

Table 16. Effects of territory location and time of 

year on Known Fates survival estimates from 23 

radio-marked adult gray wolves in and adjacent to 

Voyageurs National Park, Minnesota, 1987–1991. 

25

Table 17. Parasites and diseases found in live and 

dead wolves in and adjacent to Voyageurs National Park, Minnesota, 1987–1991. 26

Table 18. Number of occurrences and percent occurrence of prey by season for 220 wolf scats collected in and adjacent to Voyageurs National Park, 

Minnesota, 1988–1989. 28

Table 19. Percent of total meals and relative biomass of prey consumed during spring, summer, 

and fall by wolves in and adjacent to Voyageurs 

National Park, Minnesota, 1988 and 1989. 30

Table 20. Percent of total meals and relative biomass of prey consumed during winter by wolves 

in and adjacent to Voyageurs National Park, Minnesota, 1988 and 1989. 30

Table 21. Cause of mortality by sex and age class 

of 111 dead white-tailed deer found year-round 

in and adjacent to Voyageurs National Park, Minnesota, 1987–1991. 31

Table 22. Age and sex of wolf-killed white-tailed 

deer in and adjacent to Voyageurs National Park, 

Minnesota, during winter 1987–1991. 31

Table 23. Age and sex of white-tailed deer killed 

by wolves in and adjacent to Voyageurs National 

Park, Minnesota, during summer 1988 and 1989. 

31

xi

Acknowledgments

A great number of people assisted in the development and implementation of this study. J. Benedict prepared the documentation that secured the 

funding. D. Potter provided logistic and fi nancial 

support for portions of the study within Superior 

National Forest. K. D. Kozie dedicated great effort to the fi eldwork presented herein. S. Evans 

fl ew most of the aerial radiotelemetry fl ights to 

locate wolves. S. Durst proved a reliable substitute 

pilot for radiotelemetry fl ights. Volunteers in Parks 

(VIPs) K. Beirne, J. Dougan, L. Fuselier, P. Hogg, 

J. Schmidt, J. Sotsky, and E. Temple assisted with 

wolf trapping and sampling deer kill sites. S. Lammie and W. Wold provided assistance with GIS 

data layers. The National Wildlife Health Center 

diagnostic laboratories (virology, microbiology, 

parasitology) produced disease and parasite data. 

A number of individuals at VNP provided logistical 

and administrative support for this study.

We are grateful to R. Andrascik, J. Belant, L. N. 

Carbyn, J. F. Cochrane, J. Fox, D. Licht, M. E. 

Nelson, R. O. Peterson, D. W. Smith, J. Schaberl, 

and J. Winnie for providing insightful review comments on earlier drafts of this report.

National Park Service 1

Gray wolves once occupied much of North 

America (Nowak 1995), but were extirpated 

from most of their range south of Canada by 

the mid-1960s (Thiel and Ream 1995). In 1963, 

the estimated 350 – 700 wolves in extreme 

northeastern Minnesota (Stenlund 1955, Fuller et al. 1992) likely constituted the only viable 

population of gray wolves in the contiguous 

United States other than those at Isle Royale 

National Park (IRNP), Michigan. In Minnesota, a statewide wolf bounty system was 

in eff ect between 1849 and 1965 (Minnesota 

Department of Natural Resources [MnDNR] 

unpublished data). In addition, the state of 

Minnesota administered a Directed Predator 

Control Program until 1974. Aerial gunning 

was a component of these control programs 

from 1948 to 1956. The fi rst signifi cant protection for wolves in Minnesota came in 1970 

when Superior National Forest (SNF) was 

closed to the taking of wolves. In 1972, an estimated 500 to 1,000 wolves occupied 30,720 

km2

 of wolf habitat in northeastern and northcentral Minnesota (MnDNR unpublished 

data). The creation of VNP from public and 

private lands in 1975 provided additional protection for wolves and their habitat. 

Wolves became federally protected throughout their historic range in the contiguous 

United States in 1974 when they were listed as 

endangered under the Endangered Species Act 

(ESA) of 1973 (U.S. Fish and Wildlife Service 

[USFWS] 1992). By 1978, wolf numbers had 

increased in Minnesota so that the species was 

reclassifi ed as threatened under the ESA 

(USFWS 1992). Currently, wolves are expanding their range south and west across Minnesota (Berg and Benson 1998) and have reoccupied portions of Wisconsin (Wydeven et al. 

1995) and the Upper Peninsula of Michigan 

(Hammill 1997).

In the mid-1980s, VNP was one of only 

three national parks (Isle Royale, Glacier) 

in the contiguous United States known to 

support gray wolves year-round. Results of 

winter ground tracking eff orts in VNP from 

winter 1976 – 1977 through 1985 – 1986 suggested wolf numbers declined (Cole 1987). 

This trend paralleled a decade-long decline 

in wolf numbers in the central SNF ending 

in winter 1983 – 1984 (Mech 1986b). In both 

cases, the wolf population declines were attributed to a decline in the abundance of the 

primary ungulate prey species, white-tailed 

deer (Mech 1986b, Cole 1987). A review of 

historical data suggested that the ungulate 

prey base for wolves at VNP might have been 

more diverse prior to the 1920s (Cole 1987). 

In response to the observed decline in wolf 

abundance and to examine the potential for 

reintroducing extirpated woodland caribou 

(Rangifer tarandus) (Gogan et al. 1990, Gogan 

and Cochrane 1993), we conducted a study 

of wolves in and adjacent to VNP from 1987 

through 1991. Voyageurs National Park served 

as the focus of this study of wolves. However, 

it became clear early in the study that wolves 

utilizing VNP ranged extensively beyond the 

park boundaries. We therefore opted to defi ne VNP as the core study area but annually 

defi ned a survey area that included territories 

of all instrumented wolves in and adjacent to 

VNP.

Our goals were to assess the ability of VNP 

to support long-term resident and “acrossboundary” packs of wolves and to identify 

human activities within and adjacent to the 

park likely to aff ect their long-term viability. 

Specifi c objectives were to (1) determine the 

number of wolf packs using VNP and adjacent lands; (2) estimate the approximate size 

and location of pack territories; (3) estimate 

wolf density, including the number of resident 

pack wolves and lone wolves; (4) calculate the 

percentage of wolves leaving packs; (5) determine causes and timing of mortality; (6) calculate survival rates of select cohorts of wolves; 

(7) identify diseases and parasites of wolves; 

(8) examine wolf population genetics; (9) 

determine wolf food habits; and (10) evaluate 

the utility of howling surveys for assessing the 

presence or absence of wolf packs in the park.

Introduction

National Park Service 3

Study Area

Figure 1. Location of Voyageurs 

National Park, northern Minnesota. 

Voyageurs National Park covers an area of 

882 km2

 of forest and lakes atop the Canadian Shield along the United States–Canada 

boundary between northern Minnesota and 

northwestern Ontario. The park’s northern 

boundary extends from 20 to 70 km east of 

the communities of International Falls, Minnesota, and Fort Frances, Ontario. The park 

is part of a relatively unsettled region that 

includes the larger than 4,850 km2

 Boundary Waters Canoe Area Wilderness of the 

8,500 km2

 SNF, Minnesota, and the 4,450 km2

Quetico Provincial Park, Ontario (fi gure 1).

Voyageurs National Park includes a central 

landmass of the Kabetogama Peninsula and its 

adjacent islands (330 km2

), a separate southeastern landmass (210 km2), and 4 large lakes 

comprising an area of 342 km2

. The landmasses contain 26 small lakes, ranging from 

13 to 305 ha in size. As of 1986, beaver impoundments covered 13% of the Kabetogama 

Peninsula (Broschart et al. 1989). Maximum 

topographic relief is 80 to 90 m. The park lies 

within the Border Lakes subsection of the 

Laurentian Mixed Forest Province (McNab 

and Avers 1994) and along the boundary 

between the southern boreal and northern 

hardwood forest types (Pastor and Mladenoff 

1992). Vegetation in the southern boreal type 

is mostly a secondary-growth mosaic of jack 

pine (Pinus banksiana), quaking aspen (Populus tremuloides), paper birch (Betula papyrifera), white spruce (Picea glauca), and balsam 

fi r (Abies balsamea) (Kurmis et al. 1986). The 

northern hardwood forest type is characterized by red pine (Pinus resinosa), white pine 

(Pinus strobus), red maple (Acer rubrum), and 

green ash (Fraxinus pennsylvanica) (Kurmis et 

al. 1986). Extensive wildfi res in the 1920s and 

1930s (Crowley 1995) shaped current forest 

vegetative cover. Forests within the present 
4 Gray wolves in and adjacent to Voyageurs National Park, Minnesota: Research and synthesis 1987 – 1991

Figure 2. Winter Severity Index 

(WSI) for International Falls, Minnesota, for winter 1984 –1985 

through winter 1994 –1995. The 

WSI is calculated as the number 

of days below -17.7° C or with 

more than 45.7 cm snow covering the ground. Winter Severity 

Index values greater than 100 

are considered severe. Data 

provided by F. Swendsen, Minnesota Department of Natural 

Resources, International Falls, 

Minnesota.

VNP were extensively logged between 1910 

and 1930 (Crowley 1995), and approximately 

25% of the Kabetogama Peninsula was logged 

post-1940 (J. Pastor, University of Minnesota, 

personal communication). Natural fi res have 

been suppressed and logging prohibited since 

the establishment of VNP in 1975. Most lands 

adjacent to the park on both sides of the international border are managed for timber 

production.

Temperatures average 18.6o C in July and 

−6.1o C in January, but extremes vary from 

36.6o C to −43o C (National Weather Service, 

International Falls, MN). Lakes in the area 

are usually ice-covered by the third week in 

November, and spring break-up occurs about 

1 May (Kallemeyn 1987). A winter severity index for International Falls, Minnesota, shows 

that the winters of 1988 – 1989 and 1990 – 1991 

were particularly severe (fi gure 2) (F. Swendsen, 

Minnesota DNR, personal communication). 

As of 1985, wolves occurred throughout much 

of the Laurentian Mixed Forest Province of 

Minnesota and adjacent Ontario (fi gure 3) 

(Mech et al. 1988). The U.S. Department of 

Interior’s recovery plan for the eastern timber wolf identifi ed four management zones 

for wolves in Minnesota (USFWS 1992). 

Voyageurs National Park lies at the extreme 

northwest corner of the 11,423-km2

 zone one 

of primary wolf range (fi gure 3). The park’s 

western and southern boundaries are coincident with the boundary between primary 

range zones one and three (USFWS 1992). 

Both zones are identifi ed as critical habitat for 

wolves (USFWS 1992). Wolves were harvested 

legally in Ontario adjacent to VNP throughout 

the life of this study. Some 75 wolves were 

trapped in the 23,595-km2

 Fort Frances District during winter 1987 – 1988 but less than 20 

were trapped in the latter three years of our 

study (appendix 1).

Moose (Alces alces) and woodland caribou 

were likely the most common ungulates in 

terms of numbers and biomass in pre-European times (Cole 1987). Caribou were extirpated 

from the region by the 1940s. Moose densities 

within VNP were estimated at 0.23/km2

 in 

1992 (Gogan et al. 1997a). White-tailed deer 

expanded northward with logging of the mature pine forest; they became common by the 

1920s (Petraborg and Burcalow 1965). From 

1975 through 1992, estimates of deer density 

in and directly adjacent to VNP ranged from 

1.5 to 11.5/km2

 (Peterson 1976, Whitlaw and 

Lankester 1994, Gogan et al. 1997a). Densities 

of deer in the areas south of VNP ranged from 

4.2 to 5.2/km2

 between 1985 and 1995 (M. 

Lenarz, Minnesota Department of Natural 

Resources, personal communication). Density of beaver colonies on the Kabetogama 

Peninsula increased continuously from the 

mid-1930s through 1986 (J. C. Schneeweis, 

Minnesota Department of Natural Resources, 

personal communication). Beaver density 

on the Kabetogama Peninsula was estimated 

at 5.8 to 6.6/km2

 in the mid-1980s (Smith 

0

20

40

60

80

100

120

140

160

180

84–85 85–86 86–87 87–88 88–89 89–90 90–91 91–92 92–93 93–94 94–95

Winter

Winter Severity Index
National Park Service 5

Figure 3. Continuous distribution of wolves in Minnesota in 

1988 –1989 (left panel) (Fuller et 

al. 1992) and wolf management 

zones in Minnesota identifi ed 

in the 1992 wolf recovery plan 

(right panel) (USFWS 1992).

and Peterson 1988) and 9.7/km2 in the early 

1990s (Smith 1997). Statewide, snowshoe hare 

(Lepus americanus) numbers exhibited a lowamplitude high, rising from 0.5 / km2

 in 1987 

to 2.7 / km2

 in 1989 before declining to initial 

densities. Hare density in 1989 was only oneseventh that of the late 1970s (Dexter 1998:

49). Black bear (Ursus americanus) densities 

in nearby portions of SNF ranged from 0.16 

to 0.24 / km2

 from 1969 to 1985 (Rogers 1987). 

Lynx (Felis lynx) and cougar (F. concolor) may 

occur at low numbers in the region (Gerson 

1988). Based upon our observations, coyote 

(Canis latrans) are uncommon, and red fox 

(Vulpes vulpes) are common within VNP.

Human recreational activities tend to be distributed on the water and along the shorelines 

of the region’s lakes during summer. The 

freeze-up of the larger lakes in late November enables a proliferation of “ice houses” 

or fi shing shacks on the frozen lake surfaces 

of the four major lakes (Kabetogama, Rainy, 

Namakan, and Sand Point) within VNP. The 

structures on the west end of Rainy Lake are 

accessed by automobile via a plowed road 

over the frozen lake surface. Similarly, the 

onset of snow permits extensive use of snowmobiles on both the land surfaces and across 

the frozen lake surfaces. Snowmobile users 

tend to remain on groomed trails while traversing land but become more dispersed while 

crossing frozen lake surfaces, except where 

unsafe ice or portages funnel them into more 

restricted areas. Logging beyond the park 

boundaries is limited to uplands in the warmer 

months, while lowland forests are logged in 

winter when the frozen ground permits access 

by heavy equipment.

Annual visitor use of VNP rose from approximately 210,000 in 1985 to more than 270,000 

in 1991 (fi gure 4, page 6). Monthly visitation is 

more than 40,000 from June through August, 

approximately 25,000 during the “shoulder” 

months of May and September, and ranges from 

1,500 to 12,000 during winter months (fi gure 4, 

page 6) (J. Schaberl, National Park Service, personal communication). Most winter visitation is 

snowmobile use.

International Falls

Duluth

Twin Cities

City 

Wolf Distribution 50 0 50 100 Kilometers

N

International Falls

Duluth

Twin Cities

Wolf Management

Zones

Zone 1

Zone 2

Zone 3

Zone 4

Zone 5

0 50 100 Kilometers

N

50
6 Gray wolves in and adjacent to Voyageurs National Park, Minnesota: Research and synthesis 1987 – 1991

Figure 4. Annual (upper panel) 

and monthly (lower panel) 

visitation patterns for Voyageurs National Park, Minnesota, 

1985 –1995. Vertical bars are 95% 

confi dence intervals.

150,000

170,000

190,000

210,000

230,000

250,000

270,000

290,000

1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995

Year

Number of Visitors

0

10,000

20,000

30,000

40,000

50,000

60,000

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

Month

Number of Visitors 
National Park Service 7

Methods

Capture and radiotelemetry

Wolves were captured during approximately 

21-day trapping periods between 25 April and 

15 May, and from 15 August to 15 September, 

from fall 1987 to fall 1990. A single wolf was 

trapped during summer 1989 (June 6 to August 18). Wolves were captured with #14 Newhouse foothold traps (Kuehn et al. 1986) and 

immobilized using a pole-mounted syringe 

with a mixture of xylazine hydrochloride, ketamine hydrochloride, and atropine sulphate 

(Fuller and Kuehn 1983). Captured wolves 

were fi tted with mortality-sensing radio collars (164 – 166 MHz; Telonics, Inc., Mesa, Arizona). The ages of wolves were estimated at 

capture as either pup (less than eight months 

old) or adult (more than one year old). Collars 

were loosely fi tted on pups (less than eight 

months old) and were padded with foam to 

allow for growth. Captured wolves were eartagged with 3.5 × 1-cm aluminum tags issued 

by the Minnesota Department of Natural 

Resources, sexed, weighed, and given penicillin as an antibiotic (Fuller and Kuehn 1983). 

Up to 20 ml of blood were collected from 

each wolf to evaluate for diseases and endoparasites (Zarnke and Ballard 1987, Peterson 

et al. 1998), and for genetic studies (Lehman 

et al. 1991). When available, fecal material and 

ectoparasites were also collected for disease 

evaluation and parasite identifi cation (Ash and 

Orihel 1987). In 1987 and 1988, we captured 

wolves in VNP and within 16 km of the south 

boundary to ensure transboundary packs were 

instrumented. In 1989 and 1990, we restricted 

trapping to within and immediately adjacent 

to the park boundaries to focus our eff orts on 

wolves ranging into the park.

Radio-marked wolves were located at approximately weekly intervals (x = 6.9 days, 

range (0 – 57 days) using standard aerial radiotelemetry techniques (Mech 1986a, Mech et 

al. 1998) from a Piper PA-18 SuperCub or occasionally a Cessna 180. When possible, radiomarked wolves and their pack members were 

observed and counted. Wolf locations were 

obtained with an onboard LORAN-C positioning device and 1:24,000-scale topographic 

maps and recorded as Universal Transverse 

Mercator (UTM) coordinates. Some LORANC locations diff ered from mapped locations 

during a portion of the study. Subsequently, 

we incorporated a combination of LORAN-C 

and map coordinates to determine a relative directional bias in locations of 187 m at 

108°, (appendix 2). A directional bias in locations based on LORAN-C alone was 565 m at 

104.2° (appendix 2). We concluded that, given 

the wide ranging habits of wolves, these mean 

levels of bias were acceptable for assessing territory, movements, and pack affi liations.

Noninvasive population sampling

Snow tracking—We tracked wolves from 

the ground in snow from approximately midDecember through March 1987 – 1988 and 

1988 – 1989 to augment telemetry data on pack 

size and movements, and to verify the existence of packs with no radio-marked wolves. 

Most tracking was conducted on the surfaces 

of the four large lakes within VNP. Tracks 

were plotted on 1:50,000-scale topographic 

maps. We estimated the age of tracks, the 

minimum and maximum number of wolves, 

and noted evidence of predation and prey 

consumption. We did not use snow tracks in 

1989 –1990 or 1990 –1991 when most packs 

in the study area contained radio-marked 

wolves. Data from snow tracking were not 

used to calculate average territory size but 

were used to delineate the total annual survey 

area and to estimate winter pack size.

Howling surveys—Wolves respond to simulated howling (D. H. Pimlott, University of Toronto, unpublished report), and standardized 

howling surveys can be used to follow trends 

in wolf populations (Harrington and Mech 

1982, Fuller and Sampson 1988). We established a simulated wolf howling survey (Harrington and Mech 1982, Fuller and Sampson 

1988) in VNP. Twenty-four sampling stations 

were distributed approximately 6 km straightline distance apart along the shorelines of the 

four large lakes. This placed sampling stations 

within 3 km of most of the park’s landmass. 

Sampling (simulated howling) was conducted 

at each station during late July and early August from 1988 through 1991. Stations were 

sampled three nights consecutively using three 

trials of three howls each, with two minutes 

between trials (Fuller and Sampson 1988). 

Pups were distinguished from older animals 

in the responses by their distinctive yips 

(Harrington and Mech 1982). The location, 

number, and estimated age (adult or pup) of 

wolves returning howls were recorded at each 

station. We classifi ed elicited howls from more 

than two wolves as a pack response and elicited 

howls of a single wolf as a lone wolf response.

–

Wolves were captured 

during approximately 

21-day trapping periods 

between 25 April and 15 

May, and from 15 August 

to 15 September, from 

fall 1987 to fall 1990.

We tracked wolves from 

the ground in snow ... to 

augment telemetry data 

on pack size and movements, and to verify 

the existence of packs 

with no radio-marked 

wolves.
8 Gray wolves in and adjacent to Voyageurs National Park, Minnesota: Research and synthesis 1987 – 1991

Incidental observations—We recorded all 

wolf sightings and non-elicited howling detected in the course of our fi eld activities. 

These incidental observations augmented radiotelemetry locations, snow tracking surveys, 

and howling surveys.

Pack territory size 

Territory size was estimated for radio-marked 

packs that were relocated more than 30 times 

(Fuller and Snow 1988, Fuller 1989) in a biological year, beginning 1 May and continuing 

through 30 April of the following year (Mech 

1970). Territories were delineated using the 

minimum convex polygon (MCP) method 

(Mohr 1947, Odum and Kuenzler 1955). We 

excluded locations of wolves beyond the delineated territories or that entered adjacent 

pack territories (Fuller 1989). Unmarked 

packs and those with less than 30 telemetry 

locations were not used in territory area calculations. However, for density calculations, 

the territory boundaries of these packs were 

estimated using available radio locations, 

snow tracks, fall howling surveys, incidental 

observations, and landscape features such as 

large lakes and human developments.

Pack size and density estimates

We estimated minimum pack size (more than 

two wolves) between November and February 

each winter. For radio-marked packs that were 

counted more than fi ve times during telemetry 

fl ights, the estimate was the maximum number of wolves observed. For unmarked packs 

and those counted less than fi ve times during 

telemetry fl ights, we estimated the minimum 

pack size as the maximum number determined from aerial observations, snow tracks, 

and incidental observations. We defi ned a lone 

wolf as a wolf not located with other wolves 

during more than 30 telemetry locations and 

less than 15 visual observations of a specifi c 

individual.

The number of non-territorial wolves is often 

ignored in population estimates. Capture and 

sightability biases make estimating non-territorial wolves diffi cult (Fuller 1989). We calculated the percent of non-territorial wolves from 

telemetry data each year during the census period; however, because of low sample size and 

the potential for capture and sightability biases, 

we assumed that 15% of the population comprised non-territorial wolves when estimating 

population density (Fuller et al. 1992). The use 

of 15% is comparable with recent population 

estimates for Minnesota (Fuller 1989, Fuller et 

al. 1992, Berg and Benson 1998). 

We calculated wolf density each winter over a 

survey area defi ned as the area encompassed 

by all adjoining wolf packs of known size. 

This area included unoccupied space between 

territories. The total number of pack wolves, 

as estimated from snow tracking and visual 

observations, was divided by 0.85 to compensate for non-territorial wolves in the population (Fuller 1989, Fuller et al. 1992, Berg and 

Benson 1998). This quotient was then divided 

by the survey area for an annual estimate of 

density (Fuller 1989). 

Dispersal events 

We defi ned dispersal event as movement 

more than 5 km from the instrumented wolf’s 

original territory, or into another territory, 

and with the wolf not returning to its original 

territory (Fuller 1989:10). A wolf must have 

been located within its home pack territory 

more than fi ve times before being classifi ed as 

dispersing. Dispersal distance was measured 

from the most distant radio location to the 

nearest edge of the original territory (Fuller 

1989:10, Messier 1985). Dispersal date was 

inferred as the mid-date between the last 

telemetry location within and fi rst location 

beyond the original territory (Fuller 1989:10). 

Age at dispersal was inferred from estimated 

birth date. We assumed the loss of a radio signal was indicative of dispersal when signal loss 

was immediately preceded by dispersal-like 

movements (Messier 1985, Fuller 1989). 

Timing and causes of mortality

We investigated mortality signals from transmitters to recover carcasses of study animals 

and examined unmarked wolves that were 

found dead. All carcasses and sites were 

evaluated for cause of death. We removed a 

tooth from each dead wolf for aging by dental cementum annuli (Goodwin and Ballard 

1985, Ballard et al. 1995) and submitted 23 carcasses to the National Wildlife Health Center 

(NWHC), Madison, Wisconsin, for necropsy. 

Causes of mortality were classifi ed as intraspecifi c strife, starvation, vehicle collision, 

gunshot, trapped, snared, unknown humanrelated, or unknown. Mortality sites were classifi ed as in or outside of VNP. Furthermore, 

we assumed human-induced mortality in two 

instances in which instrumented wolves disappeared at the onset of the Minnesota deer rifl e 

season (Fuller 1989). However, these latter 

two mortalities were excluded from calculations of survival rates (see following). 

We removed a tooth 

from each dead wolf for 

aging by dental cementum annuli.

Causes of mortality 

were classifi ed as intraspecifi c strife, starvation, 

vehicle collision, gunshot, trapped, snared, 

unknown human-related, or unknown.
National Park Service 9

Survival rates

We used “Known Fates” models in program 

MARK (White 1998) (appendix 3) to estimate 

wolf survival. To meet assumptions of Known 

Fates survival analysis, we used only information on mortalities that was confi rmed via 

radiotelemetry and on-ground inspection of 

each location. We created seasonal encounter 

histories from radiotelemetry records and assessed the potential infl uences of (1) age, (2) 

sex, (3) territory location relative to VNP, and 

(4) time of year on survival of marked wolves 

(appendix 3). Specifi c hypotheses were:

H01: Survival is constant between pups and adults

HA1: Survival varies between pups and adults

H02: Survival is constant between males and females

HA2: Survival varies between males and females

H03: Survival is constant among wolves utilizing 

territories that are contained within VNP, 

border VNP, and are outside VNP

HA3: Survival varies among wolves utilizing territories that are contained within VNP, border 

VNP, and are outside VNP

H04: Survival is constant over time of year

HA4: Survival varies by time of year

To facilitate comparisons with other North 

American wolf populations, we assessed 

overall annual survival over a biological year, 

from 1 May through 30 April of the following 

year. A biological year was divided into four 

biological seasons (Mech 1970): pup rearing 

(1 May – 30 June), early rendezvous (1 July – 30 

September), late rendezvous or winter freezeup (1 October – 31 November), and winter 

post-iceup (1 December – 30 April). The late 

rendezvous period included the northern 

Minnesota deer rifl e-hunting season. 

To address the hypothesis of diff ering survival by age, we included relocation data for 

all instrumented wolves. Within a given biological year, each animal was classifi ed as a 

pup or an adult. Survival probabilities were 

calculated for each classifi cation only for the 

nine-month period from 1 August – 30 April. 

The pup-rearing season and fi rst month of the 

early rendezvous season were excluded from 

analysis because we did not radio-mark pups 

during these months. To address hypotheses 

two through four regarding survival by sex 

and territory location, we included relocation 

data for only instrumented adults for the entire biological year. Pups were excluded from 

analysis because they were not sampled for 

an entire biological year. Within a given biological year, each adult was coded as male or 

female and as to territory location relative to 

VNP. We addressed hypothesis four regarding 

survival over time, i.e., biological season, in 

the context of the previous three hypotheses. 

That is, we assessed survival over time in conjunction with examination of survival by age, 

sex, and territory location. 

Diseases and parasites

Necropsies, including gross and microscopic 

examination, were performed on intact and 

partial carcasses of instrumented and non-instrumented wolves collected in and adjacent 

to VNP. This included some wolves that were 

trapped legally in adjacent Ontario. Laboratory tests in bacteriology, virology, and parasitology were used to determine causes of death 

and to identify incidental abnormalities.

Blood, ectoparasites, and feces were collected 

from captured wolves, and additional fecal samples were collected opportunistically 

along trails. Tests for serum antibodies to Borrelia burgdorferi, canine parvovirus (CPV-2), 

canine distemper, infectious canine hepatitis, 

rabies, Brucella canis, Leptospira interrogans,

and blastomycosis were identical to procedures detailed in Peterson et al. (1998). Serology to detect canine heartworm (dirofi lariasis) 

was done at Colorado State University (Ft. 

Collins, Colorado). Knott’s test was used to 

detect microfi laria in blood, and fecal fl otation 

or sedimentation and direct-smear examination were used to survey for internal parasites 

(Ash and Orihel 1987). Feces from captured 

wolves, trails, and carcasses were screened for 

CPV-2 with a test kit for canine-parvovirus 

antigen (Peterson et al. 1998).

Population genetics

Blood and tissue samples obtained from 19 

wolves during trapping or at time of death 

were sent to the Department of Biology, University of California, Los Angeles, for analysis. 

Researchers there pooled our samples with 

wolf and coyote samples from across North 

America and mitochondrial DNA (mtDNA) 

genotypes were determined using restriction 

fragment length polymorphisms (Lehman et 

al. 1991). 

Feeding ecology

We collected wolf scats from January 1987 

through September 1989. Each scat was referenced with date of collection, approximate 

time of deposition, and location. Scats were 

air dried and autoclaved prior to examination 

Laboratory tests in bacteriology, virology, and 

parasitology were used 

to determine causes of 

death and to identify incidental abnormalities.
10 Gray wolves in and adjacent to Voyageurs National Park, Minnesota: Research and synthesis 1987 – 1991

with a dissecting microscope to identify prey 

(Adorjan and Kolenosky 1969, Schmidt 1990). 

Occurrence of each prey species was tallied 

by month and season. Vegetation was tallied 

if it comprised more than 50% of the scat by 

volume.

Small mammals have a relatively large ratio of 

indigestible hair to digestible meat, so may be 

over-represented in frequency of occurrence 

data (Mech 1970, Floyd et al. 1978, Fritts and 

Mech 1981, Weaver 1993). To rectify this, we 

estimated the relative biomass of each prey 

species consumed by wolves using correction factors for prey size (Weaver 1993). We 

reasoned that each scat was representative of 

a meal and that each prey species in that scat 

had equal weight in that meal. Thus, we assigned a value of 0.5 for each prey in the 10% 

of scats that contained two prey items. We 

did not fi nd more than two prey represented 

in any scat. We used data from this study 

and other nearby studies to estimate average weight of prey consumed in each season 

(Fritts and Mech 1981).

We examined the remains of wolf-killed deer 

and other prey to assess their age, sex, and nutritional status. A tooth was collected for age 

determination by dental annuli (Larson and 

Taber 1980). When teeth were not available, 

remains were classifi ed as either fawn (less 

than one year old) or adult (more than one 

year old) based upon skeletal measurements 

(Fuller et al. 1989). Sex was determined by examination of soft tissues or by the presence or 

absence of antler pedicels. We collected deer 

leg bones in the following order of preference: 

femur, humerus, tibia, radius, metacarpal, 

and metatarsus. Bones were submitted to the 

MnDNR Grand Rapids, Minnesota, for analysis of percent marrow fat to provide an index 

to physical condition of prey. When femurs 

were not available, femur percent marrow fat 

was calculated from other limb bones following the procedures of Fuller et al. (1989).

We estimated the relative biomass of each 

prey species consumed 

by wolves using correction factors for prey size.
National Park Service 11

Results and Discussion

Capture and radiotelemetry

Thirty-one wolves, 13 males and 18 females, 

were radio-marked in and adjacent to VNP 

between August 1987 and May 1991. The 

mean weight of male wolves one or more year 

old was 32.7 kg while that of females one or 

more year old was 30.8 kg (table 1). The difference was non-signifi cant (t = −0.869, df = 

16.3, P = 0.397). One of 23 adult wolves died 

because of our trapping and handling procedures. Three of eight radio-marked pups 

lost their collars within 10 days (two collars 

slipped off , and pack mates chewed off one).

The remaining 27 instrumented wolves were 

relocated 1,174 times (appendix 4): 15 (54%) 

were followed for two months to one year, nine 

(32%) for one to two years, and four (14%) for 

more than two years for a total of 307 transmitter exposure months. We radio-tracked an 

average of three adult males (range 1 – 6), seven 

adult females (6 – 9), one male pup, and one 

female pup (0 – 3) associated with from 1 to 10 

(x = 6) packs each year between 1987 and 1991 

(fi gure 5). We identifi ed 13 packs (fi gure 5, 

page12), but four study wolves were solitary or 

left the area before pack affi liation was determined. One pack of three wolves abandoned 

their territory and became nomadic.

Noninvasive population sampling 

Snow tracking—We snow-tracked wolves on 

29 and 28 days during winter 1987 – 1988 and 

1988 – 1989, respectively. Wolf tracks were encountered 152 times during the two winters. 

The exact number of wolves in a group was 

determined with confi dence on 74 (49%) track 

encounters (table 2): 41% were single wolves, 

35% were pairs, 19% were of three to fi ve, and 

5% ranged from six to nine wolves. There was 

a signifi cant diff erence (χ2

 = 6.30, df = 1, P =

0.012) in the occurrence of lone wolves and 

wolf packs (more than two wolves) in the winters of 1987 – 1988 and 1988 – 1989 (table 2). A 

possible cause for the high proportion of single 

wolves in winter 1987 – 1988 was food stress, although we collected no data on kill rates. Both 

the winters of 1986 – 1987 and 1987 – 1988 were 

relatively mild (fi gure 2). Ungulate prey is less 

vulnerable during mild winters (Mech 1970), 

and wolf pack cohesiveness declines when food 

resources are limited (Mech 1970). In contrast, 

we detected an increase in the number of packs 

during the severe winter of 1988 – 1989. Overall, 

Table 2. Frequency of wolf group sizes encountered during snow tracking in and adjacent to Voyageurs 

National Park, Minnesota, winter 1987–1988 and 1988 –1989.

1987–1988 1988 –1989 Total

Group Size Frequency % Frequency % Frequency %

1 22 55.0 8 23.5 30 40.5

2 12 30.0 14 41.2 26 35.1

3 2 5.0 4 11.8 6 8.1

4 1 2.5 2 5.9 3 4.1

5 2 5.0 3 8.8 5 6.8

6 0 0.0 1 2.9 1 1.4

7 0 0.0 0 0.0 0 0.0

8 1 2.5 1 2.9 2 2.7

9 0 0.0 1 2.9 1 1.4

 Total 40 100.0 34 100.0 74 100.0

Table 1. Weight by age class and sex of 30 wolves captured, radio-marked, and released for study in and 

adjacent to Voyageurs National Park, Minnesota, 1987 –1991.

Weight (kg)

Agea Sex nb x (kg) SD Range

>1 yr M 9 32.7 4.4 29.0– 43.1

F 13 30.8 3.4 25.0 – 35.5

<1 yr M 3 17.3 7.2 10.9 – 25.0

F 5 15.2 4.1 11.0 – 20.9

a

Estimated age at time of capture.

bOne adult male was not weighed.

–

_

Thirty-one wolves, 13 

males and 18 females, 

were radio-marked in 

and adjacent to VNP between August 1987 and 

May 1991.

Wolf tracks were encountered 152 times during the two winters.
12 Gray wolves in and adjacent to Voyageurs National Park, Minnesota: Research and synthesis 1987 – 1991

larger groups were encountered with decreasing frequency (r = −0.81, P = 0.009) (fi gure 6). 

Similar fi ndings were presented by Mech et al. 

(1998:108).

The number of wolves identifi ed as traveling 

together from snow tracks (table 2) does not 

always equal pack size because pack members 

often separate and rejoin (Mech et al. 1998). 

However, repeated snow track observations 

provide reliable estimates of pack size similar to multiple observations from telemetry 

(Stenlund 1955, Fuller et al. 1992, Wydeven 

et al. 1995, Berg and Benson 1998). Snow 

tracks were the sole data to estimate the presence and size of 5 of 6 known packs (83%) in 

1987 – 1988 and 4 of 11 (36%) in 1988 – 1989 

(appendix 4). We used a combination of both 

methods in 1988 – 1989. Estimates of pack size 

derived from snow tracks were identical to 

estimates derived from telemetry for all fi ve 

packs where both data types were available 

(appendix 4). This fi nding supports snow 

tracking as an appropriate method to determine the presence or absence of packs and to 

estimate pack size.

Snow tracking during winter 1987 – 1988 and 

1988 – 1989 showed that wolves traversed the 

shorelines and crossed the frozen surfaces, 

especially at narrow areas, of larger lakes such 

as Rainy, Kabetogama, and Namakan (fi gure 

7). However, our radiotelemetry data, collected only during daylight hours, did not 

detect wolves in these same areas (see Fox et 

al. 1999). Presumably, the tracks refl ect use of 

these areas at night. Levels of human use of 

the frozen lake surfaces are less at night than 

in daylight and wolves may move more freely 

under the cover of darkness. In contrast, winter daylight movements of wolves at the largely 

uninhabited Isle Royale included regular travel 

along the island’s shoreline, crossing large 

frozen embayments, and ranging out onto the 

open ice of Lake Superior (Peterson 1995). 

Similarly, wolves in the Boundary Waters 

Figure 5. History of radio contact 

with 31 radio-marked wolves 

in and adjacent to Voyageurs 

National Park, Minnesota. Black 

bars represent contact with 

wolves associated with packs or 

groups. Gray bars represent contact with wolves not associated 

with packs or groups or with 

wolves dispersing from packs 

or groups. Two wolves that dispersed from their original packs 

and joined other packs and one 

wolf that dispersed from a pack 

and joined a wandering group 

are represented twice.

Pack Wolf 1988 1989 1990 1991

number A S O N D J F M A M J J A S O N D J F M A M J J A S O N D J F M A M J J A S O N D J F M A M

Tom Cod 4625

5125

7870

6875B

Cruiser Lake 4375

7375B

Kohler Pit 6375A

8380

Kohler Trio 8380

Blue Moose 5375

 8880A

Dixon Creek 6625A

Moose Lake 7125

Locator Lake 7625

Middle Peninsula 4375

6375B

5620

Rat Root 9125B

Nebraska Bay 5870

 8880B

 6625B

Moose Grade 6875A

7615

 6375B

 8375

Browns Bay 9125A

8125B

 8635

6125

No Pack Association 4875

5625

6130

7375A

Year and month

1987

Levels of human use of 

the frozen lake surfaces 

are less at night than 

in daylight and wolves 

may move more freely 

under the cover of darkness.
National Park Service 13

Canoe Area Wilderness are seen regularly in 

daylight hours along the shorelines and frozen 

surfaces of lakes (M. E. Nelson, U.S. Geological Survey [USGS], personal communication). 

While snow tracking between late January 

and late February of 1988 and 1989, females 

in estrous were identifi ed by the presence of 

blood in the urine in fi ve packs. Howling surveys confi rmed that three of these packs bore 

pups, and live capture of a pup confi rmed the 

fourth. Insuffi cient data were collected to evaluate the birth rates for packs in the study area.

Howling surveys—We conducted howling 

surveys at 24 water-based sites throughout 

VNP each July and August from 1988 through 

1991 (fi gure 8, page 14). Adults and pup wolves 

responded to simulated howls in all years. Wolf 

packs responded to simulated howls at a high 

of 16.7% of howling sites in 1989 to a low of 

8.3% in 1990 (table 3, page 15). The percent of 

responding packs that contained pups varied 

from 100% in 1988 and 1991 to a low of 50% 

in 1990. Often, the responses of packs and 

lone wolves were elicited at the same sample 

site. The greatest number (n = 8) of responses 

of single wolves was in 1991.

We evaluated the utility of our howling surveys to monitor for the presence of wolf packs 

by comparing howling responses at survey 

Figure 6. Percent of encounters 

with different wolf group sizes 

during snow tracking in and 

adjacent to Voyageurs National 

Park, Minnesota, winter 1987–

1988 and 1988 –1989.

Figure 7. Location of tracks of 

all wolves encountered (upper 

left) and groups of two or more 

wolves encountered (upper 

right) in winter 1987–1988 and 

all wolves encountered (lower 

left) and groups of two or more 

(lower right) encountered in 

winter 1988 –1989 in and adjacent to Voyageurs National Park, 

Minnesota.

0

10

20

30

40

50

123456789

Group Size

1987–1988 1988–1989 Total

Females in estrous were 

identifi ed by the presence 

of blood in the urine....
14 Gray wolves in and adjacent to Voyageurs National Park, Minnesota: Research and synthesis 1987 – 1991

locations within known wolf territories. Detectability of packs known to exist the winter 

prior to the howling survey ranged from 40% 

to 67% and averaged 52% (table 4, page 16). 

The detectability of packs that were known to 

exist the following winter ranged from 33% to 

83% over three years and averaged 56% (table 

4). Detectability varied by pack with one pack 

(LLP) never being detected. Our ability to elicit responses from known packs may have been 

limited by the diffi culty of projecting simulated howls over the entire landmass from the 

shoreline (fi gure 8). For example, our failure 

to elicit responses from two known packs (the 

LLP and CLP) in 1988 was likely because both 

packs were beyond the audible range of the 

simulated howls. Fuller and Sampson (1988) 

found that human observers detected 80% of 

simulated howls between 0.3 and 1.5 km from 

sampling stations and no simulated howls at 

more than 2.5 km from sample stations.

Limitations of howling surveys were detailed 

by Harrington and Mech (1982): (1) response 

rates vary and may be biased towards detecting larger packs, (2) the method does 

not indicate the number of wolves present 

because individual animals can seldom be 

distinguished during a pack response, (3) pack 

territories cannot be determined, and (4) response rates may be low relative to the work 

eff ort to complete the survey because coverage 

of the entire survey area cannot be guaranteed 

and not all packs will respond. We add to this 

list that in VNP accessing sampling stations by 

boat at night poses numerous safety hazards. 

We reduced the possible bias of detecting 

larger packs by using a single stimulus, i.e., 

only one person howled during each trial, and 

we surveyed during late summer and early 

fall when packs are less cohesive but pups are 

more vocal. Others have judged elicited howling surveys as an unsatisfactory index of wolf 

density (Crête and Messier 1987). However, 

the sample stations may be used to determine 

the presence or absence of reproductively 

successful wolf packs—although with the 

relatively low annual response rates, it will be 

necessary to pool data from a number of years 

before any trend is detected. Cumulative effects modeling shows that pup recruitment is a 

critical population parameter in assessing the 

long-term sustainability of wolves within VNP 

(Cochrane 2000). In spite of the shortcomings, 

fall howling surveys may be one of the most effective nonintrusive means of detecting pups 

within the Voyageurs region wolf populations. A 

revised fall howling survey, perhaps land based, 

should be considered as a monitoring tool.

Snow tracking and howling as monitoring 

tools—Snow tracking was essential to estimate 

the number of wolves in packs containing no 

radio-marked animals. Estimates of pack sizes 

Figure 8. Location of howling 

survey sites with an estimated 

perimeter of audibility of 2.5 km 

(upper left) and responses by 

wolves to simulated howling for 

1988 (upper right), 1989 (lower 

left), and 1990 (lower right), 

Voyageurs National Park, Minnesota.

The detectability of 

packs that were known 

to exist the following 

winter ... averaged 56% 

[over three years].
National Park Service 15

obtained by snow tracking were identical to 

those derived from telemetry in all fi ve cases 

where we obtained both data types in winter 

1988 – 1989. This fi nding supports snow tracking as an appropriate method to determine the 

presence or absence of packs and to estimate 

pack size (see Pack numbers, territories, and 

wolf density). Other investigators have used 

snow tracks as the primary means of estimatTable 3. Results of human-elicited wolf howling surveys at 24 sites in Voyageurs 

National Park, Minnesota, 1988–1991.

Sample Perioda

Lake/ Sample Siteb 1988 1989 1990 1991

Kabetogama

 K1 n/s x x x

 K2 p(w) p(wo) x x

 K3 x x x x

 K4 p(w), l(1) x x x

 K5 x x p(w), p(wo) x

 K6 x x x x

 K7 x x x x

 K8 x p(w), l(2) x l(1)

 Pack response (%) 28.6 25.0 12.5 0.0

 Total response (%) 28.6 25.0 12.5 12.5

Namakan / Sand Point

 N1 x x x p(w)

 N2 x x x x

 N3 x x x x

 N4 x x x x

 N5 x p(w), l(1) l(1) x

 N6 p(w) x x p(w)

 N7 x x x x

 N8 x x p(wo) x

 Pack response (%) 12.5 12.5 12.5 25.0

 Total response (%) 12.5 12.5 25.0 25.0

Rainy

 R1 x x x l(1)

 R2 x x x l(2)

 R3 x x x x

 R4 x x x l(1)

 R5 x x x l(1)

 R6 x p(w) x l(2)

 R7 x x x x

 R8 x x x p(w)

 Pack response (%) 0.0 12.5 0.0 12.5

 Total response (%) 0.0 12.5 0.0 75.0

Total

 Sites sampled 23 24 24 24

 Sites with packs (%) 13.0 16.7 8.3 12.5

 Sites with responses (%) 13.0 16.7 12.5 37.5

Note: n/s = not surveyed; x = surveyed but no response; p = pack responded; (w) = with pups; 

(wo) = without pups; l = lone wolf responded; (#) = number of lone wolves responding from 

different locations.

a

Surveys conducted between late July and early August each year (see text).

bFor location of sampling sites see fi gure 8.

ing wolf abundance and movements (Mech 

1966, Berg and Benson 1998, Wydeven et al. 

1995). However, the accuracy of snow tracking is diffi cult to substantiate, and the methodology is subject to observer bias. Repeated 

sampling eff orts are often necessary to deduce 

pack size, and teasing apart the presence of 

adjacent packs can be problematic. Furthermore, the methodology is of limited utility 

in determining the numbers of pups within 

a pack (two occurrences out of 19 track encounters with packs in our study). Nevertheless, done repeatedly by experienced observers, snow tracking provides reasonably reliable 

estimates of wolf numbers. Snow tracking 

provides insights into diff erences in day and 

night movement patterns of wolves and, in 

some cases, helps elucidate pack territory 

boundaries. In addition, we found evidence of 

female reproductive activity via snow tracking. 

Finally, snow tracking led us to wolf kill sites 

where we were able to obtain information on 

prey species age, sex, and condition, and to 

scats from which we obtained information on 

food habits.

In contrast, howling surveys verifi ed the existence of only about 50% of the wolf packs 

we determined to occur within the Voyageurs 

region via radiotelemetry and snow tracking. 

Wolf abundance and pack territorial limits 

cannot be determined from howling surveys. 

Pack response rates vary with the pack’s distance from simulated howls and the presence 

or absence of pups. Packs that include pups 

may respond more frequently than packs 

without pups because pups readily respond 

to simulated howls. Howling surveys may 

provide an index of wolf reproductive success 

while snow tracking may provide an index to 

wolf abundance. 

Incidental observations—Forty-three sightings of 106 wolves (range 1 to 11 wolves) 

were made without the aid of radiotelemetry, 

and 11 occurrences of packs or single wolves 

were determined from unelicited howls (as 

opposed to those elicited during howling surveys). Of these, 17 incidental sightings and fi ve 

unelicited howlings were used to support the 

existence and size of study packs (appendix 

4). Other incidental observations provided 

evidence of movements of single wolves and 

the probable presence of unmarked packs.

Pack numbers, territories, and wolf density

Thirteen wolf packs were followed by radiotelemetry for six months to four years (fi gure 9, 

page 17). Six packs (TCP, LLP [replaced later 
16 Gray wolves in and adjacent to Voyageurs National Park, Minnesota: Research and synthesis 1987 – 1991

Table 4. Detectability of known wolf packs by human-elicited howling surveys in Voyageurs National Park, Minnesota, 1988–1991.

Sampling Perioda

1988 1989 1990 1991

Packb P D P D P D P D Detection Rate by Pack (%)

Detectability of packs known to exist the winter prior to howling surveys

 Tom Cod yes yes yes no yes yes yes no 50

 Locator Lake yes no yes no 0

 Middle Peninsula yes no yes no 0

 Cruiser Lake yes no yes yes yes yes yes yes 75

 Browns Bay yes yes yes yes yes yes 100

 Moose Grade yes no yes yes yes no yes yes 50

 Nebraska Bay yes yes yes yes yes no yes no 50

 Subtotal 6 3 6 4 5 2 6 3

 Detection rate (%) 50 67 40 50

 x (%) 52

Detectability of packs known to exist the winter following howling surveys

 Tom Cod yes yes yes no yes yes 67

 Locator Lake yes no 0

 Middle Peninsula yes yes yes no 50

 Cruiser Lake yes no yes yes yes yes 67

 Browns Bay yes yes yes yes yes no 67

 Moose Grade yes no yes yes yes no 33

 Nebraska Bay yes yes yes yes yes no 67

 Subtotal 6 3 6 5 6 2

 Detection rate (%) 50 83 33

 x (%) 56

Note: Pack presence (P) and its territory were determined by radiotelemetry, snow tracking, and incidental observations during the winter preceding and 

following the howling survey. Pack detection (D) was affi rmative if >1 howling response was heard from a pack (>2 wolves) within its known territory.

a

Surveys conducted between late July and early August each year (see text).

bSee fi gure 9 for pack territories.

by MPP], CLP, MGP, BBP, and NBP) used 

the park each year, and two to three of these 

packs occupied portions of the Kabetogama 

Peninsula each year (fi gure 9). The large lakes, 

notably Rainy Lake and to a lesser extent 

Kabetogama, Namakan, and Sand Point, appeared to be eff ective obstacles to movement, 

even when frozen, and served as boundaries 

to territories, as did the open water and thin 

ice of the narrow channel at the east end of 

the Kabetogama Peninsula. After May 1989, 

we ceased eff orts to capture and instrument 

wolves in fi ve packs (KPP, BMP, DCP, MLP, 

and RRP) that ranged primarily beyond the 

boundaries of VNP. However, we did continue to relocate instrumented wolves from 

these packs for the life of the study. One pack 

(KTP) dispersed from the area, and one pack 

(LLP) apparently dissolved after a territorial 

dispute (see Dispersal events, appendix 5). The 

13 packs were relocated a mean of 58 times 

per wolf year (range 30 – 100), and mean territory size was 152 km2

 (range 48 km2 to 296 

km2

) based on 16 annual pack territories (x = 4 

Table 5. Minimum territory size for radio-marked wolf packs where 30 or more radiotelemetry locations 

were obtained in and adjacent to Voyageurs National Park, Minnesota, 1987–1991.

No. of Locations Territory Size (km2) Pack Size

Pack Yeara No. of Packs x Range x Range x Range

1987 – 1988 1 59 — 122 n /a 5 —

1988 – 1989 5 41 32 – 65 120 48 – 232 4.8 2–8

1989 – 1990 3 66 62 – 82 216 145 – 296 5 4–6

1990 – 1991 7 70 41 – 100 148 70 – 289 5 2–9

x 4 58 30 – 100 152 48 – 296 5 2–9

a

Pack year defi ned as May 1 through April 30.

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National Park Service 17

packs per year) determined by 30 or more 

locations (table 5). We combined our observations during winter telemetry fl ights with 

snow tracking and incidental sightings (appendix 4) to estimate the numbers of wolves in 

nine packs at least once during the study for a 

total of 23 pack years (table 6, page 18). Packs 

ranged in size from 2 to 11 wolves. We adjusted the number of pack wolves upward by 15% 

to estimate winter densities of wolves in the 

Voyageurs region (table 6). Territory sizes for 

wolves in the Voyageurs region were within 

the range of other wolf populations that exist on 

a white-tailed deer economy (table 7, page 19).

The mean mid-winter pack size was 5.5 

wolves, ranging from 6.3 during 1988 – 1989 

to 4.5 during 1989 – 1990 and did not diff er 

signifi cantly (P > 0.05) from those in other 

studies of wolves preying primarily on whitetailed deer (n = 12, unweighted x = 5.6; table 

7). Excluding newly forming packs or expanding populations (table 7), the mean pack size 

for Voyageurs region wolves falls at the lower 

range of estimated pack sizes for wolves on a 

white-tailed deer economy (5.3 to 8.0), but the 

means did not diff er signifi cantly (two-tailed 

t-test; P > 0.05).

Pack sizes were smallest in the winter of 

1989 – 1990. However, our estimate of mean 

pack size that winter is likely low; we did no 

snow tracking that winter, and our eff orts 

the previous two trapping periods to capture 

and radio-mark wolves in three of the largest 

packs within the park were unsuccessful. 

Four of 31 (13%) captured wolves were lone 

wolves (fi gure 5). In three of the four years, we 

detected only one solitary and non-territorial 

wolf. A subadult female wolf trapped in 1987 

in the territory of the CLP was radio-located 

56 times and observed 14 times from August 

1987 to September 1988. She was solitary on 

all occasions and ranged over an area larger 

than 6,000 km2

. This wolf was classifi ed as 

solitary (Fuller 1989). In 1988 – 1989, two 

single wolves and a trio of wolves (KTP) were 

non-territorial. Other studies suggest that the 

number of single, non-resident wolves varies 

from 2 to 29% of the population (Pimlott et al. 

1969; Mech 1966, 1973; Fuller and Keith 1980; 

Figure 9. Locations of wolf 

packs within and adjacent to 

Voyageurs National Park, Minnesota, by year, 1987 through 

1991. Three-letter abbreviations 

correspond with pack names in 

table 6. Stippled polygons indicate pack territories determined 

by 30 or more radiotelemetry 

locations. Other polygons were 

estimated from less than 30 

radiotelemetry locations, snow 

tracking, howling surveys, incidental observations, terrain, and 

human developments. Area estimates are for areas within the 

bold line.

_
18 Gray wolves in and adjacent to Voyageurs National Park, Minnesota: Research and synthesis 1987 – 1991

Peterson and Page 1988). Fuller (1989) noted 

that estimates of non-territorial wolves from 

radiotelemetry data alone could be biased because non-territorial wolves are more diffi cult to 

observe and because researchers tend to focus 

trapping eff orts within known pack territories. 

Because of this, Fuller (1989) used 16%, the 

midpoint in the range of estimates from the 

literature, to estimate the number of non-resident single or paired wolves. Subsequently, 

Fuller et al. (1992) and Berg and Benson (1998) 

used 15% single non-resident wolves to calculate the total wolf numbers in Minnesota. Given our small sample of captured wolves and 

the potential for observability and sampling 

bias, we assumed 15% of wolves in the study 

area were solitary and non-territorial (table 6). 

Wolf densities averaged 33/1,000 km2

 over 

the four years and ranged from a high of 42/

1,000 km2

 in 1988 – 1989 to 24/1,000 km2 in 

1989 – 1990 (table 6). Mean wolf density in the 

Voyageurs region did not diff er signifi cantly (P

> 0.05) from other locations either when including (x = 30 wolves / 1,000 km2

) or excluding 

(x = 33 wolves/1,000 km2

) newly forming packs 

or expanding wolf populations (table 8, page 

20). The estimated low density of wolves for the 

winter of 1989 – 1990 was likely due to a lack of 

information on three large packs during that 

winter (see earlier discussion).

Dispersal

Eight (29%) of 20 instrumented adult wolves 

with known pack affi liation dispersed and one 

dispersed twice for a total of nine dispersal 

events (table 9, page 20). These nine included 

four wolves dispersing beyond the study area, 

two disappearing, one being killed by wolves 

after dispersing, and two joining or forming 

neighboring packs. Two incidents of dispersal 

involved three to fi ve wolves in “pack-splitting” events (Mech et al. 1998) (see following 

discussion). Animals less than two years old 

dispersed in December and January while 

those more than two years old dispersed in 

October, December, and March. The timing 

of dispersal from late fall through early spring 

is consistent with timing of dispersal in northcentral Minnesota (Fuller 1989) and elsewhere 

in North America (Messier 1985). The mean 

dispersal distance was 33 km (0.9 – 83.7) (table 

9). Both instances of dispersal where we determined that a pack was joined or formed were 

within 2 km of VNP. However, three solitary 

wolves dispersed more than 50 km. All except 

one dispersal were to the south or west, suggesting that even when the area’s large lakes 

were frozen in winter, they were partial barriers to dispersal. The mean age of dispersing 

wolves was four years (1.5 – 7.5 years). Three 

of the dispersing wolves were yearlings while 

three additional dispersing wolves were more 

Table 6. Minimum estimates of pack size (E) and wolf density for nine packs, as estimated from track counts (T), incidental observations (I), 

and direct counts with the aid of radiotelemetry (R), in and adjacent to Voyageurs National Park, Minnesota, 1987–1991.

Census Perioda

1987–1988 1988 –1989 1989 –1990 1990 –1991

Pack T I R E T I R E T I R E T I R E

Tom Cod (TCP) 5 5 5 5 5 5 5 5 5 2 2

Locator Lake (LLP) 4 3 3 7 7 7

Middle Peninsula (MPP) 4 4 9 9

Cruiser Lake (CLP) 8 8 8 8 8 8 6 6

Browns Bay (BBP) 7 7 9 9 9 9

Moose Grade (MGP) 9 11 11 8 8 8 3 3

Blue Moose (BMP) 2 2 2

Nebraska Bay (NBP) 2 2 5 5 6 6

Rat Root (RRP) 3 3 2 2

 Total packs enumerated 6 7 4 6

x pack size 6.0 6.3 4.5 5.2

 Range of pack sizes 2 – 11 2 – 9 3 – 6 2 – 9

 Estimated no. pack wolves 36 44 18 31

 Estimated no. single wolvesb 6 8 3 5

 Total wolves 42 52 21 36

 Survey area (km2

)c 1,190 1,242 866 1, 150

 Density (wolves/ 1,000 km2) 36 42 24 32

Note: Final estimates (E) take into account the reliability, frequency, and type of observations.

a

Census period defi ned as November through February of each winter.

bCalculated as 15% of the total population (Fuller et al. 1992, Berg and Benson 1998).

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National Park Service 19

Table 7. Mean territory size and pack size for wolf populations on a white-tailed deer economy.

Territory Size (km2) Pack Size

Location No. of Packs x Range x Range Reference

Northeast Minnesota 5 110 52 – 145 8.0 5 – 10 Van Ballenberghe et al. 1975

East-central Ontario 1 224 — 8.0 — Kolenosky 1972

Northeast Minnesota 11 243 — 7.0 3 – 11 Mech 1973

East-central Ontario 4 175 — 7.0 — Pimlott et al. 1969

North-central Minnesota 5 215 161 – 272 6.6 5 – 8 Berg and Kuehn 1980, 1982

North-central Minnesota 33 116 51 – 223 5.7 2 – 12 Fuller 1989

Southern Quebec 21 199 85 – 325 5.6 — Potvin 1988

Northern Minnesota 16 152 48 – 296 5.5 This study

Northeast Minnesota 9 183 59 – 323 5.3 4 – 7 Mech 1986b

Northwest Minnesotaa 22 260 77 – 664 4.6 2 – 9 Fritts and Mech 1981

Northern Wisconsina 72 137 47 – 287 3.9 — Wydevan et al. 1995

North-central Minnesotaa 3 87 40 – 135 2.7 2– 4 Fuller 1989

Wisconsin-Minnesota bordera 5 196 67 – 310 2.6 2 – 4 R. Thiel, in Fuller et al. 1992

x withb n = 12c 179 5.6

 Median withb n = 12c 190 5.7

x withoutb n = 8c 183 6.7

 Median withoutb n = 8c 191 6.8

Note: Adapted from Fuller (1989) and Fuller et al. (1992).

a

Newly forming packs or expanding population.

bWith or without studies of newly forming packs or expanding populations.

c

Number of studies excluding this study.

than seven years old (table 9). The mean age of 

dispersing wolves excluding the three oldest 

animals was 2.3 years (table 9). The proportion of wolves more than two years old and the 

incidence of wolves more than seven years old 

dispersing from the Voyageurs region is exceptional. More than 75% of dispersing wolves 

in SNF were pups or one-year-olds (Gese and 

Mech 1991). The oldest known aged dispersing wolf was fi ve years (Gese and Mech 1991). 

Eleven of 18 dispersing wolves on the Kenai 

Peninsula, Alaska, were yearlings or two-yearolds (Peterson et al. 1984). The mean annual 

dispersal rate in the Voyageurs region from 

1987 through 1991 of 0.37 (table 10, page 21) is 

one of the highest reported (Mech et al. 1998, 

Fuller 1989). We cannot explain the high rate 

of dispersal in the Voyageurs region.

Dispersing wolves in the Voyageurs region 

made an average minimum of 2.1 pre-dispersal movements (range 0 – 5) (table 11, page 21). 

Similarly, Messier (1985) reported an average 

minimum of 2.1 pre-dispersal movements, and 

Fuller (1989) reported wolves made from one 

to six pre-dispersal movements (mean minimum of 0.9). The mean distances between 

consecutive locations within new territories 

were greater than in the original territory (P 

< 0.008, t-test) indicating that wolves occupying new areas expended greater eff ort (travel 

distance), presumably to explore, mark, and 

defend their new territory.

The observed incidents of pack splitting 

(Mech et al. 1998) or of a dwindling pack 

dispersing from its home territory deserve additional discussion. 

Cruiser Lake Pack split—In fall and early 

winter 1988, radio tracking of instrumented 

wolves of the LLP (seven wolves) and CLP 

(eight wolves) packs indicated non-overlapping territories (fi gure 9). On 20 January 1989 

all eight members of the CLP were located in 

the LLP territory, and the single radio-marked 

LLP wolf and an unmarked wolf had been 

killed by wolves (appendix 5). Visual inspection of the site where the LLP pack members 

were killed confi rmed that the packs had 

encountered one another. Because all eight 

CLP wolves were located alive after this date, 

we believe the dead unmarked wolf was also 

from the LLP. Thus, two of the seven LLP 

members were likely killed. We were unable to 

determine the size or fate of the LLP after the 

death of the instrumented wolf. However, the 

instrumented CLP wolf and at least four others occupied the LLP area after this dispute.

The previously instrumented CLP wolf along 

with two newly radio-marked wolves and one 

_ _

The mean annual dispersal rate in the Voyageurs region ... is one of 

the highest reported.

_

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20 Gray wolves in and adjacent to Voyageurs National Park, Minnesota: Research and synthesis 1987 – 1991

Table 8. Density of wolves that exist primarily on a white-tailed deer economy.

Location

Wolf 

Density / 1,000 

km2 of Habitat Reference

Northwest Minnesotaa 17 Fritts and Mech 1981

Northern Wisconsina 19 Wydevan et al. 1995

Northeast Minnesota 23 Stenlund 1955

Northeast Minnesota 25 Mech 1986b, Nelson and Mech 1986a,b, MDNR fi les

North-central Minnesota 28 Berg and Kuehn 1980

Southern Quebec 28 Potvin 1988

Northern Minnesota 33 This study

East-central Ontario 36 Pimlott et al. 1969, Kolenosky 1972

East-central Ontario 38 Pimlott et al. 1969

North-central Minnesota 39 Fuller 1989

Northeast Minnesota 40 Mech et al. 1971, Peek et al. 1976, Nelson and Mech 1986a

Northeast Minnesota 42 Van Ballenberghe et al. 1975

x withb 30

 Median withb 28

x withoutb 33

 Median withoutb 36

Note: After Fuller 1989.

a

Newly forming packs or expanding population.

bWith or without studies of newly forming packs or expanding populations.

Table 9. Sex, pack affi liations, age, and dates of nine dispersals for eight different wolves radio-marked in and adjacent to Voyageurs 

National Park, Minnesota, 1987–1991.

Dispersal 

Wolf 

Number Sex

Pack Affi liations:

Original / After Dispersal

Age 

(yrs) Date Location and Status

Distance 

(km) Direction

In /Out 

of Study 

Area

 4375 M Cruiser Lake Pack (CLP) / Middle 

Peninsula Pack (MPP)

1.5 01/29/89 Split from CLP with 4 others to 

form MPP after taking over LLP 

territory. Dispersed again later 

(see below).

 0.9 west in

 4375 M Middle Peninsula Pack (MPP) 2.5 10/26/89 Likely killed by deer hunter Nov. 

1989.

 17.0 west in

 5375 F Blue Moose Pack (BMP) 3.5 10/12/89 Likely killed by deer hunter Nov. 

1989.

 23.4 west in

 7125 F Moose Lake Pack (MLP) 7.5 12/03/88 Dispersed to Nett Lake area; 

found dead by hunter in Fall 1992 

near Big Fork.

 83.7 southwestout

 8380 M Kohler Trio Pack (KTP) 7.5 12/10/88 Began to settle near Black Bay 

with 2 other wolves then killed by 

other wolves (likely MPP) in April 

1989.

 26.3 north in

 6375B F Middle Peninsula Pack (MPP) / 

Moose Grade Pack (MGP)

1.5 01/12/89 Joined / formed MGP, still 

transmitting when study ended in 

April 1991.

 1.8 southeastin

 6625A M Dixon Creek Pack (DCP) 7.5 10/09/88 Dispersed to Chub Lake area; 

illegally snared March 1989.

 24.5 south out

 8125B F Browns Bay Pack (BBP) 1.5 12/01/90 Moved near Vermilion Lake, then 

returned near home territory 

(n = 1 location), then missing.

 60.8 south out

 8880B F Nebraska Bay Pack (NBP) 3.0 03/31/90 Remains found by hunter in Nov. 

1990 west of Cook.

 59.5 south out

 Totals 9 x 4.0 x 33.1

 M 4 SD 2.7 SD 28.5

 F 5 x excluding 3 older wolves 2.3 x without 2 dispersing to 

adjacent packs

 42.2

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National Park Service 21

the alpha female injured in separate vehicle 

collisions. The injured alpha female survived, 

but we lost contact with her in early October 

when other pack members chewed off her 

collar. In late November 1989, an instrumented adult male wolf left the pack with at least 

two other wolves. This group of more than 

three wolves, designated the Kohler Trio Pack 

(KTP), roamed northwest into Canada more 

than 16 km from the original pack territory. 

This wandering pack then returned south and 

began localizing in the Black Bay area. However, the single instrumented wolf was killed 

by other wolves in early April 1990 before we 

could determine whether the pack had established a territory.

We may have detected a wolf immigrating into 

the study area to form or join the Rat Root 

Pack (RRP) in 1989 – 1990. A newly instrumented 

wolf made erratic movements (n = 12) before 

localizing in the RRP territory (fi gure 9) with 

two other wolves in 1989 – 1990 and with a 

single wolf in 1990 – 1991 (table 9). Detection of wolves immigrating into a study area 

was diffi cult due to the lack of capture eff ort 

beyond the study area boundaries. Thus, 

other immigration may have been undetected. 

Cumulative eff ects modeling suggested that 

immigration was important in determining 

whether wolves in the Voyageurs region will 

decline to low numbers or go to extinction 

within the next 100 years (Cochrane 2000). 

Current rates of non-territorial wolves passing 

through more than one wolf pack territory in 

the Voyageurs region are estimated at 50/ year 

(L. D. Mech, USGS, personal communication 

in Cochrane 2000). This rate of immigration is 

suffi cient for predicted long-term persistence 

of wolves in the Voyageurs region (Cochrane 

2000). The modeling highlights the importance of adjacent wolf populations in maintaining a viable wolf population within VNP.

Timing and causes of mortality

We recovered 12 radio collars transmitting 

mortality signals, and two instrumented 

wolves disappeared within the study area. An 

additional two instrumented wolves classifi ed 

as dispersers were found dead beyond the 

boundaries of our study area more than one 

year after we lost radio contact and are not 

considered further. Study animals that died 

ranged from 0.5 to 8 years of age. Mortalities 

occurred between September and May for all 

years combined (fi gure 10, page 22). Six instrumented wolves died of natural causes: four 

from intraspecifi c strife and two from starvation (table 12, page 22). The four mortalities 

Table 10. Estimated annual dispersal rates for wolves in and adjacent to Voyageurs 

National Park, Minnesota, 1987–1991.

Total Dispersers Left Study Area

Year

Wolves 

Collared

WolfYearsaNo. 

Wolves Rate

No. 

Wolves Rate

1987 – 1988 3 1.34 0 0.00 0 0.00

1988 – 1989 15 7.35 5 0.68 2 0.27

1989 –19 90 10 7.30 3 0.41 1 0.14

1990 –19 91 10 8.14 1 0.12 1 0.12

 Total 24.13 9 0.37 4 0.17

a

A wolf-year is 1 wolf (>5 months old) radio-tracked for 12 months.

Table 11. Mean straight-line distance between consecutive locations and number of 

pre-dispersal movements for dispersing wolves in and adjacent to Voyageurs National 

Park, Minnesota, 1987–1991.

Pre-dispersal Post-dispersal

Wolf 

Number

Mean 

Distance 

Between 

Locations

Total 

Locations

No. Extraterritorial 

Locations

Mean 

Distance 

Between 

Locations

Total 

Locations

4375a 4.97 40 1 8.10 37

4375 8.10 37 3 11.03 2

5375 3.26 63 0 14.46 4

7125 5.28 32 4 15.22 11

8380 4.70 12 2 9.86 11

6375Ba 8.08 16 5 7.92 8

6625A 4.88 26 2 3.89 6

8125B 6.15 41 2 21.63 8

8880B 5.00 45 0

x 5.60 35 2.1 11.51 11

 SD 1.60 16 1.7 5.48 11

a

Dispersed to occupy a nearby pack territory.

Modeling highlights the 

importance of adjacent 

wolf populations in 

maintaining a viable 

wolf population within 

VNP.

_

unmarked adult wolf (four total) continued 

to occupy the original LLP territory during 

winter 1989 – 1990 (fi gure 9). This group was 

subsequently named the Middle Peninsula 

Pack (MPP). Responses to simulated howls 

(see Howling surveys, tables 3 and 4) indicate 

the MPP included pups during spring 1989 

and that an unmarked pack within the original CLP territory also had pups. From these 

observations, we speculate that the CLP split 

during winter 1988 – 1989 with fi ve members 

taking over the LLP territory and forming the 

MPP and that three other CLP members remained in the eastern portion of the original 

CLP territory. Indeed, in the spring of 1990 we 

captured and radio-marked an adult male wolf 

that, with fi ve other wolves, occupied a portion of the original CLP territory (fi gure 9). 

Kohler Pit Pack split—The second case involved the Kohler Pit Pack (KPP), which contained more than fi ve wolves (two adults and 

more than three pups) in summer 1989 (appendix 5). By fall, one pup had been killed and 
22 Gray wolves in and adjacent to Voyageurs National Park, Minnesota: Research and synthesis 1987 – 1991

Figure 10. Number of mortalities by month of instrumented 

wolves in and adjacent to Voyageurs National Park, Minnesota, 

1987–1991.

wolves was the result of mortalities caused 

by deer hunters (Fuller 1989). However, to 

be conservative, the fates of these two wolves 

were classifi ed as unknown in our analysis of 

survival with program MARK (see Survival 

rates).

The same general pattern of mortality was 

evident for 10 non-radio-marked wolves 

found within 10 km of the territories of instrumented wolves (table 13). Two non-radiomarked wolves found dead within VNP died 

of natural causes (one pup died from starvation and one adult from intraspecifi c strife) 

and eight found beyond VNP were attributed 

to human-induced mortality. Notably, 3 of the 

10 non-radio-marked wolves were killed by 

vehicle collisions whereas none of our instrumented wolves was killed by vehicles. However, we did document an instrumented wolf 

being struck and injured by a vehicle, and one 

of her non-radio-marked pups was killed in a 

separate automobile accident. We suggest that 

the higher number of automobile-induced 

mortalities among non-radio-marked wolves 

is attributable to the greater probability of locating carcasses along roadways. Conversely, 

most of our instrumented wolves occupied 

lightly roaded areas within a national park and 

national forest.

The high proportion of illegally killed wolves 

in our study (43% of deaths) is consistent with 

fi ndings from other studies in Minnesota. 

Fuller (1989) found that in north-central Minnesota, 80% of wolf mortality was humancaused. Further, he found that 26% of all wolf 

mortality was attributable to shootings by deer 

hunters during northern Minnesota’s 16-day 

Table 12. Cause, residency, and location of death for known deaths of 14 radio-marked wolves in and adjacent to Voyageurs National Park, 

Minnesota, 1987–1991.

Status Within Populationa Location of Deathb

Cause Total Mortalities Resident Non-resident In Park Out of Park

Gunshot, by deer hunter 1 1 0 0 1

Gunshot, other than deer hunter 1 1 0 0 1

Trapped or snaredc 2 0 1 0 2

Human, method unknown 2 1 1 0 2

Intraspecifi c strife 4 3 1 2 2

Starvation 2 2 0 2 0

Presumed human caused 2 2 0 0 2

 Total 14 10 3 4 10

Note: One study-related mortality is excluded.

a

Considered resident if within 5 km of its territory and nonresident if beyond. Residency unknown for 1 wolf.

bConsiders the actual location where death occurred in relation to park boundaries.

c

Residency status unknown for 1 wolf in this category.

dThese met Fuller’s (1989) criteria to be assumed killed by humans during the Minnesota deer rifl e season or land trapping season.

0

1

2

3

4

5

6

May Jun Jul Aug Sept Oct Nov Dec Jan Feb Mar

Month

Natural Human-caused

within VNP’s boundaries were attributed to 

natural causes (table 12). By contrast, six of 

eight confi rmed mortalities outside of VNP’s 

boundaries were human induced while two 

were from natural causes (table 13). Six human-induced mortalities beyond the boundaries of VNP included two killed by gunshot, 

two trapped or snared, and two by unknown 

cause yet human involvement was certain, i.e., 

the radio collars were recovered from a river 

bottom with collar belting cut with a knife and 

at a garbage dumpster site, respectively. An additional two instrumented wolves disappeared 

during or immediately prior to the Minnesota 

deer rifl e hunting season. Both had been followed consistently by telemetry for more than 

one year and were adult members of territorial packs. We were unable to locate either of 

these wolves by telemetry again. We feel justifi ed in presuming the disappearance of both 
National Park Service 23

rifl e season in November and an additional 

27% were shot, snared, or killed by vehicles 

during other times of the year. These fi ndings 

are consistent with a survey of Minnesotan’s 

attitudes toward wolves that found that 30% 

of white-tailed deer hunters would shoot any 

wolf during the northern Minnesota deer 

season in November (Kellert 1986). This represents 5,000 – 6,000 hunters in wildlife management units adjacent to VNP (J. Schneeweis, 

Minnesota Department of Natural Resources, 

personal communication). Moreover, 17% of 

trappers in northern Minnesota admitted to 

capturing or killing wolves (Kellert 1986). The 

lower percentage of human-induced mortalities in our study relative to Fuller (1989) likely 

refl ects the considerable portion of our study 

area within the boundaries of VNP that is 

closed to hunting and trapping. 

Survival rates

Of the 14 mortalities identifi ed, only those 

with fates confi rmed as mortalities via radiotelemetry and subsequent physical evidence 

(n = 12) were so classifi ed in our survival 

analysis. Thus, the two instrumented wolves 

that disappeared during Minnesota deer rifl e 

season were classifi ed as missing rather than 

mortalities for the purposes of this survival 

analysis. While categorizing the latter two 

as “presumed killed by hunters” permits 

comparisons between this and other studies 

in Minnesota (Fuller 1989), classifi cation as 

“missing” is more appropriate for an analysis 

of survival rates with a Known Fates model.

Known Fates survival models were particularly 

suited for analysis of these radiotelemetry data 

because sampling occasions documented both 

live and dead relocations. These procedures 

provided maximum likelihood estimates 

of survival and a rigorous means for model 

comparison (Lebreton et al. 1992). Diff erences in survival models were assessed via 

Akaike’s Information Criterion corrected for 

small sample sizes (AICc

) and Likelihood Ratio (LR) tests (Burnham and Anderson 1998). 

All information criteria are constructed as 

−2 * (log − likelihood) + (an adjustment). The 

adjustment for AIC is 2 * p where p = the number of parameters included in the error variance). The model with the lowest value for the 

information criterion is selected as the best 

supported model. Diff erences in information 

criterion values of ≥2 are generally considered 

to indicate that models are statistically distinguishable (Sakamoto et al. 1986). Additionally, 

program MARK provides AIC weights that 

permit objectively comparing each model relative to other models run in a suite from the 

same data set. An LR test provides p-values 

indicating whether addition of a term to a base 

model signifi cantly improves fi t. Because of 

low sample sizes when testing for diff erences 

in survival among groups of wolves, we considered p-values signifi cant when less than <0.10.

Survival by age—We developed an overall 

nine-month survival model for 30 instrumented wolves meeting Known Fates criteria. The 

probability of a wolf surviving nine months 

was 0.67 for this constant-survival model {S(.)} 

(table 14, page 24). We then tested for diff erences in nine-month survival between pups 

and adults. Adults had a nine-month survival 

rate of 0.73, 1.9 times higher than pups. AICc

values showed a model allowing survival to 

vary by age {S(age)} to be more parsimonious 

than {S(.)} (table 14). AIC weights suggested 

that the age-varying model was 1.3 times as 

well supported as the constant-survival model. 

However, an LR test indicated that addition of 

Table 13. Cause and location of death for 10 unmarked wolves found less than 10 km from study wolf pack territories in and adjacent to 

Voyageurs National Park, Minnesota, 1987–1991.

Location of Deatha

Cause Total Mortalities In Park Out of Park Relationship to Park Wolf Population

Accidental 

vehicle collisionb

 3 0 3 Includes 1 pup from KPP and 2 adults of unknown pack affi liation.

Illegally shotc 3 0 3 Pack associations and affi liation with park wolves unknown.

Illegally trapped 2 0 2 One adult known to be member of TCP, other unknown.

Intraspecifi c 

strife

 1 1 0 Pup, likely a member of NBP.

Starvation 1 1 0 Adult, likely a member of LLP and died in CLP territory.

 Total 10 2 8

a

Considers the actual location where death occurred in relation to park boundaries.

bAnother uncollared wolf was observed hit by a vehicle and presumed killed, although a follow-up search (< 24 hr) revealed no carcass. 

c

One shot from the air in Ontario <2 km from the international border.

The high proportion of 

illegally killed wolves 

in our study (43% of 

deaths) is consistent with 

fi ndings from other studies in Minnesota.
24 Gray wolves in and adjacent to Voyageurs National Park, Minnesota: Research and synthesis 1987 – 1991

an age term to the constant-survival model did 

not signifi cantly improve fi t (table 14). Thus, 

we found weak evidence that survival was different between ages possibly because the LR 

test result is infl uenced by our relatively small 

sample sizes, giving little power to identify differences in survival between adults and pups.

Survival by sex—We fi rst developed an 

overall 12-month survival model for all 23 

adults. The probability of an adult surviving 

12 months was 0.75 {S(.)} (table 15). Next, 

we tested for diff erences in 12-month adult 

survival between males and females. For this 

sample, females had a 12-month survival rate 

of 0.90, two times higher than males. AICc

 values showed a model allowing survival to vary 

by sex {S(sex)} to be more parsimonious than 

{S(.)} (table 15). AIC weights suggested that 

the sex-varying model was 14.7 times as well 

supported as the constant-survival model. An 

LR test indicated that addition of a sex term 

to the constant-survival model improved fi t 

(table 15). Thus, there was evidence that adult 

female survival was higher than that of adult 

males.

Survival by territory location—We began 

with the overall 12-month survival model 

{S(.)} for all 23 adults, showing adult survival 

at 0.75 (table 16), and tested for diff erences 

in 12-month adult survival among territory 

locations. Wolves with territories within VNP 

had a calculated survival rate of 1.0 and those 

with territories straddling the boundaries of 

VNP had the lowest survival rate (table 16). 

The calculated survival rate of 1.0 for adult 

wolves with territories exclusively within the 

park boundaries refl ects that no radio-collared wolves in this category died during the 

study. Those wolves with territories beyond 

the boundaries of VNP were intermediate in 

survival rate. AICc

 values showed a model allowing survival to vary by territory location 

{S(territory)} to be slightly more parsimonious 

than {S(.)} (table 16). AIC weights suggested 

that the territory location-varying model was 

two times as well supported as the constantsurvival model. An LR test also indicated that 

addition of a territory location term to the 

constant-survival model marginally improved 

fi t (table 16). Thus, there was evidence that 

adult survival diff ered based on territory location.

Survival by time of year—To assess the effects that time of year had on survival of pup 

and adult wolves combined, we fi rst tested to 

see if nine-month survival varied by biological 

season for all wolves. Mean seasonal survival 

estimates were 0.97, 0.82, and 0.78 for a twomonth rendezvous period, a two-month winter pre-iceup period, and a fi ve-month winter 

post-iceup period, respectively. Monthly 

survival rates within the three seasons were 

0.99, 0.91, and 0.95, respectively. AICc

 values 

showed {S(.)} to be less parsimonious than 

a model allowing survival to vary by season 

Table 14. Effects of age and time of year on Known Fates survival estimates from 30 radio-marked gray wolves in and adjacent to Voyageurs 

National Park, Minnesota, 1987–1991.

Model AICc AICc Weight

Likelihood Ratio Test.

Model Versus S(.)

9-month 

Survival 

Estimate

95% Confi dence 

Interval

Number of 

Wolvesa

S(.) 74.1 0.13863 n/a 0.667 0.501 – 0.799 30

S(age) 73.5 0.18462 χ2 = 2.66, P = 0.103 0.394 pups

0.729 adults

0.126 – 0.747

0.545 – 0.858

 8

23

S(season) 70.9 0.67675 χ2 = 7.39, P = 0.025 0.624 0.445 – 0.774 30

Note: Survival estimates based on 9-month period from August–April.

a

Total number of wolves <pups + adults because 1 wolf was both a pup and an adult during the study.

Table 15. Effects of sex and time of year on Known Fates survival estimates from 23 radio-marked adult gray wolves in and adjacent to 

Voyageurs National Park, Minnesota, 1987–1991.

Model AICc AICc Weight

Likelihood Ratio Test.

Model Versus S(.)

12-month 

Survival 

Estimate

95% 

Confi dence 

Interval

Number of 

Wolves

S(.) 59.8 0.01403 n/a 0.745 0.568 – 0.867 23

S(sex) 54.5 0.20590 χ2 = 7.45, P = 0.006 0.456 males

0.903 females

0.212 – 0.729

0.683 – 0.975

 9

14

S(season) 51.8 0.78007 χ2 = 14.37, P = 0.002 0.694 0.495 – 0.839 23

Note: Survival estimates based on 12-month period from May–April.

There was evidence that 

adult survival diff ered 

based on territory location.
National Park Service 25

{S(season)} (table 16). AIC weights suggested 

that the season-varying model was 4.9 times as 

well supported as the constant-survival model. 

An LR test indicated that addition of a season 

term to the constant-survival model improved 

fi t (table 16). Thus, there was evidence that 

pup and adult survival varied among seasons, 

and that the lowest survival rates occurred in 

the two-month pre-iceup period, which coincides with the Minnesota deer rifl e-hunting 

season.

To assess the eff ects of time on survival of 

wolves more than one year old only, we tested 

to see if 12-month survival varied by biological 

season. In each suite of models, AICc

 values 

showed {S(.)} to be less parsimonious than 

{S(season)} (tables 14 – 16). AIC weights suggested that a season-varying model was 55.6 

times as well supported as a constant-survival 

model. An LR test indicated that addition of 

a season term to the constant-survival model 

improved fi t (tables 14 – 16). Mean seasonal 

adult survival estimates were 1.000, 1.000, 

0.86, and 0.81 for pup-rearing, rendezvous, 

winter pre-iceup, and winter post-iceup periods, respectively. This converted to monthly 

survival estimates of 1.000, 1.000, 0.93, and 

0.96 within the respective seasons. Thus, there 

was strong evidence that survival of wolves 

more than one year old diff ered among seasons and evidence that survival was lowest in 

the two-month pre-iceup period.

Survival summary—The order in which 

models best explained survival for all wolves 

including pups, based on AICc

 values, was (1) 

season, (2) age, and (3) constant survival. The 

order in which models best explained survival 

for adult wolves, based on AICc

 values, was 

(1) season, (2) sex, (3) territory location, and 

(4) constant survival. Season had the greatest 

infl uence on overall wolf survival. Season and 

sex had the greatest infl uence on adult wolf 

survival.

The fi ndings from our analysis with program 

MARK are largely consistent with a preliminary survival analysis (Gogan et al. 1997b) undertaken with Kaplan-Meier survival estimates 

and log rank tests for diff erences between 

groups of wolves (Pollock et al. 1989). However, the preliminary analysis indicated that 

survival was lowest for wolves occupying territories beyond the park boundaries whereas 

this latter analysis shows survival to be lowest 

in wolves occupying territories that overlap 

the park boundaries. The preliminary analysis 

found that wolves occupying territories overlapping the park boundaries were intermediate in survival between those occupying territories exclusively within the VNP boundaries 

(highest survival) or exclusively beyond VNP 

boundaries (lowest) (Gogan et al. 1997b). The 

following diff erences in classifi cation of causes 

of mortality among instrumented wolves (as a 

result of more detailed evaluation of available 

data under more rigorous criteria) contributed 

to diff erences in the survival estimates from 

the Kaplan-Meier and program MARK analyses include (1) two wolves initially presumed 

to have been killed by hunters at the onset of 

the Minnesota deer rifl e-hunting season but 

whose collars were never found were reclassifi ed as unknown fate, (2) a wolf pup identifi ed 

as hunter-killed in the Kaplan-Meier analysis 

was reclassifi ed as having lost its collar, (3) a 

second wolf pup was reclassifi ed from a research-induced mortality to a natural mortality due to starvation, and (4) an adult wolf initially classifi ed as shot was reclassifi ed as being 

killed by wolves. Furthermore, the territorial 

boundaries of instrumented wolves utilized 

for the analysis with program MARK were reevaluated through a more complete analysis of 

our radiotelemetry data. The analysis presented herein is more complete and accurate than 

the preliminary analysis (Gogan et al. 1997b) 

and represents our fi nal assessment of survival 

rates for wolves in the Voyageurs region.

Table 16. Effects of territory location and time of year on Known Fates survival estimates from 23 radio-marked adult gray wolves in and 

adjacent to Voyageurs National Park, Minnesota, 1987–1991.

Model AICc AICc Weight

Likelihood Ratio Test.

Model Versus S(.)

12-month 

Survival 

Estimate

95% Confi dence 

Interval

Number of 

Wolvesa

S(.) 59.8 0.01708 n/a 0.745 0.568 – 0.867 23

S(territory) 58.5 0.03372 X 2 = 5.55, P = 0.063

1.000 in

0.614 border

0.873 out

1.000 – 1.000

0.384 – 0.802

0.458 – 0.982

 4

16

 7

S(season) 51.8 0.94920 X 2 = 14.37, P = 0.002 0.694 0.495 – 0.839 23

Note: Survival estimates based on a 12-month period from May–April.

a

Total number of wolves < in + border + out because 4 wolves had range locations that changed during the study.

The lowest survival 

rates occurred in the 

two-month pre-iceup 

period, which coincides 

with the Minnesota deer 

rifl e-hunting season....

Season had the greatest infl uence on overall 

wolf survival. Season 

and sex had the greatest 

infl uence on adult wolf 

survival.
26 Gray wolves in and adjacent to Voyageurs National Park, Minnesota: Research and synthesis 1987 – 1991

Diseases and parasites

Diseases and parasites were identifi ed in livecaptured wolves via disease screening tests and 

in moribund wolves at necropsy (table 17). No 

disease fatalities were identifi ed in this study. 

Localized abscesses or fi stulas were incidental 

to other causes of death and probably arose 

from wounds or embedded plant material.

Borrelia burgdorferi, the spirochete that causes 

Lyme disease in humans, was found in the 

shoulder joint of a wolf killed by a gunshot. 

No abnormalities were present in that joint so 

the signifi cance of the Lyme disease organism 

is uncertain. Kazmierczak et al. (1988) demonstrated that wolves inoculated with B. burgdorferi exhibit lymph node enlargement and 

develop antibodies to the disease. Antibodies 

Table 17. Parasites and diseases found in live and dead wolves in and adjacent to Voyageurs National Park, Minnesota, 1987–1991.

 Cases

Parasites and Diseases Sample Type Positive Negative

Disease Screening (whole blood, serum, feces)

 Blastomyces dermatitidis (blastomycosis) Serum 6

 Borrelia burgdorferi (lyme disease) Serum 3

 Brucella canis (brucellosis) Serum 6

 Canine distemper Serum 0 18

 Canine parvovirus (CPV-2) Serum 11 13

 Canine parvovirus (CPV-2) Feces 28

 Canine parvovirus (CPV-2) Scats from trails 47

 Dirofi laria immitis (canine heartworm) Serum 5 1

 Dirofi laria immitis microfi laria (Knott’s test) Whole blood 18

 Infectious canine hepatitis (ICH) Serum 5 1

 Leptospira pomona (leptospirosis) Serum 6

 L. icterohemorrhagica Serum 6

 L. hardjo Serum 6

 L. grippotyphosa Serum 6

 L. canicola Serum 6

 Rabies Serum 6

Examination of Carcasses, Feces, and Pelage

 Alaria sp. Small intestine, feces 6

 Ancylostoma caninum (hookworm), adult, eggs Intestine, feces 5

 Baylisascaris egg Feces (probably from prey) 1

 Borrelia burgdorferi (lyme disease) Joint tissue 1

 Cestode sp., adults, larvae, eggs Duodenum, jejunum 9

 Dermacentor sp. (ticks) Pelage 13

 Dioctophyma renale (giant kidney worm) Abdominal cavity 1

 Echinococcus granulosus Small intestine 1

 Echinococcus multilocularis Small intestine 1

 Echinococcus sp. Intestine, duodenum 1

 Filaroides (Oslerus) osleri Trachea and bronchi 7

 Filaroides sp. Trachea and bronchi 1

 Moraxella phenylpyruvica Fistula (bite wound) 1

Moraxella sp. Abcess 1

Sarcocystis spp. (coccidiosis) Intestine, feces 7

Staphylococcus sp. Abcess 2

Streptococcus equisimilis Abcess, fi stula 2

 Strigeid eggs (probably Alaria) Fecal 12

Taenia sp., adults, larvae, eggs Intestine, feces 12

Toxocara sp. Intestine 2

 Trematode eggs Feces 2

Trichodectes canis (dog louse) Pelage 9

Unicinaria sp. (hookworm) Intestine 3

 No parasites detected Feces 6

 No parasites detected Fecal swab 2

No disease fatalities 

were identifi ed in this 

study.
National Park Service 27

against Lyme disease were found in 43% of 

the wolves we tested, much higher than reported for wolves in other parts of Minnesota 

and Wisconsin (3%) (Kazmierczak et al. 1988: 

525). In domestic dogs, Lyme disease has been 

shown to cause arthralgia, fever, inappetence, 

arthritis, and glomerulonephritis (Kornblatt et 

al. 1985), and in coyotes the agent is known to 

be transmitted across the placenta (Burgess and 

Windberg 1989). The upper Midwest is an epicenter of this disease of public health concern. 

The primary vector in the Midwest is believed to 

be the deer tick (Ixodes damini); however, Lyme 

disease has been isolated from other ticks including the winter tick (Dermacenter albipictus)

that infests moose (Anderson and Magnarelli 

1984, Magnarelli et al. 1986). Ticks of the genus 

Dermacenter were common on the pelage of 

wolves examined in this study (table 17). Whitefooted mice (Peromyscus spp.) and white-tailed 

deer are the principal reservoirs for B. burgdorferi (Bosler et al. 1984).

Parasites were varied and infections were 

small to moderate in number. Overall, parasitism was an incidental fi nding. The giant kidney worm (Dioctophyma renale) has not been 

found in wolves in Wisconsin or IRNP, Michigan, and could be acquired by eating an intermediate form associated with crustaceans, 

fi sh, or possibly when drinking fresh water. 

The tracheal worm (Filaroides osleri), found in 

seven of the Voyageurs region wolves, is uncommon in IRNP or Wisconsin wolves; heavy 

infections may cause respiratory diffi culty or 

bronchopneumonia in dogs. The cestodes 

Echinococcus granulosus and E. multilocularis, 

found in two Voyageurs region wolves, are 

benign in wolves but cause hydatid disease in 

humans by encysting in internal organs. The 

hookworms (Ancylostoma and Uncinaria) and 

the trematode (Alaria sp.) were common in 

wolves at necropsy and in fecal samples taken 

from live-captured wolves or collected feces. 

These parasites could be debilitating in neonatal pups if infection rates are high; they can 

cause infections at a very young and vulnerable 

age by passage through the mammary gland.

Forty-six percent of the Voyageurs region 

wolves tested had been exposed to canine 

parvovirus (CPV); this frequency is similar 

in other wolf populations in North America 

(Zarnke and Ballard 1987). In addition to 

serologic tests for exposure, samples of feces 

from live-captured wolves or feces collected in 

the fi eld were tested for the presence of CPV, 

and no virus was found in any sample. These 

results indicate that though a large proportion of the wolves had contacted CPV at some 

time, current infections were uncommon. 

Evidence has linked CPV, a disease transmitted through the feces of domestic dogs or 

wolves, to a major decline in the population 

of wolves in IRNP in 1980 –1982 (Peterson 

et al. 1998), and to low wolf and coyote pup 

survival when introduced into canid populations (Mech and Goyal 1993, 1995; Thomas et 

al. 1984; Johnson et al. 1994; Windberg 1995). 

Cumulative eff ects modeling suggests that pup 

mortality related to diseases is a critical factor 

in determining whether wolves within VNP 

maintain high population densities (Cochrane 

2000). Given the high rates of immigration of 

wolves into the Voyageurs region, estimated at 

50 wolves / year traveling through more than 

one Voyageurs region wolf pack territory (L. D. 

Mech USGS, personal communication in Cochrane 2000) and the proximity of VNP wolves 

to domestic dogs, the potential transmission of 

diseases to Voyageurs region wolves must be 

considered high.

Antibodies against infectious canine hepatitis 

virus were found in most (83%) wolves tested, 

similar to Alaskan and IRNP wolves (Zarnke 

and Ballard 1987, Peterson et al. 1998). The 

signifi cance of these results is unclear for 

wolves in the Voyageurs region and elsewhere 

because no evidence of detrimental consequences of this disease has been found.

Five of six wolves that were tested had low 

concentrations of antibodies to canine heartworm, but no larval heartworms were found 

in blood tests of live-captured wolves, and 

no adult heartworms were found at necropsy 

of dead wolves (table 17). The antibodies 

detected in Voyageurs region wolves may 

have been formed to a parasite that resembles 

canine heartworm but resides elsewhere because there is no confi rmed evidence of canine heartworm in the Voyageurs region wolf 

population.

There was no evidence of Voyageurs region 

wolf exposure to canine distemper virus, 

rabies virus, blastomycosis (fungal disease), 

brucellosis, or several forms of leptospirosis 

(bacterial diseases) (table 17).

Population genetics

Of 13 wolf and 4 wolf-coyote hybrid genotypes identifi ed across North America, Voyageurs region wolves were classifi ed as belonging to a single wolf genotype (W1) (n = 11) 

and 2 of the wolf-coyote hybrid genotypes 

(W7, W9) (n = 8) (Lehman et al. 1991). Both 

Cumulative eff ects modeling suggests that pup 

mortality related to diseases is a critical factor 

in determining whether 

wolves within VNP 

maintain high population densities.
28 Gray wolves in and adjacent to Voyageurs National Park, Minnesota: Research and synthesis 1987 – 1991

wolf and wolf-coyote hybrid genotypes occurred throughout the Voyageurs region 

(fi gure 11). The single wolf genotype is relatively common throughout Minnesota and 

northwestern Ontario (Lehman et al. 1991, 

Wayne et al. 1991). Hybridization is likely the 

result of introgression of coyote mtDNA into 

wolves via male wolves breeding with female 

coyotes and the resulting off spring backcrossing into the wolf population (Lehman et al. 

1991). Opportunities for wolf-coyote breeding may increase when wolves move beyond 

the park boundaries into areas occupied by 

coyotes during the breeding season or when 

coyote-like canids move into the park. At Algonquin Provincial Park, Ontario, the latter is 

thought to be more likely to occur when wolf 

packs have been eliminated from an area or 

when the wolf social order has been disrupted 

through high mortality (Theberge and Theberge 1998).

Feeding ecology

The 220 wolf scats examined contained 243 

items of nine prey types (table 18) (Schmidt 

1990). White-tailed deer comprised 186 (77%) 

occurrences of which 91% were adult and 9% 

were fawn. Fawn deer hair was identifi able in 

scats from May through August but was then 

indistinguishable from that of adults. Beaver 

occurred in 42 scats, accounting for 17% of 

occurrences. In combination, deer and beaver 

made up 94% of the annual wolf diet (table 

18). The occurrence of deer remains (both 

adult and fawn) in scats increased from 56% in 

spring to 91% in winter while beaver decreased 

from 35% to 7% (fi gure 12). Moose was found 

in 4 of the 220 scats, 2% of total occurrences. 

Other prey consumed by wolves included 

muskrat (2% of occurrences), snowshoe hare 

Figure 11. Capture sites of 

wolves with a common wolf 

genome (W1) or with two distinct wolf-coyote genomes (W7, 

W9) in and adjacent to Voyageurs National Park, Minnesota, 

1987–1991. 

Table 18. Number of occurrences and percent occurrence of prey by season for 220 wolf scats collected in 

and adjacent to Voyageurs National Park, Minnesota, 1988–1989.

Seasona

Spring (64) Summer (32) Fall (27) Winter (97) Total (220)

Preyb Occ.c %d Occ. % Occ. % Occ. % Occ. %

Adult deere 42 54 10 28 24 89 93 91 169 70

Fawn deere 2 3 15 42 0 0 0 0 17 7

 Subtotal deer 44 56 25 69 24 89 93 91 186 77

Beaver 27 35 5 14 3 11 7 7 42 17

Muskrat 4 5 0 0 0 0 0 0 4 2

Moose 0 0 2 6 0 0 2 2 4 2

Mice 2 3 0 0 0 0 0 0 2 1

Hare 0 0 2 6 0 0 0 0 2 1

Livestockf 1 1 0 0 0 0 0 0 1 0

Grouse 0 0 1 3 0 0 0 0 1 0

Bird unknown 0 0 1 3 0 0 0 0 1 0

 Total 78 100 36 100 27 100 102 100 243 100

Note: Sample size for each season shown in parentheses.

a

Spring = April, May; summer = June, July, August; fall = September, October, November; winter = December, January, 

February, March.

bDoes not include occurrences of dirt (n = 29), vegetation (n = 27), rope (n = 3), pieces of plastic bag (n = 1), and insects 

(n = 1).

c

Number of times this prey item was identifi ed in scats during this time period.

dPercent of total occurrences this time period.

e

The remains of fawn deer could be distinguished from adult deer only during spring and summer seasons.

f

A single scat containing cattle hair was found on the southern boundary of the study area.

Opportunities for wolfcoyote breeding may 

increase when wolves 

move beyond the park 

boundaries into areas 

occupied by coyotes during the breeding season 

or when coyote-like canids move into the park.
National Park Service 29

Figure 12. Percent occurrence of 

white-tailed deer and beaver in 

the wolf diet (upper panel) and 

relationship between occurrence 

and estimated biomass of prey 

species in the wolf diet (lower 

panel) in and adjacent to Voyageurs National Park, Minnesota, 

1988 and 1989.

(1%), mice (1%), livestock (<1%), grouse 

(<1%), and unknown bird (<1%). Insects occurred in one scat in small numbers, and they 

were not included in the scat analysis. However, such low frequency items may increase dietary variety: the stomach of a wolf necropsied 

in July 1989 contained 0.38 kg of grasshoppers, 

eight juvenile mice, and blueberries (Vaccinium

sp.). The scat containing livestock hair came 

from the southernmost area of the Voyageurs 

region where wolf depredation on livestock has 

been documented (Fritts 1982).

Small mammals have a relatively large ratio of 

indigestible hair to digestible meat so biomass 

may be overestimated in frequency of occurrence data (Mech 1970, Floyd et al. 1978, 

Fritts and Mech 1981, Weaver 1993). To correct for this we estimated the relative biomass 

of prey represented in non-winter (appendix 

6; table 19, page 30) and winter scats (appendix 7; table 20, page 30). Biomass estimates, 

when compared against occurrence data, 

underscored further the prevalence of deer 

in the diet of wolves in the Voyageurs region 

(fi gure 12). Moose, owing to their large size, 

increased slightly in prevalence while smaller 

prey (beaver, fawn deer, other) declined in 

prevalence relative to the percent occurrence 

data (fi gure 12, table 19, and table 20).

Deer remains were located on the frozen surfaces of the large lakes (60%) and inland (40%) 

during systematic winter track surveys by 

snowmobile and opportunistically during other 

fi eldwork (fi gure 13, page 32). The cause of 

death of 80% of all deer year-round was attributed to wolf predation with adults of both sexes making up approximately 60% of the wolfkilled deer (table 21, page 31). The age and sex 

classifi cation of 65 deer killed by wolves during 

three winters was 14 (22%) fawns, 2 (3%) yearlings, 36 (55%) adults, and 13 (20%) unknown 

(table 22). There was no diff erence in the sex 

ratio of adult deer killed by wolves over the 

three winters combined (χ2

 = 0.257, P = 0.612, 

n = 1). However, there was a signifi cant diff erence in the age and sex composition of wolfkilled deer between the winter 1987 – 1988 and 

winter 1988 – 1989 (χ2

 = 19.632, P = 0.0001, 

n = 2) with more males and fewer adult females 

and fawns taken by wolves during the winter of 

1987 – 1988 than the winter of 1988 – 1989. We 

can off er no defi nite reason for the observed 

diff erences between winters. However, the 

1987 – 1988 winter was far less severe than the 

1988 – 1989 winter (fi gure 2). It may be that 

adult female and fawn white-tailed deer are less 

vulnerable than adult males to wolf predation 

during mild winters. Fuller (1989) reported that 

in north-central Minnesota 54% of instances 

of winter wolf predation on deer was of fawns, 

and 60% of predation on deer more than one 

year old was of females. We speculate that such 

diff erences between our work and his study may 

be due to a higher proportion of males and a 

lower proportion of fawns in the unhunted herd 

of deer within VNP.

The age and sex classifi cation of 24 deer killed 

by wolves in summer was 8 (33%) fawn, 2 

(8%) yearling and 14 (58%) adult (table 23).

Of the 89 wolf-killed deer, age was determined 

for 50 (65%) by dental annuli and an additional 

8 by foreleg length (fi gure 14, page 32). Males 

ranged in age from less than 1 to 12 years with 

a median age of 7 years. Females ranged in age 

0

10

20

30

40

50

60

70

80

90

100

Spring Summer Fall Winter

Deer Beaver

Season

Percent Wolf Diet

0

10

20

30

40

50

60

70

Deer

(adult)

Beaver Deer

(fawn)

Moose Other

Occurrence Biomass

Percent Wolf Diet

Prey Item
30 Gray wolves in and adjacent to Voyageurs National Park, Minnesota: Research and synthesis 1987 – 1991

from less than 1 to 14 years with a median age 

of 6.5 years. Mech et al. (1971) reported wolves 

in SNF killed deer of both sexes ranging from 

less than 1 to more than 14 years. Fuller (1989) 

reported the median age for 9 adult male and 

13 adult female deer killed by wolves to be 3.3 

years and 9.5 years, respectively, in an area of 

north-central Minnesota where deer were subjected to intensive sport hunting. We attribute 

the younger age of wolf-killed deer in Fuller’s 

(1988) study to the impact of sport hunting on 

deer age structure (Fuller 1989).

Wolf predation has been identifi ed as an important cause of mortality among white-tailed 

deer where both species coexist (Kolenosky 

1972, Fuller 1989) but its role in regulating deer 

numbers is less clear. The numerical and functional responses of wolves to prey abundance 

are mediated by winter severity (Messier 1991). 

In SNF, wolf density negatively impacts deer 

Table 19. Percent of total meals and relative biomass of prey consumed during spring, summer, and fall 

by wolves in and adjacent to Voyageurs National Park, Minnesota, 1988 and 1989.

Preya

Estimated 

Live Weight 

of Prey (kg)b No. of Mealsc

% of Total 

Meals

Estimated 

Biomass 

Consumed 

(kg)d

% Relative 

Biomass

Adult deere 62.9 68.5 55.7 64.57 66.8

Fawn deere 7.1 16.0 13.0 7.93 8.2

 Subtotal deer 84.5 68.7 72.5 75.0

Beaver 13.3 29.0 23.6 15.82 16.4

Moose 247.5 2.0 1.6 4.84 5.0

Muskrat 1.2 2.5 2.0 1.12 1.2

Hare 1.3 1.5 1.2 0.67 0.7

Otherf 0.1 2.0 1.6 0.88 0.9

Livestockg 25.0 1.0 0.8 0.64 0.7

Grouse 0.7 0.5 0.4 0.22 0.2

 Total 123.0 100.0 96.7 100.0

Note: n = 123 scats.

a

Non-prey items found: 4 unknowns, 29 scats with dirt, 21 with vegetation, and 1 with insects.

bWeight calculations are provided in appendix 6.

c

In scats with 2 prey types (14.5%), each was assigned an occurrence of 0.5 meal (see text; appendix 5).

dEstimated kg of prey biomass consumed: Y = 0.439 + 0.008 X (Weaver 1993) multiplied by number of occurrences, 

where X = estimated live weight of prey.

e

The remains of fawn deer could be distinguished from adult deer through summer.

f

Includes 2 occurrences of microtine rodents and 1 unknown bird.

gIncludes 1 scat containing cattle hair found on the southern edge of the study area.

Table 20. Percent of total meals and relative biomass of prey consumed during winter by wolves in and 

adjacent to Voyageurs National Park, Minnesota, 1988 and 1989.

Preya

Est. live wt. 

of prey (kg)b No. of mealsc

% of total 

meals

Est. biomass 

consumed 

(kg)d

% Relative 

biomass

Deere 58.6 90.5 93.3 82.13 90.4

Beaver 15.7 4.5 4.6 2.54 2.8

Moose 330.0 2.0 2.1 6.16 6.8

 Total 97.0 100.0 90.8 100.0

Note: n = 97 scats.

a

Non-prey items: 3 scats with rope, 1 with plastic bag, and 6 with vegetation.

bWeight calculations are provided in appendix 6.

c

In scats with 2 prey types (5%), each was assigned an occurrence of 0.5 meal (see text; appendix 2). 

dEstimated kg of prey biomass consumed: Y = 0.439 + 0.008 X (Weaver 1993) multiplied by number of occurrences, 

where X = estimated live weight of prey.

e

The remains of fawn deer and adult deer could not be distinguished from one another in winter scats.
National Park Service 31

Table 21. Cause of mortality by sex and age class of 111 dead white-tailed deer found year-round in and adjacent to Voyageurs National Park, 

Minnesota, 1987–1991.

Fawn Yearling Adult % of

Cause M F Unknown M F Unknown M F Unknown Unknown Totals Total

Killed by wolves 3 2 17 3 1 0 16 22 11 14 89 80.2

Accidenta 4 0 0 0 0 0 4 2 0 0 10 9.0

Unknown 0 0 0 1 0 0 2 0 2 0 5 4.5

Starvationb 1 1 0 0 0 0 1 1 0 0 4 3.6

Humanc 0 0 0 0 0 0 2 1 0 0 3 2.7

 Total 8 3 17 4 1 0 25 26 13 14 111

 % of Total 7.2 2.7 15.3 3.6 0.9 0.0 22.5 23.4 11.7 12.6

a

Three drowned after falling through thin ice and 7 died of exposure or were euthanized after being stranded on glare ice.

bAll occurred in late winter 1989; the adults were 9 years of age.

c

Believed killed illegally as evidenced by wounds and vehicle tracks near remains.

Table 22. Age and sex of wolf-killed white-tailed deer in and adjacent to Voyageurs National Park, 

Minnesota, during winter 1987–1991.

Age Class

Year / Sex Fawn Yearling Adult Age Unknown Total

1987 – 1988

 Female 0 0 4 0 4

 Male 0 0 11 0 11

 Sex unknown 3 0 4 7 14

 Subtotal 3 0 19 7 29

1988 – 1989

 Female 2 1 11 0 14

 Male 2 1 3 0 6

 Sex unknown 6 0 0 5 11

 Subtotal 10 2 14 5 31

1989 – 1990

 Female 0 0 1 0 1

 Male 0 0 0 0 0

 Sex unknown 1 0 2 1 4

 Subtotal 1 0 3 1 5

 Total 14 2 36 13 65

Note: Wolf kills were found on the surface of the large lakes (60%) and inland (40%) during systematic track surveys 

and opportunistically during other fi eldwork.

Table 23. Age and sex of white-tailed deer killed by wolves in and adjacent to Voyageurs National Park, 

Minnesota, during summer 1988 and 1989.

Age Class

Sex Fawn Yearling Adult Age Unknown Total

Female 0 0 6 0 6

Male 1 2 2 0 5

Sex unknown 7 0 6 0 13

 Total 8 2 14 0 24

Note: One male fawn and 1 male adult were examined in 1988; all others were sampled in 1989.
32 Gray wolves in and adjacent to Voyageurs National Park, Minnesota: Research and synthesis 1987 – 1991

Figure 13. Number of deer found 

dead as a result of wolf predation and other causes in and 

adjacent to Voyageurs National 

Park, Minnesota, December 1987 

through May 1990.

Figure 14. Age and sex structure 

of deer killed by wolves in and 

adjacent to Voyageurs National 

Park, Minnesota, December 1987 

through May 1990.

population growth rates (Messier 1991). Yet, 

white-tailed deer herds in northern Minnesota 

respond to winter severity with time lags infl uenced by both wolf predation and negative-density dependent factors (Post and Stenseth 1998). 

This combination of factors is of particular 

importance in our study given the mild winters of 1986 – 1987 and 1987 – 1988 and harsh 

winters of 1988 – 1989 and 1990 – 1991 as measured by an index of winter severity (fi gure 

2). Wolves are more successful in killing deer 

in winters of greater snow depth (Nelson and 

Mech 1986b).

0

2

4

6

8

10

12

14

16

Jan Mar May Jul Sep Nov Jan Mar May Jul Sep Nov Jan Mar May 

Wolf-Killed Other Mortality

Number of deer carcasses

1987 1988 1989 1990

0

5

10

15

20

25

<1 1 2 3 4 5 6 7 8 9 10 11 12 13 14

Age

Males Females Unknown

Percent

The numerical and 

functional responses of 

wolves to prey abundance are mediated by 

winter severity.
National Park Service 33

Conclusions

The relatively high density of wolves (33/1,000 

km2

) in and adjacent to VNP, Minnesota, was 

supported by high densities of white-tailed 

deer and beaver. The mean pack size of 5.5 in 

mid-winter and mean pack territory size of 

152 km2

 for wolves in the Voyageurs region 

were consistent with wolves elsewhere dependent on white-tailed deer (Mech 1986b, 

Potvin 1988, Fuller 1989). Territories of the 

two to three wolf packs on the Kabetogama 

Peninsula were entirely within the boundaries 

of VNP. The territories of wolf packs utilizing 

VNP’s southern landmass ranged beyond the 

park boundaries, although two packs ranged 

almost entirely within VNP. We found no evidence of wolf packs with territories straddling 

the international border between Canada and 

the United States.

Snow tracking revealed a diff erent pattern of 

use of frozen lake surfaces and shorelines than 

did daytime aerial radiotelemetry. Presumably, much of this diff erence is attributable to 

wolves using such areas at night when we did 

not conduct telemetry fl ights. Such use patterns may refl ect a response to diurnal human 

activities within VNP (Fox et al. 1999).

Howling surveys provided a means of determining the presence or absence of reproductively successful wolf packs within VNP. 

However, averages of only 52 – 56% of known 

packs were detected by solicited howling. The 

method required nighttime access to many 

locations. This created hazardous working 

conditions for sampling crews because access 

to many sampling stations was by small boat 

only. The low rate of wolf responses coupled 

with the hazards of sampling renders howling surveys a poor technique for monitoring 

population trends within VNP. 

We documented nine dispersals among 20 instrumented wolves. One of the instrumented 

wolves dispersed twice. Permanent dispersal 

was preceded by a mean of 2.1 pre-dispersal 

movements. Two dispersals resulted in wolves 

joining neighboring packs while two others 

involved pack splitting. Ages of dispersing 

wolves ranged from 1.5 to 7.5 years. The rate 

of dispersal was high relative to other wolf 

populations.

Causes of mortality in wolves diff ered by location. The four mortalities of instrumented 

wolves within VNP were all attributed to 

natural causes. Only 2 of 10 mortalities beyond the boundaries of VNP were attributed 

to natural causes while 8 were attributed to 

human activities. Similarly, two non-instrumented wolves found dead within VNP died 

of natural causes while eight non-instrumented wolves found beyond the boundaries of 

VNP died as the result of human activities. All 

dead instrumented wolves and only one of the 

dead non-instrumented wolves were found 

in Minnesota. The carcass of a single non-instrumented wolf was found on a frozen lake 

surface immediately north of the international 

border. However, information suggested that 

the wolf had been killed by aerial gunning in 

Minnesota and the carcass abandoned in Ontario. The high rate of human-induced mortality indicates that the federal Endangered Species Act and other federal and state regulations 

provided only limited protection to wolves in 

non-park areas in northern Minnesota. The 

lack of human-induced mortality within VNP 

underscores the eff ectiveness of national parks 

and other lightly roaded areas in protecting 

wolves. 

The nine-month survival rate for pup and 

adult wolves combined was 0.73. We found 

little evidence of a signifi cant diff erence in 

survival between pups and adults, although 

our small sample sizes undoubtedly limited 

the power of our statistical tests. The annual 

survival rate for adult wolves was 0.75. Annual survival diff ered between the sexes with 

females surviving at a rate twice that of males. 

Adult wolves with territories entirely within 

the boundaries of VNP survived at higher 

rates than did those with territories crossing 

or beyond the park boundary. Survival of all 

instrumented wolves and adult wolves varied 

by season with the lowest survival rates in the 

two-month pre-ice-up period in winter, which 

included the Minnesota rifl e-hunting season 

for deer.

Wolves have been exposed to a number of 

diseases and parasites, including Lyme disease and infectious canine hepatitis, but the 

signifi cance of these fi ndings is unclear. Approximately half the wolves had been exposed 

to CPV, but actual infections were uncommon 

at the time of the study. Parasitism was an incidental fi nding. No fatalities were attributable 

to diseases or parasites.

Snow tracking revealed 

a diff erent pattern of use 

of frozen lake surfaces 

and shorelines than did 

daytime aerial radiotelemetry.

The lack of human-induced mortality within 

VNP underscores the 

eff ectiveness of national 

parks and other lightly 

roaded areas in protecting wolves.
34 Gray wolves in and adjacent to Voyageurs National Park, Minnesota: Research and synthesis 1987 – 1991

Wolves of the Voyageurs region belong to a 

single common wolf genotype and two wolfcoyote genotypes. Such wolf-coyote hybrids 

have backcrossed into the wolf population.

White-tailed deer provided the majority of 

the wolf diet, and combined with deer and 

beaver made up approximately 95% of the annual wolf diet. Ages of wolf-killed deer ranged 

from less than 1 to 14 years.
National Park Service 35

Management Implications

The National Park Service is committed to 

“manage the natural resources of the national park system to maintain, rehabilitate, 

and perpetuate their inherent integrity” 

(National Park Service 1988). Maintaining 

a viable population of wolves at VNP in the 

future could be a challenge. Wolves within the 

Voyageurs region presently occur at a high 

density, and those within park boundaries are 

largely protected from illegal take. However, 

wolves in areas of Minnesota adjacent to VNP 

are subjected to illegal killing, and wolves 

are taken legally in adjacent Ontario. Voyageurs National Park is not of adequate size 

to support a self-sustaining wolf population. 

A population of wolves completely isolated 

within VNP might be expected to experience 

the population viability diffi culties exhibited 

recently by wolves at IRNP (Peterson 1999). 

Isolation of wolves at VNP may result from 

changes in land use on both sides of the international border—both increased logging (timber harvest and associated roads) and other 

development, or increased harvest of wolves 

beyond the park boundaries. Fortunately, 

there are a number of large protected, mostly 

roadless areas, close to VNP, including the 

SNF’s Boundary Waters Canoe Area Wilderness, Minnesota, and Quetico Provincial Park, 

Ontario. Successful conservation of wolves 

will require management agencies to identify 

and maintain potential wolf movement corridors between these protected areas. Such an 

eff ort will involve cooperation with multiple 

agencies at the international level. In addition, 

VNP should begin to monitor trends in land 

use practices along its boundaries. 

Our radiotelemetry data and that of others 

(Fox et al. 1999) show wolves making relatively little use of the shorelines of larger lakes and 

frozen lake surfaces during the day, especially 

in comparison to wolves at IRNP. The implication is that human winter activities at VNP 

could be impacting wolf behavior patterns. 

The issue begs further resolution. At present, 

wolves are abundant in VNP, and there is no 

evidence that the current types and levels of 

human activities are depressing wolf numbers. 

However, the potential eff ects of increasing 

levels of human activity, especially snowmobiling, and the take of wolves beyond the park 

that could reduce immigration necessitate 

continuous data gathering and evaluation by 

the National Park Service.

Wolves at VNP are currently dependent on 

a high-density prey base of deer and beaver. 

Changes in prey density resulting from natural 

vegetative succession or consecutive harsh 

winters could impact wolf density. Applications of models predicting plant succession 

for northern Minnesota (Tester et al. 1997) 

and linked estimates of the ecological carrying capacity of deer and beaver would provide 

insights of the likelihood of VNP continuing 

to support wolves. Such insight could provide 

direction to the use of prescribed burning and 

response to wildfi res in and out of VNP. 

Wolves at VNP have been exposed to Lyme 

disease and CPV with no detectable impact on 

survival of individuals or measurable population parameters. However, these instances 

highlight the vulnerability of wolves to the 

introduction of other diseases and parasites. 

The potential establishment of additional diseases and parasites requires careful monitoring.

Similarly, the evidence of past hybridization 

with coyotes in VNP wolves underscores the 

threat of such events in the future, particularly as the postulated scenario of pioneering 

wolves breeding with coyotes exists across a 

broad front as wolves expand into southern 

Minnesota, Wisconsin, and Michigan.

Voyageurs National 

Park should begin to 

monitor trends in land 

use practices along its 

boundaries.

Changes in prey density 

resulting from natural 

vegetative succession or 

consecutive harsh winters could impact wolf 

density. 

National Park Service 37

Appendix 1. Number of wolves harvested in the Fort 

Frances District, Ontario, 1948 –1998

0

10

20

30

40

50

60

70

80

90

100

110

120

130

140

48/4950/5152/5354/5556/5758/5960/6162/6364/6566/6768/6970/7172/7374/7576/7778/7980/8182/8384/8586/8788/8990/9192/9394/9596/97

* NOTE: Harvest data for 1970/71 trapping season is estimate only

Number of Animals Harvested by Trappers

Annual Timber Wolf Harvest (1948–1998) Fort Frances District

Study Years
38 Gray wolves in and adjacent to Voyageurs National Park, Minnesota: Research and synthesis 1987 – 1991

Appendix 2. Accuracy of aerial-telemetry location 

estimates for gray wolves in and adjacent to 

Voyageurs National Park, Minnesota, 1989 – 1991.

Background

From August 1987 to May 1991, 31 wolves 

were captured within and up to 16 km south 

of VNP. Each animal was fi tted with a radio collar and monitored every 2–10 days 

throughout the year until (1) a mortality sensor on the radio transmitter indicated that the 

animal had died, (2) the individual dispersed 

from the study area, or (3) the radio transmitter failed. Wolves were relocated from fi xedwing aircraft and location x-y coordinates 

were recorded based on LORAN-C fi xes and 

visual estimates marked on 1:50,000-scale 

topographic maps (topographic mapping).

A total of 1,174 location estimates was recorded for wolves in and near VNP during 

the study. Prior to mid-December 1989, 544 

location estimates consisted solely of x-y 

coordinates read from an onboard LORANC positioning device. Bias and precision of 

LORAN-C location estimates during this 

early period were unknown. After mid-December 1989, 630 location estimate “fi nal 

calls” consisted of x-y coordinates read from 

an onboard LORAN-C positioning device, x-y 

coordinates estimated off topographic maps 

via a graduated grid overlay (topographic 

mapping), or a combination of LORAN-C 

and topographic mapping (e.g., LORAN-C 

northing and topographic-mapped easting). 

As with the early period, bias and precision of 

“fi nal call” location estimates during this later 

period were unknown. Potential errors aff ecting bias and precision existed for all location 

methods (i.e., LORAN-C, topographic mapping, and combination).

Most error associated with LORAN-C is likely 

due to inherent system error. Precision and 

bias of LORAN-C location estimates can be 

aff ected by the geographic arrangement of 

transmitting towers, proximity of receiver to 

transmitting tower(s), elevation of aircraft, 

terrain/topography, proximity to power lines, 

location relative to mineral deposits, and 

weather (IIMorrow 1989, Rhoades et al. 1990, 

Anonymous 1991, Keating 1994, Leptich et al. 

1994). Additionally, equipment malfunction 

may lead to erroneous coordinates. For example, tower(s) within a LORAN-C transmitter chain may become temporarily inoperable, 

changing their geographic confi guration, or a 

LORAN-C receiver may malfunction. Finally, 

human error may lead to erroneous coordinates; LORAN-C coordinates may be misread 

off the receiver or misentered onto data sheets. 

Previous studies have reported on both precision and bias associated with LORAN-C location estimates. LORAN-C location estimates 

have diff ered from actual locations by mean 

distances of 20 –97 m for land-borne receivers 

(Patric et al. 1988, Rhoades et al. 1990), 200 –

386 m for airborne receivers (Boer et al. 1989, 

Brown 1992, Leptich et al. 1994, Carrell et al 

1997), and 128 –328 m for airborne receivers 

after bias adjustment (Jaeger et al. 1993, Carrell et al. 1997). Locational bias is a known 

issue for inland LORAN-C locations and can 

vary from study area to study area (Jaeger et al. 

1993, Leptich et al. 1994). Reported locational 

bias has ranged from 99 –265 m in a northsouth direction and from 163 – 484 m in an 

east-west direction (Jaeger et al. 1993, Carrell 

et al. 1997).

Most error associated with topographic mapping likely can be attributed to human error. 

Mapped coordinates may be placed in wrong 

positions on the topographic map, interpolation from a coarse-scale grid overlay may 

provide incorrect or non-precise coordinates, 

and mapped coordinates may be misread or 

misentered. Previous studies have reported 

on the precision associated with topographic 

mapping location estimates. Topographic 

mapping location estimates have diff ered 

from actual locations by mean distances of 

77–1,414 m (Krausman et al. 1984, Garrott et 

al. 1987, Walsh et al. 1992, Carrell et al. 1997). 

No study has reported a directional bias associated with topographic mapping.

Error associated with combination coordinates can be ascribed to the above sources 

for LORAN-C and for topographic mapping. 

However, another source of error is also introduced. The decision to choose a LORAN-C 

fi x or topographic mapping coordinate may be 

incorrect (e.g., map coordinate was chosen yet 

LORAN-C fi x for that location was more correct). This fi nal source of error may be infl ated 

if no set criteria are followed consistently 

throughout a study by all observers. Arbitrary 

Most error associated 

with topographic mapping likely can be attributed to human error.
National Park Service 39

decisions on whether to use a LORAN-C fi x 

or topographic mapping coordinate could 

lead to discrepancies that cannot easily be 

adjusted.

To fully describe the accuracy (i.e., precision 

and bias) of “fi nal call” location estimates and 

LORAN-C location estimates, optimally we 

would compare their estimated coordinates 

to known true coordinates. However, we did 

not know the true locations of the wolves and 

could not quantify the precision of the location estimates. Yet we can potentially report 

locational bias. Bias can be calculated for 

“fi nal call” or LORAN-C coordinates if their 

coordinates are compared to those of another 

method that is not biased. We can then remove bias post hoc as suggested by Carrell et 

al. (1997).

We determined the relative directional bias of 

“fi nal call” x-y coordinates and LORAN-C coordinates collected for wolf aerial locations in 

and adjacent to VNP from 1989 to 1991. This 

provided an objective means of correcting for 

potential locational errors based on LORANC prior to mid-December 1989 and correcting for potential locational errors based on 

“fi nal calls” after mid-December 1989. We 

also provide recommendations regarding the 

utility of various x-y coordinate sources (e.g., 

LORAN-C, topographic mapping) for home 

range analysis.

Methods

To quantify potential biases of various location estimates, we used data available from 

16 December 1989 to 16 May 1991 (i.e., the 

period when both LORAN-C and topographic 

mapping were employed). The fi rst coordinate 

data set consisted of the potentially biased 

“fi nal call” x-y coordinates (i.e., the wolf location estimates used in subsequent movement 

analysis). These coordinates were coded as 

LORAN-C estimates, topographic mapping 

estimates, or combination estimates. LORAN-C 

estimates were those with both x and y coordinates originating from a LORAN-C positioning device. LORAN-C x-y coordinates 

read off the positioning device as longitude 

and latitude were converted to Universal 

Transverse Mercator (UTM) coordinates (zone 

15, datum NAD27) using the coordinate conversion program Tralaine (Mentor Software 

Inc., Thornton, Colorado, USA). LORAN-C 

was not calibrated to the study area as suggested by Jaeger et al. (1993). Topographic 

mapping estimates were those with both x and 

y coordinates originating from a graduated 

grid overlay placed over a topographic map. 

Coordinates were read as longitude and latitude and were converted to UTM coordinates 

(zone 15, datum NAD27) using the coordinate 

conversion program Tralaine. Combination 

estimates were those with x and y coordinates 

originating from LORAN-C or topographic 

mapping. The second coordinate data set 

consisted of the potentially biased LORAN-C 

x-y coordinates collected for all of the above 

location estimates. The fi nal coordinate data 

set consisted of x-y coordinates taken from a 

digital topographic map for those “X”s plotted 

directly onto study-area maps (digital mapping). We obtained precise x-y coordinates 

(UTM zone 15, datum NAD27) for the plotted 

locations using DLG Viewer (USGS, MidContinent Mapping Center, Rolla, Missouri). 

A mouse cursor placed on a digital topographic map at the exact position where the 

center of the “X” plotted on the paper map 

fell provided appropriate coordinates. For all 

plotted “X”s, digital mapping provided x-y 

coordinates with sub-meter precision (relative 

to where the “X” was placed, not relative to 

the true location). Digital mapping removed 

the error associated with interpolation from a 

course grid overlay and misread or misentered 

data from topographic mapping.

To calculate locational bias, we compared “fi nal 

call” coordinates and LORAN-C coordinates 

(the biased estimates) to coordinates generated 

from an unbiased estimate. By subtracting the 

estimated “fi nal call” or LORAN-C location 

coordinates from coordinates obtained from 

the unbiased method, the resulting discrepancies were used to calculate a mean vector 

whose coordinates could be used to adjust 

the original x-y coordinate values. The new 

adjusted coordinates should then be unbiased. 

Precision would still be unknown (assumed to 

be ~200 m from literature). Although we did 

not know the precision of digitally mapped 

coordinates, we assumed those mapped coordinates to be unbiased and used them to 

detect and adjust for bias.

Results

Of 630 “fi nal call” location estimates collected 

from 16 December 1989 to 16 May 1991, 

598 (95%) had LORAN-C x-y coordinates 

and topographic mapping “X” s plotted on 

paper maps. We calculated x-y coordinates 

for mapped “X”s via digital mapping. We acknowledge that plotted map coordinates may 

only have had a precision of approximately 

100 –1,000 m, however, it has been demonstrated that plotted coordinates are at least unDigital mapping removed the error associated with interpolation 

from a course grid 

overlay and misread or 

misentered data from 

topographic mapping.
40 Gray wolves in and adjacent to Voyageurs National Park, Minnesota: Research and synthesis 1987 – 1991

biased. The bias of reported “fi nal calls” and 

LORAN-C location estimates was then calculated by subtracting those x and y coordinates 

from unbiased x and y coordinates provided 

by digital mapping.

When we compared coordinates reported as 

fi nal wolf locations to the unbiased estimate 

(digitally mapped coordinates minus “fi nal 

call” coordinates) we got a distribution of discrepancies (fi gure 1). The “fi nal call” estimates 

were, on average, 177.5 m west and 58.0 m 

north of the digitally mapped coordinates. 

This translated to a mean vector distance of 

186.7 m at an angle of 108° from the arithmetic center of the digitally mapped coordinates. 

The coordinate errors do not appear to come 

from a bivariate normal distribution and it 

would be diffi cult if not impossible to compute a single adjustment factor to transform 

the fi nal calls to unbiased estimates.

Upon closer examination, it was apparent that 

the distribution of x-y discrepancies actually 

consisted of three separate distributions (fi gure 2). These three distributions were the coordinate diff erences between LORAN-C and 

digital mapping, topographic mapping and 

digital mapping, and combination coordinates 

and digital mapping.

“Final call” coordinates estimated from a paper topographic map via grid overlay diff ered 

by as much as approximately 2,000 m from 

digitally mapped coordinate estimates (fi gure 

2). These large errors likely were the result of 

reading coordinates incorrectly off the grid 

or transcription error. The “fi nal call” estimates based on topographic mapping were, 

on average, 21.1 m west and 39.3 m south of 

the digitally mapped coordinates. This translated to a mean vector distance of 44.6 m at 

an angle of 28.2° from the arithmetic center 

of the digitally mapped coordinates. Most 

points were very close to the digitized points 

and showed no signifi cant bias (Hotelling’s 

T 2

2,55 = 2.02, P = 0.143). The 95% confi dence 

ellipse encompassed the origin also indicating 

no diff erence from digital mapping estimates 

(fi gure 3, page 49). Thus, “fi nal call” estimates 

based on topographic mapping coordinates 

did not require a post hoc adjustment to correct for bias.

“Final call” coordinates estimated from LORAN-C diff ered by as much as approximately 

5,000 m from digitally mapped coordinate 

estimates (fi gure 2). Errors of this magnitude 

may have been caused by problems in the 

LORAN-C transmitter chain (these larger errors only occurred on two days). The “fi nal 

call” estimates based on LORAN-C were, on 

average, 437.2 m west and 98.2 m north of the 

digitally mapped coordinates. This translated 

to a mean vector distance of 448.1 m at an 

angle of 102.7° from the arithmetic center of 

the digitally mapped coordinates. LORANC coordinates diff ered signifi cantly from 

digitally estimated coordinates and showed 

signifi cant bias (Hotelling’s T 2

2,232 = 372.91, P

< 0.001). The 95% confi dence ellipse did not 

encompass the origin also indicating a diff erence from digital mapping estimates (fi gure 3). 

Thus, “fi nal call” estimates based on LORANC coordinates required a post hoc adjustment 

to correct for bias.

Because most “fi nal call” coordinates were 

a combination of LORAN-C northing and 

mapped easting, the diff erences from digitally 

mapped coordinates showed some easting 

error with more dispersed northing errors 

(fi gure 2). The “fi nal call” estimates based 

on combination coordinates were, on average, 9.97 m west and 45.3 m north of the 

digitally mapped coordinates. This translated 

to a mean vector distance of 46.3 m at an 

angle of 167.6° from the arithmetic center 

of the digitally mapped coordinates. Location estimates with coordinates consisting of 

a combination of mapped coordinates and 

LORAN-C coordinates also diff ered signifi -

cantly from digitally estimated coordinates 

(Hotelling’s T 2

2,308 = 7.77, P = 0.001). The 95% 

confi dence ellipse did not encompass the 

origin also indicating a diff erence from digital 

mapping estimates (fi gure 3, page 43). Thus, 

“fi nal call” estimates based on combination 

coordinates required a post hoc adjustment to 

correct for bias (likely, the LORAN-C portion 

of the combination coordinates created most 

of the detected bias).

We adjusted individual location estimates by 

the mean vector coordinates for the two cases 

that produced signifi cantly diff erent means 

than digital coordinates (fi gure 4, page 43). 

The adjusted “fi nal call” estimates were, on 

average, 2.0 m west and 3.7 m south of the digitally mapped coordinates. This translated to 

a mean vector distance of 4.2 m at an angle of 

28.2° from the arithmetic center of the digitally mapped coordinates. The new adjusted fi nal 

coordinates produced errors that were unbiased and were not signifi cantly diff erent from 

the origin (Hotelling’s T 2

2,597 = 0.11, P = 0.895). 

A 95% confi dence ellipse (not shown) also 

encompassed the origin indicating no diff erThe coordinate errors 

do not appear to come 

from a bivariate normal 

distribution....
National Park Service 41

Figure 2a. Discrepancies (m) between paper-mapped “fi nal call” 

x-y coordinates and digitally 

mapped coordinates for aerialtelemetry locations of wolves 

in the Voyageurs National Park 

region, Minnesota, 1989 –1991. 

Differences were calculated by 

subtracting topographic mapping and combination “fi nal call” 

coordinates from unbiased, digitally mapped coordinates.

Figure 1. Locational discrepancies 

(m) between “fi nal call” x-y coordinates and digitally mapped 

coordinates for aerial-telemetry 

locations of wolves in the Voyageurs National Park region, Minnesota, 1989 –1991. Differences 

were calculated by subtracting 

“fi nal call” coordinates from 

unbiased, digitally mapped coordinates.

-6000

-5000

-4000

-3000

-2000

-1000

0

1000

2000

3000

4000

5000

6000

-6000 -5000 -4000 -3000 -2000 -1000 0 1000 2000 3000 4000 5000 6000

Easting Difference (m)

Northing Difference (m)

Paper Map Coordinates

-6000

-5000

-4000

-3000

-2000

-1000

0

1000

2000

3000

4000

5000

6000

-6000 -5000 -4000 -3000 -2000 -1000 0 1000 2000 3000 4000 5000 6000

Easting Difference (m)

Northing Difference (m)

Final Call Coordinates

Legend
42 Gray wolves in and adjacent to Voyageurs National Park, Minnesota: Research and synthesis 1987 – 1991

Figure 2b. Discrepancies (m) 

between LORAN-C–only based 

“fi nal call” x-y coordinates and 

digitally mapped coordinates 

for aerial-telemetry locations 

of wolves in the Voyageurs National Park region, Minnesota, 

1989 –1991. Differences were calculated by subtracting LORAN-C 

and combination “fi nal call” 

coordinates from unbiased, digitally mapped coordinates.

Figure 2c. Discrepancies (m) 

between combined coordinatebased “fi nal call” x-y coordinates 

and digitally mapped coordinates for aerial-telemetry locations of wolves in the Voyageurs 

National Park region, Minnesota, 

1989 –1991. Differences were 

calculated by subtracting combination “fi nal call” coordinates 

from unbiased, digitally mapped 

coordinates.

-6000

-5000

-4000

-3000

-2000

-1000

0

1000

2000

3000

4000

5000

6000

-6000 -5000 -4000 -3000 -2000 -1000 0 1000 2000 3000 4000 5000 6000

Easting Difference (m)

Northing Difference (m)

LORAN Coordinates

Legend

-6000

-5000

-4000

-3000

-2000

-1000

0

1000

2000

3000

4000

5000

6000

-6000 -5000 -4000 -3000 -2000 -1000 0 1000 2000 3000 4000 5000 6000

Easting Difference (m)

Northing Difference (m)

Combined Coordinates

Legend
National Park Service 43

Figure 3. Ninety-fi ve percent 

confi dence ellipses for locational 

discrepancies (m) between “fi nal 

call” x-y coordinates and digitally mapped coordinates for aerialtelemetry locations of wolves in 

the Voyageurs National Park region, Minnesota, 1989 –1991. Differences were calculated by subtracting LORAN-C, topographic 

mapping, and combination “fi nal 

call” coordinates from unbiased, 

digitally mapped coordinates.

Figure 4. Locational discrepancies 

(m) between adjusted “fi nal call” 

x-y coordinates and digitally 

mapped coordinates for aerialtelemetry locations of wolves 

in the Voyageurs National Park 

region, Minnesota, 1989 –1991. 

Differences were calculated by 

subtracting adjusted LORAN-C, 

raw topographic mapping, and 

adjusted combination “fi nal call” 

coordinates from unbiased, digitally mapped coordinates.

-1000

-800

-600

-400

-200

0

200

400

600

800

1000

-1000 -800 -600 -400 -200 0 200 400 600 800 1000

Easting Difference (m)

Northing Difference (m)

LORAN Coordinates

Combined Coordinates

Paper Map Coordinates

Legend

-6000

-5000

-4000

-3000

-2000

-1000

0

1000

2000

3000

4000

5000

6000

-6000 -5000 -4000 -3000 -2000 -1000 0 1000 2000 3000 4000 5000 6000

Easting Difference (m)

Northing Difference (m)

Adjusted Coordinates

Legend
44 Gray wolves in and adjacent to Voyageurs National Park, Minnesota: Research and synthesis 1987 – 1991

ence from digital mapping estimates. However, the distribution of x-y deviations still did 

not appear to show a classic bivariate normal 

shape. There still appeared to be an unnatural 

compression of points on either side of the 

y-axis for part of the data (i.e., the adjusted 

combination coordinates). An additional and 

more serious problem exists because to correct for biases in wolf locations, two separate 

corrections were required, one for LORAN-C 

and one for combination coordinates (if paper 

map coordinates would have been signifi -

cantly diff erent from digital coordinates, three 

adjustments would have been required). A 

fi nal serious problem with the separate adjustments was that no set criteria were followed 

to determine when to use LORAN-C or paper 

map coordinates. The corrections developed 

could only be used for this sample.

Coordinates estimated via LORAN-C diff ered 

by as much as approximately 6,000 m from 

digitally mapped coordinate estimates (fi gure 

5). As with “fi nal call” LORAN-C discrepancies, the extreme large diff erences are likely 

the result of two days with diff erent transmitting tower confi gurations (i.e., there were 

consistent biases for each of the two days). 

Estimates based on LORAN-C were, on average, 547.8 m west and 138.3 m north of the 

digitally mapped coordinates. This translated 

to a mean vector distance of 564.9 m at an 

angle of 104.2° from the arithmetic center of 

the digitally mapped coordinates. LORAN-C 

coordinates diff ered signifi cantly from digitally 

estimated coordinates and showed signifi cant 

bias (Hotelling’s T 2

2,597 = 941.90, P < 0.001). 

The 95% confi dence ellipse did not encompass the origin, which also indicates a diff erence from digital estimates (fi gure 6). Telemetry data gathered during these two days were 

not used in our assessments of wolf territory 

sizes or movements.

Discussion and recommendations

For the purposes of the VNP wolf study, “fi nal 

call” estimates are likely accurate enough to 

meet the needs of home range and movement 

analysis. In many cases “fi nal call” coordinates 

may be more accurate than either LORAN-C 

or topographic mapping. However, locations 

based on several diff erent types of “fi nal call” 

x-y coordinates (LORAN-C, topographic 

mapping, and combination) will be diffi cult to 

defend under stringent peer review. Without 

a strict protocol for basing “fi nal call” estimates on LORAN-C, topographic mapping, or 

combination coordinates, the resulting error 

distribution is unpredictable and makes meeting statistical assumptions diffi cult if not impossible. It would be more appropriate to use 

only topographic mapping or bias-adjusted 

LORAN-C x-y coordinates whose resulting error distributions show a typical bivariate normal shape. We recommend not using combination coordinates to describe wolf locations.

Topographic mapping has the advantage of 

producing unbiased estimates without adjustment. Also, topographic mapping coordinates 

can be more precise than LORAN-C (see Carrell et al. 1997), especially in heterogeneous 

environments or varied terrain. But both topographic mapping and LORAN-C precision 

vary by area. Since we do not know the true 

locations we cannot assume that precision is 

better with topographic mapping in the VNP 

region.

Due to limited precision, Jaeger et al. (1993) 

were critical of the use of LORAN-C in aerialtelemetry studies, and suggested locations 

from which they were based had limited utility. Rhoades et al. (1990) indicated that the 

type of analysis LORAN-C location estimates 

could provide would be scale dependent. 

However, LORAN-C has advantages over 

topographic mapping. LORAN-C can provide 

location estimates in fl at or featureless terrain 

or habitats that would otherwise preclude 

accurate topographic mapping; it also is less 

labor intensive and time consuming, reduces 

costs and increases effi ciency, and gives the 

ability of diff erent work crews to achieve similar results (Patric et al. 1988, Boer et al. 1989). 

Carrell et al. (1997) maintain that LORAN-C 

location estimates should provide adequate 

accuracy for home range studies.

With regard to VNP wolf data, we recommend 

that bias-adjusted LORAN-C coordinates be 

used to describe wolf locations for the fi rst 

portion of the study when only LORAN-C 

was employed. When both topographic mapping and LORAN-C were employed in the 

latter part of the study, we recommend either 

using all topographic mapping coordinates or 

using all bias-adjusted LORAN-C coordinates 

to describe wolf locations. We cannot recommend using both coordinate types for the latter period of the study. For this latter period, 

topographic mapping likely provided more 

precise and unbiased estimates than LORANC. Thus, we recommend using topographic 

mapping if accurate locations are the main 

concern. But, using bias-adjusted LORAN-C 

will provide a single, consistent adjustment for 

the entire period of study with less eff ort. If 

“Final call” estimates 

are likely accurate 

enough to meet the needs 

of home range and 

movement analysis.
National Park Service 45

Figure 5. Locational discrepancies (m) between LORAN-C 

x-y coordinates and digitally 

mapped coordinates for aerialtelemetry locations of wolves 

in the Voyageurs National Park 

region, Minnesota, 1989 –1991. 

Differences were calculated by 

subtracting LORAN-C coordinates 

from unbiased, digitally mapped 

coordinates.

Figure 6. Ninety-fi ve percent confi dence ellipse for locational discrepancies (m) between LORAN-C 

x-y coordinates and digitally 

mapped coordinates for aerialtelemetry locations of wolves 

in the Voyageurs National Park 

region, Minnesota, 1989 –1991. 

Differences were calculated by 

subtracting LORAN-C coordinates 

from unbiased, digitally mapped 

coordinates.

-6000

-5000

-4000

-3000

-2000

-1000

0

1000

2000

3000

4000

5000

6000

-6000 -5000 -4000 -3000 -2000 -1000 0 1000 2000 3000 4000 5000 6000

Easting Difference (m)

Northing Difference (m)

LORAN Coordinates

Legend

-1000

-800

-600

-400

-200

0

200

400

600

800

1000

-1000 -800 -600 -400 -200 0 200 400 600 800 1000

Easting Difference (m)

Northing Difference (m)

LORAN Coordinates

Legend
46 Gray wolves in and adjacent to Voyageurs National Park, Minnesota: Research and synthesis 1987 – 1991

the level of accuracy provided by bias-adjusted LORAN-C is suffi cient for study objectives, 

we recommend using bias-adjusted LORANC. Regardless of the location estimate method 

chosen, a more objective means of excluding 

potentially low-quality location data may be 

developed following Keating (1994).

Global positioning systems (GPS) technology 

has essentially replaced LORAN-C in recent 

years because of low cost and increased precision (Leptich et al. 1994, Carrell et al. 1997). 

However, location data may exist based on 

previously gathered LORAN-C results. Therefore these results provided an example of 

how it may be possible to correct previously 

unreported or uncorrected bias. In the case 

of other studies conducted in the same study 

area during the same period (e.g., white-tailed 

deer and moose), adjustments based on wolf 

location discrepancies may be used to correct 

these locations.

These results provided 

an example of how it 

may be possible to correct previously unreported or uncorrected 

bias.
National Park Service 47

Appendix 3. Examples of use of Program Mark in 

analysis of survival of instrumented wolves in and 

adjacent to Voyageurs National Park, Minnesota.

Example of Known Fates model data entry in program MARK

Encounter histories fi les included seasonal records for radio-marked gray wolves and facilitated 

Known Fates models in program MARK. Known Fates models were able to document both live 

and dead captures or relocations. Data were coded in the encounter histories fi le with a series of 

“1”s or “0”s, entered in pairs, to represent either live or dead encounters via radiotelemetry.

Examples of encounters included:

“10” = live on encounter occasion (includes initial capture occasion and subsequent relocations)

“11” = dead on encounter occasion

Consider the following excerpt from an encounter histories fi le:

 / * 4.6375B 89–90 pack A F P I */ 0 0 1 0 1 0 0 0 0 1;

/* 4.6375B 89–90 disp A F N B */ 0 0 0 0 0 0 1 0 0 1;

/* 4.6375B 90–91 pack A F P B */ 1 0 1 0 1 0 1 0 0 1;

/* 4.6375B 91–92 pack A F P B */ 1 0 0 0 0 0 0 0 0 1;

Data within the “/ * */” are comments and are used to break down the data into appropriate periods. Thus, the same animal can be coded several ways, even in a given year. All four 

lines are for animal 4.6375. The fi rst two lines represent the biological year 1989 –1990, the third 

line represents the biological year 1990 –1991, and the fourth line represents the biological year 

1991–1992. This animal was an adult during each year (A). It was a female (F). For seasons two 

and three of year 1989 –1990, immediately after being trapped, it belonged to packs (P) whose 

home ranges were in VNP (I). It dispersed from the pack and was a non-pack member (N) during season four in 1989 –1990. During this period its range bordered VNP. From the fi rst season 

in 1990 –1991 to the end of the study it belonged to a new pack. This pack’s home range bordered VNP every biological year. In this excerpt, the code at the end of each line fi rst includes 

data on survival for the given periods. There are four sets of two numbers representing each of 

the four seasons of the biological year. Survival codes for each season include “10” (found alive) 

or “11” (found dead). This animal did not die during the study period so there was never a “11” 

in the data string. In this example, the last two single numbers in each line represent a pack animal “1 0” or a non-pack animal “0 1”. This code changes for the particular model that was run 

depending on the research hypothesis being investigated (e.g., age, sex, pack status, home range 

location).

(Continued)

Known Fates models 

were able to document 

both live and dead captures or relocations.
48 Gray wolves in and adjacent to Voyageurs National Park, Minnesota: Research and synthesis 1987 – 1991

Survival by age and time of year

/*

Comments (/* * /) included in each row: 

Wolf ID

Wolf year

Age class—pup, adult

Sex—male, female

Pack status—pack member, non-pack animal (disperser, loner, unknown)

Location of pack home range (pack members) or individual home range (non-pack members) relative to VNP—in VNP, bordering VNP, out of VNP

Encounter histories entered seasonally within wolf years, August–April 1987–1991:

10 = confi rmed alive via radiotelemetry within season,

11 = confi rmed dead via radiotelemetry within season

Data codes: 

1 0 = adults,

0 1 = pups

 */ 

/* 4.4375 88–89 pack A M P I */ 1 0 1 0 1 0 1 0;

/* 4.4375 89–90 pack A M P I */ 1 0 0 0 0 0 1 0;

/* 4.4375 89–90 disp A M N B */ 0 0 1 0 0 0 1 0;

/* 4.4625 87–88 pack P M P B */ 1 0 1 1 0 0 0 1;

/* 4.4875 87–88 none A F N B */ 1 0 1 0 1 0 1 0;

/* 4.4875 88–89 none A F N B */ 1 0 0 0 0 0 1 0;

/* 4.5125 87–88 pack P F P B */ 1 0 1 0 1 0 0 1;

/* 4.5125 88–89 pack A F P B */ 1 0 1 0 1 0 1 0;

/* 4.5125 89–90 pack A F P B */ 1 0 1 0 1 1 1 0;

/* 4.5375 88–89 pack A F P O */ 1 0 1 0 1 0 1 0;

/* 4.5375 89–90 pack A F P O */ 1 0 0 0 0 0 1 0;

/* 4.5375 89–90 disp A F N B */ 0 0 1 0 0 0 1 0;

/* 4.5620 89–90 pack A F P I */ 1 0 1 0 1 0 1 0;

/* 4.5620 90–91 pack A F P I */ 1 0 1 0 1 0 1 0;

/* 4.5625 88–89 none A M N B */ 1 0 1 1 0 0 1 0;

/* 4.5870 89–90 pack A F P B */ 1 0 0 0 0 0 1 0;

/* 4.6125 90–91 pack P M P B */ 1 0 1 0 0 0 0 1;

/* 4.6130 88–89 unkn A F N O */ 1 0 1 0 0 0 1 0;

/* 4.6375A 88–89 pack A F P O */ 1 0 0 0 0 0 1 0;

/* 4.6375B 89–90 pack A F P I * / 1 0 1 0 0 0 1 0 ;

/* 4.6375B 89–90 disp A F N B */ 0 0 0 0 1 0 1 0;

/* 4.6375B 90–91 pack A F P B */ 1 0 1 0 1 0 1 0;
National Park Service 49

/* 4.6625A 88–89 pack A M P O */ 1 0 0 0 0 0 1 0;

/* 4.6625A 88–89 disp A M N O */ 0 0 1 0 1 1 1 0;

/* 4.6625B 89–90 pack A F P B */ 1 0 1 0 1 1 1 0;

/* 4.6875A 89–90 pack P F P B */ 1 1 0 0 0 0 0 1;

/* 4.6875B 89–90 pack A F P B * / 1 0 1 0 1 0 1 0;

/* 4.6875B 90–91 pack A F P B * / 1 0 1 0 1 0 1 0;

/* 4.7125 88–89 pack A F P O */ 1 0 1 0 0 0 1 0;

/* 4.7125 88–89 disp A F N O */ 0 0 0 0 1 0 1 0;

/* 4.7615 89–90 pack P M B P */ 1 0 0 0 0 0 0 1;

/* 6.7375A 88–89 unkn A M N B */ 1 0 1 1 0 0 1 0;

/* 6.7375B 90–91 pack A M P I */ 1 0 1 0 1 0 1 0;

/* 6.7625 88–89 pack P M B I */ 1 0 1 0 1 1 0 1;

/* 6.7870 88–89 pack A M P B */ 1 0 1 1 0 0 1 0;

/* 6.8125B 90–91 pack A F P B */ 1 0 1 0 0 0 1 0;

/* 6.8125B 90–91 disp A F N B */ 0 0 0 0 1 0 1 0;

/* 6.8375 90–91 pack A M P B */ 1 0 1 1 0 0 1 0;

/* 6.8380 88–89 pack A M P O */ 1 0 1 0 0 0 1 0;

/* 6.8380 88–89 disp A M N B */ 0 0 0 0 1 1 1 0;

/* 6.8635 90–91 pack A M P B */ 1 0 1 0 1 0 1 0;

/* 6.8880A 88–89 pack P F P O */ 1 0 0 0 0 0 0 1;

/* 6.8880B 89–90 pack A F P B */ 1 0 1 0 1 0 1 0;

/* 6.9125A 88–89 pack P F P B */ 1 0 1 1 0 0 0 1;

/* 6.9125B 89–90 pack A F P O* / 1 0 1 0 1 0 1 0;

/* 6.9125B 90–91 pack A F P O * / 1 0 1 0 1 0 1 0;
50 Gray wolves in and adjacent to Voyageurs National Park, Minnesota: Research and synthesis 1987 – 1991

Adult survival by sex and time of year

/*

Comments ( /* * /) included in each row: 

Wolf ID

Wolf year

Age class—pup, adult

Sex—male, female

Pack status—pack member, non-pack animal (disperser, loner, unknown)

Location of pack home range (pack members) or individual home range (non-pack 

members) relative to VNP—in VNP, bordering VNP, out of VNP

Encounter histories entered seasonally within wolf years, August–April 1987–1991:

10 = confi rmed alive via radiotelemetry within season,

11 = confi rmed dead via radiotelemetry within season

Data codes: 

1 0 = males,

0 1 = females

*/

/* 4.4375 88–89 pack A M P I */ 1 0 1 0 1 0 1 0 1 0;

/* 4.4375 89–90 pack A M P I */ 1 0 1 0 0 0 0 0 1 0;

/* 4.4375 89–90 disp A M N B */ 0 0 0 0 1 0 0 0 1 0;

/* 4.4875 87–88 none A F N B */ 0 0 1 0 1 0 1 0 0 1;

/* 4.4875 88–89 none A F N B */ 1 0 1 0 0 0 0 0 0 1;

/* 4.5125 88–89 pack A F P B */ 1 0 1 0 1 0 1 0 0 1;

/* 4.5125 89–90 pack A F P B */ 1 0 1 0 1 0 1 1 0 1;

/* 4.5375 88–89 pack A F P O */ 1 0 1 0 1 0 1 0 0 1;

/* 4.5375 89–90 pack A F P O */ 1 0 1 0 0 0 0 0 0 1;

/* 4.5375 89–90 disp A F N B */ 0 0 0 0 1 0 0 0 0 1;

/* 4.5620 89–90 pack A F P I */ 1 0 1 0 1 0 1 0 0 1;

/* 4.5620 90–91 pack A F P I */ 1 0 1 0 1 0 1 0 0 1;

/* 4.5620 91–92 pack A F P I */ 1 0 0 0 0 0 0 0 0 1;

/* 4.5625 88–89 none A M N B */ 1 0 1 0 1 1 0 0 1 0;

/* 4.5870 89–90 pack A F P B */ 1 0 1 0 0 0 0 0 0 1;

/* 4.6130 88–89 unkn A F N O */ 0 0 1 0 1 0 0 0 0 1;

/* 4.6375A 88–89 pack A F P O */ 1 0 1 0 0 0 0 0 0 1;

/* 4.6375B 89–90 pack A F P I */ 0 0 1 0 1 0 0 0 0 1;

/* 4.6375B 89–90 disp A F N B * / 0 0 0 0 0 0 1 0 0 1;

/* 4.6375B 90–91 pack A F P B */ 1 0 1 0 1 0 1 0 0 1;

/* 4.6375B 91–92 pack A F P B * / 1 0 0 0 0 0 0 0 0 1;

/* 4.6625A 88–89 pack A M P O * / 1 0 1 0 0 0 0 0 1 0;

/* 4.6625A 88–89 disp A M N O * / 0 0 0 0 1 0 1 1 1 0;

/* 4.6625B 89–90 pack A F P B * / 1 0 1 0 1 0 1 1 0 1;
National Park Service 51

/* 4.6875B 89–90 pack A F P B */ 1 0 1 0 1 0 1 0 0 1;

/* 4.6875B 90–91 pack A F P B */ 1 0 1 0 1 0 1 0 0 1;

/* 4.6875B 91–92 pack A F P B */ 1 0 0 0 0 0 0 0 0 1;

/* 4.7125 88–89 pack A F P O */ 1 0 1 0 1 0 0 0 0 1;

/* 4.7125 88–89 disp A F N O */ 0 0 0 0 0 0 1 0 0 1;

/* 4.7125 89–90 disp A F N O */ 1 0 0 0 0 0 0 0 0 1;

/* 6.7375A 88–89 unkn A M N B */ 0 0 1 0 1 1 0 0 1 0;

/* 6.7375B 90–91 pack A M P I */ 1 0 1 0 1 0 1 0 1 0;

/* 6.7375B 91–92 pack A M P I */ 1 0 0 0 0 0 0 0 1 0 ;

/* 6.7870 88–89 pack A M P B */ 0 0 1 0 1 1 0 0 1 0;

/* 6.8125B 90–91 pack A F P B */ 1 0 1 0 1 0 0 0 0 1;

/* 6.8125B 90–91 disp A F N B */ 0 0 0 0 0 0 1 0 0 1;

/* 6.8125B 91–92 disp A F N B */ 1 0 0 0 0 0 0 0 0 1;

/* 6.8375 90–91 pack A M P B */ 1 0 1 0 1 1 0 0 1 0;

/* 6.8380 88–89 pack A M P O */ 0 0 1 0 1 0 0 0 1 0;

/* 6.8380 88–89 disp A M N B */ 0 0 0 0 0 0 1 1 1 0;

/* 6.8635 90–91 pack A M P B */ 1 0 1 0 1 0 1 0 1 0;

/* 6.8635 91–92 pack A M P B */ 1 0 0 0 0 0 0 0 1 0;

/* 6.8880B 89–90 pack A F P B */ 1 0 1 0 1 0 1 0 0 1;

/* 6.9125B 89–90 pack A F P O */ 1 0 1 0 1 0 1 0 0 1;

/* 6.9125B 90–91 pack A F P O */ 1 0 1 0 1 0 1 0 0 1;

/* 6.9125B 91–92 pack A F P O */ 1 0 0 0 0 0 0 0 0 1;
52 Gray wolves in and adjacent to Voyageurs National Park, Minnesota: Research and synthesis 1987 – 1991

Adult survival by home range location and time of year 

/ *

Comments (/* * /) included in each row:

Wolf ID

Wolf year

Age class—pup, adult

Sex—male, female

Pack status—pack member, non-pack animal (disperser, loner, unknown)

Location of pack home range (pack members) or individual home range (non-pack members) relative to VNP—in VNP, bordering VNP, out of VNP

Encounter histories entered seasonally within wolf years, August–April 1987–1991:

10 = confi rmed alive via radiotelemetry within season,

11 = confi rmed dead via radiotelemetry within season

Data codes: 

1 0 0 = in VNP,

0 1 0 = bordering VNP,

0 0 1 = out of VNP

*/

/* 4.4375 88–89 pack A M P I */ 1 0 1 0 1 0 1 0 1 0 0;

/* 4.4375 89–90 pack A M P I */ 1 0 1 0 0 0 0 0 0 1 0;

/* 4.4375 89–90 disp A M N B */ 0 0 0 0 1 0 0 0 0 1 0;

/* 4.4875 87–88 none A F N B */ 0 0 1 0 1 0 1 0 0 1 0;

/* 4.4875 88–89 none A F N B */ 1 0 1 0 0 0 0 0 0 1 0;

/* 4.5125 88–89 pack A F P B */ 1 0 1 0 1 0 1 0 0 1 0;

/* 4.5125 89–90 pack A F P B */ 1 0 1 0 1 0 1 1 0 1 0;

/* 4.5375 88–89 pack A F P O */ 1 0 1 0 1 0 1 0 0 0 1;

/* 4.5375 89–90 pack A F P O */ 1 0 1 0 0 0 0 0 0 0 1;

/* 4.5375 89–90 disp A F N B */ 0 0 0 0 1 0 0 0 0 1 0;

/* 4.5620 89–90 pack A F P I */ 1 0 1 0 1 0 1 0 1 0 0;

/* 4.5620 90–91 pack A F P I */ 1 0 1 0 1 0 1 0 1 0 0;

/* 4.5620 91–92 pack A F P I */ 1 0 0 0 0 0 0 0 1 0 0;

/* 4.5625 88–89 none A M N B */ 1 0 1 0 1 1 0 0 0 1 0;

/* 4.5870 89–90 pack A F P B */ 1 0 1 0 0 0 0 0 0 1 0;

/* 4.6130 88–89 unkn A F N O */ 0 0 1 0 1 0 0 0 0 0 1;

/* 4.6375A 88–89 pack A F P O */ 1 0 1 0 0 0 0 0 0 0 1;

/* 4.6375B 89–90 pack A F P I * / 0 0 1 0 1 0 0 0 1 0 0;

/* 4.6375B 89–90 disp A F N B * / 0 0 0 0 0 0 1 0 0 1 0;

/* 4.6375B 90–91 pack A F P B */ 1 0 1 0 1 0 1 0 0 1 0 ;

/* 4.6375B 91–92 pack A F P B * / 1 0 0 0 0 0 0 0 0 1 0;

/* 4.6625A 88–89 pack A M P O */ 1 0 1 0 0 0 0 0 0 0 1 ;

/* 4.6625A 88–89 disp A M N O * / 0 0 0 0 1 0 1 1 0 0 1 ;
National Park Service 53

/* 4.6625B 89–90 pack A F P B * / 1 0 1 0 1 0 1 1 0 1 0;

/* 4.6875B 89–90 pack A F P B * / 1 0 1 0 1 0 1 0 0 1 0;

/* 4.6875B 90–91 pack A F P B * / 1 0 1 0 1 0 1 0 0 1 0;

/* 4.6875B 91–92 pack A F P B * / 1 0 0 0 0 0 0 0 0 1 0;

/* 4.7125 88–89 pack A F P O */ 1 0 1 0 1 0 0 0 0 0 1;

/* 4.7125 88–89 disp A F N O */ 0 0 0 0 0 0 1 0 0 0 1;

/* 4.7125 89–90 disp A F N O */ 1 0 0 0 0 0 0 0 0 0 1;

/* 6.7375A 88–89 unkn A M N B * / 0 0 1 0 1 1 0 0 0 1 0;

/* 6.7375B 90–91 pack A M P I * / 1 0 1 0 1 0 1 0 1 0 0;

/* 6.7375B 91–92 pack A M P I * / 1 0 0 0 0 0 0 0 1 0 0;

/* 6.7870 88–89 pack A M P B */ 0 0 1 0 1 1 0 0 0 1 0;

/* 6.8125B 90–91 pack A F P B */ 1 0 1 0 1 0 0 0 0 1 0;

/* 6.8125B 90–91 disp A F N B */ 0 0 0 0 0 0 1 0 0 1 0;

/* 6.8125B 91–92 disp A F N B */ 1 0 0 0 0 0 0 0 0 1 0 ;

/* 6.8375 90–91 pack A M P B */ 1 0 1 0 1 1 0 0 0 1 0;

/* 6.8380 88–89 pack A M P O */ 0 0 1 0 1 0 0 0 0 0 1;

/* 6.8380 88–89 disp A M N B */ 0 0 0 0 0 0 1 1 0 1 0;

/* 6.8635 90–91 pack A M P B */ 1 0 1 0 1 0 1 0 0 1 0;

/* 6.8635 91–92 pack A M P B */ 1 0 0 0 0 0 0 0 0 1 0;

/* 6.8880B 89–90 pack A F P B */ 1 0 1 0 1 0 1 0 0 1 0;

/* 6.9125B 89–90 pack A F P O */ 1 0 1 0 1 0 1 0 0 0 1;

/* 6.9125B 90–91 pack A F P O */ 1 0 1 0 1 0 1 0 0 0 1 ;

/* 6.9125B 91–92 pack A F P O */ 1 0 0 0 0 0 0 0 0 0 1;
54 Gray wolves in and adjacent to Voyageurs National Park, Minnesota: Research and synthesis 1987 – 1991

Appendix 4. Number of track encounters, incidental observations, howling responses, radiotelemetry locations and 

counts during flights for wolf packs studied in and adjacent 

to Voyageurs National Park, Minnesota, 1987–1991.

Pack Yeara Pack

Track 

Encountersb

Incidental 

Visualsc

Howling 

Responsesd

Radiotelemetry 

Locationse

Radiotelemetry 

Countsf

1987– 1988 Cruiser Lake (CLP) 15 1

Browns Bay (BBP) 6

Locator Lake (LLP) 16 4

Moose Grade (MGP) 4 1

Nebraska Bay (NBP) 7

Tom Cod (TCP) 5 59 15

 Subtotal 53 6 59 15

x 9 2 59 15

1988 –19 89 Blue Moose (BMP) 1 48 7

Cruiser Lake (CLP) 14 4 w 60 18

Dixon Creek (DCP) 0 32 0

Browns Bay (BBP) 7 w 8 0

Kohler Pitg (KPP) 0 4 w 34 0

Kohler Triog (KTP) 0 14 5

Locator Lake (LLP) 19 1 w 18 3

Moose Grade (MGP) 5 1 3 0

Moose Lake (MLP) 0 32 0

Nebraska Bay (NBP) 9 w 0 0

Tom Cod (TCP) 4 1 w 65 11

 Subtotal 59 11 6 314 44

x 5 2 n/a 29 4

1989–1990 Blue Moose (BMP) 22 0

Cruiser Lake (CLP) w

Browns Bay (BBP) w, wo

Middle Peninsula (MPP) w 82 19

Moose Grade (MGP) w, w 11 4

Nebraska Bay (NBP) wo 62 11

Rat Root (RRP) 25 9

Tom Cod (TCP) 78 12

 Subtotal 0 0 5 280 55

x n/a n/a n/a 47 9

1990–1991 Cruiser Lake (CLP) wo 63 10

Browns Bay (BBP) 115 10

Middle Peninsula (MPP) 66 17

Moose Grade (MGP) 104 10

Nebraska Bay (NBP) 41 3

Rat Root (RRP) 66 9

Tom Cod (TCP) w 66 8

 Subtotal 0 0 2 521 67

x n/a n/a n/a 74 10

 Total 112 17 13 1,174 181

a

Pack year defi ned as May 1 through April 30.

bTracks that could be attributed to a known pack (>2 wolves); winters of 1987–1988 and 1988 –1989 only.

c

Visual counts of pack (>2 wolves) other than during radio-telemetry fl ights.

dPack (>2 wolves) heard howling; w = with pups, wo = without pups; underlined letters denote incidentals, see text.

e

Cumulative number of locations for all collared wolves in the pack this period.

f

Visual count of pack (>2 wolves) during telemetry relocation fl ight.

gKPP either dispersed as the KTP or divided into two groups; see text.

_

_

_

_
National Park Service 55

Tom Cod Bay Pack (TCP)

198 7–1988: This was the fi rst pack radiomarked during the study and the only pack 

radio-marked for the fi rst eight months. During the fall of 1987, male pup 4625 and female 

pup 5125 were captured and radio-marked 

along old logging roads south of Tom Cod Bay 

off park lands. The male pup was shot illegally 

in early November 1987 during the small-game 

hunting season. The female continued to associate with the TCP for more than two years 

until she died from undetermined causes in 

December 1989. After observing fi ve wolves 

consistently during telemetry fl ights the winter of 1987–1988, the pack was observed on 2 

March as four animals. The pack was subsequently tracked on the ground on 5 March to 

a site where one wolf was illegally trapped and 

killed as evidenced by blood, wolf hair, wolf 

scat, and tracks, which showed fi ve wolves 

came to the site and only four wolves left. The 

wolves had been following a snowmobile trail 

southwest of Tom Cod Bay. The mid-winter 

estimate of pack size was fi ve wolves. From 

visual counts and trapping histories, this pack 

was at least six wolves in fall 1987. Two wolves 

(33%) were illegally killed by humans between 

fall 1987 and the end of March 1988.

1988–1989: Female pup 5125 from the previous year was still with the TCP, now as a 

yearling. Adult male 7870 was captured in 

August 1988, but was illegally shot in early 

November. Adults and pups responded to 

simulated howls during the 1988 fall survey. 

From sightings during winter telemetry fl ights 

we estimate the mid-winter pack size was fi ve 

wolves. The TCP territory was primarily south 

of Black Bay in 1988–1989. Of 65 telemetry 

locations, the pack was only located on the 

Kabetogama Peninsula twice (3%).

1989–1990: Female 5125 continued to associate with the pack, but died from undetermined causes in December 1989. In May, 

adult female 6875B was captured and this 

wolf remained with the pack for the rest of 

the study. The pack did not respond to simulated howls the fall of 1989. No tracking was 

conducted the winter of 1989–1990, but from 

sightings during telemetry fl ights the mid-winter pack size was again fi ve wolves. In 1989–

1990 the TCP began ranging farther north and 

west onto the Kabetogama Peninsula. Along 

with this change in territory came an extensive 

overlap with the newly formed MPP who we 

believe split from the CLP and displaced the 

LLP (see LLP, MPP, and CLP histories). 

1990–1991: Adult female 6875B continued to 

occupy a territory that included the western 

one-third of the Kabetogama Peninsula, and 

she was now the only radio-marked wolf in 

the TCP. The pack did not respond to simulated howls during the fall 1990 survey, and 

during winter telemetry fl ights 6875B was 

observed with only one other wolf. This pair 

used a well-delineated territory, about half of 

which now included the Kabetogama Peninsula.

Locator Lake Pack (LLP)

1987–88: This pack was not radio-marked in 

1987–1988, but from repeated track encounters and incidental visual counts the mid-winter pack size was estimated as three wolves. 

However, tracks suggest a fourth wolf accompanied them occasionally or scavenged from 

their kills. For example, on 19 February 1988 

I jumped a wolf off Sugarbush Island while investigating a kill made by three wolves on the 

island. This wolf could have been one of the 

three wolves returning for a meal; however, 

repeated observations of a single wolf track 

disassociated from tracks of three suggest a 

fourth animal. 

1988–1989: In fall 1988 male pup 7625 was 

radio-marked in the LLP. The pack did not 

respond to simulated howls during the routine 

fall survey, but unsolicited howls were heard 

from a pack northwest of Locator Lake in 

early October. During early winter telemetry 

fl ights, the pack was counted once as seven 

wolves. Until late January 1989 the LLP territory was non-overlapping with the adjacent 

CLP, which was also radio-marked and with 

eight wolves (see also CLP history). On 20 

January all eight members of the CLP were located well within the known territory of LLP 

and 7625 (LLP pup) was located in mortality 

Appendix 5. Histories of radio-marked wolves and 

wolf packs studied in and adjacent to Voyageurs National Park, Minnesota, 1987–1991.1

1

Information compiled from all data sources including fi eld 

notes.
56 Gray wolves in and adjacent to Voyageurs National Park, Minnesota: Research and synthesis 1987 – 1991

mode. We subsequently found 7625 and one 

other wolf dead from wolf-infl icted wounds. 

Previous radio locations for both packs were 

on 28 December, but based on sign (snow 

tracks and the lack of scavenging) we estimate 

the two packs collided sometime between 12 

and 19 January. All eight members of CLP 

were located on 20 January, so the unmarked 

dead wolf was also from the LLP. After losing radio contact with LLP we were unable to 

confi rm their existence, though tracks suggest 

that two to four wolves persisted in the area in 

addition to at least fi ve members of the CLP 

who ranged widely throughout LLP’s territory 

and the entire Kabetogama Peninsula. 

Middle Peninsula Pack (MPP)

1989–1990: During the winter of 1989 –1990 

a pack of fi ve wolves, including male 4375, 

originally of CLP, and newly radio-marked 

adult females 5620 and 6375B, continued to 

roam across most of the Kabetogama Peninsula. Three factors indicate that this pack of fi ve 

originated from CLP to form the MPP pack. 

First, all eight CLP wolves were observed 

together within days of the territorial dispute 

with LLP during winter 1988 –1989, yet on 12 

subsequent observations CLP male 4375 was 

never observed with more than four other 

wolves and that group roamed widely into 

LLP territory. Pack size was four or fi ve on six 

(50%) of the observations and one to two on 

six (50%) of the observations. We could not 

account for the remaining three CLP wolves 

that winter. Second, during howling surveys in 

fall 1989, packs with pups responded to simulated howls at three howling sites within the 

original (1988 –1989) CLP territory. These sites 

were separated by more than 12 km and, while 

wolves will easily cover this distance in a day, 

male 4375 and females 5620 and 6375B were 

associated with only one of the howling sites 

(K8). And though they could not be excluded 

from having been at the second site (R6), they 

were never located near the third site (N8) 

and were 30 km away the day of the howling 

response at R6. Finally, 4375, 5620, and 6375B 

spent very little time on the eastern end of the 

peninsula in 1989 –1990, and by 1990 –1991 

female 5620 (the other two had dispersed by 

this time) was consistently in the central portion of the peninsula between the TCP and a 

newly radio-marked pack on the east end of 

the peninsula. This newly radio-marked pack 

now occupied a somewhat smaller version of 

the original 1988 –1989 CLP territory.

Two of the MPP wolves began making forays 

off the peninsula in 1989 –1990 and later dispersed or disappeared. Male 4375 made forays 

to the southwest in late October 1989. He was 

located four times off the Kabetogama peninsula deep into TCP territory, and on 21 October he was located in close proximity to TCP 

female 5125. Male 4375 was last located on 3 

November, 27 km southwest of Black Bay. His 

disappearance was preceded by dispersal-type 

movements, but with the deer hunting season 

beginning about the time of his disappearance, human involvement could not be ruled 

out. The wolf was offi cially listed as “missing.” 

Female 6375B was located directly south along 

the Moose River corridor on more than 14 

occasions. By 30 April 1990 she had dispersed 

from the MPP and had joined with two other 

wolves to occupy the MGP territory (see 

MGP history starting 1990 –1991). 

1990–1991: By the winter of 1990 –1991 the 

MPP numbered nine wolves, including adult 

female 5620. The pack consistently occupied 

the center of the Kabetogama Peninsula. 

MPP’s territory was well defi ned between TCP 

and CLP in contrast to the wide-ranging and 

extensively overlapping situation the previous 

year. Whatever social disruption occurred 

during winter 1989 –1990, pack territories 

were well sorted by the winter of 1990 –1991.

Cruiser Lake Pack (CLP)

1987–1988: The CLP was not radio-marked 

in 1987, but from snow tracks the pack was 

estimated at eight wolves during winter 1987 –

1988, and they occupied the eastern portion 

of the Kabetogama Peninsula.

1988–1989: In May, 1988 adult male 4375 was 

radio-marked and in September adult alpha 

female 8125A was radio-marked. The alpha 

female was lactating, and pups were heard 

yipping around the trap site as she was being 

fi tted with a radio collar before release. This 

female was found dead from malnutrition 

20 days later. Necropsy at the USFWS lab in 

Madison, Wisconsin, revealed that a stick was 

wedged between her upper carnasial teeth on 

the pallet of her mouth, which likely inhibited 

proper feeding. It probably became wedged 

in her mouth when she bit down on sticks 

and saplings at the capture site. Meanwhile, 

male 4375 continued to occupy the eastern 

end of the Kabetogama Peninsula. The death 

of 8125A, the alpha female of CLP, may have 

lead to the territorial dispute with the LLP followed by a splitting of CLP and subsequent 

formation of the MPP. 
National Park Service 57

We received no howling response within CLP 

territory during howling surveys in fall 1988, 

but unsolicited howls were heard from a pack 

with pups just north of Ek Lake in CLP territory. Early winter telemetry fl ights verifi ed 

there were eight wolves in the CLP, and they 

occupied the eastern half of the Kabetogama 

Peninsula. Between radio locations on 28 

December and 20 January, however, the CLP 

began moving west into LLP’s territory. On 

20 January the LLP pup (7625) was located 

in mortality mode and the CLP, consisting of 

eight wolves, was located on the boundary 

of LLP and CLP territories. We recovered 

the carcass of the LLP pup within 24 hours 

of the last location, and at the site we found 

another unmarked wolf, both dead from wolfinfl icted wounds. From the profusion of wolf 

tracks, blood, wounds on the carcasses, and 

the lack of scavenging, we surmised that the 

two packs had collided sometime during the 

week preceding 20 January and that two LLP 

wolves (all eight CLP wolves were observed 

on 20 January) were killed in the ensuing fi ght. 

Thereafter, at least fi ve members of the CLP 

pack continued to roam across the peninsula 

and were often located in LLP’s territory. As 

evidenced from telemetry the following year, 

we believe fi ve wolves from the original CLP 

of eight split off and took over the LLP territory. In 1989 –1990 these fi ve wolves became 

the MPP (see LLP and MPP descriptions). 

Whether the remaining three CLP animals 

continued to occupy the Cruiser Lake area is 

not known (but see below). 

1989–1990: The CLP likely existed at the far 

eastern end of the Kabetogama Peninsula, 

but the pack was not radio-marked and snow 

tracking was not done during this winter. The 

newly formed MPP, including male 4375 who 

originated from the CLP, roamed across the 

Kabetogama Peninsula, but they were located 

only occasionally on the far eastern end. During howling surveys in fall 1989, packs with 

pups responded to simulated howls from 

three sites within the original (1988–1989) 

CLP territory. At least one and possibly two of 

these sites were associated with the MPP, but 

the response from site N8 was likely the CLP. 

The wolves were heard on the evening of 9 

October, and on 8 October the MPP was radio-located 30 km away at the far western end 

of the peninsula. The MPP could have easily 

covered that distance in the elapsed time, but 

MPP continued to be located on the western 

end of the peninsula the rest of October, and 

at no time were they located within 3.5 km of 

this howling site.

1990 –1991: Adult male 7375B was radiomarked in CLP territory in May 1990 and was 

consistently located on the east end of the 

Kabetogama Peninsula with fi ve other wolves. 

The territorial boundary between MPP and 

CLP was well delineated. A pack (no pups 

were heard) responded to simulated howls 

during the fall 1990 howling survey. They 

howled from the same location as the previous 

fall survey (N8), providing further evidence 

that a third pack existed on the Kabetogama 

Peninsula in 1989 –1990. These wolves may 

have originated from three wolves that remained in the CLP territory after the LLP and 

CLP clashed in January 1989.

Moose River Grade Pack (MGP)

1987–1988: No wolves were radio-marked in 

the MGP territory in 1987 –1988, but a large 

pack was snow tracked on four occasions. 

Twice tracks of between 9 and 11 wolves 

were encountered and tracks on 23 January 

indicated at least four were pups. Blood was 

observed in scent marks (urine) of one adult 

wolf suggesting the pack contained a female in 

estrous. On 9 March during a telemetry fl ight 

for other radio-marked wolves, a pack of 11 

wolves, believed to be the MGP, was observed 

and photographed on the ice of Little Johnson 

Lake.

1988–1989: In September, 1988, female pup 

6875A was radio-marked west of Junction 

Bay, but this pup died from undetermined 

causes within four days. No wolves responded 

to simulated howls in fall 1988. From snow 

tracks and one incidental observation of eight 

wolves on Franklin Lake (22 November), this 

pack was estimated at eight wolves during 

winter 1988 –1989.

1989–1990: In August 1989, male pup 7615 

was radio-marked, but this pup dropped its 

collar within nine days. During the fall 1989 

howling survey, a pack with pups responded 

to simulated howls from southeast of Hoist 

Bay. With no wolves radio-marked and no 

snow tracking, no estimate on pack size was 

available.

By January 1990, radio-marked adult female 

6375B was making dispersal-type movements 

from the MPP south along the Moose and 

Ash Rivers which was considered the western 

boundary of the MGP territory. This wolf later 

settled in to the MGP territory (see following). 

1990–1991: Adult female 6375B dispersed 

from the MPP and occupied the MGP terriWe believe fi ve wolves 

from the original CLP 

of eight split off and took 

over the LLP territory.
58 Gray wolves in and adjacent to Voyageurs National Park, Minnesota: Research and synthesis 1987 – 1991

tory by May 1990. However, she returned to 

the peninsula occasionally as evidenced by 

fi ve telemetry locations in her original MPP 

territory. In May, adult male 8375 was radiomarked and, along with 6375B and one unmarked wolf, comprised the MGP and occupied a well-delineated territory between BBP 

to the east and NBP to the west.

Browns Bay Pack (BBP)

1987–1988: A large pack of four to seven 

wolves was snow tracked in the Browns Bay 

area and on 29 February tracks of seven 

wolves were followed from Hammer Bay to 

Grassy Bay, a distance of approximately 11 

km over numerous islands, peninsulas, and 

lake ice. It was previously reported that 11 

wolves observed on Little Johnson Lake were 

the BBP; however, we now believe these were 

the MGP (see MGP history) and from snow 

tracks we estimate the minimum size of BBP 

was seven this winter. 

1988–1989: Female pup 9125A was radiomarked southwest of Browns Bay in September 1988, but was later found dead from 

starvation. A pack with pups responded to 

simulated howls from southeast of Staege Bay 

during the fall 1988 howling survey. Snow 

tracks provided a minimum estimated nine 

wolves in the BBP this winter.

1989–1990: No wolves were radio-marked 

during this census period, and tracking was 

not conducted in winter 1989 –1990; however, 

a pack with pups responded to simulated 

howls west of Browns Bay during fall 1989. A 

pack with pups also responded to simulated 

howls south of Hoist Bay within MGP territory, further supporting our belief that there 

were two packs between Moose River and 

Crane Lake (see also MGP history). Unfortunately, there are no data available to estimate 

pack size for BBP during this period.

1990–1991: In May 1990, two adult wolves, 

female 8125B and male 8635, were fi nally 

radio-marked from the BBP. A pup was also 

radio-marked in September, but the radio collar dropped off . Only a lone wolf responded 

to simulated howls from west of Browns Bay 

in fall 1990. From direct visual counts during telemetry fl ights, minimum pack size was 

estimated as nine wolves during the winter of 

1990 –1991 and the territory was well defi ned.

Nebraska Bay Pack (NBP)

1987–1988: From snow tracks it was estimated 

a minimum of two wolves used the Nebraska 

Bay area this winter. However, a pack of six 

wolves traveled from Nebraska Bay north to 

the Kabetogama Peninsula on 22 March. Possibly these were tracks of a portion of the CL 

(eight wolves). Yet a larger pack has existed in 

the Nebraska Bay area in the recent past. Unsolicited pack howls were heard by one of the 

authors (Route) from east of Daley Bay during 

fall 1986, and Minnesota Conservation Offi cer 

Lloyd Steen observed and counted fi ve wolves 

in winter 1986 –1987 on the Meadwood Road. 

1988–1989: A pack with pups responded to 

simulated howls in fall 1988 from south and 

east of Nebraska Bay, and from snow tracks 

the NBP was estimated at fi ve wolves in 1988–

1989. The territory was delineated by howls, 

tracks, and from knowledge of adjacent territories (see KPP and MGP).

1989–1990: In May 1989, adult females 5870 

and 8880B were captured and radio-marked 

in the NBP, and during the fall howling survey 

a pack (adults only) responded to simulated 

howls from south of Nebraska Bay. The two 

radio-marked wolves provided the fi rst telemetry-aided glimpse of the NBP territory; however, 5870 disappeared after she was located 

on 29 September and 8880B died of unknown 

causes. Her radio collar and skeletal remains 

were found in November 1990 about 64 km 

southwest of Nebraska Bay. The mid winter 

estimate of pack size was six based on visual 

counts. At least seven wolves were present 

in fall (5870 disappeared in September). By 

spring the pack had dropped to at least fi ve 

with the loss of 8880B and may have dropped 

as low as two based on visuals, though sample 

size was too low to be certain (n = 2 visuals after February). Suffi cient telemetry data existed 

to get a good estimate of territory size even 

with the loss of both radio-marked wolves.

1990–1991: Adult female 6625B was captured 

in May 1990 and remained in the NBP territory until at least 19 November when she was 

last located. Her radio collar was detected in 

mortality mode on 13 December about 21 km 

south of the NBP territory. She was killed by 

other wolves. This wolf provided a reasonable 

delineation of pack territory through mid-November, but with minimal visual counts, the 

pack size estimate of three must be considered 

a minimum. 

Kohler Pit (KPP) and Kohler Trio (KTP) Packs

In April 1988, project personnel were informed that a couple living near the corner of 

Highway 53 and the Ash River Trail were feed-
National Park Service 59

ing wolves. We visited the couple and found 

that they had been feeding meat scraps and 

dog food to wolves for several months. The 

couple said they began feeding a coyote who 

came around their house, but later this coyote 

was displaced by wolves. They were placing 

food at the edge of their yard about 30 m from 

their home. They had named the wolf that 

consistently came to the food pile, and they 

observed other less bold wolves further back 

in the woods. They had Polaroid photographs, 

taken from their kitchen window, of an adult 

wolf at the edge of their yard as evidence. Reportedly, the man was eventually able to stand 

outside his door near the house while the wolf 

grabbed food off the food pile. We told the 

couple that feeding wildlife was not a good 

idea, but clearly this was a highlight of their 

evenings and they were not going to give it up 

easily.

On 11 May a lactating adult female (6375A) was 

captured and radio-marked along the Kohler 

Pit Road. She was subsequently found to occupy an area centered to the south of Highway 

53, but she was often located near the corner 

of Highway 53 and the Ash River Trail. The 

couple that was feeding wolves subsequently 

reported “their” wolf was limping slightly. 

We informed them we may have trapped and 

radio-marked the wolf. They later confi rmed 

they could see the collar. On 11 June this female 

was accidentally hit at night on highway 53 by a 

vehicle driven by a VNP employee. A telemetry 

location the following day found her near an 

uprooted tree south and west of where she was 

hit. She was found at the same location four 

days later, but during the next fl ight, eight days 

after the accident, she had moved. The couple 

later reported she had returned to feed at their 

home. We explained that their feeding likely 

contributed to her being hit since she had to 

cross a major highway to get to the food. However, they now wanted to feed her all the more, 

believing the food would get her and her pups 

through this injury.

On 25 July a park employee reported that at 

~10:15 p.m. fi ve to seven wolves, “several” 

believed to be pups, were playing on the Ash 

River Trail near the corner of Highway 53. 

This pack responded to simulated howls (not 

as a part of a survey) on several occasions in 

late July and early August. Again on 11 and 12 

August, two diff erent park employees reported observing three pups on the Ash River Trail 

near the corner of Highway 53. One observer 

was able to stop her vehicle, get out, and take 

several steps towards the pups before they ran 

off the road. She described being able to see 

the yellow eyes.

On 29 August a wolf pup was found dead from 

a vehicle collision on Highway 53 about 400 m 

southeast of the corner of Ash River Trail. 

The couple fi nally stopped feeding the wolves 

after being told of this pup’s death. The radiomarked female continued to be located in her 

territory, but on 6 October her radio was detected in mortality mode. The radio collar was 

found later that day with the collar-belting and 

antennae cable chewed completely through. 

We presume her pups or other wolves had 

chewed the collar off during routine social activities of the pack.

On 25 September adult male 8380 was captured and radio-marked. This male was located near the alpha female of the KPP (6375A) 

on one occasion before she lost her collar. 

He continued to occupy the same territory 

delineated from locations of the alpha female. 

We presume this male was a member of the 

KPP, and from the above incidental observations this pack went into winter with at least 

two adults and two pups (three observed but 

one later killed, see above). By late November 

this male had dispersed northwest and was 

observed twice with two other wolves. Several 

locations of this pack of three were centered 

west of the TCP territory south of Black Bay, 

but on 15 March all three were observed 

northeast of Brule Narrows in Canada more 

than 16 km from the KPP territory. This pack 

of wandering wolves was named the Kohler 

Trio Pack (KTP). Wolf 8380 was located south 

of Black Bay again, but was found dead in 

April from injuries infl icted by other wolves. 

Likely these three wandering wolves met up 

with the TCP. Except for this wandering pack 

of three wolves, the disposition of the KPP 

was unknown during winter 1988 –1989. Because it was at the edge of the study area, the 

pack was not trapped in the remaining years 

of the study.

Blue Moose Pack (BMP) 

1988–1989: A lactating adult female wolf 

(5375) was captured and radio-marked off 

logging roads south of VNP in May 1988, and 

her pup, female 8880A, was radio-marked that 

September. The pup provided little data on 

movements because her collar dropped off 

15 days after capture. The female provided 

suffi cient data to delineate the BMP territory. 

The female was observed with one adult wolf 

in winter 1988–1989, but the pup was not observed.

We explained that their 

feeding likely contributed to her being hit 

since she had to cross a 

major highway to get to 

the food.
60 Gray wolves in and adjacent to Voyageurs National Park, Minnesota: Research and synthesis 1987 – 1991

1989–1990: Female 5375 continued to occupy 

the BMP territory until mid-October 1989 

when she dispersed north then west from her 

territory. She was last located on 30 October 

more than 8 km from the center of her territory. The cause of her disappearance was never 

determined, and no eff ort was expended to 

radio-mark this pack again. Very little snow 

tracking and no howling was done in this area. 

Dixon Creek Pack (DCP) 

1988–1989: Adult male 6625A was captured 

and radio-marked in May 1988 and provided 

some information on the location of this 

pack until early October when he dispersed 

southwest to the Chub Lake area. This male 

was located in mortality mode and later found 

dead from a wire snare on 15 March 1989. 

This pack territory was not trapped for study 

purposes again because it was outside of the 

study area. No snow tracking and no howling 

was done in this area.

Moose Lake Pack (MLP) 

1988–1990: Adult female 7125 was captured 

and radio-marked in May 1988. She provided 

a reasonable estimate of a territory boundary, 

but dispersed west to the Nett Lake area in 

late November. She was never observed while 

in the Moose Lake area and was observed 

only once, alone, while in the Nett Lake area. 

She was last located on 17 February 1990 

while we fl ew at a search altitude of 1,525 m 

south of Nett Lake. No snow tracking and no 

howling was done in this area.
National Park Service 61

Appendix 6. Calculations for estimating biomass and 

number of prey represented in 123 scats collected 

during summer 1987 and 1988 in and adjacent to 

Voyageurs National Park, Minnesota.

Prey

Estimated Prey 

Biomass (kg)

Prey Biomass 

(kg) / scat

No. of Scats 

With Prey Item 

Prey Biomass 

(kg) Consumed

Ratio of 

Biomass 

Consumed to 

Adult Deer

No. of 

Individuals 

Eaten (Prey 

Biomass / 

Biomass 

Consumed)

Ratios of 

Individuals 

Eaten to 

Adult Deer

Adult deerb 62.9 0.94 68.5 64.57 1.000 1.0 1.00

Beaverc 13.3 0.55 29.0 15.82 0.24 1.2 1.1

Moosed 247.5 2.42 2.0 4.84 0.07 0.02 0.0

Fawn deere 7.1 0.50 16.0 7.93 0.12 1.1 0.4

Livestockf 25.0 0.64 1.0 0.64 0.01 0.03 0.0

Muskratg 1.2 0.45 2.5 1.12 0.007 0.9 0.2

Snowshoe hareh 1.3 0.45 1.5 0.67 0.004 0.5 0.2

Otheri 0.1 0.44 2.0 0.88 0.005 10.1 2.7

Grousej 0.68 0.44 0.5 0.29 0.001 0.3 0.1

Note: Calculations for biomass follow Weaver (1993) where Y = 0.439 + 0.008 X and Y= kg of prey biomass consumed / scat and X = estimated weight of prey 

animals.

a

In scats with 2 prey types (14.5%), each was assigned an occurrence of 0.5 for biomass calculations.

bAdult deer = Based on an observed summer kill ratio of 2 yearlings to 15 “adults” with assumed even-sex ratios for yearlings and an observed sex ratio of 6 

females to 3 males for adults. Estimated yearling weights = 48.8 kg (Sauer 1984) adult does = 57.7 kg (Kunkel and Mech 1994) and adult bucks = 79.1 kg (M. 

Nelson unpublished data).

c

Beaver = Based on an assumed kill ratio of 1 kit to 2 yearlings to 1 adult and weights of 6.3 kg, 13.5 kg, and 20 kg, respectively (D. Smith unpublished data).

dMoose = Based on an assumed kill of 1 calf (June) to 1 adult (July) and weights of 14.5 kg and 480 kg, respectively (Bubenik 1998).

e

Fawn deer = Based on 2 occurrences in May, 2 in June, 8 in July, and 5 in August with mid-month calf weights estimated using Y = 2.74 + 0.075 X where X = days 

since birth (Kunkel and Mech 1994).

f

Livestock = Based on 1 occurrence assumed to be a calf with estimated weight of 25 kg (Spector 1956; cited in Fritts and Mech 1981).

gMuskrat = Assumed weight of 1.2 kg (Perry 1982).

hSnowshoe hare = Assumed weight of 1.3 kg (Bittner and Rongstad 1982).

i

Other = Based on 1 occurrence of an unknown bird and 2 occurrences of small rodents assumed to be microtines with estimated weights of 20 g (Terres 1991) and 

3 g (Johnson and Johnson 1982), respectively.

j

Grouse = Assumed weight of 68 g (Terres 1991).
62 Gray wolves in and adjacent to Voyageurs National Park, Minnesota: Research and synthesis 1987 – 1991

Appendix 7. Calculations for estimating biomass and 

number of prey represented in 97 scats collected 

during winter 1987 and 1988 in and adjacent to 

Voyageurs National Park, Minnesota.

Prey

Estimated Prey 

Biomass (kg)a

Prey Biomass 

(kg) / Scat

No. of Scats 

With Prey Itema

Prey Biomass 

(kg) Consumed

Ratios of 

Biomass 

Consumed to 

Deer

No. of 

Individuals 

Eaten

Ratio of 

Individuals 

Eaten

Deer 58.6 0.91 90.5 82.13 1.000 1.4 1.00

Beaver 15.7 0.56 4.5 2.54 0.015 0.2 0.06

Moose 330.0 3.08 2.0 6.16 0.037 0.02 0.01

Note: Calculations follow Weaver (1993) where Y = 0.439 + 0.008 X and Y = kg of prey biomass consumed/scat and X = estimated weight of prey animals.

a

In scats with 2 prey types (5%), each was assigned an occurrence of 0.5 for biomass calculations. 

bBased on an observed winter kill ratio of 13 fawns to 4 yearlings to 33 “adults” with observed even-sex ratios for fawns, assumed even-sex ratios for yearlings, 

and an observed even-sex ratio for adults. Estimated fawn weight = 36.6 kg (M. Nelson unpublished data), yearling weight = 48.8 kg (Sauer 1984), adult doe 

weight = 57.7 kg (Kunkel and Mech 1994), and adult buck weight = 79.1 kg (M. Nelson unpublished data).

c

Based on an assumed kill ratio of 2 yearlings to 1 adult with respective weights of 13.5 g and 20 kg (D. Smith unpublished data).

dBased on an assumed kill of 1 calf to 1 adult and weights of 180 kg (Coady 1982) and 480 kg (Bubenik 1998).
National Park Service 63

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ABOVE

A biologist inspects the teeth of 

an instrumented wolf.

NPS Photo

ON THE COVER

Gray wolf, northern Minnesota.

NPS photo by W. Route
Midwest Regional Office

1609 Jackson St.

Omaha, Nebraska 60609

www.nps.gov

National Park Service

U.S. Department of the Interior

E x p e r i e n c e Y o u r A m e r i c a TM