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Invasive Burmese pythons (Python bivittatus) in the Everglades of Florida, United States, have drastically reduced populations of mammals, yet populations of some rodents appear unaffected by the invasion. To understand this pattern, we radio-tagged cotton rats (Sigmodon hispidus) in areas of high and low python occurrence densities (hereafter occurrence) and quantified the effects of python occurrence, seasonality, and sex on their survival and cause-specific mortality. Cotton rat survival was not influenced by difference in python occurrence (hazard ratio = 1.32, 95% CI = 0.77–2.26, P = 0.30). However, cotton rats were at greater risk from mortalities caused by mammals in areas of low python occurrence. In areas with elevated python occurrence, we attributed most cotton rat mortalities to birds of prey (48.6%) and reptiles (non-python = 24.3%, python = 16.2%). Where python occurrence was relatively low, we attributed cotton rat mortalities to native reptilian (28.6%), avian (35.7%), and mammalian predators (35.7%) with no python-related deaths. In total, pythons were responsible for 11.8% of all cotton rat mortalities. Finding no difference in the survival of cotton rats, despite differences in the causative agents of mortality, suggests that predation pressure from an invasive predator was compensatory for cotton rat population dynamics. This type of compensatory mortality is common for small mammals and helps explain why mammal communities in python-invaded portions of the Greater Everglades Ecosystem are increasingly dominated by cotton rats and other rodents. [ABSTRACT FROM AUTHOR]

Harnessing the fear animals have of humans has the potential to aid in the conservation of wildlife. Most vertebrates perceive humans as "super predators." While predator cues are an important nonlethal management tool, the use of human cues for management has rarely been implemented or experimentally tested. Extensive poaching is threatening the persistence of white rhinos (Ceratotherium simum simum), and there is a need to deter them from areas with elevated poaching risks. To investigate the feasibility of harnessing the fear white rhinos have of humans to aid in their conservation, we conducted playback experiments at rhino middens. We broadcasted repeated human (treatment) and bird (control) vocalizations, and measured changes in visitations and antipredator responses. We found that overall rhino visitations did not change in response to controls but decreased by 46% in response to human vocalizations. This pattern appears to be driven by the response of females, who decreased their visitations by 70% in response to human vocalizations, while visitations by males remained unchanged. This difference is likely related to males defending small exclusive territories. Providing evidence that changes in female visitation rates were a function of the perceived fear of white rhinos, we found that both sexes exhibited more vigilance in response to human vocalizations (males 69.5%, females 96%) compared to controls. We also saw a 63% reduction of other herbivores at treatment sites. Our findings provide evidence that the fear of humans can be used to alter the movements and behavior of female white rhinos, critical for population recovery, as well as other large herbivores. [ABSTRACT FROM AUTHOR]

An animal's pelage, feather, or skin color can serve a variety of functions, so it is important to have multiple standardized methods for measuring color. One of the most common and reliable methods for measuring animal coloration is the use of standardized digital photographs of animals. New technology in the form of a commercially available handheld digital color sensor could provide an alternative to photography-based animal color measurements. To determine whether a digital color sensor could be used to measure animal coloration, we tested the ability of a digital color sensor to measure coloration of mammalian, avian, and lepidopteran museums specimens. We compared results from the sensor to measurements taken using traditional photography methods. Our study yielded significant differences between photography-based and digital color sensor measurements of brightness (light to dark) and colors along the green to red spectrum. There was no difference between photographs and the digital color sensor measurements for colors along the blue to yellow spectrum. The average difference in recorded color (ΔE) by the 2 methods was above the threshold at which humans can perceive a difference. There were significant correlations between the sensor and photographs for all measurements indicating that the sensor is an effective animal coloration measuring tool. However, the sensor's small aperture and narrow light spectrum range designed for human-vision limit its value for ecological research. We discuss the conditions in which a digital color sensor can be an effective tool for measuring animal coloration in both laboratory settings and in the field. [ABSTRACT FROM AUTHOR]

Disturbance by large herbivores, fires, and humans shapes the structure of savannas, altering the amount of woody vegetation and grass. Due to change in the intensity and frequency of these disturbances, savannas are shifting toward grass-dominated or shrub-dominated systems, likely altering animal communities. Small mammals are critical components of savannas, and their distributions likely are affected by these ecosystem-wide changes in vegetative cover. We assessed the responses of small mammals to a gradient of woody cover in low-lying savannas of southeastern Africa. In Kruger National Park (South Africa) and in three nearby reserves (Eswatini), we livetrapped for over 2 years to build multispecies occupancy models that assessed the responses of the small mammal community to grass and woody cover. Overall, whole-community occupancy increased with grass biomass. More species responded positively to woody cover than to grass biomass, but woody cover was associated with reduced occurrence of one species (Mastomys natalensis). Our results suggest that an increase in grass biomass enhances whole-community occupancy of small mammals, but regional diversity is likely to be higher in areas that contain patches of high grass biomass as well as patches of woody cover. [ABSTRACT FROM AUTHOR]

For polytypic mammal species, biogeographic barriers including rivers have often been used to delineate taxonomic units under the assumption that barriers have structured their distribution. We tested the importance of major riverine systems as biogeographic barriers in fox squirrels (Sciurus niger) across the state of Florida, where 4 currently recognized subspecies are delineated at major rivers. We also explored whether phylogeographic structure may be limited to ecologically divergent subspecies, specifically between S. n. avicennia and S. n. shermani. Using a multilocus approach to examine diversity, we found that restricted gene flow was only present between S. n. avicennia, located south of the Caloosahatchee River in south Florida, and the rest of S. niger, which is widespread across the state. Mitochondrial DNA revealed that 2 divergent groups of haplotypes are present and widespread across Florida, thus supporting the hypothesis that fox squirrels persisted in multiple refugia during the Pleistocene, and that S. n. avicennia diverged ecologically from other populations of fox squirrels relatively recently. This was supported by isolation with migration models that indicated matrilineal isolation since the onset of divergence between S. n. avicennia and S. n. shermani, which corresponds to the onset of ecological divergence in south Florida during the early Holocene. Isolation by distance at 8 microsatellite loci from the western panhandle to the southern end of the peninsula was significant only when S. n. avicennia was included; however, this was due to the hierarchical genetic patterns identified between S. n. avicennia and the other subspecies as determined by Bayesian clustering, and not due to spatially restricted dispersal. We postulate that the demographic isolation of S. n. avicennia is the result of adaptation to the unique ecological conditions of south Florida. [ABSTRACT FROM AUTHOR]

Understanding the distributions and environmental associations of rare species is a critical 1st step in their conservation and management. Federally endangered Florida bonneted bats (Eumops floridanus) are endemic to southern Florida and are believed to have one of the most limited geographic distributions of any bat in the United States. We conducted a large-scale acoustic survey of 330 points spread across approximately 38,000 km2 over a 2-year period and used a hierarchical Bayesian approach accounting for imperfect detection to model the distribution and environmental associations of the Florida bonneted bat. Bat occupancy was negatively correlated with the amount of developed land within 5 km of the sampling point and positively correlated with the amount of crop-based agriculture within 5 km of the sampling point. Bat occupancy probabilities increased with the 30- year mean for minimum spring temperature and levels of annual precipitation, and decreased with the 30-year mean for levels of spring precipitation. Bat detection was positively influenced by Julian date and minimum temperature of the survey night. This study offers new insight into the habitat use of this endangered species. Results confirm that predicted changes in land cover and climate will be threats to the Florida bonneted bat. [ABSTRACT FROM AUTHOR]

Restoration of the longleaf pine (Pinus palustris; LLP) ecosystem and its associated fauna is a principal goal of many land-management agencies in the southeastern United States. Prescribed fire and herbicide application are 2 common methods of LLP restoration. We employed a multi-scale approach to investigate how occurrence of fox squirrels (Sciurus niger) was influenced by fire frequency and herbicide application in LLP communities of northern Florida. We sampled 9-point, 4-ha grids of camera traps with 106 grids in fire treatments, 23 herbicide treatment grids, and 27 control grids. We evaluated a priori models for occurrence of fox squirrels at point, 4-ha patch, and home-range scales, and the influence of fire and herbicides on vegetation structure. Fox squirrel occurrence was positively associated with densities of turkey oak (Quercus laevis) at the patch scale, which were significantly less abundant in herbicide-treated areas. Fox squirrel occurrence was negatively correlated with fire interval and positively correlated with oak densities at a localized point scale. Additionally, fox squirrel point occurrences declined over time since the last fire. Fire produced habitat more favorable for fox squirrels than did herbicide treatments. [ABSTRACT FROM AUTHOR]

Estimates of the demographic information necessary to project future population changes are lacking for the endangered Florida bonneted bat (Eumops floridanus). We conducted a mark-recapture study on a population of bonneted bats using bat houses on Babcock-Webb Wildlife Management Area, Charlotte County, Florida, United States. We captured 175 individuals during 6 capture events that recurred every 4 months between April 2014 and December 2015. We implanted passive integrated transponder tags in all captured individuals and used open population capture-recapture models to estimate apparent survival, recruitment, and population growth rates of this population. Key model assumptions were evaluated via simulation. Apparent survival estimates were lower than estimates for most other bat species. Juveniles had lower annual apparent survival (φ = 0.09 [95% confidence interval [CI]: 0.04-0.19]) than adults (φ = 0.46 [0.36-0.57]). Recruitment was constant between sexes and over time (f = 0.48 [0.23-0.75]). Apparent survival had a greater influence on population growth rates than did recruitment, indicating that low survival rates could lead to population declines. Models of population growth rates showed a stable to potentially declining population trend, although the trend was highly variable, with estimates ranging from large declines to increases (λ = 0.89 [0.65-1.22]). Any potential declines in the population may be more pronounced in adult females (λ = 0.81 [0.58-1.13] compared to λ = 1.11 [0.74-1.69] for males); however, the 95% CI of the population growth rate included 1, indicating a need for additional research to derive more precise estimates. This work represents the 1st estimates of demographic parameters of this endangered species. [ABSTRACT FROM AUTHOR]

We used southeastern fox squirrels (Sciurus niger) in the southeastern United States as an example of how modern approaches to estimate density coupled with a reevaluation of previous estimates can provide important new insights into the management and conservation of mammals. There are few rigorous density estimates of southeastern fox squirrels, which hinders our ability to manage and conserve their populations. Based on an initial estimate from 1957 of 38 squirrels/km2 and subsequent decreases in estimates of population densities, noted decreases in hunter harvest reports, and anecdotal observations, southeastern fox squirrels are believed to be declining. To assess the extent of this decline, we first estimated the density of a subspecies of southeastern fox squirrel, Sherman's fox squirrel (S. n. shermani), using live trapping and camera trapping and modern analytical approaches for mark-recapture analysis. Then, to compare our densities to previous work, we calculated a standardized effective survey area correction factor for past studies and recalculated their population densities. Once standardized, we found little temporal or geographic variation in densities of southeastern fox squirrels (2.4-8.5 squirrels/km2) spanning nearly 70 years of research. Past densities were substantially lower than initially reported with corrected survey areas, suggesting that densities may have always been naturally low but were incorrectly inflated due to study designs and statistical approaches. Moreover, corrected densities from all studies were correlated with the bounded survey area, suggesting that researches aiming to estimate population densities of southeastern fox squirrels were frequently conducted at scales too small relative to the size of their home ranges. The use of methodological and analytical approaches such as those used in this study may help to avoid misdirected conservation designations or management actions and misuse of conservation funding. [ABSTRACT FROM AUTHOR]

We were able to substantially increase our knowledge of what is likely the least understood endangered terrestrial mammal in the United States, the Florida salt marsh vole (FSMV; Microtus pennsylvanicus dukecampbelli). We developed a predictive landscape model that estimated 264 ha of potential habitat for FSMVs. Evaluating our model, we found voles at 8 of the 36 sites sampled, yielding a model accuracy of 22% for a subspecies that previously was known from only 3 locations. Within areas of potential habitat, FSMVs selected patches of marsh vegetation > 0.49 ha with at least some (≥ 16.75% and ≤ 43.61%) smooth cordgrass (Spartina alterniflora) cover. Suggestive of a meta-population dynamic, FSMV activity decreased outside of patches of smooth cordgrass and saltgrass (Distichlis spicata) identified by the predictive landscape model. Our hierarchical approach to studying FSMVs allowed us to leverage a limited amount of data to ultimately produce important ecological information about an endangered species. This approach easily may be adapted to other mammals with similar information needs. [ABSTRACT FROM AUTHOR]

Yellow warblers, Setophaga petechia, respond to brood parasitic brown-headed cowbirds, Molothrus ater, by giving "seet" alarm calls and rushing to protect their nests. These responses are typically given in populations sympatric with cowbirds, but rarely in allopatric populations. Whether the lower expression in allopatry has a genetic basis or instead could be explained by behavioral plasticity has not been investigated. We found that warblers exposed to cowbirds in Montana (sympatric) responded significantly more often to cowbird models with seet calls (85.7%) and nest protection behavior (80.0%) than conspecifics breeding in long-term isolation from cowbirds in Alaska (allopatric, 27.3% and 16.7%, respectively). Warblers breeding in Idaho, which were locally isolated from cowbirds (naive) but presumed to be genetically similar to nearby parasitized warblers, were significantly less likely than sympatric warblers to respond to cowbird models with seet calls (30.3%) and nest protection (17.3%). The lower responsiveness of naive warblers implies behavioral plasticity in trait expression, indicating that the lower responsiveness of allopatric warblers relative to sympatric warblers could be explained entirely by plasticity. The lower expression of these defenses in the absence of cowbirds may contribute to their persistence by minimizing potentially costly recognition errors. [ABSTRACT FROM AUTHOR]

We used the imported red-ire ant (Solenopsis invicta; hereafter ire ant) and hispid cotton rat (Sigmodon hispidus) as model species to address the population-level effects of an invasive ant on a semiprecocial small mammal. We stocked cotton rats into 8 enclosures, implementing a 2-way factorial design with predator (ambient or excluded) and ire ant (ambient or reduced) treatments as factors. We trapped monthly from June 2012 to June 2013 and calculated monthly recruitment and survival. Rats in enclosures with ambient predators had a risk of mortality approximately 2 times greater than rats in enclosures with predators excluded. The risk of mortality was 3 and 4.5 times greater for female and male cotton rats, respectively, in enclosures with ambient ire ants and predators compared to enclosures with reduced ire ants and excluded predators. We found no effects on recruitment. Our results indicate that native predators had the greatest influence on cotton rat populations. Nevertheless, in the absence of other predators, the effects of ire ants on cotton rat survival are compensatory. [ABSTRACT FROM AUTHOR]

The article presents a list of reviewers for the "Journal of Mammalogy" in 2013 and 2014 which includes Lone Aagesen, Layne George Adams, and Todd Ahearn.