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Browsing by Author "Dietz, Nancy"

Now showing 1 - 4 of 4
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    Bat Acoustic Surveys in Minnesota 2015 - 2017
    (University of Minnesota Duluth, 2018-12) Moen, Ronald; Swingen, Morgan; Walker, Marcus; Baker, Richard; Nordquist, Gerda; Catton, Timothy; Kirschbaum, Kari; Dirks, Brian; Dietz, Nancy
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    Bat Radiotelemetry in Forested Areas of Minnesota 2015-2017
    (University of Minnesota Duluth, 2018-12) Swingen, Morgan; Moen, Ronald; Walker, Marcus; Baker, Richard; Nordquist, Gerda; Catton, Timothy; Kirschbaum, Kari; Dirks, Brian; Dietz, Nancy
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    Northern Long-Eared Bat Roost Tree Characteristics 2015-2017
    (University of Minnesota Duluth, 2018-12) Swingen, Morgan; Moen, Ronald; Walker, Marcus; Baker, Richard; Nordquist, Gerda; Catton, Timothy; Kirschbaum, Kari; Dirks, Brian; Dietz, Nancy
    Female northern long-eared bats (Myotis septentrionalis) give birth to a single young, which is raised in a maternity roosting colony in trees. Young are born and lactation occurs from mid-June through at least late July in Minnesota. Bat pups are unable to fly for 3-4 weeks after birth, so the adult females leave the young in the maternity roost while they forage. We tracked bats with VHF radiotransmitters to their roosts each day. At dusk, field crews conducted emergence surveys to count the number of bats emerging and find the roost entrance. In total we found 238 day roost locations of 83 female northern long-eared bats across the forested region of Minnesota. We returned to each roost tree to measure habitat characteristics. Female northern long-eared bats roosted in at least 27 different tree species. Almost all of the roost trees were in upland forests. In northern Minnesota, aspen (Populus tremuloides) was most commonly used as roosts. In central Minnesota, maple (Acer spp.) and aspen trees were most commonly used, and in southern Minnesota, oak trees (Quercus spp.) were most commonly used as roosts. About 90% of roost trees were deciduous species, and 10% of roost trees were coniferous species. Roost trees were more decayed and larger in diameter than available trees. Northern long-eared bats most often roosted in cavities and crevices of trees, although some roosted under loose bark or where branches had broken off. Four roosts were in unoccupied buildings. Each roost tree location buffer and random location was overlaid on NLCD, GAP, and LandFire cover type classifications to calculate percent of area in forest cover variables. Variables related to deciduous forest were characteristic of roost tree locations. The LandFire variable TreeDom was the best predictor variable for identifying potential maternity roost habitat at the landscape level. In the forested area of Minnesota, the 50th percentile of random locations had 55% tree cover on average, compared to 80% tree cover for the roost tree locations. The relationship held at smaller scales, which meant that we could create maps of habitat suitability for northern long-eared bat maternity roosts across the forested region of the state. Northern long-eared bats in southern Minnesota, with more development and agriculture, used roost tree locations in patches of forest. In northern Minnesota, roost trees were within forest stands instead of on the edges of forest stands, and roost trees tended to be located in areas with trees present in most of an 800 m foraging radius. We also tracked 13 little brown bats and 8 big brown bats to roosts in trees and buildings. The 13 little brown bats were tracked to 12 roost trees of at least five species, and five roosts in buildings. The eight big brown bats were tracked to 13 roost trees of at least seven species, and two roosts in buildings. All bats with transmitters that roosted in buildings were females that were either pregnant or lactating
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    Summary of Bat Research in Camp Ripley Training Center and Arden Hills Army Training Site, MN 2016
    (University of Minnesota Duluth, 2016-12) Dirks, Brian; Dietz, Nancy; Baker, Richard; Swingen, Morgan
    Crews from the Environmental Office at Camp Ripley Training Center (CRTC) captured 92 bats in CRTC from June 6th – 24th, and 99 bats at Arden Hills Army Training Site (AHATS) July 6th – 10th, 2016. Bats of seven species were captured during mist-netting surveys, including the first recorded capture of an evening bat (Nycticeius humeralis) in the state of Minnesota. We attached transmitters to 3 pregnant northern long-eared bats at CRTC and 3 lactating little brown bats at AHATS. Three northern long-eared bat roost trees were identified at CRTC. The little brown bats captured at AHATS were tracked to two roosts, both in buildings. Roost trees at CRTC varied in height and decay stage. The roosting patterns observed at CRTC were similar to roosting patterns we have observed in other areas of Minnesota, where bats appear to be using a variety of available trees. This report details work done at CRTC and AHATS as part of a statewide study of northern long-eared bats. A report summarizing results of the statewide project will be available in early 2017.