The habitat of winter ticks (Dermacentor albipictus) in the moose (Alces alces) range of Northeast Minnesota
2015-03
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The habitat of winter ticks (Dermacentor albipictus) in the moose (Alces alces) range of Northeast Minnesota
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2015-03
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Winter ticks occur throughout moose range south of 60º N, but little is known about how habitat influences tick density in Minnesota. Adult female winter ticks drop off moose in the spring to lay eggs and larvae attach to moose in the fall. The habitat that a tick drops off into could increase or decrease either survival or reproduction. Moose select different cover types for foraging and for bedding. We used locations of moose wearing GPS collars to identify tick sampling locations. Moose GPS locations could be identified as either movement or bedding. Targeted sampling at moose GPS locations allowed us to evaluate flag and walking surveys for winter tick collection. Bed sites and movement paths were identified from the 2013 and 2014 spring tracks to assess the effect of moose behavior and habitat characteristics on tick density. Moose GPS locations had more ticks than random sites (p = 0.001). Tick densities at moose sites were higher in 2013 (10.8 ± 2.9 ticks/m2) than in 2014 (2.8 ± 1.2 ticks/m2; p=0.0003). Ticks were found at 52% of 2013 sites and at 27% of 2014 sites. More movement paths than bed sites had ticks in 2013 (p = 0.01), but tick densities were similar in bed sites (11.2 ± 6.3 ticks/m2) and movement paths (10.7 ± 7.5 ticks/m2). In both years, tick density was higher in areas with litter depths < 3 cm (p < 0.06) and with canopy closures < 50% (p < 0.008). A high percentage of sites in lowland conifer, mixedwood, and regenerating forests had ticks present, but no upland conifer sites had ticks present (p = 0.0001). Spring locations from GPS collared moose were converted to paths. These paths were areas where ticks would have dropped off of moose. We created paths of moose in the fall by connecting GPS locations. Fall paths were overlaid with spring movement paths to identify areas where moose could acquire ticks. Overlaps of the 2011-2012 spring and fall path accounted for 6 and 13% (3.1 ± 0.4 ha and 2.2 ± 0.5 ha) of the paths. All moose overlapped with their own path in the fall for about 4% of their spring paths (1.1 ha). The greatest areas of overlap occurred in mixedwood and wet cover types (p = 0.0002). Mixedwood and wet cover types, especially with open canopies and shallow litter depths, have the highest potential to produce high larval tick densities. Mixedwood and wet cover types also have the greatest area of overlap between spring and fall paths and could be the areas with the highest tick transfer.Tick densities estimated from walking surveys and tick densities estimated from flag surveys were similar (p=0.9). Walking surveys with chaps allowed us to identify the height of winter ticks on the vegetation. The largest clumps of ticks were found at 38.2 ± 3.4 cm, but ticks were found from 0-100 cm. When more ticks were collected with walking surveys, ticks were generally found below 66 cm. When more ticks were collected with flag surveys, ticks were found above 66 cm and were likely higher than chap height.
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University of Minnesota Master of Science thesis. March 2015. Major: Integrated Biosciences. Advisor: Ron Moen. 1 computer file (PDF); vii, 65 pages.
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Terry, Juliann. (2015). The habitat of winter ticks (Dermacentor albipictus) in the moose (Alces alces) range of Northeast Minnesota. Retrieved from the University Digital Conservancy, https://hdl.handle.net/11299/172138.
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