4 Discussion
Understanding the overlap in the suitable habitat (i.e., spatially) or niches (i.e., environmentally) between native and introduced species can help determine the potential spread of invasive species and conserve habitat for rare species. Overall, we found high overlap between the suitable habitat and niches of New England and eastern cottontail, where all the highly suitable New England cottontail habitat was also highly suitable for eastern cottontail, and the two cottontail niches were statistically more similar than random, yet not equivalent. We observed some covariates could reduce the overlap in niches and suitable habitat. Sites of higher elevation and lower precipitation shifted niches in favor of New England cottontail and led to less overlap with the eastern cottontail niche. Proximity to shrublands and mixed invasive understory were more important for New England cottontail habitat suitability than eastern cottontail habitat suitability. A novel finding was the importance of spatial arrangement of vegetation types for New England cottontail habitat suitability, specifically patches of mature forest without understory intermixed within complexes of young forest, shrubland, and understory habitat. Thus, vegetation management that focuses on habitat heterogeneity may create new patches or increase suitability of existing patches for New England cottontail (Figure 6). However, these habitat conditions did not alter the niches dynamics of either species or negatively influence eastern cottontail habitat suitability thus vegetation management alone may not be enough to discourage eastern cottontail populations. Direct species management options, such as strategic eastern cottontail removal, should be explored especially as future conditions, such as higher predicted precipitation totals (Jong et al. 2023) and increased urbanization, will likely further favor eastern cottontail expansion.
We report high winter habitat association and niche overlap for the native New England cottontail and its congener, the introduced and range-expanding eastern cottontail. We focused on winter presence records because of the high-quality data produced by the New England Cottontail Regional Monitoring Program, with its standardized and consistent protocol. The regional monitoring data had high detection (Brubaker et al. 2014, Bischoff et al. 2023a ) because pellets were more visible on snow and cold conditions retained sample quality (Kovach et al. 2003, Brubaker et al. 2014, Whipps et al. 2020). During winter, New England cottontail survival is low and competition is high (Cheeseman et al. 2018, 2021), thus our results reflect suitable habitat during the time of year when the ecological burden is highest. Although including summer cottontail occurrence data may yield differences in niche dynamics and habitat suitability because habitat selection, survival, and competition for cottontails can vary seasonally (Cheeseman et al. 2018, 2019a , 2021, Kilpatrick and Goodie 2020), our results shed new light on the importance of inter-mixing young forest, shrubland, and understory habitats within mature forest for New England cottontail.