4.1 Spatial overlap and habitat suitability
From our study, we found the importance of young forest and shrublands
for cottontail habitat suitability largely reflects what is known about
the habitat associations of the two species in the northeastern United
States. Both species’ suitable habitat was influenced by the presence of
young forests, shrublands, and understory (Cheeseman et al. 2018,
2019a , 2021, Bischoff et al. 2023a , b ).
Specifically, proximity to shrublands increased New England cottontail
habitat suitability, which increased New England cottontail occupancy
and colonization at the landscape scale (Bischoff et al. 2023a )
and abundance at the patch level (Bischoff et al. 2023b ).
However, we found not only is the proximity to these vegetation types
influential to New England cottontail habitat suitability, but the
spatial arrangement of these vegetation types contributed most to
habitat suitability for New England cottontail. Specifically, patches of
mature forest without understory components within complexes of young
forest, shrubland, and mature forest with understory components
increased New England cottontail habitat suitability the most. This
agrees with many studies that have demonstrated the importance of high
vegetation height and canopy closure for New England cottontail,
especially in patches co-occupied by eastern cottontail (Buffum et al.
2015, O’Connor 2015, Cheeseman et al. 2018, 2019a , 2021, Bischoff
et al. 2023b , a ) and a recent study that found New England
cottontail increased the proportion of their home range that included
vegetation management areas if some canopy was retained (Eline et al.
2023b ). Because of these findings, guidance for New England
cottontail habitat management suggests utilizing shelterwood cuts and
leaving residual trees to maintain vegetation height and some canopy
closure (Cheeseman and Cohen 2019). Our study supports these
recommendations but adds that residual trees clumped in small patches
within young forest and shrubland habitat may enhance existing patches
and create new patches suitable for New England cottontail.
Despite the benefits of habitat management to New England cottontail,
focusing on vegetation management alone will likely not be enough to
discourage eastern cottontail populations. We found that eastern
cottontail habitat suitability with New England cottontail was high
regardless of spatial arrangement of habitat and the distance to young
forest, shrubland, and understory habitat. Higher vegetation height was
found to decrease eastern cottontail survival and occupancy in several
other studies (Buffum et al. 2015, O’Connor 2015, Cheeseman et al. 2018,
2019a , 2021, Bischoff et al. 2023b , a ). However,
this association did not translate into measurable differences in
suitable habitat between the two species. Thus, vegetation management
within strategic areas is still crucial for New England cottontail
management to establish connectivity between populations (Ferry 2023)
but may need to be coupled with population augmentation or translocation
to sustain New England cottontail populations (Bauer et al. 2020). Other
states have found coupling habitat connectivity and population
augmentation to be a successful strategy for maintaining New England
cottontail populations (Bauer et al. 2020). Another potential management
action is removal of eastern cottontail to limit or reduce the expansion
of the species in suitable New England cottontail habitat. Removal of
eastern cottontail was tested at a few patches in Connecticut but was
not effective in reducing eastern cottontail abundance (Kilpatrick n.d.,
unpublished data). Removal of invasive mammalian species has long been a
management practice for problematic species, and has largely been
successful, but the success depends on the predator response to species
removal (Norbury 2001), consistent effort of the program, and
controlling large areas (Robertson et al. 2017). The removal of eastern
cottontail would contain many complexities and considerations. Eastern
cottontail has been present in the northeastern US for over 100 years
(Johnston 1972) and has successfully expanded across most of the region.
Additionally, the mechanism for removal may be difficult because
cottontail hunting is not common in the state and cottontail trapping
success is relatively low (Cheeseman et al. 2021). Furthermore, New
England and eastern cottontail can only be differentiated confidently
through genetic analysis, which requires large amounts of time and
resources. Despite these challenges, strategic removal of eastern
cottontail in newly managed areas for New England cottontail may offer
New England cottontail the advantage of colonizing habitat before
eastern cottontail.
Predicting New England cottontail suitable habitat across the state is
crucial for planning New England cottontail conservation, management,
and monitoring for the future. Some of these highly suitable areas for
New England cottontail have not been sampled in recent years, thus areas
of highly suitable New England cottontail habitat with limited
occurrence data provide opportunities for identifying new populations,
locations for eastern cottontail removal, and potential sites for
habitat enhancement or New England cottontail reintroductions. The maps
of suitable habitat also allow further direction for managing New
England cottontail in the two regions of Connecticut where New England
cottontail is extant, the eastern and western portion of the state.
Differences in New England and eastern cottontail populations in eastern
and western Connecticut have been found in other studies (Kristensen and
Kovach 2018, Bischoff et al. 2023b ). Specifically, the low
habitat suitability for New England cottontail and generally high
habitat suitability for eastern cottontail in eastern Connecticut is
evidence that explains the decline in New England cottontail relative
abundance observed in the eastern portion of the state over the past few
years (Bischoff et al. 2023b ). Identifying new areas suitable for
New England cottontail in the region of the state where New England
cottontail occupancy is not declining will provide enhanced
opportunities for management and possibly provide more connections
between isolated patches currently occupied by New England cottontail.
We argue that additional conservation actions, including augmentation
and translocation of New England cottontail, vegetation management to
establish, enhance, or maintain inter-mixed habitats, and consideration
of eastern cottontail removal, may be needed to benefit New England
cottontail.