Explore the vast range of titles available.

Fluorescence of visible wavelengths under ultraviolet (UV) light has been previously detected in a wide range of birds, reptiles, and amphibians and a few marsupial mammals. Here, we report the discovery of vivid UV fluorescence of the pelage in Glaucomys, the New World flying squirrels. Fluorescence in varying intensities of pink was observed in females and males of all extant species (G. oregonensis, G. sabrinus, and G. volans) across all sampled geographic areas in North and Central America and a temporal range of 130 years. We observed fluorescence in museum specimens (n = 109) and wild individuals (n = 5) on both dorsal and ventral surfaces. Museum specimens of three co-occurring, diurnal sciurid species (Sciurus carolinensis, S. niger, and Tamiasciurus hudsonicus) were also examined but did not fluoresce. The ecological significance of this trait in the nocturnal–crepuscular flying squirrels warrants further investigation.

The genus Glaucomys (New World flying squirrels) is currently considered to be comprised of 2 species, the northern flying squirrel (G. sabrinus) and the southern flying squirrel (G. volans). We synthesize new information from mitochondrial DNA (mtDNA) control region sequences and microsatellite data to demonstrate that the genus consists of 3, rather than 2 species, and that Glaucomys sabrinus, as currently recognized, is actually composed of 2 separate, apparently non-hybridizing species. Control region mtDNA data from 185 individuals across North America revealed 2 distinct clades embedded within G. sabrinus: a widespread “Continental” lineage and a more geographically restricted “Pacific Coastal” lineage. The geographic distributions of these 2 lineages are largely mutually exclusive, with sympatry observed at only 3 sites in the Pacific Northwest. Analysis of 8 microsatellite loci showed no evidence of hybridization between the 2 lineages of G. sabrinus in the region of sympatry. This lack of gene flow is noteworthy given that populations of the Continental lineage of G. sabrinus have been shown to hybridize with G. volans in southeastern Canada. Finally, phylogenetic analyses and estimates of divergence times show that G. volans and Continental G. sabrinus are actually sister taxa that diverged from one another more recently than either did from Pacific Coastal G. sabrinus. We propose that these observations provide strong evidence for a third, previously unrecognized species of North American flying squirrel, whose geographic range extends along the Pacific Coast from southern British Columbia to southern California. Glaucomys oregonensis (Bachman, 1839), whose type locality is in Oregon, is the senior available name for this taxon. We propose that this newly recognized species be given the common name “Humboldt's flying squirrel.”

Camera traps are becoming an increasingly important tool to survey wildlife populations. However, the application of camera trapping for reliable species identification between nondistinctive, morphologically similar sympatric species is untested for most small mammals, including North American flying squirrels (Glaucomys spp.). Camera traps are a successful monitoring technique where flying squirrel species are allopatric, however there are zones of sympatry between Humboldt's flying squirrel (HFS, G. oregonensis) and northern flying squirrel (NFS, G. sabrinus) in the Pacific Northwest and NFS and southern flying squirrels (SFS, G. volans) in eastern North America. We used camera trap data collected during flying squirrel surveys in 2013–2020 at 59 sites in California, North Carolina, and Virginia, USA, to determine if a reliable method could be used to differentiate the species. With a subset of 100 high-quality, independent capture events per species (50 of dorsal views, 50 of lateral views), we used body measurements and pelage characteristics to differentiate species using random forest classification models. Our models predicted species identification accuracy rates of 90.9% for dorsal views and 68.2% for lateral views. Species misclassification rates between HFS and NFS were 23.5% for dorsal views and 26.5% for lateral views, whereas misclassification rates between NFS and SFS were 16.6% for dorsal views and 5.7% for lateral views. Although misclassification rates were lower than we expected between NFS and SFS, we are cautious about recommending camera trapping as opposed to ultrasonic acoustics for NorthAmerican flying squirrel species identification, especially in areas of species sympatry due to potential false positive rates and high numbers of unusable images. However, camera trap settings and white-flash photography should be explored to determine their potential for improving flying squirrel species classification rates and the percentage of usable photos.

The northern flying squirrel (Glaucomys sabrinus) is a mycophagous specialist (i.e., having a fungi‐dominated diet) which might be displaced following northward range expansion by the congeneric southern flying squirrel (Glaucomys volans). Loss of the northern flying squirrel could, in turn, limit fungi spore dispersal in forest communities. To understand the potential implications of squirrel species turnover on fungal dispersal, we investigated the home ranges, habitat selection, and fungi consumption of the two flying squirrel species living in sympatry in Ontario, Canada. We live‐trapped flying squirrels for more than one year (2020–2021), deployed 31 radio collars (northern, n = 13; southern, n = 18), and radio‐tracked individuals to investigate home range size. We also collected fecal pellets to quantify fungi in the squirrels' diet. Both squirrel species had similar home range sizes, and there was evidence of considerable home‐range overlap between the species. Habitat selection analysis using a binomial generalized linear model of mean selection ratios indicated that southern flying squirrels selected deciduous‐dominated habitats more than northern flying squirrels did within their home ranges and that both species selected pine‐oak‐barren habitats. Finally, we identified that northern flying squirrels had significantly higher spore loads and spore richness in their scat than their southern counterparts. Nevertheless, southern flying squirrels consumed fungi during each season. We conclude that the two squirrel species share many aspects of the landscape but habitat partitioning and differences in diet between species facilitated sympatry. Southern flying squirrels do make a contribution to spore dispersal at this location through fungus consumption and relatively large home ranges.

Effective conservation and management of small mammals require knowledge of the population dynamics of co-occurring species. We estimated the abundances, autocorrelations, and spatiotemporal associations of 4 small-mammal species from 2011–2016 using live-trapping mark-recapture methods on 9 sites across elevation and canopy openness gradients of a late-successional forest in the H. J. Andrews Experimental Forest, on the west slope of the Oregon Cascades. We also quantified species-specific spatial variation in adult sex ratios and body mass. We used Huggins closed capture models to estimate site- and year-specific abundances of 4 target species: Humboldt’s flying squirrels (Glaucomys oregonensis), Townsend’s chipmunks (Neotamias townsendii), western red-backed voles (Myodes californicus), and deer mice (Peromyscus maniculatus). We estimated the temporal autocorrelations among site- and species-specific abundance estimates and used generalized linear mixed effects models to investigate the effects of 7 spatiotemporal covariates on species-specific mean abundance estimates. Species-specific adult sex ratios, juvenile to adult ratios, and adult body masses were not widely variable among study sites. Abundance estimates varied by as much as 4-fold among years and 6-fold among sites. Humboldt’s flying squirrel abundance was temporally autocorrelated at intervals of 1 and 5 years, Townsend’s chipmunk abundance was temporally autocorrelated at intervals of 1–4 years, and western red-backed vole abundance was temporally autocorrelated at 1, 4, and 5 years. Mean fall abundance estimates were associated with elevation and climate and in some cases, canopy openness and berry-producing shrubs, but the direction of the association differed among species for some covariates. Our findings could provide additional management tools for small-mammal abundance objectives, and highlight the importance of careful covariate selection in studies using indices of small-mammal abundance.

New World flying squirrels, Glaucomys spp., are nocturnal arboreal sciurid rodents that have been previously surveyed for coccidial parasites. To date, 4 species of Eimeria have been reported from 2 species of Glaucomys. Here we report 2 species of eimerians from southern flying squirrels (Glaucomys volans) and the endemic Prince of Wales flying squirrel (Glaucomys sabrinus griseifrons). Oocysts of Eimeria dorneyi Levine and Ivens were found to be passing in the feces of 4 G. s. griseifrons from Alaska and a new species of Eimeria was present in feces from 6 G. volans from Arkansas. Oocysts of Eimeria hnidai n. sp. are ellipsoidal with a bilayered wall, measure 23.7 × 13.7 µm, and have a length/ width (L/W) ratio of 1.7; a micropyle and oocyst residuum are absent but polar granule(s) are present. Sporocysts are ellipsoidal–elongate and measure 11.8 × 4.9 µm, L/W 2.2; Stieda body is present but sub-Stieda and para-Stieda bodies are absent. The sporocyst residuum is composed of small indistinct granules along the edge or in the center of the sporocyst. This is the first coccidian reported from G. volans from Arkansas as well as the initial coccidian (E. dorneyi) reported from G. s. griseifrons from Alaska. We also provide a summation of the coccidia known from North American flying squirrels.

New technologies allow for more efficient and effective monitoring of rare or elusive species. However, standardizing protocol to ensure high detection rates is important prior to widespread use of a new technique. The use of ultrasonic acoustic detectors to survey for flying squirrels (Glaucomys spp.) is a novel method that is more efficient than traditional methods. However, certain methodologies for this technique still need to be refined. During 2015, we conducted a seasonal and habitat quality study on the endangered Carolina northern flying squirrel (G. sabrinus coloratus) in western North Carolina, USA. Our seasonal study examined differences in probability of detection (POD) and latency to detection (LTD) at 30 high-quality sites across 10 survey nights in spring, summer, and autumn. The habitat quality study focused on POD and LTD among 15 sites with varying habitat quality (5 High, 5 Medium, 5 Low) across 20 survey nights. We found POD similar between seasons, with POD 15–20% greater during spring. The LTD was comparable among seasons. We found that POD and LTD varied at sites with different habitat quality. The POD was similar between High and Medium sites (0.26 ± 0.04 SE and 0.29 ± 0.05, respectively), but greater than Low sites (0.02 ± 0.02). The LTD was not different among sites with differing habitat quality, although LTD at High sites was 2.7 and 4.5 times lower than Medium and Low sites, respectively. Trill calls, the most distinctive species-specific call type produced by species of flying squirrels, was recorded at greater rates in spring versus other times of the year. Our results indicate flying squirrels can be surveyed during any season, although habitat quality needs to be considered when determining survey length. For Carolina northern flying squirrel, the optimal time to perform acoustic surveys is during the spring season for 6–10 survey nights at sites with high or medium habitat quality.

1. Glucocorticoids (GC) are integral to the stress response of vertebrates to environmental challenges. Their impact is immediate and widespread, and prolonged exposure can result in major activational and organizational changes. The vertebrate body has two mechanisms to limit GC impact: first, a rapid negative feedback system to turn off their release, and second, a protein — corticosteroid-binding globulin (CBG) — to prevent them being free in the blood. Species used in biomedical research have CBG levels that normally bind 90—95% of blood GC. This evidence was the basis for the 'Free Hormone Hypothesis,' which posits that only unbound, free hormone is available for use by tissues and is biologically active. High levels of free GC typically occur only under conditions of chronic stress and are associated with major suppression of key body functions. The hypothesis proposes that the primary role of CBG is to render GCs unavailable, thereby preventing tissue exposure. 2. From a field study in southern Ontario on northern (Glaucomys sabrinus) and southern (Glaucomys volans) flying squirrels, we found virtually no CBG binding capacity in their plasma, resulting in only about 10% of cortisol being bound throughout the year. However, neither species showed any evidence of being physiologically compromised. This presents a major challenge to the potential consequences of chronically high levels of free GC. 3. To assess the generality of this finding, we carried out a phylogenetic comparison of 91 vertebrate species in which both GC and CBG levels were measured. In 93%, CBG levels were sufficient to bind about 90% of circulating GCs. This evidence is thus concordant with that from biomedical research. However, both flying squirrel species and four species of New World monkeys were extreme outliers. These two groups had the highest GC concentrations, but relatively little binding capacity (10% or less of their GC was bound). 4. An ancestor state reconstruction of the proportion of GCs bound indicated that the flying squirrels and New World monkeys evolved this character state from ancestors that followed the common 90% bound pattern. It also indicated that the original vertebrates — the earliest fishes — have most of their GC in the free state and little or no steroid-binding protein. 5. We thus demonstrate a dichotomous pattern with respect to CBG: a dominant branch, where high levels of CBG bind most of the GC, applies to the majority of vertebrates; and a secondary branch, where low levels of CBG bind almost none of the GC, applies to a very small subset. For the latter, the critical unknown is how these species mitigate the impact of the high free GC levels and how such a dramatic trait shift could evolve.

Studies determining and categorizing ultrasonic calls in mammals have generally been limited to laboratory experiments with mice and rats or field research on bats. However, recent studies have discovered high-frequency sounds in several mammalian taxa. We describe the vocal repertoire of high-frequency calls in two species of North American flying squirrels (Glaucomys sabrinus and G. volans). We collected passive recordings from captive colonies of G. sabrinus and G. volans to generate a library of calls for each species. Using visual and auditory assessments, as well as quantitative measurements (i.e., spectral and temporal characteristics), we identified 10 specific call-types for G. sabrinus and 27 specific call-types for G. volans. The most common call-types emitted by G. sabrinus included arc chirps, tonal chirps, two-toned chirps, trills, and upsweeps; and for G. volans included arc chirps, barks, descending crows, tonal chirps, and trills. Additionally, we recorded two call-types made by G. volans juveniles: trills and tonal chirps. Most call-types emitted by G. sabrinus were also emitted by G. volans, showing overlap in the repertoire of both species, although variation between species is evident in certain call-types. We also found both species displayed evidence of frequency alteration (i.e., modification of the frequency of one squirrel's call when simultaneously calling with another squirrel using similar call-types). Our call library demonstrates a complex vocal range of tonal and frequency-modulated calls emitted by both species. Acoustic detection of North American flying squirrels is a new monitoring technique that can be used for conservation and management purposes. Differences in the trills, tonal chirps, and arc chirps provide a means to distinguish calls between these species. Increasing understanding of behavior associated with vocalizations may provide a more complete understanding of flying squirrel ecology, including intra- and interspecific interactions.

The San Bernardino flying squirrel (Glaucomys oregonensis californicus) is a California Species of Special Concern restricted to montane forests of southern California. We confirmed the distribution of this species in residential areas of the San Bernardino and San Jacinto Mountains with the assistance of citizen scientist volunteers. Project participants placed motion sensor camera traps near bird feeders on their property and uploaded their results to a project webpage and associated iNaturalist project. Flying squirrels were documented at all sites monitored in the San Bernardino Mountains but were not detected in the San Jacinto Mountains, consistent with survey results in recent decades. Forest structure plots between the 2 ranges differed in tree density, tree height, litter depth, and canopy closure, but it is unclear whether these differences alone can explain the lack of detections in the San Jacinto Mountains. Habitat in residential areas may provide subsidized food and water resources that are attractive to flying squirrels and important to their persistence, especially in seasonally dry forests and areas subject to prolonged drought, such as those in the study area.