Management Strategies, Predator Occupancy, and a Declining Prey Species, the New
England Cottontail
Amanda Cheeseman, State University of New York College of Environmental Science and
Forestry
Final Report to the Edna Baily Sussman Foundation Internship 2014
Introduction
The New England cottontail (Sylvilagus transitionalis), hereafter referred to as NEC, is a
shrubland obligate lagomorph and the only native cottontail species in the Northeast, east of the
Hudson River. Historically common, the NEC has experienced a drastic range contraction
(Fenderson et al. 2011). This species is now only found in five geographically separated
populations at the edges of its historic range (Fenderson et al. 2011). Large scale range
contractions and population declines have prompted the United States Fish and Wildlife Service
to designate the NEC as a Candidate species for listing under the Endangered Species Act
(USFWS 2006). These range contractions and declines have largely been attributed to loss of
shrubland, and forest management to increase NEC populations has been proposed in many
places but has yet to be widely implemented (Litvaitis et al. 2008, Fuller and Tur 2012).
The New York State Department of Environmental Conservation in collaboration with
the New York Office of Parks, Recreation, and Historic Preservation have performed some
limited shrubland restoration, and are implementing further land management for NEC within
the next year. However, concern exists over the efficacy of proposed management strategies. Of
primary concern are the impacts of management strategies on predator communities. Predation
by mesocarnivores and raptors accounts for nearly all NEC mortality (Barbour and Litvaitis
1993). Furthermore, most NEC populations persist at low densities, and patch colonization is
severely limited by small individual dispersal range, so small alterations in predator communities
in NEC habitat could have large impacts on NEC population persistence (Barbour and Litvaitis
1993). Several NEC predators thrive in shrublands, including the coyote (Canis latrans), which
is recently naturalized in the northeast. If proposed habitat restoration strategies result in
attraction of predators and higher predation rates, then management of predators may be
necessary to ensure successful habitat restoration, which could affect the cost/benefit ratio of
restoration in some places.
Cheeseman | 2
To determine the impact of management strategies on predator communities I addressed
three hypotheses: 1. Predator assemblages differ between extant “optimal” NEC habitat and
proposed restoration areas, and 2. Optimal NEC habitat has lower NEC predation rates than
unmanaged shrubland or pre-management reference sites. The first hypothesis will require the
Sussman Internship to address, and will allow me to perform summer camera-trapping and avian
point counts to assess predator communities.
The second is a focus of my Ph.D. research, for
which I plan on using radio-telemetry to study predation of NEC.
Methods
To examine NEC predator communities, I randomly selected 22 sites where NEC are known
to occur. Extant sites could further be divided into 11 persistent unmanaged shrubland habitats,
often characterized by association with wetland or riparian areas, and 11 successional
shrublands, generally characterized as mid successional forest post disturbance. The latter
category closely emulates current NEC habitat management strategies. I also selected 23
reference sites within mature forest with the potential to be converted to NEC habitat (figure 1).
To assess predator assemblage, I set remotely triggered trail cameras with infrared flash at each
randomly selected location. Scent lures were securely affixed to a post or tree 1.5 m high to
attract mammalian carnivores to the front of the camera. Cameras were set approximately 5 m
Figure 1. Map of
randomly selected
extant NEC habitat
(blue) and potential
proposed restoration
areas (orange) for
NEC predator
occupancy assessment
Cheeseman | 3
from the scent bait at a height of 0.5 m. Cameras were checked approximately every 28 days. To
attract avian predators, we affixed a 0.5 m perch constructed from 2” x 4” to each bait tree within
the camera viewing area. To increase the probability of avian detections, point count surveys to
detect diurnal avian predators were also conducted every 28 days. Avian surveys were conducted
for 30 minutes.
Program aardwolf was used to visually review all photos, and tag images (Krishnappa and
Turner 2014). All images of mammalian and avian taxa were identified to species when possible.
Preliminary Results
Camera data was collected at each site for 3 months between 5/27/14 and 10/12/14. A
total of 10,076 photos of potential avian and mammalian predators were taken during this time
(table 1). I pooled extant NEC habitat types for clarity. No differences were observed for any
mammalian predator species between extant habitat and potential restoration areas from a naïve
assessment of photo number (figure 2); however, cats were only observed in restored areas and
there were a more than twice as many photos taken of black bear and bobcat in extant NEC
habitat. A naïve assessment of predator species richness indicated more predator species were
Table 2. Number of avian predators
observed during point-count surveys.
Number
Species
Observed
Northern Harrier
Sharp-shinned Hawk
Northern Goshawk
Red-shouldered Hawk
Broad-winged Hawk
Red-tailed Hawk
Rough-legged Hawk
Eastern Screech Owl
Barred Owl
Unidentified Med. Hawk
Unidentified Lg. Hawk
Total
1
2
3
5
2
7
2
1
2
1
3
29
Table 1. Number of photos
taken of potential NEC
predators by species
Species
Photos
Barred Owl
5
Black Bear
341
Bobcat
175
Cat
29
Coyote
1614
Fisher
3
Long-tailed
18
Weasel
Mink
6
Opossum
1541
Raccoon
5839
Red Fox
233
Striped Skunk
66
Unknown
143
Hawk
63
Total
10076
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present in extant NEC habitat, thought this difference was not significant (t-test: t = -1.23, df =
42.99, p = 0.22) (figure 3). Cameras poorly detected avian predators, and no avian predators
were observed to use the provided perches. I conducted 103 point-count surveys during the
study. Detection of avian predators was universally low, 29 avian predators were recorded
throughout all surveys (table 2). While no significant trends have yet appeared in the collected
Figure 2. Number of photos taken in extant NEC habitat and potential proposed habitat
restoration areas by mammalian NEC predators.
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data, number of photos of a particular species is a crude and naïve assessment of predator
occupancy. First, some species, such as coyotes and raccoons, appear to spend considerable time
inspecting the scent bait. This greatly increased the number of photos taken, but does not
necessarily indicate a larger number of detection events. Second, estimates presented here are
naïve estimates of occupancy and do not account for the issue imperfect detection common to
occupancy sampling. Further analyses may alter or clarify the relationships observed here.
Figure 3. NEC
mammalian predator
species richness in
extant NEC habitat and
potential proposed
restoration areas.
Future Work
To improve assessment of carnivore occupancy between sites, I will use occupancy
modelling, accounting for imperfect detections, to predict site occupancy by each predator
species. I will also include the site level probability of predator occupancy in NEC survival
models that will be based on my ongoing radio-telemetry data.
Acknowledgments
Foremost, I thank the Edna Bailey Sussman Foundation and Mr. Jesse Jaycox with the
New York State Office Parks, Recreation, and Historical Preservation for this opportunity. I
thank my advisor Dr. Jonathan Cohen for his support and advice, as well as my committee
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members Drs. Chris Whipps, Sadie Ryan, and Dan Rosenblatt. Field assistance was provided
Tamara Hillman, John DeCotis, Emily Reuber, and Kelly Dewessee. Lastly, this project would
not have been possible without the tremendous support and generous funding of Scott Silver and
the Queen’s Zoo, the New England cottontail working group.
Literature Cited
Barbour, M. S., and J. A. Litvaitis. 1993. Niche dimensions of New-England cottontails in
relation to habitat patch size. Oecologia 95:321-327.
Fenderson, L. E., A. I. Kovach, J. A. Litvaitis, and M. K. Litvaitis. 2011. Population genetic
structure and history of fragmented remnant populations of the New England cottontail
(Sylvilagus transitionalis). Conservation Genetics 12:943-958.
Fuller, S., and A. Tur. 2012. Conservation strategy for the New England cottontail (Sylvilagus
transitionalis).
Krishnappa, Y. S., and W. C. Turner. 2014. Software for minimalistic data management in large
camera trap studies. Ecological Informatics.
Litvaitis, J. A., M. S. Barbour, A. L. Brown, A. I. Kovach, M. K. Litvaitis, J. D. Oehler, B. L.
Probert, D. F. Smith, J. P. Tash, and R. Villafuerte. 2008. Testing multiple hypotheses to
identify causes of the decline of a lagomorph species: the New England cottontail as a
case study. Pages 167-185 in P. C. Alves, N. Ferrand, andK. Hacklander, editors.
Lagomorph Biology: Evolution, Ecology, and Conservation. Springer-Verlag, Berlin,
Germany.
USFWS. 2006. Endangered and threatened wildlife and plants; review of native species that are
candidates or proposed for listing as endangered or threatened; annual notice of findings
on resubmitted petitions; annual description of progress on listing actions.
Cheeseman | 7
Raccoon inspecting scent station within NEC
habitat
Bear and cubs inspecting scent station within
NEC habitat
Bobcat passing camera in area with restoration
potential
Coyote passing camera within NEC habitat
Red fox passing camera with chipmunk in NEC
habitat
Barred Owl in area with restoration potential