Neotoma Floridana Research Articles

Towards recovery of an endangered island endemic: Distributional and behavioral responses of Key Largo woodrats associated with exotic predator removal

Exotic predators create novel ecological contexts for native species, particularly when prey exhibit predator naïve behaviors. Population recovery of island endemic species following predator eradication has been documented broadly, but studies examining mammalian prey behavioral responses to exotic predator removal are less common. The Key Largo woodrat (Neotoma floridana smalli) is an endangered Florida endemic species that exhibited drastic declines, signified by the loss of natural stick-nests, over the past three decades due to habitat loss and effects from exotic predators. We conducted camera trap surveys of woodrats at supplemental nests and used dynamic multistate occupancy models to evaluate changes in woodrat distribution and stick-nest building behavior over a two-year period of exotic predator (domestic cats [Felis catus] and Burmese pythons [Python bivittatus]) removal. The distribution of woodrats using supplemental nests increased from 27% to 39% in the two-year period, while the proportion of occupied supplemental nests with stick-nests increased from 37% in 2013 to 54% in 2015. The probabilities of supplemental nest use and stick-nest building behavior increased over time following a gradient away from the northern extent of Key Largo, an area associated with high cat activity and the only sites of python captures during the surveys. Woodrats that built stick-nests were more detectable than those that did not, which suggests that stick-nest building could make woodrats more susceptible to predation from novel predators when performing the behavior. We documented increasing woodrat occurrence, along with increasing stick-nest building behavior, which supports recovery and management objectives focused on exotic predator removal.

Pursuing packrats: An evaluation of noninvasive detection methods for Neotoma

ABSTRACTWoodrats (Neotoma spp.) are imperiled in large swathes of the United States. Their populations have previously been monitored mainly through live‐trapping and sign surveys. However, these methods are labor‐intensive and either stress captured animals or limited by sign visibility and persistence. As noninvasive alternatives, we deployed baited camera traps and baited track plates to monitor eastern woodrat (N. floridana) presence along rocky outcrops at 4 woodrat reintroduction sites in southern Illinois, USA, during May 2013 (5 camera and track‐plate stations/site) and May and September 2014 (4 camera and track‐plate stations/site) to compare their effectiveness. During each deployment, camera traps detected woodrat presence at all 4 sites while track plates only detected presence at 2–3 sites. A greater proportion of camera traps than track plates recorded detections during each deployment. Camera traps required more person‐hours to deploy and retrieve, but resulted in more detections per hour effort than track plates. We conclude that baited camera traps are superior to baited track plates for detecting and monitoring woodrat presence. © 2018 The Wildlife Society.

Status of Eastern Woodrats in Isolated Remnant Populations Following Genetic Augmentation and Habitat Disturbance

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 <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.

Evaluating nest supplementation as a recovery strategy for the endangered rodents of the Florida Keys

The Key Largo woodrat (Neotoma floridana smalli) and Key Largo cotton mouse (Peromyscus gossypinus allapaticola) are federally endangered subspecies endemic to the tropical hardwood hammocks of Key Largo, Florida. Woodrats are considered generalists in habitat and diet, yet a steady decline in natural stick nests and capture rates over the past several decades suggests that they are limited by the availability of nesting habitat due to habitat loss and fragmentation. The more specialized Key Largo cotton mouse appears to rely on old growth hammock, a habitat type that is rare following past land clearing. In 2004, the U.S. Fish and Wildlife Service started building supplemental nest structures to restore habitat quality and connectivity for these endangered rodents, but nest use requires evaluation. We used camera traps and occupancy models to evaluate the factors influencing woodrat and cotton mouse use of the supplemental nests. We detected woodrats at 65 and cotton mice at 175 of 284 sampled nest structures, with co‐occurrence at 38 nests. Woodrat nest use followed a gradient from low nest use in the north to high nest use in the south, which might relate to the proximity of free‐ranging domestic cat (Felis catus) colonies in residential developments. Cotton mouse nest use, however, was related positively to mature hammock and related negatively to disturbed areas (e.g. scarified lands). The two species occurred independently of each other. Stick‐stacking behavior was observed at supplemental nests and, although it was correlated with detection of woodrats, it was not a strong predictor of their occurrence. We suggest that nest supplementation can be an important tool for species recovery as habitat quality continues to improve with succession.

Effects of habitat modification on cotton rat population dynamics and rodent community structure

Concerns over climate change and finite fossil fuels have generated interest in biofuels. Switchgrass (Panicum virgatum), a biofuel feedstock, was planted in intensively managed loblolly pine (Pinus taeda) stands to investigate sustainability of this system for producing an alternative energy source. We hypothesized that changes in understory habitat conditions caused by intercropping switchgrass in pine stands would affect rodent population and community dynamics within three years. Therefore, we assessed effects of three treatments (control pine, switchgrass intercropped in pine, and switchgrass monocrop) on rodent population (abundance, survival, and recruitment) and community (diversity, richness, evenness, and community assemblages) measures. We conducted vegetation surveys and live-trapping during 2013–2015 summers in Kemper County, Mississippi, USA. We conducted 6 trapping sessions each summer (n=14,112 trap nights per year) and captured 1,733 cotton rats (Sigmodon hispidus), 102 Oryzomys palustris, 31 Mus musculus, 28 Reithrodontomys fulvescens, 22 Reithrodontomys humulis, 20 Peromyscus leucopus, 9 Microtus pinetorum, 9 Peromyscus gossypinus, and 2 Neotoma floridana. We found greater cotton rat abundance and lower recruitment in monocrop versus control plots. Rodent diversity was lower in monocrop than control plots. Intercropped plots had intermediate levels of cotton rat abundance and recruitment, and rodent diversity. More dispersal may have occurred in monocrop plots because of high population abundance and limited habitat availability. Cotton rat survival and rodent community assemblage were similar among treatments but differed among years. Although rodents responded negatively to monocrop plots, our results suggested intercropped plots would be an appropriate management practice in pine plantations to produce biofuel feedstocks while maintaining rodent diversity.

Pondberry (Lindera melissifolia, Lauraceae) seed and seedling dispersers and predators

Pondberry (Lindera melissifolia(Walter) Blume) is an endangered dioecious, clonal shrub that grows in periodically flooded forests of the southeastern United States. The probability of survival of dispersed pondberry seeds and new germinants is unknown, but few seedlings are noted in the forest. This study was undertaken to: (1) identify herbivores and predators of pondberry seeds and seedlings, (2) record the fate of pondberry seeds and seedlings after simulated dispersal in areas with lower and higher understory cover, and (3) calculate the probability of seed survival in the two cover types. The study was conducted in or near the Delta National Forest and the Delta Experimental Forest, MS. Pondberry seed and seedling plots were established at sites with high or low cover. Video cameras with infrared illumination were set up to monitor animal visitors to the plots. Image analysis indicated that swamp rabbits (Sylvilagus aquaticus (Bachman)) and wood rats (Neotoma floridana Ord) cut or ate seedlings, while other animals visited the plots without damaging seedlings. Numerous bird species and mammals visited the seed plots and some were filmed eating seeds. Pondberry seeds exposed in open habitats had a significantly higher survival rate than those exposed in habitats with more herbaceous and woody understory cover. The novelty and quality of the temporal data collected via video monitoring indicate the importance of this method in collecting data that are not otherwise available on endangered and rare species.

Seasonal Variation in Composition of Key Largo Woodrat (Neotoma floridana smalli) Diets

Abstract Neotoma floridana smalli (Key Largo Woodrat) is currently at high risk of extinction from anthropogenic disturbances, including loss and degradation of habitat and non-native predators. Habitat degradation may affect food-resource availability, yet food habits are poorly understood. Therefore, we examined seasonal diets of Key Largo Woodrats using microhistological analysis of fecal samples. We collected fecal material from captured individuals between January 2005 and February 2006 and identified food items to the lowest possible taxon. We classified food items as leaves, fruit, and insects to examine differences in diets between seasons (wet versus dry) and sexes. Fruit and leaves made up a greater percentage of Key Largo Woodrat diets during the wet and dry seasons, respectively, likely reflecting higher fruit availability during the wet season. Across seasons, diets of males had a higher percentage of fruit and insects, but a lower percentage of leaves than females. Greater fruit consumption ...

Multilocus Characterization of a Woodrat (Genus Neotoma) Hybrid Zone

In order to investigate hybridization between 2 species of woodrats, Neotoma floridana and Neotoma micropus, 103 specimens were collected, in March of 1988, from a known area of sympatry, and compared with reference collections from areas of allopatry. Ten genetic markers, consisting of 7 microsatellite loci, 1 mitochondrial gene (cytochrome-b [Cytb]), and 2 nuclear introns (intron 2 of the vertebrate alcohol dehydrogenase gene [Adh1-I2] and intron 7 of the beta-fibrinogen gene [Fgb-I7]) were used to develop a composite genotype for each individual and for detection of hybridization. Six individuals were identified as pure parental N. micropus, 96 as hybrids, and 1 as pure parental N. floridana Hybrids were formed primarily through matings between complex genotypes, resulting in a high prevalence of individuals classified as backcrosses. The ratio of hybrid classes, population substructure, and presence of significant linkage disequilibrium within the zone of contact could not reject either the hybrid superiority or hybrid equilibrium model as responsible for maintenance of this hybrid zone. The collection date of this dataset (1988) provided not only a point in time assessment of the hybrid zone but also provided opportunities for future comparisons of temporal datasets with the purpose of examining hybrid zone characteristics over multiple generations.

Better off in the wild? Evaluating a captive breeding and release program for the recovery of an endangered rodent

The critical question for the success of all captive breeding and release programs (CBRPs) is the same: will the benefit of augmenting or reestablishing a population with captive animals outweigh the loss of taking individuals from the wild? Yet, few studies have simultaneously evaluated the impact of removal of animals for captive breeding on the source population and the potential contribution of the released animals to the augmented populations. We used the endangered Key Largo woodrat (Neotoma floridana smalli, KLWR) as a model system to simultaneously examine the effect of animal removal, captive breeding, and reintroduction on the dynamics and persistence of a wild population. We used mark-recapture and telemetry data, as well as zoo records from a recent CBRP for the endangered KLWR to parameterize a matrix population model and to simulate the response of the KLWR population to alternative captive breeding and release strategies. Our results suggest that a CBRP as practiced previously would not contribute to KLWR recovery; instead, removal of wild KLWR for captive breeding could harm the population. Captive breeding programs will not contribute to the recovery of KLWR unless survival of released animals and breeding success of captive individuals are improved. Our study provides a framework for simultaneous consideration of animal removal from the wild, breeding success in captivity and survival of released animals for a comprehensive evaluation of captive breeding programs.

Are declines of an endangered mammal predation‐driven, and can a captive‐breeding and release program aid their recovery?

AbstractDeclines of imperiled small mammals are often attributed to predation without investigating the relative influence of survival and reproductive parameters on population growth. Accordingly, declines in the endangered Key Largo woodrat Neotoma floridana smalli (KLWR) population have been attributed to predation by feral cats Felis catus, Burmese pythons Python molurus bivittatus and raccoons Procyon lotor. We estimated survival, recruitment and realized population growth rates from four capture–mark–recapture studies to determine if the pattern of demographic variation was consistent with predation as the primary cause of KLWR declines. Additionally, we evaluated the KLWR captive‐breeding and release program by comparing survival of captive‐born and released KLWRs to wild‐born KLWRs. The realized population growth rate of wild‐born KLWRs had a strong pattern of covariation with recruitment; covariation between the realized population growth rate and apparent survival was negligible. Consistent with demographic theory, our results suggest that KLWR population dynamics were driven primarily by variation in recruitment, and that periodic reductions in recruitment led to population declines. We found that the survival curve and the first month (S1) and first 3‐month (S1–3) survival estimates for the wild‐born KLWRs [S1 = 0.929 (0.890–0.968); S1–3 = 0.942 (0.919–0.965)] were considerably higher (χ2 = 33.9, 1 d.f., P &lt; 0.001) than released KLWRs [S1 = 0.521 (0.442–0.600); S1–3 = 0.561 (0.493–0.629)]. Low survival rates from predation limited the success of the captive‐breeding and release program. This study illustrates the importance of pre‐release conditioning of captive‐bred animals and the importance of considering reproductive parameters in conjunction with survival estimates to understand the drivers of population decline.

Reintroduction of the Eastern Woodrat (Neotoma floridana) in Southern Illinois

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.

The vocal repertoire of the Key Largo woodrat (Neotoma floridana smalli)

The Key Largo woodrat (Neotoma floridana smalli) is an endangered rodent endemic to the island of Key Largo, FL. There is little information on vocal communication in this species and descriptions of the acoustic structure of calls are lacking. A captive breeding program was established as part of the recovery plan for the species, providing the opportunity to investigate the vocal repertoire and acoustic structure of calls in both wild and captive contexts. Audio and video recordings were conducted at the Crocodile Lake National Wildlife Refuge in Key Largo and at Disney's Animal Kingdom(®). Analysis of the acoustic structure of calls resulted in four provisional call types: "Tonal calls" consisted of "ultrasonic vocalizations" (40 kHz fundamental frequency, F(0)), "high squeaks" (10 kHz F(0)), and "squeaks" (1.8 kHz F(0)). "Noisy," broadband calls known as "raspy" vocalizations did not exhibit fundamental frequencies, but contained several prominent spectral peaks (from 9 to 40 kHz). The social contexts of vocal production showed that all four call types were associated with pup need or interactions between pups and dams, and that raspy vocalizations were associated with courtship and copulation. Adults without pups exhibited little or no vocal activity, which may result from solitary lifestyles and predator avoidance.

New Records ofOnthophagus cavernicollisHowden and Cartwright (Coleoptera: Scarabaeidae) from Ozark Caves, with a Review of Scarabaeoids Reported from North American Caves

ABSTRACT Recent collecting in caves in the Ozark region of the USA produced a number of new scarab beetle records (Coleoptera: Scarabaeoidea). We report our collections and review literature records of scarabs reported from caves in the USA and Canada. Most of these records are accidental occurrences, but a few represent widespread species with known associations to host vertebrates that may occupy a cave. Two species, Onthophagus cavernicollis Howden and Cartwright (Scarabaeidae: Scarabaeinae), and Stenotothorax gardneri (Gordon) (Scarabaeidae: Aphodiinae), appear closely tied to woodrat, Neotoma floridana (Ord) (Rodentia: Cricetidae), nests. We consider the cave association of these two species, categorizing them as troglophiles. The distribution of O. cavernicollis is mainly in the Ozark region, but this pattern may be due to inadequate sampling in other locations. Stenotothorax gardneri is known only from caves in the Ozark region. All available collection records from recent work, museum specimens an...

Notes on the Distribution of Bailey's Eastern Woodrat (Neotoma Floridana Baileyi) in Nebraska

ABSTRACT. The eastern woodrat (Neotoma floridana) occurs in eastern and central parts of the United States, with 3 subspecies inhabiting Nebraska. Herein, we report on distributional records of N. f. baileyi—an isolated, disjunct subspecies in north-central Nebraska. We searched for diagnostic sign of woodrats in 4 counties in Nebraska and 1 county in South Dakota. We obtained distributional records for N. f. baileyi east, west, and north of known distribution limits in Nebraska, but none in South Dakota. Most distributional records represent range extensions because of lack of prior mammalian surveys in those areas. Observations of woodrats in isolated, human-established woodlots surrounded by prairies represent range expansions because such habitats were not present in the past.

Estimating abundance of cryptic but trappable animals using trapping point transects: a case study for Key Largo woodrats

Summary1. Obtaining robust abundance or density estimates is problematic for many rare or cryptic species. We combine elements of capture–recapture and distance sampling, to develop a method called trapping point transects (TPT), and we applied this method to estimate the abundance of the endangered Key Largo woodrat (Neotoma floridana smalli).2. Trapping point transects requires two separate surveys to be held concurrently in space and time. In the main survey, the encounter rate (number of animals caught per trap per session) is measured. In the trial survey, animals whose locations are known prior to opening traps are used to estimate the detection function g(r) (the probability of capturing an animal given it is distance r from a trap when it is set), so the effective trapping area in the main survey can be estimated. It is assumed animals in the trial survey are a representative sample of all animals in the population. Individual heterogeneity in trappability is accommodated using random effects in g(r).3. Performance of two TPT estimators was assessed by simulation. Generally, when underlying capture probabilities were high [g(0) = 0·8] and between‐individual variation was small, modest survey effort (360 trap nights in the trial survey) generated little bias in estimated abundance (c. 5%). Uncertainty and relative bias in population estimates increased with decreasing capture probabilities and increasing between‐individual variation. Survey effort required to obtain unbiased estimates was also investigated.4. Given the challenges of working with cryptic, sparse or nocturnal species, we tested the validity of this method to estimate the abundance of the Key Largo woodrats between 2008 and 2011.5. Trapping point transects was found to be an effective monitoring method yielding annual estimates of the extant wild population of 693, 248, 78 and 256 animals, with CVs of 0·45, 0·55, 0·82 and 0·43, respectively. The TPT method could be adapted to a range of species that are otherwise very difficult to monitor.

Glomerulonephropathy in Aged Captive Key Largo Woodrats (Neotoma floridana smalli)

A retrospective review of mortality records of Key Largo woodrats (Neotoma floridana smalli) in a captive breeding program revealed chronic renal disease in 5 of 6 woodrats older than 4 years of age. Two of the 5 woodrats with chronic renal disease also had clinical evidence of diabetes mellitus. Kidneys from all 5 woodrats were examined via light microscopy, histochemical staining, immunohistochemical staining, and transmission electron microscopy. The dietary histories of the affected animals were examined as well. The most striking histopathologic abnormality in the affected kidneys was the presence of large protein casts within cortical and medullary tubules in combination with lesions of membranous glomerulopathy and glomerulosclerosis. Transmission electron microscopy revealed thickening and undulation of the tubular and glomerular mesangial basement membranes with the variable presence of electron-dense deposits within the capillary endothelial basement membrane. Patchy glomerular immunoreactivity for IgG was noted in 2 cases, but IgA and IgM immunoreactivity were not present. The pathologic changes in the kidneys of the Key Largo woodrats mirrored many of the features of chronic progressive nephropathy commonly diagnosed in laboratory rats. Woodrats in the captive population were fed an ad libitum high-protein diet similar to diets that have been shown in laboratory rats to exacerbate the development and progression of chronic progressive nephropathy. It is concluded that Key Largo woodrats develop glomerulonephropathy with features similar to chronic progressive nephropathy described in laboratory rats. Age, concomitant disease, and dietary factors may contribute to the development and severity of this potentially age-limiting disease in Key Largo woodrats.

Attributes of Rock Crevices Selected by Allegheny and Eastern Woodrats in the Zone of Contact in the Appalachian Mountains of North Carolina

We investigated the attributes of rock crevices selected by Allegheny (Neotoma magister) and eastern woodrats (N. floridana haematoreia) in their zone of contact in the Appalachian Mountains of North Carolina. In North Carolina, N. magister and N. f. haematoreia both occur in rocky habitats above 300 m, and are listed as species of special concern. We studied 14 active sites (N. magister: n = 9; N. f. haematoreia: n = 5) where woodrats had been captured 1 y prior to our study and identified to species using the mitochondrial DNA D-loop analysis. At each site, we measured the attributes of 10 crevices used by woodrats and 10 corresponding random crevices located < 15 m from each used crevice. Neotoma magister and N. f. haematoreia selected crevices with larger dimensions (height, width and depth) and more internal fissures (openings >5 cm in diameter) than those available in the surrounding environments. All crevices used by N. magister (n = 90) and N. f. haematoreia (n = 50) were dry. Neotoma magister were more specialized than N. f. haematoreia, as they selected crevices that were south-facing. These results suggest that both N. magister and N. f. haematoreia are habitat specialists in the southern Appalachians, preferring crevices with larger dimensions and more internal fissures to enhance their protection against severe weather and predators. The preference for south-facing crevices by N. magister suggests that they may be better adapted at surviving colder climatic conditions, thus enabling them to inhabit higher elevations in the mountains. Based on these specialized habitat preferences, we suggest that suitable rock crevices may be a limiting factor to both species in the southern Appalachians. In addition, the similarity in attributes of rock crevices selected by these species suggests that habitat is not a factor that will prevent hybridization between these species where they co-occur in the mountains of North Carolina.

Distribution of the Eastern Woodrat (Neotoma Floridana Campestris) in Southern Nebraska

The eastern woodrat (Neotoma floridana) occurs throughout eastern and central parts of the United States. In Nebraska, 3 of 9 subspecies inhabit the state, including N. f. campestris, N. f. attwateri, and N. f. baileyi. We determined distributional limits of N. f. campestris along 2 river systems in southern Nebraska. As observed with other mammalian species in the Great Plains, we suspected that the distribution of woodrats likely had expanded, reflecting continued regulation of rivers and the concomitant increase in forests along them. We documented N. f. campestris at 7 sites in 5 counties, including a recent (since the 1960s) eastward expansion along the Republican River. We observed little movement along the Platte River. The greatest concentration of houses constructed by woodrats occurred in a shelterbelt near the Republican River; otherwise, abundances of houses tended to be greater along the Platte River. We suspect that the distribution of woodrats will continue to change in Nebraska unless breaks exist or are established in riparian forests along the Platte and Republican rivers.

Evaluation of Factors Restricting Distribution of the Endangered Key Largo Woodrat

ABSTRACT We examined a suite of models in an information theoretic framework to identify factors restricting presence of the endangered Key Largo woodrat (Neotoma floridana smalli) throughout its remaining habitat. Models containing variables related to availability of nest sites and mammalian predator abundances were supported by our data. Abundance of natural (large overstory trees) and artificial (rock and debris piles) nest substrate were the most important predictor variables, followed by indices of feral cat and raccoon (Procyon lotor) abundance. We recommend increasing abundance of nest substrate in the short term through addition of artificial nest substrate and in the long term through continued protection of remaining forest habitat.

Summer Resting and Den Site Selection by Eastern Spotted Skunks (Spilogale putorius) in Arkansas

Denning and resting site use by radiocollared eastern spotted skunks (Spilogale putorius) in the Ouachita Mountains of western Arkansas was investigated from May through August 2005 and 2006. We identified and characterized microhabitat and landscape characteristics of 127 resting and den sites. Sites were located in burrows excavated by other mammal species (48%), in decayed or burned root systems (22%), in rocky outcrops (14%), in eastern woodrat (Neotoma floridana) nests (9%), or in ground-level tree or log cavities (7%). Reuse of sites by the same individual was common (32.3%), but use of the same site by different individuals was rare, as was communal use of sites (<1.0% each). Contrasting used and putatively available dens and resting sites, we found that sites were selected based primarily on increased vegetative cover, which supports hypotheses that thermal regulation and predator avoidance may underlie den and resting site selection. Higher rock and vine densities, younger pine forest stands, older hardwood stands, steeper slope, and smaller site entrance also positively influenced resting and den site selection. These findings suggest that eastern spotted skunks select structurally complex sites, likely to enhance protection from predators. Eastern spotted skunks may thus be vulnerable to habitat alterations that reduce this structural complexity.