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    Co-Occurrence and Habitat Use Overlap of Snowshoe Hares (Lepus americanus) and American Martens (Martes americana) in the Boreal – Temperate Ecotone of the Northeastern U.S.

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    Courtot_Thesis_April_20_2022.pdf (1.317Mb)
    Date
    2022-05
    Keyword
    Snowshoe hares (Lepus americanus), American martens (Martes americana), White Mountain National Forest (WMNF), New Hampshire
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    Author
    COURTOT, KATELYN
    Description
    AN ABSTRACT OF THE THESIS OF Katelyn A. Courtot for the degree of Master of Science in Biology presented on Title: Co-Occurrence and Habitat Use Overlap of Snowshoe Hares (Lepus americanus) and American Martens (Martes americana) in the Boreal – Temperate Ecotone of the Northeastern U.S. Abstract approved: ___________ Leonard R. Reitsma, Ph.D. Managing forests for wildlife with different habitat preferences in addition to providing economic-based outcomes related to forest products poses a unique set of challenges for natural resource professionals. Snowshoe hares (Lepus americanus) are a keystone species influencing community dynamics, and American martens (Martes americana) are an umbrella species indicating ecosystem health. Hares prefer early successional forest habitat in contrast to martens, which are typically associated with older forests. To evaluate the shared habitat preferences of both species, we collected forest structure data between May and November 2020 in 14 forested stands located in the Nulhegan Basin (NB), Vermont (n = 7) and the White Mountain National Forest (WMNF), New Hampshire (n = 7). My objective was to test the hypothesis that the co-occurrence of hares and martens is contingent on habitat availability at several scales. Specifically, I predicted that patches of early-successional forest within a matrix of mid- to late-successional forest allowed for habitat overlap of hares and martens. We measured basal area, canopy closure, diameter at breast height and counted stems at 45-50 plots within each of the 14 stands. We also measured coarse woody debris along three randomly selected transects in each stand. We compared these data with 2 years (2016 and 2017) of live-trapping data to determine what forest structure variables were associated with the habitat use overlap of hares and martens. The NB has a robust population of hares with few martens and the opposite pattern is observed in the WMNF, except that hares are relatively common, although at lower abundance in these forests. First, we fit a univariate, two-level categorical model (NB vs WMNF) to evaluate differences in second-order habitat selection. To evaluate fourth-order habitat selection, we fit 7 additive occupancy models for each species using forest structure variables and live-capture data. To further evaluate fourth-order habitat selection, we used three Principal Component Analysis (PCA) models to assess habitat use overlap. Results from the additive models suggest that hares selected areas with high stems counts and against areas with high basal area. Martens selected against areas with high stem counts, although basal area had only a weak effect. Visual-exploratory analysis using PCA suggested that deciduous stems accounted for the habitat use overlap between hares and martens at a finer spatial scale. The WMNF experiences moderate amounts of disturbance that create small patches, typically resulting from windthrow events. This study suggests that these early-successional patches of forest within a later-successional landscape allow for the co-occurrence of both species, with deciduous stems driving the habitat use overlap. Deciduous stems have three phases that contribute to the habitat use overlap of hares and martens; seedlings/saplings, mature trees and coarse woody debris. The presence of keystone and umbrella species within the same community may increase biodiversity, and is consistent with the Intermediate Disturbance Hypothesis, however, more empirical support is needed to correctly guide and solidify future management.
    URI
    https://summit.plymouth.edu/handle/20.500.12774/441
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