Why some animals have big brains and others do not has intrigued scholars for millennia. Yet, the taxonomic scope of brain size research is limited to a few mammal lineages. Here, we present a brain size dataset compiled from the literature for 1,552 species with representation from 28 extant taxonomic orders. The brain–body size allometry across all mammals is (Brain) = –1.26 (Body)^0.75. This relationship shows strong phylogenetic signal. Thus, we conducted additional allometries using median species values for each order, family, and genus to ensure evolutionary independence. Slopes from these analyses at different taxonomic levels all approximate ∼0.75 scaling. Why brain size scales to the 3/4 power to body size across mammals is to our knowledge unknown. Slopes within taxonomic orders, exhibiting smaller size ranges, are generally shallower than 0.75 and range from 0.24 to 0.81 with a median slope of 0.64. Published data on brain size are lacking for the majority of extant mammals (> 70% of species) with strong bias in representation from Primates, Carnivora, Perissodactyla, and Australidelphian marsupials (orders Dasyuromorphia, Diprotodontia, Peramelemorphia). Several orders are particularly underrepresented. For example, data on brain size are available for less than 20% of species in each of the following speciose lineages: Soricomorpha, Rodentia, Lagomorpha, Didelphimorphia, and Scandentia. Use of museum collections can decrease the current taxonomic bias in mammal brain size data and tests of hypothesis.

Studies on mammalian community ecology and biogeography are increasingly using functional diversity to advance our understanding of how diversity is maintained and how it varies across space and over time. Functional diversity quantifies the range and prevalence of species traits in an assemblage and provides a means of linking patterns of diversity to the ecological processes that generate them. Measuring the most appropriate and informative traits is critically important, yet the variety of traits applied to mammalian systems has been relatively limited and most are categorical rather than continuous. As a result, finer variation among species is often overlooked, which may obscure more detailed and accurate conclusions, particularly for studies on smaller species pools. We seek to improve the quality of trait information for mammals by investigating the value of three continuous ecomorphological traits: the relative medullary thickness of the kidney (an indicator of urine concentrating ability) as a metric of habitat moisture requirements, hair density as a measure of temperature limitations, and an integrated suite of cranial and dental measurements as an indicator of dietary specialization. We measured these traits for the small mammal assemblage of the Great Basin ecoregion using fluid-preserved and skeletal specimens housed in natural history collections and accounted for phylogenetic and allometric relationships. Kidney morphology, hair density, and craniodental morphology each exhibited phylogenetic signal and revealed ecologically meaningful variation that is overlooked by associated categorical traits. The greater resolution of these continuous trait data will facilitate more refined assessments of functional diversity and improve efforts to test ecological theories or track responses to environmental change.

Bats are assumed not to use vision for communication, despite recent evidence of their capacity for color vision. The possibility that bats use color traits as signals has thus been overlooked. Some tent-roosting bats have a potential for visual signaling because they exhibit bright yellow skin, a trait that in birds often acts as a sexual signal. We searched for evidence of sexual dichromatism in the yellow bare skin of Honduran white bats Ectophylla alba, the first reported mammal with a capacity to deposit significant amounts of carotenoid pigments in the skin. We found that skin yellow chroma, a measure that reflects carotenoid content, increases in the ears and nose-leaf during development probably due to an increase in dietary carotenoid accumulation. Once in the adulthood, the yellow color of the nose-leaf becomes brighter in males, representing the first evidence of sexual dichromatism in a bat. The nose-leaf brightness tends to covary positively with the body condition of males. We also found that the skin shows a reflectance peak at 530 nm that virtually coincides with the main reflectance peak (540 nm) of the back side of Heliconia leaves used as roosts. This suggests that these leaves were selected because of camouflage benefits, and the rich lighting conditions of these roosting places then favored the use of skin coloration as a sexual signal. These findings open a new perspective in the physiological and behavioral ecology of bats in which vision has a more relevant role than previously thought.

The platypus (Ornithorhynchus anatinus) is one of the world's most evolutionarily distinct mammals, one of five extant species of egg-laying mammals, and the only living species within the family Ornithorhynchidae. Modern platypuses are endemic to eastern mainland Australia, Tasmania, and adjacent King Island, with a small introduced population on Kangaroo Island, South Australia, and are widely distributed in permanent river systems from tropical to alpine environments. Accumulating knowledge and technological advancements have provided insights into many aspects of its evolutionary history and biology but have also raised concern about significant knowledge gaps surrounding distribution, population sizes, and trends. The platypus' distribution coincides with many of Australia's major threatening processes, including highly regulated and disrupted rivers, intensive habitat destruction, and fragmentation, and they were extensively hunted for their fur until the early 20th century. Emerging evidence of local population declines and extinctions identifies that ecological thresholds have been crossed in some populations and, if threats are not addressed, the species will continue to decline. In 2016, the IUCN Red Listing for the platypus was elevated to “Near Threatened,” but the platypus remains unlisted on threatened species schedules of any Australian state, apart from South Australia, or nationally. In this synthesis, we review the evolutionary history, genetics, biology, and ecology of this extraordinary mammal and highlight prevailing threats. We also outline future research directions and challenges that need to be met to help conserve the species.

Many species that occupy high latitudes of North America were historically restricted to relatively small refugia during the Last Glacial Maximum (LGM). The geographic ranges of many of these species then expanded widely across the continent after glacial ice receded. In contrast, species whose LGM distributions spanned lower (relatively ice-free) latitudes may have been less likely to experience demographic and geographic retraction during glacial periods, or expansion during interglacial periods. For example, species in North America's Intermountain West occupied a topographically complex landscape across which widespread patches of suitable habitat could have helped maintain a relatively stable range-wide effective population size even if local populations fluctuated in response to shifting climates. We test for these alternative demographic signals in southern versus northern species by comparing patterns of genetic diversity of the more southern yellow-bellied marmot (Marmota flaviventris) with those of the more northern hoary marmot (M. caligata). Our data reveal high diversity but no deep structure across the distribution of yellow-bellied marmots. In contrast, hoary marmots have previously been shown to exhibit a deep divergence between regional mitochondrial clades of relatively low diversity. We suggest that these differences reflect differences in habitat availability through time, with hoary marmots persistently isolated in small glacial refugia and yellow-bellied marmots more broadly distributed across the Intermountain West through both glacial and interglacial periods. Our results highlight the importance of historical patterns of habitat availability as key drivers of current genetic structure.

Many organisms worldwide are responding to rapid climate change by shifting their geographic ranges. The white-footed mouse, Peromyscus leucopus, has expanded its range northward in Michigan and Wisconsin since 1980 and is now common in localities where it was previously unknown. To investigate the origin and history of the newly established populations, complete D-loop sequences were analyzed from 595 white-footed mice collected throughout the northern Great Lakes region. Mice from Wisconsin and the western Upper Peninsula (UP) of Michigan make up a well-differentiated lineage, while the eastern UP and the Lower Peninsula (LP) of Michigan form a second lineage. The two lineages diverged about 34,000 BP, well before they migrated to the Great Lakes region. The close genetic relationship between mice in the LP and those in the eastern UP is probably due primarily to accidental transport by humans and may have implications for the spread of Lyme disease in the Upper Midwest.

Animal populations can react to climate change by adapting to selection pressures, dispersing to new habitats, or undergoing plastic development at the individual level. These processes interact to form a net response, but it is difficult to determine the relative contributions of each process. In central and northern Michigan, two distinct mitochondrial lineages of Peromyscus leucopus (Upper Peninsula [UP] and Lower Peninsula [LP]) appear to have responded to climate change differently; one lineage (UP) has migrated into new geographic areas, while the other (LP) cannot. Six Michigan populations were sampled using genetic and geometric morphometric methods to test the effects of expansion versus nonexpansion demographic histories on genetic diversity and phenotypic variation. In pairwise population comparisons, there were no differences in genetic population structure or diversity between LP and UP populations or between older and newly established populations. However, the morphology of the cranium and especially the mandible were localized to each population, although moderate overlaps between the crania of UP populations and between the mandibles of Cheboygan (LP) and Menominee (UP) mice were observed. The results indicate that the UP lineage has rapidly dispersed into new areas without losing nuclear genetic diversity and that the morphological differences displayed among the populations are most likely due to plastic responses to local conditions.

Determining the environmental and ecological drivers of variation in mammalian life histories is essential for effectively monitoring responses of these taxa to global change. We investigated relationships between climate and an integral life history trait (litter size) in the geographically widespread North American deer mouse (Peromyscus maniculatus). Using a spatiotemporally comprehensive data set of P. maniculatus embryo counts assembled from digitized museum specimens and small mammal census records (> 2,000 observations spanning more than a century), we modeled the associations of litter size with short- and long-term climate variables, and tested for shifts in litter size in response to recent climate change. Litter size in P. maniculatus was correlated with length of the frost-free period, suggesting the former trait may have evolved partly as a response to abiotic or resource-driven constraints on the number of annual breeding opportunities. Short-term climate variables (temperature and precipitation during breeding) were significant predictors of litter size in some models; however, all short-and long-term climate variables other than number of frost-free days added marginal predictive power. Further analyses confirmed age-structured breeding in the most seasonal regions, where maternal body sizes and litter sizes both decrease within a year, although maternal body size itself was poorly predictive of litter size in these populations. We also found a statistically significant decrease in P. maniculatus litter size through time and across known frost-free period regimes (pre- and post-1980), as predicted if longer frost-free periods are increasing lifetime breeding opportunities in this species, although more work is required to confirm this trend and identify underlying mechanisms. Our study refines understanding of climate impacts on P. maniculatus life history and reiterates the great potential of digitized specimen data to help address outstanding questions in mammalian life history and climate change response.

Museum specimens play an increasingly important role in predicting the outcomes and revealing the consequences of anthropogenically driven disruption of the biosphere. As ecological communities respond to ongoing environmental change, host–parasite interactions are also altered. This shifting landscape of host–parasite associations creates opportunities for colonization of different hosts and emergence of new pathogens, with implications for wildlife conservation and management, public health, and other societal concerns. Integrated archives that document and preserve mammal specimens along with their communities of associated parasites and ancillary data provide a powerful resource for investigating, anticipating, and mitigating the epidemiological, ecological, and evolutionary impacts of environmental perturbation. Mammalogists who collect and archive mammal specimens have a unique opportunity to expand the scope and impact of their field work by collecting the parasites that are associated with their study organisms. We encourage mammalogists to embrace an integrated and holistic sampling paradigm and advocate for this to become standard practice for museum-based collecting. To this end, we provide a detailed, field-tested protocol to give mammalogists the tools to collect and preserve host and parasite materials that are of high quality and suitable for a range of potential downstream analyses (e.g., genetic, morphological). Finally, we also encourage increased global cooperation across taxonomic disciplines to build an integrated series of baselines and snapshots of the changing biosphere.

Habitat loss has caused bat populations to decline globally and urbanization represents a major contributor to this loss. Yet, recent studies have indicated that urban parks can support a diverse and abundant bat community. These anthropogenically dominated areas must be providing readily available, potentially unconventional, resources. Identifying such resources could therefore give insight into how we can effectively improve urban habitat for bats. Thus, we investigated the use of residential swimming pools by bats as a water resource in behavioral surveys. We also used acoustic activity to determine species presence and identify trends in activity. We recorded 274 bats drinking at swimming pools from April to September 2016. We also acoustically identified all species present in the area. Furthermore, among pools closest to the park (< 200 m), bats only drank as the summer progressed, which corresponded to more ???natural??? sources in the park becoming less accessible. The quality of swimming pools may dictate their use and if we can identify features that influence quality, these insights may be used to improve resource availability for urban bats.

Mammals are known to vary in their sensitivity to urbanization. In heavily urbanized southern California, bobcats (Lynx rufus) prey on rabbits (Sylvilagus spp.) that forage for lush vegetation in developed areas. We collected data on the density of rabbits in adjacent urban and natural areas using visual line surveys. We also measured habitat use for seven GPS-collared female bobcats to determine if bobcats selected areas with higher rabbit densities. Estimated rabbit densities did not vary between urban, urban edge, and natural areas during wet or dry seasons, reflecting their consistent presence across the landscape. During daytime and crepuscular hours, bobcats used natural coastal sage scrub and grassland habitats more frequently (76–84% of the time) than urban areas. Conversely, at night, bobcats decreased their use of coastal sage scrub and doubled their time in urban areas. In summary, we found that rabbits were present across the landscape, and bobcats are likely selecting urban areas at night to prey on rabbits and avoid people.

Dietary (scat) analysis is a key tool for assessing the potential effects of predators on prey and for comparing resource use between predators, information that is crucial for effective wildlife management. However, misidentification of the species from which scats originate could result in inaccurate conclusions regarding predator–prey interactions and their consequences for ecosystems, which may ultimately compromise conservation and management actions. To address this issue, we developed a framework for decision-making in the face of uncertain scat species origin by incorporating field, laboratory, and molecular identification techniques. We used the framework to examine the diets of two predators, a native apex predator (dingo, Canis lupus dingo) and an invasive mesopredator (feral cat, Felis catus), from 696 field-collected scats in the arid zone of Australia. We examined how uncertainty regarding scat species origin changed perceptions of the nature of the relationship between coexisting predators and their prey. The extent of dietary overlap between dingoes and cats varied with the method used to identify scat species origin. Dietary overlap assessed by laboratory identifications was twice as high as when uncertainty in scat species origin was resolved through our decision framework. If uncertainty in scat species origin is not resolved in dietary studies, practitioners and decision-makers relying on this information run the risk of making misinformed conclusions regarding the ecological function of predators (including potential impacts on threatened species), which could have perverse outcomes if the wrong predators are targeted for management. With uncertainty in scat species origin resolved through our decision framework, a low level of dietary overlap between the two predators was demonstrated, and medium-sized mammals most threatened with extinction were shown to be more at risk of impact from feral cat than from dingo depredations.

Natal dispersal is influenced by many environmental and biological factors and can be a time of elevated mortality risk. We aimed to understand how physical, behavioral, and demographic traits of mothers and juveniles influenced natal dispersal by studying a population of brushtail possums (Trichosurus vulpecula) reintroduced to their former range. We used radiotracking and trapping to intensively monitor the growth, survival, shelter use, and movement of juveniles and their mothers from pouch young to adulthood over a 22-month study period. We recorded multiple dispersal movement phases, with males undergoing more phases than females (6 versus 4) and dispersing 16 times farther. Dispersal age was positively related to maternal body mass for males but not females. Mothering behavior varied with offspring sex, with mothers tending to shelter daughters in a higher proportion of new shelter sites compared to sons. Females matured at a younger age and mass than males, and possums that left their mother at an earlier age reached sexual maturity earlier, regardless of sex. The timing of dispersal by males was not influenced by body mass, age, sexual maturity, rainfall, or the age of their younger sibling. Survival of juveniles (63%) was not related to sex or dispersal phase but instead sexual maturity, suggesting an effect of experience. Sex, maternal effects, and an interaction between the two influenced the development and movement of juvenile possums, suggesting that at least some sex-related differences in natal dispersal may be influenced by the mother rather than simply being the innate behavior of offspring. Although sex effects on dispersal have been reported in marsupials, the interaction with maternal characteristics has been previously overlooked.

Land-use changes impact biodiversity, and biofuel crop production and its expansion pose as an important driver of negative effects in the tropics. Understanding the influence of land-use changes on suitable habitats for species is a worldwide conservation challenge, particularly on large-sized mammals. We modeled habitat suitability of the threatened giant anteater (Myrmecophaga tridactyla) in the Brazilian State of São Paulo. The region is the most populous and economically developed of the country and is the world's main sugarcane production area. We aimed to 1) map habitat suitability for the giant anteater population in the State; 2) assess the contributions of selected landscape and anthropogenic predictors to species habitat suitability; and 3) quantify suitable habitats in environmental protection areas and in areas threatened by the sugarcane expansion. We used a two-step analysis: First, we created a suitability map in the species' distributional range (Drange); from this map, we extracted the results for São Paulo State. Second, we built a regional model to predict the current scenario of São Paulo using the following environmental layers: 1) the resulting distributional range map for giant anteater (Drange); 2) landscape metrics; and 3) anthropogenic factors that might affect anteaters. The State of São Paulo presented, in general, very low values of habitat suitability. The following predictors made the greatest contribution: Drange, vegetation connectivity and distance to protected areas. Suitable habitats for anteaters within strictly protected areas are very scarce (1.6% of the total area), and 22% of the suitable areas are expected to be altered by future sugarcane expansion. Suitable habitats on private lands must play a role in conserving biodiversity.

Communication is an integral part of animal behavior, impacting population structure and individual fitness and regulating spatial distributions. Scent marking is common among solitary, low-density, and wide-ranging carnivores, such as felids. Understanding the functional role of scent marking will inform our understanding of the behavioral ecology of carnivores. We investigated patterns of scent marking by pumas (Puma concolor) and jaguars (Panthera onca) via weekly surveys of trails for scrapes and documenting scent-marking behaviors and responses using motion-triggered video cameras. Jaguars mainly sprayed vegetation, whereas pumas mainly scraped the ground. Only a subset of individuals for both pumas and jaguars were responsible for the majority of scent-marking activity. On average, male pumas scraped more frequently (scrapes/km) than male jaguars, and the scrape rate of male pumas increased following the presence of potential mates and competitors. Male pumas returned to trails more quickly following the presence of conspecifics (potential competitors or mates) than in their absence, however, visitation by male jaguars increased in response to competitors only. A male puma detected travelling with three different females on separate occasions scraped more frequently than males who were not detected with females. This study suggests that jaguars and pumas are constantly assessing, and reacting to, the presence and marks of competitors and potential mates, facilitating the maintenance of complex social structures.

One of the major challenges in studies of activity and movement ecology is discovering how and why animals behave differently in certain environments. The gray brocket deer (Mazama gouazoubira) is widely distributed in the Neotropic region. In the Brazilian Pantanal wetland, gray brocket deer inhabit a unique landscape with varying ecotypes arranged in a mosaic, where seasonal flooding alters resource availability for the deer. Documenting animal activity and movement can be the key to understanding how a species interacts with its dynamic environment. We used data from accelerometers and characteristics of movement on six GPS-monitored gray brocket deer in the Pantanal wetland to investigate how habitat type, periods of the day, and cycles of flooding and drought affect activity, movement behavior, and displacement. Deer exhibited the lowest activity and encamped movement in closed habitat during diurnal and nocturnal periods, suggesting resting and foraging behaviors. The highest activity and exploratory movement occurred in open habitats, and potentially was related to deer searching for locations with greater resource availability. Individuals were displaced the most during floods, which was a response to access feeding sites that were free of water. Our results not only represent an unprecedented and refined view of the activity and movement behavior of brocket deer, but they also stress the importance of preserving multiple habitat types for species that express variable foraging strategies in heterogeneous landscapes.

White-lipped peccaries (WLPs; Tayassu pecari, Tayassuidae, Cetartiodactyla) are forest-dwelling ungulates critical to maintaining healthy Neotropical forest ecosystems through key aspects of their dietary behaviors, including seed predation and dispersal. Land-use change and deforestation threaten WLP access to food resources, and thus knowledge of how WLP diet varies spatially is necessary to frame conservation efforts for the species. Here, we use stable carbon (δ¹³C) and nitrogen (δ¹⁵N) isotopes from WLP hair and food resources to assess whether WLP diet varies among four regions in three Brazilian biomes: the Pantanal, the Cerrado, and the Atlantic Forest (semi-deciduous and ombrophilous), each varying in forest canopy cover, climatic characteristics, and degrees of agricultural impacts. We find that in all regions WLPs are consuming primarily C₃ resources, with mean δ¹³C values ranging from –28.7‰ to –26.9‰. In the heavily fragmented semi-deciduous Atlantic Forest, δ¹³C values are the highest, and may indicate that some individuals are consuming a small amount of C₄ crops or demonstrating increased levels of insectivory. A through-time comparison of WLP hair in the semi-deciduous Atlantic Forest suggests the recorded slight departure from an exclusive C₃ diet may be a recent phenomenon, as hairs collected prior to the year 2000 have lower δ¹³C values than those collected in 2016. While some individual WLPs may slightly alter diet in heavily anthropogenically modified areas, C₄ crops are not a main component of WLP diet. Our results suggest that WLPs are still highly dependent on forest resources, even in human-altered landscapes, and conservation and management plans for the species must consider these dietary needs in order to be successful.

A primary requirement of the mammalian skull is to exert forces on different foods and to resist the forces imposed on it during feeding. Skull shape patterns within and among mammals are generally well known, but the biomechanical relevance of this variation remains limited for some groups. By integrating geometric morphometric and biomechanical analyses, we test the hypothesis that skull shape in peccaries reflects biomechanical attributes to generate and dissipate powerful forces, presumably in response to tough foods. We obtained skull shape and size from 213 specimens of the three living peccary species and estimated bite force, bite stress at molars, bending and shear stress on the mandibular corpus, and condylar stress. We found larger estimated bite forces, greater resistance to bending loads, and lower stress emerging from the larger muscle attachment areas and shorter and deeper mandibular corpora for both Pecari tajacu and Tayassu pecari relative to Parachoerus wagneri. Peccaries (P. tajacu and T. pecari) with more powerful biomechanical attributes feed mainly on tougher foods (e.g., palm fruits). These results support the hypothesis that species eating tough foods tend to have a feeding morphology mechanically adapted to stronger bites and greater biting resistance, which must be closely reflected in their craniomandibular shape.

Reproductive rates in bats are higher when there is a greater availability of food, and when temperatures and rainfall are higher. Along elevational gradients, variation in these factors occurs over a small area, making them ideal natural laboratories for studies that aim to describe reproductive patterns and to identify possible vertical migrations for reproduction. We characterized the seasonal and elevational variation in reproductive rates of female and male Artibeus spp., Carollia perspicillata, and Sturnira lilium in the Brazilian Atlantic Forest. We sampled bats with mist nets at 13 sites in southeastern Brazil, between 23° and 24° of latitude, at elevations between 60 and 1,800 m a.s.l. The reproductive patterns of Artibeus spp. and S. lilium were seasonal, with higher reproductive rates in the period with higher rainfall, temperatures, and, consequently, greater availability of food. Moreover, elevation influenced reproductive activity in all study species. Reproductive rates for females of Artibeus spp. were higher at intermediate elevations (between 501 and 1,000 m a.s.l.), and for females of S. lilium at high elevations (above 1,000 m a.s.l.) with a less evident peak at intermediate elevations. Similarly, the proportions of reproductively active male Artibeus spp. and S. lilium were greater at intermediate and high elevations, respectively. In the dry season, reproductive rates of all females increased with local abundance of all females. Differences in reproductive rates along elevational gradients could influence population dynamics, and therefore entire elevational ranges should be protected to ensure conservation of the best reproductive habitats for a variety of bat species. Public policies are needed to ensure effective conservation of biodiversity, biological processes, and the ecosystem services provided by local fauna from the lower lands to the mountain peaks.

Fire is an important natural disturbance recently reintroduced into many North American ecosystems, spurring questions regarding how fire affects forest wildlife. Bats are an ecologically significant group within North American forests, and the diversity of this group includes species that may benefit or suffer negative impacts from habitat changes initiated by prescribed fires. To determine how fire affects a rare bat species that specializes on gleaning moths from forest vegetation, we studied home ranges and nocturnal habitat selection in Rafinesque's big-eared bats (Corynorhinus rafinesquii) in an upland forest ecosystem where small-scale, low-to-moderate intensity prescribed burning occurs in spring. We found home ranges of big-eared bats to be notably small (x = 169 ha; n = 41), not different in size among sexes and reproductive classes, and located nonrandomly on the landscape. Home ranges of females were located farthest from riparian areas, whereas home ranges of males were farthest from burned forests. Home ranges of lactating and postlactating females were closer to burned forests than expected, but no group of females had home ranges located closer to or farther from burned forests relative to unburned forests. All groups used habitats randomly within home ranges. Moth abundance and diversity (number of families) were lowest in riparian habitats, indicating that habitat selection by female bats at the landscape, but not home range, scale was influenced by prey availability. Results indicate that low-to-moderate intensity prescribed fires weakly affected the foraging patterns of Rafinesque's big-eared bats in upland forest ecosystems, provided burned forests exist in a matrix of unburned or less-frequently burned forest stands that support a diverse and abundant lepidopteran prey base.

Wildlife species exhibit changes in behavior, population dynamics, and abundance after disturbances to forests. In western North America, large swathes of dead trees have resulted from unusually large outbreaks of bark beetles (Dendroctonus spp.) over recent decades. For bats, these tree mortality events could be either negative or positive, depending on whether cavities and crevices for roosting increase in response to beetle outbreaks and how the food supply is affected. It is therefore important to determine bat presence and activity in areas with many beetle-killed trees. We examined bat species richness in the southern interior of British Columbia, Canada, in areas with light and severe beetle-kill. We identified six bat species from acoustic recorders; the federally endangered little brown myotis (Myotis lucifugus) had the most detections. Although we surveyed stand-level vegetation, we found no systematic difference between areas identified from government aerial surveys as having had high or low beetle-kill within the previous decade. Neither beetle-kill severity nor the fine-scale vegetation that we measured correlated with bat presence or activity. We conclude that bats in this region use beetle-killed forests and that the severity of beetle-killed trees is neither adversely affecting bat presence or activity, nor enabling increased use by bats of affected forest stands in comparison to activity levels found in other high elevation forests.

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.

Seed-caching rodents store large quantities of seeds during the summer and autumn but the number of stored seeds has rarely been estimated. Understanding how many seeds each individual stores has implications for energetics during the period of food scarcity, and the number of seeds scatter hoarded has implications for how well animals disperse the seed of plants and thereby effect ecological processes. The number of seeds of antelope bitterbrush (Purshia tridentata) and Jeffrey pine (Pinus jeffreyi) scatter hoarded by yellow pine chipmunks (Tamias amoenus) was estimated in a year of good seed production. Both of these plant species are adapted for seed dispersal by scatter-hoarding animals. Individual chipmunks scatter hoarded an estimated 29,629 bitterbrush seeds and 5,945 Jeffrey pine seeds each year. These estimates are likely underestimates and do not include the many thousands of seeds eaten during the harvest period. Combined, the number of seeds of these two species that chipmunks scatter hoard in soil provided 2.8 times more energy than required to survive the autumn and winter. Populations of yellow pine chipmunks have the potential to scatter hoard nearly a million seeds per hectare in good seed years.

Selection occurs when animals choose from among alternative habitat resources they find available in the environment. As selection is a hierarchical process, it can be studied at multiple spatial scales. Subterranean rodents are a good model to study habitat selection because of their low dispersal ability and easily identifiable perturbed areas. Using a comparative data from multiple distinct locations, we analyzed if Ctenomys mendocinus selects different habitat units at a macroscale and identify which variables most influence its activity at a microscale. We conducted this study in an extreme environment in terms of resource abundance and climatic conditions, generating interesting new insights into patterns of habitat selection by this species. We found that minimum soil depth and the abundance of Fabiana punensis shrub were the most important variables determining C. mendocinus activity at the microscale. Also, the changes in these variables may probably influence the selection of habitat units found at the macroscale.

Dietary niche separation is often crucial for promoting coexistence of sympatric species sharing similar habitats. In this study, we used cafeteria experiments to explore feeding preferences of two sympatric small herbivores in Hulunber meadow steppe, the narrow-headed vole (Microtus gregalis) and the Daurian pika (Ochotona dauurica), and used microhistological analysis of stomach contents to measure their actual diets and evaluate their niche overlap. To evaluate the effects of scale, we conducted dietary analyses at two commonly documented taxonomic scales of food type categorization: a fine scale based on the species level, and a coarse scale based on a roughly family-level categorization. Niche analysis at the fine and the coarse scales generated qualitatively similar results, although niche overlap was larger at the coarse scale than at the fine scale. In cafeteria experiments, voles and pikas showed similar feeding preference patterns. When foraging in the field, the two species differed in food use and feeding preference, without a significant dietary niche overlap. In the laboratory, both species preferred to eat Leguminosae and Asteraceae species. In the field, pikas still preferred Leguminosae species and voles switched to prefer Liliaceae species. These results suggest the existence of dietary niche partitioning, and competition might have driven the observed niche shift.

For ruminants and arboreal herbivores (sloths and colobine monkeys), an influence of digestive physiology on resting postures has been postulated that is linked to the interplay of digestive anatomy and the gravity vector. To further explore this putative relationship, we observed 253 individual terrestrial mammalian herbivores at zoological gardens, noting 29,478 resting events in 36 species during the day and 7,383 resting events of 18 species at night, providing a catalogue of mammalian resting postures. We confirm the constraint of ruminants to sternal recumbency and expand this observation to camelids, which rely on a similar sorting mechanism in their forestomach for rumination, but which use lateral recumbency to a slight but distinctively larger proportion. Generally, larger herbivores rest more in a standing position, and use lateral recumbency more when lying. The use of lateral recumbency in large hindgut fermenters (perissodactyls, elephants) and nonruminant foregut fermenters (macropods, hippos) corresponds to the concept that there is no interplay between gravity and digestive physiology in these species. By contrast, peccaries, hyraxes, and hystricomorph rodents never used lateral recumbency. While this may be related to body size, body shape, or other species-specific characteristics, it also suggests that the interplay of gravity and digestive processes, in particular with the colonic separation mechanism in hystricomorph rodents, should be further investigated.

We assessed the level of genetic variability and population structure of the common bottlenose dolphin (Tursiops truncatus) in the tropical and subtropical portions of the southwestern Atlantic Ocean and compared the results with previous morphological findings. We analyzed 109 samples of common bottlenose dolphins that were sequenced for control region mtDNA and genotyped for seven polymorphic microsatellite loci. The results suggested that the species in this region can be separated in two major biological units, northern and southern, with an area of parapatry at southern Brazil. The northern unit seems to occur in a wide range of depths, including offshore waters, is consistent with the canonical morphology of T. truncatus, and can be divided into three management units: 1) Saint Paul's Rocks, 2) north and northeast of Brazil, and 3) Campos and Santos Basins (that extend at least to southernmost Brazil). The southern unit is coastal, occurring exclusively in very shallow waters (< 10 m) and estuaries, and is consistent with the previously described (putative) Tursiops gephyreus. Nevertheless, a formal decision on the taxonomic status of T. gephyreus should wait for a more geographically comprehensive and data-integrative study.

We describe a new species of the cricetid rodent Oxymycterus (Sigmodontinae), which inhabits a transitional area between the southern Cerrado and the Atlantic Forest in south-southeastern Brazil. Compared to other Oxymycterus, the new species is large-sized with a tawny-brown pelage coloration. The new species could be differentiated from other Oxymycterus species by a combination of cranial characteristics that includes markedly large and inflated auditory bulla; a narrow rostrum and large incisive foramen, with the posterior extremity reaching the posterior region of the M1 protocone or hypoflexus; a wide parapterygoid fossa; the presence of a foramen ovale in the posterior region of the parapterygoid plate; and a thin hamular process of the squamosal. Bayesian analysis based on the mitochondrial and nuclear genes (cytochrome-b and acid phosphatase type V—Intron 2, respectively) recovered from the Oxymycterus sp. nov. showed it to be phylogenetically closely related to O. amazonicus and O. delator, all three species associated with open vegetation. The lineage leading to this clade likely emerged around 1.14 million years ago during the Early-Middle Pleistocene. Genetic distances between the new taxa and these two species calculated from comparison of cytochrome-b sequences are 3.7% and 4.1%, respectively. Currently, Oxymycterus sp. nov. is known from only two unprotected sites, with the type locality inserted in an area under the process of conurbation. Our study raises the number of living species in the genus to 16.