Reintroduction of the Eastern Woodrat (Neotoma
floridana) in Southern Illinois
Aaron K. Poole, Brian A. Novosak, Aaron C. Gooley, David M. Ing, Robert D. Bluett, Timothy C. Carter, and George A. Feldhamer
Southeastern Naturalist, Volume 12, Issue 1 (2013): 1–10
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2013 SOUTHEASTERN NATURALIST 12(1):1–10
Reintroduction of the Eastern Woodrat (Neotoma
floridana) in Southern Illinois
Aaron K. Poole1,2, Brian A. Novosak1,3, Aaron C. Gooley1,4, David M. Ing1,5,
Robert D. Bluett6, Timothy C. Carter7, and George A. Feldhamer1,*
Abstract - Populations of Neotoma floridana (Eastern Woodrat) are decreasing in parts
of their geographic range in the southeastern United States, and the species is stateendangered
in Illinois. Once found throughout the Shawnee Hills region of southern
Illinois, woodrats were restricted to four known populations in Jackson and Union counties
by the late 1980s. We used reintroductions to establish viable populations of Eastern
Woodrats at previously occupied sites in Illinois. From April 2003 through March 2009,
we released 422 Eastern Woodrats live trapped in Arkansas and Missouri into 5 historically
occupied sites in southeastern Illinois. Recapture rate 1 month after release was
12.5%. The continued presence of woodrats at release sites, reproduction, and wide dispersal
beyond reintroduction sites all suggest preliminary success of the reintroduction
of this r-selected species.
Introduction
Historically, Neotoma floridana Ord (Eastern Woodrat) was widespread in
suitable habitats throughout southern Illinois, where it was considered common
(Howell 1910), but is now one of the most endangered mammalian species in the
state (Nÿboer et al. 2006). Nawrot and Klimstra (1976) found direct evidence of
past habitation (e.g., skeletal remains, scat, stick nests) at 24 sites throughout Jackson,
Union, Johnson, Pope, Gallatin, and Hardin counties. Additional sites seemed
to offer suitable habitat, but no direct evidence of past habitation was observed,
possibly because artifacts were destroyed by weathering and disturbance (Nawrot
1974). Four extant, remnant populations remain in Jackson and Union counties
(Fig. 1). The largest, most secure, and best studied of these populations is at Pine
Hills (Crim 1961, Ing 2008, Layne 1958, Monty 1997). Smaller populations remain
at Fountain Bluff (Wagle and Feldhamer 1997), Horseshoe Bluff, and Little
Grand Canyon (Monty et al. 1995, Wagle 1996). Although these populations are
separated by only 2 to 14 km, all exhibit significant genetic differentiation and low
heterozygosity (Monty et al. 2003). Although Eastern Woodrats can occupy forests,
swamps, thickets, grasslands, hedgerows, and abandoned buildings (Rainey
1956), the remnant populations in southern Illinois primarily occupy rocky bluffs
in parts of Shawnee National Forest.
1Department of Zoology, Southern Illinois University, Carbondale, IL 62901-6501.
2Mathematics and Science Division, Southeastern Illinois College, Harrisburg, IL 62946.
3US Fish and Wildlife Service, 4701 North Torrey Pines Drive, Las Vegas, NV 89130.
4Cooperative Wildlife Research Laboratory, Southern Illinois University, Carbondale,
IL 62901. 5Department of Life Sciences, John A. Logan College, Carterville, IL 62918.
6Illinois Department of Natural Resources, One Natural Resources Way, Springfield, IL
62702. 7Department of Biology, Ball State University, Muncie, IN 47306. *Corresponding
author - feldhamer@zoology.siu.edu.
2 Southeastern Naturalist Vol. 12, No. 1
Protocols for reintroducing large, long-lived, K-selected species are fairly
well established (Fischer and Lindenmayer 2000, Kleiman 1989). However, this
is not the case for smaller, r-selected species such as woodrats (Serfrass 2008).
Our objectives were to implement and evaluate a recovery project (Bluett 2003)
by: 1) reintroducing (sensu IUCN 1998) and establishing Eastern Woodrat populations
at selected sites in southern Illinois where they had occurred historically;
and 2) monitoring populations at all sites for persistence, dispersal, and reproductive
success. Our efforts to establish self-sustaining populations of Eastern
Woodrats at previously occupied sites in Illinois were within the context of a
general framework for reintroducing r-selected species (Serfrass 2008).
Study Sites
The Shawnee Hills region of southern Illinois encompasses 16 counties bordered
by the Mississippi and Ohio rivers. Much of this region includes the highly
fragmented Shawnee National Forest, which is primarily dominated by a variety
Figure 1. Extant and release sites of translocated populations of Eastern Woodrats (Neotoma
floridana) in southern Illinois.
2013 A.K. Poole, et al. 3
of species of Quercus spp. (oak) and Carya spp. (hickory), with interspersed
in-holdings of croplands. Understory often includes Vitis spp. (wild grape),
Lonicera japonica L. (Japanese Honeysuckle), and Toxicodendron radicans L.
(Poison Ivy). Steep slopes, often with rocky outcrops, occur throughout much of
the area, as do permanent and intermittent streams.
Methods
Selection of release sites
All potential reintroduction sites were within the historical range of the species
in Illinois. We used ArcView 3.2 and ArcView 8.2 (Environmental Systems
Research Institute) to locate potential reintroduction areas and model connectivity
at a macro scale. We developed GIS models to identify steep forested areas (Novosak
2004) using forest cover from the Regional Gap Analysis Project National
Elevation Dataset (USGS 2002a) and the National Land Cover Dataset (USGS
2002b). The areas of highest value, including those formerly occupied by woodrats
in southern Illinois, were buffered at 0.85 and 1.60 km distances to identify
suitable release sites and dispersal corridors because we anticipated that forested
corridors that provide connectivity between bluff sites would enhance dispersal
and population maintenance (Hilty et al. 2006, Lidicker and Patton 1989). We then
used ground surveys to confirm the presence of bluff habitat (rocky outcrops) and
ranked quantity and quality of food and cover using the methods described in Novosak
(2004). Based on suitability of both macrohabitat (bluff habitat and potential
connectivity to other sites) and microhabitat (food and cover), we selected four
reintroduction sites in 2004: Garden of the Gods (Saline County), Pounds Escarpment/
Rim Rock (Gallatin County), High Knob (Gallatin County), and Buzzard’s
Point (Gallatin County). These sites were 2 to 4 km from each other to facilitate
natural dispersal of translocated woodrats among sites through corridors of suitable
habitat. Castleberry et al. (2001) documented a maximum distance of 704.4 m
traveled in one night in the similar N. magister Baird (Allegheny Woodrat), and
individuals have been known to travel 1.5 km upon release (LoGuidice 2006). In
2008, we added another reintroduction site based on the same habitat criteria—
Lusk Creek (Pope County), approximately 16.5 km southwest of Garden of the
Gods (Fig. 1)—to extend the potential dispersal range.
Trapping
From April 2003 through March 2009, we translocated Eastern Woodrats
to southern Illinois from locations in Butler, Carter, Iron, Shannon, and Wayne
counties in Missouri, and Cross, Lee, St. Francis, and Woodruff counties in Arkansas.
The same subspecies (N. f. illinoensis) occurs in the three states (Hall
1981). Source sites were at similar latitudes as release sites, but did not always
include bluff habitat. We set Tomahawk live traps (16.5 x 16.5 x 48 cm; Tomahawk
Live Trap Co., Tomahawk, WI) in areas believed to contain woodrats or
where sign was evident. Trapping sessions and the numbers of traps operated varied
according to area and weather conditions. We baited traps with a mixture of
peanut butter, sunflower seeds, cracked corn, and apple, and provided polyester
4 Southeastern Naturalist Vol. 12, No. 1
fiber for bedding. We marked animals with two individually numbered Monel #3
ear tags (Model 1005-3, National Tag and Band Co., Newport, KY). We recorded
body mass (nearest g), gender, and reproductive status. We assigned age classes
according to body mass: <150 g = juvenile, 150–200 g = subadult, and >200 g =
adult (Rainey 1956). Descended (scrotal) testes indicated reproductively active
males. A perforated vagina, swollen teats, or lactation was evidence of reproductive
activity in females. Using a 3.5-mm biopsy punch, we collected a small
amount of ear tissue for future genetic analyses. We held animals in separate
cages for the least amount of time feasible prior to release (usually one to two
nights maximum) in a dark, quiet room. Woodrats were fed acorns or “rat chow”
(Mizuri rodent feed 6F, size M30), as well as apple slices. We transported animals
in an enclosed, temperature-controlled vehicle to the release site.
Release
We did not acclimate woodrats to the reintroduction sites as in a true soft
release (Serfrass 2008), but we attempted to minimize the stress on animals
from gathering food and nesting material in an unfamiliar area. We constructed
artificial nests by placing nest materials—including half-gallon cardboard juice
or milk containers, polyester fiber bedding, and covered with sticks—at release
sites with about 1 kg of acorns or “rat chow”. Artificial nests were constructed
in microhabitats similar to those woodrats use naturally to construct nests, i.e.,
deep, dry rock crevices, hollow logs, and the base of hollow trees. We then released
woodrats in the artificial nests. We maximized post-release population
persistence by two to four “pulsed releases” of 6–32 individuals (depending on
capture success from source populations) for a total of 50 to 121 individuals
at each release site. Releases commenced in early spring after leaf-out when
weather became warmer.
Subsequent monitoring
Approximately 1 month following releases, we used live trapping to monitor
translocated animals for survival, reproduction, and movements among and
between reintroduction sites. We used the same trapping methods but included
large Sherman live traps (13 x 13 x 38 cm; H.B. Sherman Traps, Tallahassee,
FL) to facilitate the capture of small juveniles because they can escape from the
Tomahawk traps. From September 2011 through March 2012, we visually surveyed
surrounding non-agricultural, bluff habitat for woodrat sign to document
minimum extent of dispersal. We considered recent scat, fresh food caches,
and stick nests as presence of woodrats in an area. From January 2012 through
February 2012, we used Tomahawk live traps to document woodrat survival at
Lusk Creek.
Results
From April 2003 through March 2009, we translocated 422 woodrats to
Garden of the Gods, Rim Rock/Pounds Escarpment, High Knob, Buzzard’s
Point, and Lusk Creek (Tables 1 and 2). The minimum number known alive
2013 A.K. Poole, et al. 5
about 1 month after release at all sites except Lusk Creek was approximately
12.5% based on 47 recaptured woodrats. Because of limited personnel and
funding, Lusk Creek was not monitored after initial release. Reproduction
occurred based on the capture of 61 “new” (no ear tags or biopsy punch) individuals
(Table 3) as well as another 17 unmarked individuals at Lusk Creek
taken in 89 trap nights from January through February 2012. Several animals
emigrated from reintroduction sites. Based on visual surveys for woodrat sign
in bluff areas north and east of release sites during 2011 and 2012, widespread
Table 1. Number and gender of translocated Eastern Woodrats (Neotoma floridana) at sites in
southern Illinois from April 2003 through March 2009.
Site Total number released Number of males Number of females
Garden of Gods 121A 39 49
Rim Rock 108 43 65
High Knob 81 26 55
Buzzard’s Point 50B 16 33
Lusk Creek 62 29 33
A33 Unknown sex, data lost.
B1 unknown sex, animal escaped.
Table 2. Number and date of release of translocated Eastern Woodrats (Neotoma floridana) at sites
in southern Illinois from April 2003 through March 2009.
Garden of the Gods Rim Rock High Knob Buzzard's Point Lusk Creek
April 2003 18
May–June 2003 21
September 2003 7
February 2004 33
23 May 2004 23
February 2005 6
March/April 2005 7
May 2005 6
June 2003 9
July 2003 16
September 2003 11
March 2004 24
April 2004 16
February 2005 1
May 2005 6
April 2005 6
February 2006 19
October 2005 20
February 2006 24
April 2006 14
March 2007 23
February 2007 25
March 2007 25
March 2008 31
February/March 2009 31
6 Southeastern Naturalist Vol. 12, No. 1
dispersal is suggested, extending approximately 8 km northwest of Garden of
the Gods, 2.7 km east of Rim Rock, and throughout the area between Garden
of the Gods and Lusk Creek (Fig. 2).
Discussion
There are several possible reasons for the decline and extirpation of Eastern
Woodrat populations in southern Illinois (Feldhamer and Poole 2008)—reasons
that also likely apply to the decline of closely related Allegheny Woodrats (see
LoGiudice 2008). Nawrot and Klimstra (1976) speculated that unusually harsh
Table 3. Number of recaptured and “new” (unmarked) Eastern Woodrats (Neotoma floridana) at
reintroduction sites in southeastern Illinois from June 2003 through February 2012.
Number of
Site Number recaptured “new” woodrats Number of trap nights
Garden of Gods 12 20 596
Rim Rock 6 9 444
High Knob 22 18 574
Buzzard’s Point 7 14 100
Lusk Creek 0 17 89
Figure 2. Eastern Woodrat (Neotoma floridana) sign (recent scat, fresh food caches, and
stick nests) found during visual surveys from September 2011 through March 2012 in
southeastern Illinois.
2013 A.K. Poole, et al. 7
winters during 1912 and 1918 could have caused extirpation of colonies in the
eastern part of the Shawnee Hills region. Extreme climatic conditions in association
with other mortality factors—predation, the nematode parasite Baylisascaris
procyonis carried by Procyon lotor L. (Raccoon), irregular mast production, increased
density of competitors, continued habitat loss and fragmentation—could
have further reduced population numbers and viability. However, this project
was based on the assumption that the primary factor in decline was landscape
fragmentation and loss of habitat.
Our reintroductions were intended to compensate for extirpation of isolated,
often small populations because Eastern Woodrats could not naturally recolonize
previously occupied sites throughout southern Illinois (Nawrot and Klimstra
1976). Nonetheless, there is more contiguous habitat available now than when
the species declined throughout the early decades of the 1900s, during which
time the area that now comprises Shawnee National Forest was cleared for farming
and grazing (Fralish and McArdle 2009). Whether other potential population
mortality factors remain operative is unknown, although occurrence of the raccoon
roundworm B. procyonis appears to be negligible in southern Illinois (Birch et al.
1994, Nielson et al. 2007) and particularly on the release sites (Bade et al. 2012).
Reintroduced populations have persisted to date and natural reproduction occurred—
documented by the 78 unmarked individuals trapped following releases.
Only 12.5% of individuals were known to be alive about 1 month after reintroductions,
but this certainly is a conservative estimate. Mortality rate was most
likely less than 87.5% given the current extent of distribution and reproduction (Fig. 2).
We facilitated dispersal by selecting release sites with suitable habitat corridors
to increase the probability of establishing a successful metapopulation (Armstrong
and Seddon 2008, Wood 2008).
Management implications
Several species of woodrats are of conservation concern (Feldhamer and
Poole 2008). Although previous woodrat reintroductions in Florida (Barbour
and Humphrey 1982) and Pennsylvania (Corbett and Shinkle 1997) met
with mixed success, our reintroduction was successful based on the extent of
natural dispersal and reproduction. Several factors contribute to the success
of reintroductions (Bright and Morris 1994, Fischer and Lindenmayer 2000,
Kleiman 1989, Wolf et al. 1996), including release in the core of the historical
range (although see Lomolino and Channell 1995, Sagarin and Gaines 2002),
extent of quality habitat, release of a large number of animals, an omnivorous
diet, wild-caught rather than captive-reared source animals, and soft rather
than hard release. Wolf et al. (1996) suggested that reproductive potential of
the reintroduced species and the duration of the release may be less critical for
success. Several of these concepts and practical considerations applied to our
project. Although southern Illinois is not in the core of the range for Eastern
Woodrats, we released animals at historically occupied sites based on current
macro- and microhabitat conditions. We also attempted to release the optimal
number of individuals at each site based on available food, shelter, and space.
8 Southeastern Naturalist Vol. 12, No. 1
We maximized post-release population persistence by 2 to 4 “pulsed releases”
for a total of 50 to 121 individuals at each release site. All source individuals
were wild-caught, and trapping and reintroduction commenced in early spring
after leaf-out when weather became warmer. Additionally, sex ratios of released
animals at all sites favored females (Table 1). We provided nesting material and
food caches to enhance acclimatization and mimic a soft release to the extent possible
given that the bluff habitat precluded confining individuals. High rates of
dispersal and increased mortality are associated with hard release in some mammalian
species (Fritts et al. 1984, Morris et al. 1993, O’Bryan and McCullough
1985). However, because woodrats are highly territorial and dispersal rates are
naturally high (Wood 2008), we anticipated many animals would leave the reintroduction
sites regardless of hard or soft release.
Continued persistence of the reintroduced populations in our study is not assured,
and we agree with Dodd and Seigel (1991:343) that “researchers should
temper claims of success with a recognition of the need for long-term evaluation.”
Nonetheless, given our metapopulation approach with reintroductions of
a large number of woodrats over a multi-year time scale, and the documented
extent of dispersal from release sites, we believe that the probability of failure
due to demographic stochasticity is low, and progress toward improving the conservation
status of the Eastern Woodrat in Illinois is encouraging.
Acknowledgments
This project was funded in part by Federal Aid in Wildlife Restoration Project W-
135-R, a cooperative effort among the US Fish and Wildlife Service, Illinois Department
of Natural Resources, and the Department of Zoology at Southern Illinois University
Carbondale. D. Woolard, B. Steffen, and J. Hammersley were instrumental in capture,
release, and monitoring efforts. We also thank C. Bartman, D. Corgiat, J. Gaffney, M. Hilton,
J. Hubert, A. Hulin, J. Kath, J. Kube, R. Lindsay, D. Ludwig, M. Murphy, P. Shelton,
and S. Widowski for their assistance.
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