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Status of Eastern Woodrats in Isolated Remnant Populations Following Genetic Augmentation and Habitat Disturbance
Aaron C. Gooley and Eric M. Schauber

Southeastern Naturalist, Volume 17, Issue 2 (2018): 327–344

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Southeastern Naturalist 327 A.C. Gooley and E.M. Schauber 22001188 SOUTHEASTERN NATURALIST 1V7o(2l.) :1372,7 N–3o4. 42 Status of Eastern Woodrats in Isolated Remnant Populations Following Genetic Augmentation and Habitat Disturbance Aaron C. Gooley1,* and Eric M. Schauber1 Abstract - In Illinois, Neotoma floridana (Eastern Woodrat) experienced range reductions and population bottlenecking over the past century. During the period 2004–2005, the isolated remnant populations along the Mississippi bluffs in southwestern Illinois were genetically augmented with 47 Eastern Woodrats from Arkansas and Missouri, resulting in 40% admixture within the largest population. In 2009, a strong windstorm created canopy gaps and woody debris throughout this area, potentially improving habitat for Eastern Woodrats. We investigated the status of Eastern Woodrat populations in southwestern Illinois by livetrapping remnant populations and conducting sign surveys from 2011 to 2015. We captured 263 Eastern Woodrats; mean trapping success was 62.5% higher than trapping during the 1990s, and the number of individuals captured per trap-night was 3–6 times higher than trapping events during the previous 18 years (all P less than 0.001). We also located sign of Eastern Woodrat 8.9 km east of the remnant populations. We recommend further genetic monitoring to evaluate whether population increases are coupled with increased admixture and recommend forest-management actions that create habitat disturbance and resultant piles of woody debris that increase woodrat habitat quality. Introduction Isolated populations at the periphery of a species’ range are often more prone to population fluctuations (Williams et al. 2003), local extirpations, inbreeding, and loss of genetic diversity than populations at the center of the species’ range (Peterman et al. 2013, Westemeier et al. 1998). However, these populations can also represent critical refugia with great importance to conservation and the species’ long-term survival (Channell and Lomolino 2000, Fraser 2000, Lomolino and Channell 1995). Neotoma floridana illinoensis Howell (Illinois Woodrat), a subspecies of N. floridana (Ord) (Eastern Woodrat), was once common in southern Illinois (Howell 1910, Nawrot and Klimstra 1976), where the subspecies reaches the northern extent of its range (Hall 1981) and is isolated by the Mississippi and Ohio rivers. However, by 1950, populations in Illinois only persisted along the Mississippi Bluffs in the southwestern margin of the state (Nawrot and Klimstra 1976). Periodic trapping and investigation of these remnant populations indicated that the number of Eastern Woodrats declined through the 1960s (Crim 1961, Krull and Bryant 1972) and 1970s (Nawrot and Klimstra 1976) to a bottleneck of approximately 15–35 individuals at Pine Hills (Union County) during the 1980s (Hoffmeister 1989, West 1986). The remnant population then increased during the early 1990s to an estimated high of 101 in 1994 before decreasing to 60 in 1996 (Monty 1997; 1Cooperative Wildlife Research Laboratory, Department of Zoology, Southern Illinois University Carbondale, IL 62901. *Corresponding author - Manuscript Editor: Michael Cove Southeastern Naturalist A.C. Gooley and E.M. Schauber 2018 Vol. 17, No. 2 328 Monty et al. 1995, 2003; Wagle 1996). During the 1990s, small satellite populations were found at Horseshoe Bluff, Little Grand Canyon, and Fountain Bluff (Jackson County; Monty 1997, Monty et al. 1995). As a possible consequence of the population bottleneck during the 1980s, Eastern Woodrats in Illinois possessed lower heterozygosity at microsatellite markers (6 loci) than Eastern Woodrats from a more contiguous population in Missouri (Monty 1997, Monty et al. 2003). As part of a state recovery plan for Eastern Woodrats (Bluett 2003), 59 individuals were removed from remnant populations along the Mississippi Bluffs for reintroduction to other unoccupied areas in Illinois. Forty-nine Eastern Woodrats were removed from Pine Hills and 10 from Fountain Bluff between 2003 and 2004 (Feldhamer et al. 2007). During June 2004 and February 2005, biologists translocated 47 Eastern Woodrats from Arkansas and Missouri to the remnant populations—41 were released across the known range of Eastern Woodrat at Pine Hills and 6 were released at Fountain Bluff (Feldhamer et al. 2007, Novosak 2004; Fig. 1). The goals of the translocation to the Mississippi Bluffs were to genetically augment those populations and facilitate population growth (Bluett 2003). After the translocation, microsatellite heterozygosity at 12 polymorphic microsatellite loci (Nfu01, Nfu03, Nfu05, Nlep08, Nma01, Nma02, Nma06, Nma08, Nma10, Nma11, Nma14, Nma15) in 41 Eastern Woodrats captured at Pine Hills between 2005 and 2009 were compared to the 49 removed from Pine Hills. The augmentation resulted in a 12% increase in average microsatellite heterozygosity, as well as representation of Arkansas and Missouri genes in 40% of Eastern Woodrats in the Pine Hills population (A. Poole, Southern Illinois University, Carbondale, IL, unpubl. data). However, following the augmentation, the Pine Hills population appeared to decline: trapping success in 2006–2007 was ~⅓ the trapping-success rate during the 1990s, and trapping was less productive in the northern areas of Pine Hills even though stick nests identified in the 1990s were still present on the outcrops (Ing 2008). Continued population declines following the genetic augmentation could indicate outbreeding depression where dilution of local adaptation or chromosomal incompatibilities results in reduced fitness in outcrossed individuals or their offspring (Allendorf et al. 2013). Beginning with their initial description, Eastern Woodrats in Illinois have been noted for building nests on bluffs instead of in woody structures (Howell 1910) and nearly all captures over the past century have occurred on bluffs or other rocky structures with sparse evidence of Eastern Woodrats inhabiting the adjacent bottomland woods (Crim 1961, Hoffmeister 1989, Howell 1910, Krull and Bryant 1972, Layne 1958, Monty 1997, Monty et al. 2003, Nawrot 1974, Nawrot and Klimstra 1976, Swayne 1949, Wagle 1996, West 1986). However, suitable shelter for nest construction was the limiting resource for Eastern Woodrats in southern Illinois (Crim 1961). The apparent restriction of Eastern Woodrats to the bluffs may have been a result of limited hollow trees, stumps, and other coarse woody debris in the landscape. On 8 May 2009, an unusually strong derecho (straight-line windstorm; Coniglio et al. 2011) caused widespread windthrows in the Illinois Ozark Hills and western Shawnee Hills, with some areas experiencing over 75% canopy loss Southeastern Naturalist 329 A.C. Gooley and E.M. Schauber 2018 Vol. 17, No. 2 (Romano et al. 2013). The US Forest Service further increased the availability of coarse woody debris on the ground by piling logs and brush along roadsides during the subsequent cleanup. Thus, the derecho altered forested habitat of the Eastern Woodrat that had been largely undisturbed during the previous 70 y (Hutchinson 1987, van de Gevel and Ruffner 2007) by opening the canopy and creating an abundance of woody debris for nest construction (Figs. 2, 3). This habitat change may have removed the primary limiting factor for remnant populations of Eastern Woodrat in the Illinois Ozark Hills and western Shawnee Hills. Our objective was Figure 1. Capture and release locations o f Neotoma floridana (Eastern Woodrat) translocated to Illinois during 2004 and 2005 for the purpose of genetically a u gme n t i n g remnant populations. Southeastern Naturalist A.C. Gooley and E.M. Schauber 2018 Vol. 17, No. 2 330 Figure 2. An example of the of canopy loss and windthrows at Pine Hills, IL, caused by the 2009 derecho. The understory release resulted in growth of dense tangles of woody vines. Note the limestone outcrops in the background. Figure 3. A Neotoma floridana (Eastern Woodrat) stick nest built into a windthrow in the bottomlands at Pine Hills, IL. Note the vine tangles and saplings in the background and use of sticks up to 2.5 cm in diameter for nest construction. Southeastern Naturalist 331 A.C. Gooley and E.M. Schauber 2018 Vol. 17, No. 2 to investigate the status of these populations of Eastern Woodrat in southwestern Illinois following the genetic augmentation and widespread habitat disturbance. Field-site Description The Mississippi Bluffs lie along the western side of the Illinois Ozark Hills and overlook the bottomland forest, wetlands, and agricultural fields of the Mississippi Alluvial Plain. The bluffs of the Ozark Hills are composed of cherty limestone and sandstone, whereas the outcrops of the Shawnee Hills to the east are composed primarily of sandstone (Schwegman 1973). The Western Mesophytic Forest (Braun 1950) of these regions is rich in plant diversity (Mohlenbrock 1982), with a canopy dominated by a variety of Quercus (oak) and Carya (hickory) species (Bazzaz 1968). The Pine Hills Bluffs, Horseshoe Bluff, and Little Grand Canyon are in a north–south line along the east side of the Big Muddy River while Fountain Bluff is isolated from other bluffs by bottomlands on the west side of the Big Muddy River. The majority of our study area was situated within the Shawnee National Forest. Methods Trapping and analysis We conducted 7 live-trapping sessions within the assumed range of the Pine Hills population, each lasting 2–76 d, between November 2011 and August 2014 (Table 1). We generally set 30 Tomahawk live traps (16.5 cm x 16.5 cm x 48 cm) per day along rock outcrops, woody-debris piles, and locations of sign (stick nests or latrines), as well as in areas of dense brush or vines. During each session, we left traps in place for 2 nights before moving them to new locations. An exception to this pattern was during 30 September–2 October 2013, when we placed 30 traps 20 m apart on each side of a 280-m section of gravel road and trapped for 3 consecutive nights to investigate if additional Eastern Woodrats would be detected on the 3rd night. This section of road was bordered on both sides by woodydebris piles and dense vegetation. We also trapped at Fountain Bluff on 3–4 December (12 traps) and Little Grand Canyon on 13–14 December 2012 (6 traps) to confirm the continued presence of Eastern Woodrats at those sites. Previous researchers typically recorded areas of activity (stick nests, latrines, piles of feeding debris) along outcrops and placed traps at them. However, after the derecho, areas of activity as well as other likely habitat (woody-debris piles, dense brush, or vines) were not limited to the outcrops. Also, previously accessible sections of outcrop were rendered inaccessible by blowdowns, dense vine tangles, and thick vegetation. Consequently, unlike previous researchers, we were only able to identify and place traps at a fraction of the areas of activity and were not able to trap every area repeatedly. We baited traps with Helianthus annuus L. (Sunflower) seeds, placed a ball of polyester stuffing in the rear of each trap to provide bedding material, and covered traps with natural debris to provide shelter. Traps were checked the morning after deployment because Eastern Woodrats are primarily nocturnal (Wiley 1971). We Southeastern Naturalist A.C. Gooley and E.M. Schauber 2018 Vol. 17, No. 2 332 Table 1. Results of trapping for the Neotoma floridana (Eastern Woodrat) remnant-population along the Mississippi Bluffs, IL, November 2011–August 2014. Trapping success = woodrat captures per trap night. Individuals captured # recaptured # recaptured Trapping Adult Subadult Juvenile Unknown during from Site Dates trapped (m/d/y) Trap-nights success ♂ ♀ ♂ ♀ ♂ ♀ trapping bout previous dates Pine Hills 11/7/2011–1/21/2012A 261 0.368 31 38 5 10 0 2 1 9 n/a 8/6–17/2012 237 0.477 37 26 10 10 0 3 0 23 12 10/18–19/2012 24 0.708 4 12 0 0 0 1 0 n/a 11 1/25/2013–2/3/2013 127 0.638 25 28 1 5 0 0 0 22 19 9/30/2013–10/2/2013 90 0.756 14 14 0 4 0 0 0 36 7 2/17–18/2014 56 0.464 6 6 0 1 0 0 0 n/a 9 8/12–15/2014 54 0.444 9 10 3 1 0 1 0 0 5 Fountain Bluff 12/3–4/2012 12 0.5 2 2 0 1 1 0 0 n/a n/a Little Grand Canyon 12/13–14/2012 8 0.25 1 0 0 1 0 0 0 n/a n/a AComprised of 9 short bouts totaling 22 d. Southeastern Naturalist 333 A.C. Gooley and E.M. Schauber 2018 Vol. 17, No. 2 anesthetized captured woodrats with isoflurane, attached an individually numbered #1005-1 Monel ear tag (National Brand and Tag Co., Newport, KY) to each ear and recorded body mass and sex prior to release. We assigned age class based on body mass (juvenile = <150 g, subadult = 150–200 g, and adult = >200 g; adapted from Rainey 1956). We conducted chi-square tests to determine if our number of previously uncaptured individuals captured per trap-night differed from trapping conducted from 1993 to 2007 (Feldhamer et al. 2007), with α = 0.05 for each test. We considered an increase in the number of previously uncaptured individuals captured per trap-night indicative of an increase in abundance. A shift from the female-biased sex ratio observed during the 1990s (Monty 1997) could indicate that demographic processes have changed within the Pine Hills population. We conducted chi-square tests to determine if sex ratios of 1st captures (i.e., unique individuals) and recaptures differed from 1:1, with α = 0.05 for each test. We conducted our research according to Southern Illinois University Animal Care and Use Protocol # 11-003. Distribution surveys From 2011 through 2015, we documented the distribution of Eastern Woodrats in the western Shawnee National Forest by visually surveying for recent Eastern Woodrat sign (latrines, fresh scat, fresh food caches, or maintained stick-nests) at rocky outcrops located on public land. We located rocky outcrops via aerial photos, surficial geologic maps, and topographic maps, and surveyed them at increasing distance from the remnant populations (Monty 1997, Monty et al. 1995, Wagle 1996) until we did not find Eastern Woodrat sign. We also investigated reports of Eastern Woodrat captures or Eastern Woodrats inhabiting human structures in southwestern Illinois. Results Trapping and analysis We captured 255 individual Eastern Woodrats, including 200 adults (101 ♂, 99 ♀), 47 subadults (18 ♂, 29 ♀), 7 juveniles (♀), and 1 of unkown age class, with 153 recaptures during 7 trapping bouts (848 trap-nights) at Pine Hills (Fig. 4). After initial capture, we recaptured 1 juvenile female and 9 subadults (3 ♂, 6 ♀) as adults. During the first trapping bout, 3 Eastern Woodrats escaped prior to tagging and were not included in the overall number of individuals captured. Overall trapping success was 0.480 woodrats captured per trap night, with trapping successes of individual bouts varying from 0.368 to 0.708 (mean = 0.551, SE = 0.056; Table 1). We captured 0.30 previously uncaptured individuals per trap-night, which was significantly higher than all trapping efforts during the period 1993–2007 (all P less than 0.001) (Table 2). Sex ratios did not differ significantly from 1:1 for all individuals (χ2 = 1.00, df = 1, P = 0.32), adults (χ2 = 0.02, df = 1, P = 0.89), subadults (χ2 = 2.57, df = 1, P = 0.11), or recaptures (χ2 = 0.16, df = 1, P = 0.69). Our bout with 3 consecutive nights of trapping (30 September–2 October 2014) yielded 32 individual Eastern Woodrats (included in the above), with only 8 new individuals captured on Southeastern Naturalist A.C. Gooley and E.M. Schauber 2018 Vol. 17, No. 2 334 Figure 4. Locations of Neotoma floridana (Eastern Woodrat) captures, reported (but unconfirmed) captures, and sign in relation to the remnant populations along the Mississippi Bluffs and a recently introduced population at Giant City State Park, IL. Elevation model from Illinois Statewide 30-m shaded relief image (Illinois State Geological Survey, Champaign, IL). Southeastern Naturalist 335 A.C. Gooley and E.M. Schauber 2018 Vol. 17, No. 2 the 2nd night and no new individuals captured on the 3rd night (Table 3). The mean body-masses of adult males and females at final capture were 297 g (SE = 5.08, max = 419 g) and 254 g (SE = 2.79, max = 332 g), respectively. We captured 5 male Woodrats during January–February trapping bouts with body masses of 404–419 g (record masses for Woodrats captured in Illinois), whereas the maximum bodymass of a captured female was 350 g. We captured 6 Woodrats at Fountain Bluff and 2 Woodrats at Little Grand Canyon, confirming continued population persistence; however, sign and captures at Little Grand Canyon were limited to a boulder pile beside the Big Muddy River. Distribution We located fresh sign of Eastern Woodrat (latrines and stick nests) at outcrops up to 3.5 km northeast of the Mississippi Bluffs at Pine Hills and 7.5 km east of Horseshoe Bluff (Fig. 4). We verified reports of Woodrat sign in an old vehicle 7.9 km east of Horseshoe Bluff and in 2 old vehicles 8.9 km east of the Mississippi Bluffs at Pine Hills (Fig. 5). A landowner captured an adult male Woodrat in a shed 3.5 km east–northeast of Little Grand Canyon and brought it to us for verification and tagging. We also received reports of an Eastern Woodrat 7.7 km east of Pine Hills (tail severed in a Sherman trap; W. Holland, Southern Illinois University Carbondale, IL, pers. comm.) and of an Eastern Woodrat captured in a Sherman trap deployed for Oryzomys palustris (Harlan) (Marsh Rice Rat) 29.6 km northeast of Little Grand Canyon (J. van der Merwe, Southern Illinois University, Carbondale, IL, pers. comm.). We searched both locations but were unable to locate any Eastern Woodrat Table 3. Neotoma floridana (Eastern Woodrat) captures at 2 transects along LaRue Road at Larue-Pine Hills, IL, 30 September–2 October 2014. Day 1 Day 2 Day 3 Captures 11 ♂, 13 ♀ 12 ♂, 12 ♀ 8 ♂, 12 ♀ Additional individuals captured N/A 3 ♂, 5 ♀ 0 ♂, 0 ♀ Daily trap success 0.80 0.80 0.67 Table 2. Comparison of Neotoma floridana (Eastern Woodrat) live-trapping results at Pine Hills, IL. 1993-2007 data from Feldhamer et al. 2007. An asterisk (*) denotes results from our study. Comparison of our previously uncaptured individuals captured per Previously uncaptured trap night to prior trapping Years Individuals individuals captured monitored captured Trap-nights per trap night χ2 df P 1993–1996 283 4840 0.06 480.138 1 less than 0.0001 2002–2003 29 422 0.07 85.819 1 less than 0.0001 2005 7 70 0.10 12.686 1 0.0004 2006–2007 22 410 0.05 101.087 1 less than 0.0001 2011–2014* 255* 849* 0.30* Southeastern Naturalist A.C. Gooley and E.M. Schauber 2018 Vol. 17, No. 2 336 sign or favorable locations to set traps. We also received a report of captures of Eastern Woodrats in live-traps set for Rattus norvegicus Berkenhout (Norway Rat) at a Union County State Fish and Wildlife Area grain silo located 10.2 km southeast Figure 5. Neotoma floridana (Eastern Woodrat) scat, nesting material, cached nuts, and feeding debris in an old vehicle 8.9 km east of the Mississippi Bluffs at Pine Hills, IL. Southeastern Naturalist 337 A.C. Gooley and E.M. Schauber 2018 Vol. 17, No. 2 of Pine Hills (K. Delahunt, Illinois Department of Natural Resources, Makanda, IL; pers. comm.). We searched outcrops 10.8 km northwest of Little Grand Canyon, 6.2 and 10.5 km east of Horseshoe Bluff, 10.6 km east, and 15.5 south southeast of Pine Hills, but did not locate any sign of Eastern Woodrat. Discussion Comparing our data with results of past studies provided evidence that the remnant Woodrats in southeastern Illinois have increased in abundance and have a larger distribution than previously documented. At Pine Hills, our mean trapping success (0.551) was 62.5% higher than was achieved by trapping during 1993–1996 (0.339; Monty et al. 2003), and our number of previously uncaptured individuals captured per trap-night was 3–6 times higher than any trapping study during the previous 18 y (Table 2; Feldhamer et al. 2007). Our trapping was highly productive in the northern areas of Pine Hills that had been considered not worth the effort of trapping because of low productivity immediately after the genetic augmentation (Ing 2008). The widespread woody debris and understory release resulting from the 2009 derecho likely facilitated these population increases because Eastern Woodrats are limited by availability of nesting sites (Crim 1961, Winchester et al. 2009) and security cover (Rainey 1956). We captured most Eastern Woodrats in the bottomlands at woody-debris piles surrounded by dense understory vegetation, which was in stark contrast to past studies in Illinois that captured Eastern Woodrats primarily at rock outcrops (Crim 1961, Hoffmeister 1989, Howell 1910, Krull and Bryant 1972, Layne 1958, Monty 1997, Monty et al. 2003, Nawrot 1974, Nawrot and Klimstra 1976, Swayne 1949, West 1986). We encountered numerous active stick nests of Eastern Woodrats built into woody-debris piles and windfalls, and found that most roadside debris piles at Pine Hills contained a stick nest. However, vegetative succession appears to be progressing rapidly at Pine Hills (reducing low overhead cover) and woody-debris piles deteriorated noticeably during our study (reducing the availability of nesting sites), especially in the moist bottomlands. Without periodic disturbance, habitat will eventually return to a more uniform late-successional state, with a sparse understory and little downed woody structure, perhaps again restricting Woodrats to the bluff line and reducing their abundance. In addition to increased woody structure and dense understory vegetation, genetic augmentation also may have contributed to increases in abundance of Eastern Woodrats. Although our study was not designed to determine if demographic and distributional changes in the populations of Illinois Woodrat were caused in part by the augmentation, other genetically augmented populations of woodrats have experienced increases in abundance, although not to the extent of those in Illinois (Smyser et al. 2013). Also, the Eastern Woodrats translocated from Arkansas and Missouri were captured in forest habitat or disturbed habitat (i.e., slash piles), instead of at outcrops (Feldhamer et al. 2007). It is possible that the genetic augmentation increased the population’s propensity to utilize structures other than outcroppings for stick-nest construction, thus increasing both demographic performance in situ and habitat availability in the landscape. Alternatively, the presumed Southeastern Naturalist A.C. Gooley and E.M. Schauber 2018 Vol. 17, No. 2 338 restriction of Illinois Woodrats to outcroppings may have simply been an artifact of sparse downed-woody structure in the landscape or insufficient investigation of non-outcrop habitat by past researchers. It is not unusual for Eastern Woodrats to inhabit areas away from outcrops (Rainey 1956), where they can go unnoticed due to a lack of easily visible sign (Knowles and Burger 2008). The distribution of the Eastern Woodrat in southwestern Illinois apparently has expanded eastward from remnant populations that were considered isolated in the 1990s (Monty et al. 2003); we detected latrines and stick nests almost 9 km from previously known extant populations. Our failure to locate sign at some locations may not indicate that Eastern Woodrats were not present (Peles and Wright 2008). Outcrop exposure to rain, and outcrop structure likely affected our ability to locate sign. Rain washes away and degrades scat (Wallmo et al. 1962), and outcrop structure can limit the visibility of latrines and nests (e.g., nests or latrines hidden within deep crevices or on inaccessible areas of bluff would not be detected). The reports of Eastern Woodrat captures that we received suggest the species occupies sites farther from the remnant populations than our sign-surveys indicate. Lengthy dispersal distances in woodrats have been documented (Wright et al. 1998), and we consider the sources that reported captures of Eastern Woodrat to us to be reliable. The Illinois Department of Natural Resources translocated 62 Eastern Woodrats from Pine Hills during 2013–2014 to reestablish a population in Giant City State Park (R.D. Bluett, Illinois Department of Natural Resources, Springfield, IL; unpubl. data) at historically occupied outcrops (Nawrot and Klimstra 1976). This translocated population is ~12 km from the nearest occupied sites we mapped, so if it is successful and colonizes surrounding habitat and the Mississippi Bluffs populations continue to colonize eastward, then gene flow between the 2 areas is possible. The disjunct populations may eventually become contiguous if the Eastern Woodrats continue to utilize forested habitat in addition to outcrops. Increasing the number of interconnected populations, as suggested by Monty et al. (2003), would help maintain genetic diversity and metapopulation persistence (Wood 2008). Prior to the translocation and habitat disturbance, 58.3% of Eastern Woodrats captured at Pine Hills were female (Monty 1997); the overall and subadult sex ratio was significantly female-biased (Monty et al. 2003). Although not significantly different from an equal sex ratio, 52.8% of all Woodrats and 61.7% of subadults we captured were female. However, Monty et al. (2003) captured more subadults and juveniles than we did, most likely because they trapped throughout the year, whereas we trapped between August and February. The breeding season for Eastern Woodrats in Illinois occurs February through September (Monty et al. 2003). Had we trapped throughout the year, we might have captured more subadults and juveniles and experienced a more pronounced unequal sex ratio. Eastern Woodrats reportedly display equal sex ratios at birth (Birney 1973) and female-biased sex ratios may be a result of greater site fidelity of females (Wood 2008), maternal bias against male offspring when resources are limited (McClure 1981), generally Southeastern Naturalist 339 A.C. Gooley and E.M. Schauber 2018 Vol. 17, No. 2 higher postnatal male mortality (Moses et al. 1998), or greater detection probability for females. On several occasions at Pine Hills, we captured 2 adult females at a stick nest on a single night and both returned to the stick nest upon release. This observation suggests that 2 adult females can inhabit the same stick nest, thereby increasing the number of females that can occupy an area with limited nesting sites. In captivity, N. f. smalli Sherman (Key Largo Woodrat) have exhibited alloparental care, where a daughter from a previous litter assisted her mother with rearing a subsequent litter (Wheaton et al. 2013), and the closely related N. magister Baird (Allegheny Woodrat) displayed seasonal patterns of aggregate living (Kinsey 1977), but our observation is to our knowldege the first evidence of wild Eastern Woodrat adult females living communally. The possibility of communal behavior stands in contrast to reports of strict territoriality and antagonistic behavior toward conspecifics in wild conditions (Layne 1958, Murphy 1952, Rainey 1956) and might also explain female-biased sex ratios from trapping studies. The 4 male woodrats with masses over 400 g are among the largest Eastern Woodrats recorded, although a 420-g male Eastern Woodrat was captured in Missouri (Feldhamer et al. 2007) and masses up to 425 g have been reported for male N. f. osagensis Blair (Osage Woodrat; Goertz 1970). Even when management goals are achieved, genetic augmentations (also called genetic introductions) can be controversial and perceived as humans are tampering with nature when donor populations are not taxonomically identical or geographically similar to the recipient populations (Cowlishaw et al. 2006). Potential negative consequences of genetic augmentation include disruption of evolutionary processes and outbreeding depression in the recipient population (Allendorf et al. 2013). Genetic augmentation can also affect the taxonomic status of an imperiled population and consequently the population’s legal status because hybrids (crosses between individuals from genetically distinct populations) are usually not addressed in endangered-species legislation (Allendorf et al. 2001, Haig and Allendorf 2006). Despite these potential problems, genetic augmentation is an effective yet underutilized tool for improving the fitness of genetically depauperate or inbred populations (Whiteley et al. 2015). The risk of outbreeding depression may be overemphasized (Frankham 2010, Frankham et al. 2011, Mortiz 1999). The probability of a genetic augmentation causing outbreeding depression can be estimated and used to guide management decisions when the taxonomy of the donor and recipient populations are well understood (Frankham et al. 2011). Unfortunately, lack of range-wide genetic studies for species, such as the Eastern Woodrat, whose taxonomy are primarily based on minor morphometric differences can make selection of donor populations for augmentations challenging. The results of our study were not suggestive of outbreeding depression within the Pine Hills population; however, the taxonomic relationship between the Eastern Woodrats translocated into Illinois and the remnant Illinois populations into which they were released is unclear. The Illinois Department of Natural Resources chose these source populations because they were similar in latitude and, based on published distribution maps (e.g., Hall 1981) and morphometric studies, contained the Southeastern Naturalist A.C. Gooley and E.M. Schauber 2018 Vol. 17, No. 2 340 same subspecies (Poole et al. 2013), and were the nearest populations capable of sustaining removals for translocation (R.D. Bluett, Illinois Department of Natural Resources, Springfield, IL; pers. comm.). However, genetic studies confirming the geographic range of the Eastern Woodrat subspecies are lacking. The 2 genetic studies of the taxonomy of the Eastern Woodrat either did not sample the Illinois Woodrat subspecies (Edwards and Bradley 2001), or only included 1 specimen (Hayes and Harrison 1992). Interestingly, the single Illinois Woodrat specimen utilized by Hayes and Harrison (1992) originated from west of the Mississippi River (western Arkansas) and formed a clade (based on mtDNA restriction sites) with the other subspecies found west of the Mississippi (i.e., N. f. attwateri Mearns [Attwater’s Woodrat], N. f. baileyi Merriam [Bailey’s Woodrat], N. f. campestris Allen [Kansas Woodrat]). The Mississippi River, as well as other large rivers, may present substantial barriers to woodrats and other small terrestrial animals (although smaller rivers may not be complete barriers to woodrats; e.g., Castleberry et al. 2002, Manjerovic 2004) and thus serve as a driver of allopatric speciation (Gascon et al. 2000, Haffer 1997, Wallace 1852). Though phenotypes (i.e., morphology) may appear contiguous across a large river due to the presence of the same selective pressures on both sides, populations on each side may in fact be isolated from one another and taxonomically distinct (Pyron and Burbrink 2009). A. Poole (Southern Illinois University Carbondale, IL, unpubl. data) demonstrated that remnant Illinois Woodrats could be reliably differentiated from the translocated Arkansas and Missouri Woodrats using 12 microsatellite loci. However, microsatellite differences between these groups may be a consequence of a previous bottleneck of the Illinois population, and are not by themselves indicative of taxonomic distinctiveness. Further genetic work is needed to clarify the taxonomic relationship between Eastern Woodrats from west and east of the Mississippi River and to understand the evolutionary consequences of the augmentation. Recommendations for further study and management We recommend further monitoring of genetic admixture at Pine Hills to evaluate if genetic augmentation facilitated the increase in Woodrat abundance and range or if recent habitat-changes are solely responsible. Assessing the percentage of individuals that are admixed (have genes from both Arkansas/Missouri and Illinois populations) both at and away from augmentation sites would help determine the effectiveness of genetic augmentation in addition to habitat management as population-management strategies for Woodrats and other small mammals. We also recommend forest-management practices, such as variable-density thinning (Carey and Curtis 1996), that result in periodic canopy disturbance, felled trees, and piles of woody debris to increase Woodrat habitat quality (Carey et al. 1999, Innes et al. 2007). Woodrats at Pine Hills clearly responded positively to similar habitat disturbance by increasing in abundance and establishing nests within the woody debris. Increasing periodic disturbance in southern Illinois forests should assist Woodrat dispersal and recolonization of historically occupied areas. Southeastern Naturalist 341 A.C. Gooley and E.M. Schauber 2018 Vol. 17, No. 2 Acknowledgments This project was funded in part by Federal Aid in Wildlife Restoration Project W-135-R, the US Fish and Wildlife Service, the Illinois Department of Natural Resources, and the Department of Zoology at Southern Illinois University Carbondale. E. Frieling, K. Lewis, and B. Rapier assisted greatly with the capture, processing, and release of Woodrats. We thank J. Rains and T. Jones for notifying us of Woodrat sign in old vehicles, R. Tuthill for capturing a Woodrat on his property for us, and R. Bluett, C. Deaton, S. Lietz. T. Pohlman, and E. Shimp for their assistance. R. Bluett, M. Cove, and 1 anonymous reviewer provided comments on the manuscript. Work was conducted under Illinois Department of Natural Resources permit numbers 11-37s, NH11.5552, NH12.5552, NH13.5552, NH14.5552, and NH15.5552 and with authorization from the US Forest Service. Part of this study was conducted within the Larue Pine Hills–Otter Pond Research Natural Area. 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