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Gray wolves in and adjacent to Voyageurs National Park, Minnesota: Research and Synthesis 1987-1991

Technical Report NPS/MWR/NRTR/2004-01

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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 a?? 1989 and a low of 4.5 in 1989a??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 intraspecific strife (n = 4) and starvation (n = 2). Confirmed 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 intraspecific strife (n = 1) and starvation (n = 1). Confirmed 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 confirmed 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 rifle season, but their fate was not confirmed. 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 a?? 1988 and toward females in 1988 a?? 1989. The median age of deer killed by wolves in winter was 6.5 and 7 years for females and males, respectively.

Additional Publication Details

Publication type:
Report
Publication Subtype:
Federal Government Series
Title:
Gray wolves in and adjacent to Voyageurs National Park, Minnesota: Research and Synthesis 1987-1991
Series title:
Technical Report
Series number:
NPS/MWR/NRTR/2004-01
Year Published:
2004
Language:
English
Publisher:
National Park Service
Publisher location:
Denver, CO
Contributing office(s):
National Wildlife Health Center
Description:
68 p.
First page:
1
Last page:
68
Number of Pages:
68