Squirrels on North American college and university campuses have been the subject of much animated conversation in informal venues, but a systematic assessment of their distribution across this habitat type has not been undertaken until now. We collected reports of squirrel species' presence and absence from faculty experts at 536 campuses in Canada and the continental United States, and found that squirrels are nearly ubiquitous on campuses (95% had at least one species, and 40% had three or more), but that only a select few species are common campus residents. Foremost among these is the eastern gray squirrel (Sciurus carolinensis—on 62% of surveyed campuses), followed by the eastern fox squirrel (Sciurus niger), eastern chipmunk (Tamias striatus), North American red squirrel (Tamiasciurus hudsonicus), and woodchuck (Marmota monax). Eastern gray and fox squirrels partition campuses with one another, both in their shared native/core range and on the West Coast. While these invasive eastern species are present on campuses on the West Coast, notably, contingency analysis did not provide evidence that they are the primary factor discouraging western gray squirrels (Sciurus griseus) from using these habitats. The inventory and analyses presented here can provide a basis for longitudinal studies both within and across campuses and may be productively combined with initiatives that involve students in research.

Pacific walruses (Odobenus rosmarus divergens) play a vital role in Arctic marine ecosystems and the subsistence lifestyle of Alaska Native communities. Museum collections contain numerous archaeological and historic walrus specimens that have proven useful in a variety of studies; however, for many cases, the sex of these specimens is unknown. Sexes of adult (> 5 years determined by tooth aging) Atlantic walruses (Odobenus rosmarus rosmarus) have been accurately determined in previous studies using mandible measurements. We tested the validity of this approach for Pacific walruses, and used full fusion of the mandibular symphysis to define adults. Using high precision digital calipers (± 0.01 mm), four measurements were taken either on the left or right side of 91 walrus mandibles: 80 modern mandibles (70 known-sex specimens; 10 unknown-sex specimens) and 11 archaeological mandibles of unknown sex. We used linear discriminant function analysis (LDFA) to determine what measurements best distinguished Pacific walrus males from females. Minimum mandible thickness had the most predictive power, whereas mandible length, height, and depth, were less predictive. Posterior probabilities indicated that LDFA classified the known-sex Pacific walruses with 100% accuracy, and unknown sex with ≥ 90% probability. The ability to define the sex of unknown individuals accurately could greatly increase the sample size of future projects dealing with skeletal remains, and will improve future research efforts.

Sexual dimorphism evolves as a response to different selective pressures on males and females. In mammals, sexual selection on traits that improve a male's ability to compete for access to mates is a common cause of sexual dimorphism. In addition to body mass, adaptations in specific components of the musculoskeletal system that increase strength, stability, and agility, may improve male fighting performance. Here we test the hypotheses that males, when compared to females, are more specialized for physical competition in their skeletal anatomy and that the degree of this sexual dimorphism increases with the intensity of male–male competition. In three species of voles (Cricetidae: Arvicolinae: Microtus), we found partial support for these hypotheses. Male-biased sexual dimorphism in a set of functional indices associated with improved fighting performance was identified in the postcranial anatomy. This dimorphism was greatest in the polygynous Microtus californicus, absent in the monogamous M. ochrogaster, and intermediate in the promiscuous or socially flexible M. oeconomus. However, in the skull, we found results opposite to our predictions. Females had larger skulls relative to overall skeletal size than did males. This may be associated with selection for increased food processing efficiency, which should be highly important because of the compounding effects of increased caloric requirements during gestation and lactation, and the generally low-quality diet of voles. In addition, larger heads in females may be associated with selection for greater digging ability or for defending offspring. These results suggest disparate selective pressures on the postcranial skeletons and skulls of male and female voles.

The age of an animal, determined by time (chronological age) as well as genetic and environmental factors (biological age), influences the likelihood of mortality and reproduction and thus the animal's contribution to population growth. For many long-lived species, such as bats, a lack of external and morphological indicators has made determining age a challenge, leading researchers to examine genetic markers of age for application to demographic studies. One widely studied biomarker of age is telomere length, which has been related both to chronological and biological age across taxa, but only recently has begun to be studied in bats. We assessed telomere length from the DNA of known-age and minimum known-age individuals of two bat species using a quantitative PCR assay. We determined that telomere length was quadratically related to chronological age in big brown bats (Eptesicus fuscus), although it had little predictive power for accurate age determination of unknown-age individuals. The relationship was different in little brown bats (Myotis lucifugus), where telomere length instead was correlated with biological age, apparently due to infection and wing damage associated with white-nose syndrome. Furthermore, we showed that wing biopsies currently are a better tissue source for studying telomere length in bats than guano and buccal swabs; the results from the latter group were more variable and potentially influenced by storage time. Refinement of collection and assessment methods for different non-lethally collected tissues will be important for longitudinal sampling to better understand telomere dynamics in these long-lived species. Although further work is needed to develop a biomarker capable of determining chronological age in bats, our results suggest that biological age, as reflected in telomere length, may be influenced by extrinsic stressors such as disease.

Bat guano is a noninvasive, data-rich genetic resource. However, the constituent bat DNA is relatively scant, degraded, and complexed with polymerase chain reaction inhibitors. It also is comingled with a rich pool of nontarget DNA from microbes, parasites, and dietary items. We designed and tested new DNA assays for bat species identification (COX1-Bat) and sex identification (XGXYC) for use with guano and other challenging samples. We reviewed previously published assays that can be used with guano samples to obtain the same species and sex data, and attempted to validate these assays for species in which they had not previously been tested. Our results demonstrate that guano-derived DNA can be used successfully to 1) identify nearly all US and Canadian bats at the species level, or to one of three Myotis species clusters, and 2) identify the sex of at least 23 US and Canadian bat species. Our newly developed assays, and validation of previously published assays, for guano-based identification of species and sex in bats, significantly enhance the power of noninvasive sampling and genetic analysis for bat studies, management, and conservation.

Latitudinal migration increases fitness of migrants by allowing them to exploit favorable conditions in nonadjacent geographic regions. Other consequences also may follow, such as interactions with parasites. Migrants may have lower parasite prevalence and abundance than resident individuals because of their ability to abandon infested areas or due to mortality of highly infested hosts. To further understand whether variation in ectoparasite loads is influenced by migration, we investigated whether prevalence and abundance of two species of obligate ectoparasites, the wing mite Periglischrus paracaligus (Mesostigmata: Spinturnicidae) and the bat fly Nycterophilia coxata (Diptera: Streblidae, Nycterophiliinae), of the lesser long-nosed bat, Leptonycteris yerbabuenae, varied between migratory and resident populations throughout their range in Mexico. We examined the presence or absence of migratory behavior, as well as sex and reproductive status of the host because ectoparasitism differentially affects the sexes. Our results showed that the prevalence of both ectoparasites did not vary between migrant and resident females or males, but abundance of the wing mite P. paracaligus was lower in migrant females compared with resident females, with an important influence from the reproductive status of the host. A partial negative relationship between ectoparasite loads and latitudinal migration therefore was demonstrated.

Individuals of either sex may display alternative behaviors to obtain copulations, but few studies have examined the breeding patterns of females and males in populations where individuals of both sexes exhibit alternative reproductive tactics (ARTs). In prairie voles (Microtus ochrogaster), most adults are territorial, residing at a single nest site either as male–female pairs or as solitary individuals. However, some adults adopt nonterritorial, wandering tactics. During two field seasons monitoring prairie vole populations maintained in seminatural enclosures, we found evidence that females exhibiting different ARTs bred differentially with resident and wandering males. Females residing at a nest with a male bred significantly more often with a paired resident male, primarily their social partner, and significantly less often with male wanderers compared to single resident females or wandering females. These patterns were not due to chance, because paired resident females produced offspring with paired resident males significantly more than expected based on the relative abundance of these males in the population, whereas single resident females produced offspring with male wanderers significantly more than expected based on the proportion of male wanderers in the population. We did not find any evidence that multiple paternity was greater in the litters of single resident females and wanderer females even though these females lacked a male social partner to limit mating access by multiple males. This suggests that mate guarding by a female's male social partner was not the primary determinant of multiple paternity in the litters of females exhibiting different reproductive tactics. However, male ART did affect the likelihood of multiple paternity. Females that produced offspring with single resident or wanderer males had an increased likelihood of multiple paternity relative to females producing offspring with paired resident males. The results of this study show that female and male ARTs can affect breeding patterns.

One method burrowing animals are hypothesized to use in adapting to the presumed hypoxic subterranean environment is increasing the oxygen-carrying capacity of blood. A number of recent studies have examined hematologic parameters in laboratory-reared naked mole-rats, but not in animals living under natural atmospheric conditions. To our knowledge, blood chemistry parameters have never been systematically assessed in a fossorial mammal. In this study we examined the blood of wild naked mole-rats in Kenya and Ethiopia to determine whether their blood chemistry differs significantly from naked mole-rats born and living in captivity. We also compared our results to published values for hystricomorphs, other subterranean rodents, and surface-dwelling rodents of similar size.

Despite a large body of research, little agreement has been reached on the ultimate driver(s) of geographic variation in body size (mass and/or length). Here we use skull length measurements (as a surrogate for body mass) from five Australian marsupial species to test the primary hypotheses of geographic variation in body size (relating to ambient temperature, productivity, and seasonality). We used a revised articulation of Bergmann's rule, wherein evidence for thermoregulation (heat dissipation or heat conservation) is considered supportive of Bergmann's rule. We modeled the skull lengths of four Petaurid glider species and the common brushtail possum (Trichosurus vulpecula) as a function of indices of ambient temperature, productivity, and seasonality. The skull length of Petaurus ariel, P. notatus, and the squirrel glider (P. norfolcensis), increased with increasing winter minimum temperature, while that of T. vulpecula decreased with increasing summer maximum temperature. The skull length of P. ariel decreased with indices of productivity, falsifying the productivity hypothesis. Only P. ariel met the hypothesis of seasonality, as skull length increased with increasing seasonality. Thermoregulation was the most consistently supported driver of geographic variation in body size, as we found evidence of either heat conservation or heat dissipation in four of the five species examined. We found the geographic range of the individual species and the climate space in which the species occurred was integral to understanding the species' responses to climate variables. Future studies should use specimens that are representative of a species' entire geographic range, encompass a variety of climatic regions, and use consistent methodologies and terminology when testing drivers of geographic variation in body size.

Large predators are particularly susceptible to population declines due to large area requirements, low population density, and conflict with humans. Their low density and secretive habits also make it difficult to know the spatial extent, size, and connectivity of populations; declines hence can go unnoticed. Here, we quantified decline in a large marsupial carnivore, the spotted-tailed quoll (Dasyurus maculatus gracilis), endemic to the Wet Tropics rainforest of northeast Australia. We compiled a large database of occurrence records and used species distributional modeling to estimate the distribution in four time periods (Pre-1956, 1956–1975, 1976–1995, 1996–2016) using climate layers and three human-use variables. The most supported variables in the distribution models were climatic, with highly suitable quoll habitat having relatively high precipitation, low temperatures, and a narrow annual range in temperature. Land-use type and road density also influenced quoll distribution in some time periods. The modeling revealed a significant decline in the distribution of D. m. gracilis over the last century, with contraction away from peripheral areas and from large areas of the Atherton Tablelands in the center of the distribution. Tests of the change in patch availability for populations of 20, 50, and 100 individuals revealed a substantial (17–32%) decline in available habitat for all population sizes, with a particular decline (31–40%) in core habitat (i.e., excluding edges). Six remaining populations were defined. Extrapolating capture–recapture density estimates derived from two populations in 2017 suggests these populations are small and range from about 10 to 160 individuals. Our total population estimate sums to 424 individuals, but we outline why this estimate is positively skewed and that the actual population size may be < 300 individuals. Continued decline and apparent absence in areas of highly suitable habitat suggests some threats are not being captured in our models. From our results, we provide management and research recommendations for this enigmatic predator.

Species distribution models (SDMs) use presence records to determine the relationship between species occurrence and various environmental variables to create predictive maps describing the species' distribution. The Oscura Mountains Colorado chipmunk (Neotamias quadrivittatus oscuraensis) occurs in central New Mexico and is of conservation concern due to its relict distribution and threats to habitat. We previously created an occupancy model for this taxon, but were concerned that the model may not have adequately captured the ecological factors influencing the chipmunk's distribution because of the data hungry nature of occupancy modeling. MaxEnt is another SDM method that is particularly effective at testing large numbers of variables and handling small sample sizes. Our goal was to create a MaxEnt model for the Oscura Mountains Colorado chipmunk and to compare it with our previous occupancy model for this taxon, either to strengthen our original assessment of the relevant ecological factors or identify additional factors that were not captured by our occupancy model. We created MaxEnt models using occurrence records from baited camera traps and opportunistic surveys. We adjusted model complexity using a novel method for tuning both the regularization multiplier and feature class parameters while also performing variable selection. We compared the distribution maps and variables selected by MaxEnt to the results of our occupancy model for this taxon. The MaxEnt and occupancy models selected similar environmental variables and the overall spatial pattern of occurrence was similar for each model. Likelihood of occurrence was positively related to elevation, piñon woodland vegetation type, and topographic variables associated with escarpments. The overall similarities between the MaxEnt and occupancy models increased our confidence of the ecological factors influencing the distribution of the chipmunk. We conclude that MaxEnt offers advantages for predicting the distribution of rare species, which can help inform conservation actions.

The geographic distribution of a species can provide insights into its population size, ecology, evolution, and how it responded to past (and may respond to future) environmental change. Improving our knowledge of the distribution of threatened species thus is a high priority in assessing their conservation status. However, there are few data available for many recently described yet understudied and potentially threatened primate taxa, making their conservation difficult. Here, we investigated the distribution of the Montagne d'Ambre fork-marked lemur, Phaner electromontis, a threatened nocturnal primate endemic to northern Madagascar and classified as Endangered by the IUCN. Because fork-marked lemurs are highly vocal, we used acoustic surveys to assess the species' presence-absence and relative population density within 66 distinct forest survey sites in northern Madagascar. Further, we compared data among five forest types within the study area and investigated the relationship between relative population density and climate variables. We report the presence of P. electromontis in 22 study sites; several of these populations were unknown previously. Although we found P. electromontis most frequently in dry-transitional forests, our results suggest that geography (spatial autocorrelation) rather than environmental variables explains the species' distribution. We hypothesize that environmental unpredictability and gummivory, combined with the presence of several distinct Phaner species in the studied area, could explain the observed distribution.

Preserving connectivity in the core of a species' range is crucial for long-term persistence. However, a combination of ecological characteristics, social behavior, and landscape features can reduce connectivity among wildlife populations and lead to genetic structure. Pronghorn (Antilocapra americana), for example, exhibit fluctuating herd dynamics and variable seasonal migration strategies, but GPS tracking studies show that landscape features such as highways impede their movements, leading to conflicting hypotheses about expected levels of genetic structure. Given that pronghorn populations declined significantly in the early 1900s, have only partially recovered, and are experiencing modern threats from landscape modification, conserving connectivity among populations is important for their long-term persistence in North America. To assess the genetic structure and diversity of pronghorn in the core of their range, we genotyped 4,949 genome-wide single-nucleotide polymorphisms and 11 microsatellites from 398 individuals throughout the state of Wyoming. We found no evidence of genetic subdivision and minimal evidence of isolation by distance despite a range that spans hundreds of kilometers, multiple mountain ranges, and three interstate highways. In addition, a rare variant analysis using putatively recent mutations found no genetic division between pronghorn on either side of a major highway corridor. Although we found no evidence that barriers to daily and seasonal movements of pronghorn impede gene flow, we suggest periodic monitoring of genetic structure and diversity as a part of management strategies to identify changes in connectivity.

The spectacled bear (Ursidae: Tremarctos ornatus) is an emblematic umbrella species and one of the top carnivores in the Andean mountains. It is also listed as vulnerable by IUCN and as endangered by CITES. We analyzed the genetic structure of this species in nine geographical regions representing the three Andean Cordilleras in Colombia. We sequenced six mitochondrial genes in 115 spectacled bears; a subset of these specimens (n = 61) were genotyped at seven nuclear microsatellites. We addressed three objectives: 1) determine the genetic diversity and historical demographic changes of the spectacled bear in Colombia; 2) determine phylogeographic patterns of genetic divergence among spectacled bear populations in Colombia; and 3) estimate the levels of gene flow among different regions of Colombia. Our analyses show evidence of high mitochondrial genetic diversity in spectacled bears, both in Colombia as well as in each of the nine regions, most particularly Norte de Santander, Nariño, and Antioquia-Córdoba. In addition, we detected population expansion in Colombia that occurred around 24,000 years ago, followed by a population decrease during the last 7,000 years, and a sudden expansion in the last 300 years. Phylogenetic analyses showed few well-supported clades, with some haplotypes detected in all the departments and Colombian Andean Cordilleras, and other haplotypes restricted to certain geographical areas (Antioquia, Norte de Santander, Cundinamarca, and Nariño). We detected significant genetic heterogeneity among some departments and among the three Colombian Andean Cordilleras for both mitochondrial and nuclear genes. Nevertheless, the moderate levels of gene flow estimated from F_ST statistics suggest that geographical barriers have not been definitive obstacles to the dispersion of the spectacled bear throughout Colombia. Despite these gene flow estimates, significant spatial autocorrelation was detected for spectacled bear in Colombia, where two kinds of spatial patterns were discovered: genetic patches of 144 km of diameter, and isolation by distance among bears separated from 578 to 800 km. The two most northern spectacled bear populations of Colombia (Norte de Santander and Antioquia) also were the two most differentiated. Their distinctiveness may qualify them as distinct Management Units (MUs) in the context of conservation policies for the spectacled bear in Colombia.

Plateau pikas are a keystone species and ecosystem engineers in alpine meadow ecosystems. A number of surveying methods have been used to estimate pika density, but the reliability of these methods is not known. In addition, better population density methodologies allow for more reliable density estimates. We therefore compared the relationship among several commonly used methods of estimating pika relative density and the absolute density (AD) of pika populations. This relationship was investigated in summer and winter pastures to determine whether distribution pattern of the pikas (patchy or uniform) would influence this relationship. During August of 2015 and August of 2016, we measured the relative and absolute population density of pikas in an alpine meadow in the County, Gansu province, northwestern China. Relative density was measured with three indirect and direct methods: the total burrow density (TBD), the active burrow density (ABD), and the direct counting density (DCD) at the peak of pika activity. AD was assessed by removal sampling. Our results showed that the relative population density with all three survey methods was significantly related to the absolute population density. In particular, DCD at the peak of the pika activity showed the best correlation with AD. A simple linear model showed the effect of grazing time by livestock had a significant effect on TBD and ABD. These results imply that using DCD as a method to survey at the peak of the pika activity is more reliable than other methods.

Habitat fragmentation may affect animal movement patterns due to changes in intra- and interspecific interactions as well as in habitat quality and structure. Although the effects of habitat fragmentation on terrestrial movements are relatively well-known, it is unclear whether and how they affect aboveground locomotion of individuals. We compared aboveground locomotion of a Neotropical small mammal, the gray four-eyed opossum, Philander quica, between two forest fragments and two areas of continuous forest in the Brazilian Atlantic Forest. We 1) quantified support availability and tested for active selection of different support diameters and inclinations by individuals; and 2) compared support diameters and inclinations used (observed values) among areas and between males and females. Both males and females selected supports based on diameters and inclinations in forest fragments. In continuous forests sites, females selected supports based on diameters and inclinations, but males selected only support diameters. Frequency of support diameter use differed significantly between forest fragments and continuous forest sites and between males and females. Frequency of support inclination use differed significantly between areas only for females, and between sexes only in continuous forest sites. Sex-related differences in support selection and use are likely related to differences in body size and conflicting energetic and behavioral demands related to use of arboreal space. Site-related differences in aboveground movements likely reflect the effects of forest edges that result in increased use of thinner supports in forest fragments. These results complement our previous findings that habitat fragmentation reduces daily home ranges and increases the total amount of aboveground locomotion of P. quica, and provide a more thorough picture of how forest-dependent species are able to use and persist in small forest fragments.

Attempts to reintroduce threatened species from ex situ populations (zoos or predator-free sanctuaries) regularly fail because of predation. When removed from their natural predators, animals may lose their ability to recognize predators and thus fail to adopt appropriate antipredator behaviors. Recently, northern quolls (Dasyurus hallucatus; Dasyuromorpha: Dasyuridae) conserved on a predator-free “island ark” for 13 generations were found to have no recognition of dingoes, a natural predator with which they had coevolved on mainland Australia for about 8,000 years. A subsequent reintroduction attempt using quolls acquired from this island ark failed due to predation by dingoes. In this study, we tested whether instrumental conditioning could be used to improve predator recognition in captive quolls sourced from a predator-free “island ark.” We used a previously successful scent-recognition assay (a giving-up density experiment) to compare predator-scent recognition of captive-born island animals before and after antipredator training. Our training was delivered by pairing live predators (dingo and domestic dog) with an electrified cage floor in repeat trials such that, when the predators were present, foraging animals would receive a shock. Our training methodology did not result in any discernible change in the ability of quolls to recognize and avoid dingo scent after training. We conclude either that our particular training method was ineffective (though ethically permissible); or that because these quolls appear unable to recognize natural predators, predator recognition may be extremely difficult to impart in a captive setting given ethical constraints. Our results point to the difficulty of reinstating lost behaviors, and to the value of maintaining antipredator behaviors in conservation populations before they are lost.

The Peromyscus maniculatus species complex is one of the most widespread group of small mammals in North America. However, the taxonomy and phylogenetic relationships among its constituent taxa remain unclear. As part of a revision of Peromyscus specimens from the highlands of the Trans-Mexican Volcanic Belt in central Mexico, we identified five individuals collected in 1968 that differed externally from other Peromyscus specimens, although morphologically similar to P. labecula and P. melanotis, both latter in the P. maniculatus species complex. Based on cranial measurements and mitochondrial DNA sequences, we aimed to more accurately determine the phylogenetic relationships and the taxonomic status of these individuals. Molecular phylogenetic analyses showed that the specimens formed a monophyletic clade sister to the P. maniculatus species complex. Pairwise genetic distances between those specimens and other species within the P. maniculatus species complex were greater than 7.91%. In addition, morphological analyses clearly distinguished the test specimens from P. melanotis and P. labecula. Based on the results of our molecular and morphological analyses, we conclude that these specimens represent an undescribed species of the P. maniculatus species complex, which we describe herein.

The rare cricetid rodent Bibimys Massoia, 1980 contains three extant species that are distributed in the lowlands of eastern South America between 35°S and 20°S and distinguished mostly by subtle morphological and genetic features. Several fragmented jaws belonging to this genus were recovered from Late Quaternary deposits located in northeastern Brazil, forming part of a rich archaeological and paleontological small mammal assemblage that has been recovered from caves in the Serra da Capivara, state of Piauí. This material is described herein as belonging to a new species, the most hypsodont member of the genus. The specimens also represent an extralimital occurrence of this sigmodontine, as the nearest extant population of Bibimys is ∼1,200 km to the south. Because there are few reliable records of extinct small mammals from the Pleistocene–Holocene transition on the South American continent, in describing this new sigmodontine we extend the records of past biodiversity preserved in the Quaternary deposits of tropical South America. This new species likewise highlights that the Serra da Capivara deposits are promising for understanding the evolutionary history of cricetid rodents.

Researchers are increasingly using museum collections for taxonomy, systematics, phylogenetics, and faunal analyses, and they assume that taxonomic identifications on museum labels are correct. However, identifications may be incorrect or out of date, which could result in false conclusions from subsequent research. A recent geometric morphometrics analysis of skulls of African canids by Machado and Teta (2020) suggested that Canis lupaster soudanicus is a junior synonym of Lupulella adusta. However, the holotype of soudanicus was not measured and further investigation of the putative soudanicus specimens used in this study showed that these originally were identified as L. adusta. This original identification was confirmed by dental measurements, which also confirm that the holotype of soudanicus is Canis lupaster. Hence, soudanicus should not be synonymized with L. adusta. This example highlights the importance of careful checking of species identifications of museum specimens prior to research and, where possible, including (holo)types of taxa, before making taxonomic changes that could have important consequences for species conservation and management.

Morphometric analyses of the manus skeleton have proven useful in understanding species limits and morphological divergence among tupaiid treeshrews (Scandentia: Tupaiidae). Specimens in these studies are typically limited to mature individuals with fully erupted permanent dentition, which eliminates potentially confounding variation attributable to age, but also can exclude rare taxa and small island populations that are poorly represented in systematic collections. To determine the real limits associated with including immature animals in such studies, we used multivariate analyses to study sexual and age variation of the manus skeleton in two allopatric populations of the Lesser Treeshrew (Tupaia minorGünther, 1876) from the Malay Peninsula and from Borneo that we treated as separate samples. Individuals were aged using dental eruption of the permanent dentition. We also recorded the degree of epiphyseal fusion of the bones of the manus based on x-rays of study skins. We then tested our ability to distinguish the two populations using a series of discriminant function analyses of hand measurements from samples that included varying proportions of immature individuals and adults. We found no evidence of sexual dimorphism in hand proportions, permitting us to combine females and males in our samples. Epiphyseal fusion of the metacarpals and phalanges typically occurs by the time the third molars have completely erupted, and fusion of the distal epiphyses of the radius and ulna typically occurs by the time the permanent fourth premolars are in place. There is occasional asynchrony between dental age and epiphyseal fusion. In both populations, the hands of most infants and subadults provide morphometric values within the range of variation of adults, although they are typically distributed in the lower part of the adult range and have the potential to bias the sample toward lower mean size. The inclusion of infants and subadults when attempting to discriminate between two taxa generally results in lower rates of correct classifications, although the rates increase as the sample of immature individuals is limited to older subadults. As a general rule, we recommend that specimens of infants and subadults continue to be excluded from analyses when exploring taxonomic boundaries among treeshrews. In cases of extremely small sample sizes of adults, however, older subadults—in which the permanent third premolars are erupting or in place—can be used with appropriate caution.

Tree cavities are important denning sites for many arboreal mammals. Knowledge of cavity requirements of individual species, as well as potential den overlap among species, is integral to their conservation. In Australia's tropical savannas, development of tree cavities is enhanced by high termite activity, and, conversely, reduced by frequent fires. However, it is poorly understood how the availability of tree cavities in the tropical savannas impacts tree cavity use and selection by cavity-dependent fauna. There has been a severe decline among arboreal mammal species in northern Australia over recent decades. Investigation of their cavity requirements may illuminate why these species have declined drastically in some areas but are persisting in others. Here we examined this issue in three species of arboreal mammals (Trichosurus vulpecula, Mesembriomys gouldii, Conilurus penicillatus) on Melville Island, northern Australia. We radiotracked individuals to their den sites to evaluate whether the species differ in their den tree and tree-cavity selection. The strongest influence on den tree selection was the presence of large cavities (> 10 cm entrance diameter), with all three species using larger cavities most frequently. Conilurus penicillatus, the smallest species, differed the most from the other species: it frequently was found in smaller, dead trees and its den sites were closer to the ground, including in hollow logs. The two larger species had broader den tree use, using larger live trees and dens higher up in the canopy. Dens of C. penicillatus are likely to be more susceptible to predation and destruction by high-intensity savanna fires. This may have contributed to this species' rapid decline, both on Melville Island and on the mainland. However, the apparent preference for larger tree cavities by all three arboreal species is concerning due to the limited availability of large trees across Australian savannas, which are subject to frequent, high-intensity fires.

Dens are important for species that need to survive and reproduce during harsh winters. Brown bears (Ursus arctos) in Romania, listed by the European Union as a population of concern, use dens for several months each year. To date, few quantitative assessments of denning habitat have been carried out for this population or others in Europe. In 2008–2013 and 2015–2017, we used local knowledge and telemetry data from brown bears fitted with GPS collars to identify 115 winter dens and eight open ground nests used by bears in eastern Transylvania, Romania. We located most dens in mountainous areas (64%) and fewer in foothills (36%). Den entrances in mountainous areas were significantly narrower than entrances in foothills, likely due to the need for reduced thermal loss during more severe winters at higher elevations. We selected seven habitat characteristics (abiotic and biotic) and human-related covariates associated with known locations of dens and open nests to identify potential brown bear denning habitat using maximum entropy modeling. We found that terrain ruggedness was the single most important factor when predicting bear denning habitat. The habitat map derived from this study can be used in the future to safeguard bear denning areas from potential human disturbances.

Populations of many mammal species living in grassland ecosystems across North America have been reduced greatly over the past 200 years due to conversion of native prairie to human-related uses. Foremost among these species is the black-tailed prairie dog (Cynomys ludovicianus), populations of which have declined an estimated 98% during that time. In addition to anthropogenic factors including plague, black-tailed prairie dog populations can vary in size in response to grazing by native ungulates, fire, and precipitation. Colonies in the Northern Great Plains have expanded and contracted during dry and wet periods, respectively. Drought reduces vegetation height; tall vegetation is known to limit colony expansion, possibly due to increased predation risk. We used mixed-effects models to analyze data sets of colony areas of black-tailed prairie dogs spanning 16–22 years and 983 total colony counts, from 142 unique colonies at Badlands National Park and Wind Cave National Park, South Dakota, United States, and Scotts Bluff National Monument, Nebraska, United States, to relate areal dynamics of colonies over time to total annual precipitation, drought stress, and plague. We also analyzed the relationship between active-burrow densities and precipitation and drought stress using 7 years of data from 271 colony counts at Badlands National Park. Black-tailed prairie dog colonies expanded in response to drought conditions in all three national parks, with colonies in Wind Cave National Park exhibiting a time-delayed response. In addition, colony area was negatively related to total accumulated precipitation for the preceding 12 months for Scotts Bluff National Monument. Active-burrow density at Badlands National Park decreased in response to drought stress with a time lag of 24–36 months. Plague first was reported at Badlands National Park in 2008 and colony areas decreased dramatically and rapidly during plague epizootic events. Our results support observations that black-tailed prairie dog colonies in the Northern Great Plains expand and contract in response to drought stress and wet weather. Furthermore, our findings provide new insights into the role of climate on a keystone species of conservation importance and demonstrate the value of collecting long-term ecological data.

Hair density is the most important structural parameter contributing to insulation performance of mammalian pelage, and often is measured in ecophysiological, thermal biological, and evolutionary studies. To date, hair density has been measured using invasive methods on research objects; however, such methods remain challenging despite efforts to increase their ease of use. In this paper, we develop a new method to estimate hair density without skin sampling. We expressed hair density as the inverse of the number of hairs per unit area, that is, the surface area occupied by a single hair (A_h). This area could be further estimated by measuring distances between nearest neighboring hairs (L_n) and calculating the areas of triangles (A) defined by three randomly selected nearest neighboring hairs and representing half of A_h. Empirical tests using 11 skin samples from specimens of six small mammal species showed this to be a simple, lightly invasive, but accurate and widely applicable method.