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.