Papers in this Special Feature were presented at a symposium on the biology of Glaucomys sabrinus convened at the 86th Annual Meeting of the American Society of Mammalogists in June 2006. Because G. sabrinus is an arboreal species that relies on several attributes of older forests, it is an ideal model organism for studying impacts of broad-scale habitat loss and alteration from logging, clearing, and natural disturbances. The objective of the symposium was to integrate knowledge of mammalogists from multiple disciplines to achieve a more complete biological portrait to gain insights about how forest communities are being impacted by dramatic changes in forest composition and distribution following European settlement of North America, and to identify gaps in knowledge and information needs that can guide future research. The symposium included 5 papers that encompass a diversity of biological information, including the evolutionary origin and systematics of Glaucomys, the anatomy and evolution of G. sabrinus, its biogeography, genetic variation within and among regional populations, its ecology, functional morphology, kinetics, and issues and challenges of conservation.

I summarize our current understanding of the evolutionary origin and biogeographic history of the New World flying squirrels (Glaucomys). The emerging synthesis of flying squirrel systematics supports a monophyletic origin for the group in the early Miocene followed by a divergence of New World and Eurasian flying squirrels in the late Miocene. Today, the New World flying squirrels consist of 2 recognized species, G. sabrinus and G. volans. These 2 species are closely associated with the northern coniferous and deciduous hardwood forest biomes of North America, respectively, making them especially useful as biogeographic indicator species for these 2 forest types. Molecular systematic studies have revealed the presence of 2 distinct evolutionary lineages within G. sabrinus (a widespread Continental lineage and a more geographically restricted Pacific Coastal lineage). Bacular morphology and data from nuclear loci suggest recent or ongoing gene flow between these 2 lineages where they meet in the Pacific Northwest of North America. Populations of G. volans from eastern North America represent a 3rd distinct lineage within the genus. Mesoamerican flying squirrels (traditionally considered to be southern forms of G. volans) have not been examined with molecular data and may represent 1 or more additional lineages. From a biogeographic perspective, Quaternary climatic fluctuations and associated changes in the location and extent of forest habitats appear to have been important factors in promoting early evolutionary diversification within the genus; structuring of intraspecific patterns of genetic variation; and producing geographically isolated peripheral populations in high-elevation habitats at the southern extremes of each species' range, several of which are now of conservation concern. These results have broad implications for understanding the Quaternary biogeography of the coniferous and deciduous forest biomes of North America.

We assessed the locomotor performance of captive northern flying squirrels (Glaucomys sabrinus) over short glide distances and on small branches. We used stroboscopic photography, digital video, and an instrumented force pole to estimate takeoff and landing forces, angle of attack, and velocity profiles over short glides. We determined stride phases and duty factors of the animals as they moved across small branches, and compared these results with those for a small marsupial glider. Launch velocity, initial acceleration, and glide angle were not related significantly to animal mass. Initial velocity, terminal velocity, and landing force increased with increasing glide distance. Angle of attack at launch was not related to glide distance, but at landing it increased with increasing distance, suggesting active stalling. Simultaneous observations of takeoff and landing forces suggest that at distances greater than 2 m, landing forces are smaller than takeoff forces. The flying squirrels did not demonstrate a high level of agility as they traversed small branches. As branch diameter decreased below 2.5 cm, duty factors were greater than 0.5, indicating use of a walking gait. In comparison, small marsupial gliders (Petaurus breviceps) used running gaits with duty factors less than 0.5 for the same branches. We used relative warp analysis to explore pelvic and femoral shape variation in flying squirrels, and relate these to differences in locomotor performance. Small squirrels such as Glaucomys appear to have a pelvic and femoral architecture that has greater mechanical advantage for leaping than large squirrels such as Petaurista. We interpret these differences in the context of predator avoidance and foraging strategies.

A common arboreal rodent of boreal and montane coniferous forests, the northern flying squirrel (Glaucomys sabrinus) has several life-history traits typical of K-selected species. Density varies among forest types, with core areas of use centering on food patches. Density is largely limited by food, and to a lesser extent, suitable natal dens, but also is influenced by potential competitors and predators. Local abundance of G. sabrinus frequently is correlated with density of large trees and snags, shrub and canopy cover, prevalence of old-forest features (e.g., coarse woody debris), and abundance of hypogeous mycorrhizal fungi (truffles). Diet varies seasonally and among habitats, but truffles (spring and autumn) and lichens (winter) are most often reported. In some parts of its geographic range, G. sabrinus has a more diverse diet and lower reliance on truffles in forests with a depauperate arboreal small mammal community. G. sabrinus is a keystone species in the Pacific Northwest, because its diet facilitates an obligate mutualistic relationship between mycorrhizal fungi and some trees and shrubs and because it is essential prey for mesocarnivores and avian predators. G. sabrinus achieves its highest densities in old growth, but also occurs in secondary forests. Disturbance that reduces structural complexity, canopy cover, or the availability of large, decadent trees typically results in smaller populations through effects on food, den sites, or risk of predation. The fundamental niche of G. sabrinus may be broader than suggested by early research in the Pacific Northwest. Sustaining viable and well-distributed populations in heavily modified landscapes will depend on the capability of remaining forest habitat to sustain breeding populations without immigration, or functional connectivity among fragmented populations such that viable metapopulations will persist. Future research should focus on identifying habitat conditions that sustain breeding populations in modified habitats and determining whether G. sabrinus can migrate freely through a matrix of unsuitable habitat.

Molecular evidence strongly supports the derivation of flying squirrels from tree squirrels, with the sister group being the Holarctic tree squirrels (Sciurus) and their close relatives. We present a rationale for the hypothesis that the transition occurred among small squirrels, and we propose using the northern flying squirrel (Glaucomys sabrinus) and the southern flying squirrel (Glaucomys volans) as models. Thus, we compare their morphologies with similar-sized tree squirrels (the Central American dwarf squirrel [Microsciurus alfari] and the western dwarf squirrel [M. mimulus]). We compare body proportions of Glaucomys with those of Microsciurus, considering differences as potential adaptations for gliding associated with wing loading, aspect ratio, and parasitic drag. We use the following measurements: lengths of the centra of the thoracic, lumbar, sacral, and caudal vertebrae; and lengths of the long bones (humerus, radius, femur, and tibia), metacarpals, metatarsals, and proximal phalanges of the hands and feet. We then compare these proportions of Microsciurus with those of other species of Sciurini, and the proportions of Glaucomys with other species of Pteromyini, to determine if each is representative or derived within its clade. Members of the genus Glaucomys exhibit relative elongation of the lumbar vertebrae and the forearm, relevant to wing loading and aspect ratio, relative lengthening of the midcaudal vertebrae, and relative shortening of the more distal caudal vertebrae, perhaps of importance for stability and control. Members of the genus Glaucomys also have shorter hands and feet, but these appeared to be elongated in Microsciurus, rather than shortened in Glaucomys, leaving the issue of parasitic drag moot. Finally, we speculate on the genetic changes that have produced these morphological modifications and may facilitate the evolution of gliding flight.

The northern flying squirrel (Glaucomys sabrinus) has an extensive range in North America, inhabiting boreal, coniferous, and mixed forests of the northern United States and Canada and the slopes of the mountains of the east and west. Most undisturbed northern populations are apparently thriving, but those in the southern mountains are considered disjunct relicts occupying declining remnants of suitable habitat. It is clear that range contraction in the past has been associated with climate and vegetation change in the Pleistocene and the large-scale timber harvests of the early 20th century and that today a significant threat comes from forest practices and development. However, the major problem in dealing with conservation of this species is understanding its complex ecological position in its regional communities and the subtle as well as obvious influences of human activities. Thus, to preserve this species over its extensive range one will have to consider its various roles as a biological opportunist, an important prey item, a disperser of mycorrhizae, a potential victim of biological warfare, and a small, secretive glider especially vulnerable to anthropogenic and possible climatic changes in the size, arrangement, and quality of its home forests.

The generation and analysis of mitochondrial DNA (mtDNA) sequence data has become routine in mammalogy. Unfortunately, these analyses can be confounded because fragments of the mitochondrial genome are contained in the nucleus of most eukaryotes. Furthermore, these nuclear fragments of mitochondrial genes, or numt pseudogenes, are often represented hundreds of times in mammalian nuclear genomes. Most modern analyses of mtDNA rely on the polymerase chain reaction to generate a population of molecules that can be sequenced. Templates for DNA sequencing reactions should be homogenous, and in the case of mtDNA, cytoplasmic in origin. The unwanted (and often unwitting) amplification of numts results in a heterogenous mixture of nuclear and cytoplasmic amplicons or, if a numt is preferentially amplified, a near-homogenous mixture of the wrong (nuclear) template. These nuclear sequences can cause major—although often cryptic—problems in the analyses of systematic or phylogeographic data. Here, we review the occurrence, detection, and avoidance of numts in mammals. Furthermore, we isolate a cytochrome-b numt and its corresponding mitochondrial sequence in the North American prairie vole (Microtus ochrogaster) to illustrate various methods to detect numts. Finally, we present approaches by which numts, once identified, can be utilized in molecular studies.

Until recently it was assumed that fishers (Martes pennanti) in the Rocky Mountains all were descended from reintroduced stocks. However, a recent study reported that mitochondrial DNA (cytochrome-b and control region) haplotypes of fishers found only in west-central Montana are likely derived from a relic population of fishers that escaped harvests conducted in the early 20th century. I compared fishers in west-central Montana to samples from north-central Idaho and found no evidence for substructure between these groups. A museum specimen, collected in 1896 in north-central Idaho before any known translocation, also was the same haplotype as the “native Montana haplotype” discovered in the recent study. Thus, fishers in north-central Idaho and west-central Montana are the only confirmed native fishers in the Rocky Mountains, and 1 of a few populations in the West that have maintained native genes. Fishers from Idaho and Montana are not all descendants of translocated individuals, but also are the descendants of fishers that persisted despite early 20th century trapping.

Dorsal pelage color, morphometry of cranial characteristics, and sequences of 500 base pairs from mitochondrial cytochrome-b gene of pocket gophers (Thomomys bottae) from the Cape region in Baja California Sur were used to evaluate how the environment influences morphologic and genetic structure in populations from habitats with altitudinal segregation. Gophers from temperate forest, tropical deciduous forest, and desert scrub were sampled. Among 80 individuals examined, 34 haplotypes were found. Specimens collected in each habitat were not monophyletic. Analysis of molecular variance indicated that more than one-half of the total pool of genetic variation was contained among individuals within local populations and that only 0.6% could be explained by the different habitats; there was no genetic structure and the populations were genetically similar. Individuals in the temperate forest were larger, darker, and more diverse in coloration; individuals from tropical deciduous forest were smaller; and those from desert scrub had lighter coloration. There were no differences among populations in cranial shape. Only the dorsal coloration of the specimens from the temperate forest matched the color of moist soil. There were no diagnostic characteristics to recognize T. b. alticolus, the population restricted to high-elevation temperate forests in La Sierra de La Laguna, as a valid subspecies; we consider it a junior synonym of T. b. anitae. The range of this subspecies is from the San Ignacio Lagoon to the southern end of the Baja California peninsula.

The tuco-tuco das dunas (Ctenomys flamarioni) is a subterranean rodent endemic to sand-dune ecosystems along the southern coast of Brazil. We studied 3 populations that differed in the degree of human impact, and used direct and indirect methods to assess demographic and genetic information. Field studies revealed a tendency toward a female-biased sex ratio, and sexual dimorphism in both weight and length in all 3 populations. This evidence supports a hypothesis of polygyny in C. flamarioni. Using 9 microsatellite loci, we explored patterns of variation and genetic structure among the populations. Our findings suggested that the Xangri-lá and Remanso populations, living in more-disturbed locations, could have experienced demographic reductions in population size, but not the Pinhal population. However, other factors such as a polygynous breeding system and the environmental instability that characterizes the coastal dunes may have influenced the observed pattern. Analysis of genetic structure revealed strong differentiation among populations, but no significant structure at the intrapopulation level. Nonsignificant values for the tested indices from assignment tests (F_ST, F_IS, mAIc, and vAIc) over population showed no evidence of sex-biased dispersal. The same was observed from analyses of molecular variance. Nevertheless, lower pairwise F_ST and higher Nm values between males from Xangri-lá and Remanso indicated greater gene flow among males, suggesting a slightly male-biased dispersal pattern. Significant differences in interpopulation dispersal patterns were clearer among females, with greater dispersal for females from Pinhal than those at Remanso and Xangri-lá.

Mustelids, including American mink (Neovison vison), are definitive hosts for sinus nematodes of the genus Skrjabingylus. Previous research has suggested that skrjabingylosis can cause a swelling of the frontal sinuses in mustelid hosts, leading to an inverse relationship between intensity of infection and braincase volume. We tested this hypothesis on 261 adult mink skulls collected in Ontario, Canada. Consistent with the hypothesis, we found a reduced slope in the relationship between skull size and braincase volume for male mink exhibiting lesions attributable to infection with Skrjabingylus, compared to male mink with no lesions. However, we found no differences in slope for female mink. Male mink with lesions also had shorter postorbital lengths and mastoid breadths compared to males without lesions. Our results demonstrated that sinus nematodes may cause reduced braincase volume, but only in male mink. Infection may also have broader effects on skull shape than localized damage to the frontal bones and braincase roof. We suggest that parasitism of mink by Skrjabingylus may be sex-biased because of the sexual size dimorphism of the species.

For the past century, the genus Styloctenium Matschie has been known to contain a single species restricted to Sulawesi and the nearby Togian Islands. Styloctenium has a unique pelage, characterized by white supraocular spots and a white rostral stripe on an otherwise mostly orange pelage. Several additional features characterize the genus, including the loss of i1 and m3, rudimentary state of P1, and marked reduction of the molar cusps. The genus has often been considered closely allied to Pteropus, but no explicit, broadly supported, phylogenetic hypotheses have been proposed. Herein, I describe a new species of Styloctenium from Mindoro Island, Philippines, using a variety of dental, cranial, soft tissue, and external characters. The new species possesses all characters known to be diagnostic of Styloctenium, but also multicusped lower and upper canines. It is known only from the type locality in western Mindoro Island, is hunted (along with other large pteropodids), and may be at risk of extinction because of habitat loss, hunting, or both. The presence of a midsized, conspicuously colored, undescribed mammal on Mindoro emphasizes the need for further biodiversity inventories and specimen collection in the region, and on Mindoro in particular.

We determined the foods habits of 5 species of microchiropteran bats (Hipposideros commersoni, Triaenops rufus, Triaenops furculus, Myotis goudoti, and Miniopterus manavi) in the austral winter and summer in a dry deciduous forest in western Madagascar using fecal analysis. We also assessed food availability and bat activity in 4 forest microhabitats. Despite overlap in dietary composition, H. commersoni consumed mainly Coleoptera; M. goudoti consumed mainly Hymenoptera, Neuroptera, and Araneae; M. manavi consumed mainly Hemiptera; and T. rufus and T. furculus consumed mainly Lepidoptera. Diptera were the most abundant insects in traps but were rarely encountered in feces. H. commersoni was not netted during the austral winter, but the other 4 species changed their diet according to seasonal availability, with lepidopterans the most important diet items in winter and coleopterans in summer. We consistently trapped a higher abundance of potential bat prey at the forest edge, whereas the forest interior was low in both food availability and bat activity. The 5 microchiropterans studied partitioned the available food mainly through dietary specialization, although spatial and temporal partitioning also may play a role. More research is needed to assess levels of dependency on forest by these bats, and to investigate the seasonal ecology of H. commersoni and interspecific competition between T. rufus and T. furculus.

We radiotracked 25 adult female fringed myotis (Myotis thysanodes) to day roosts in xeric ponderosa pine (Pinus ponderosa) forests on the east side of the Cascade range in Washington and Oregon from 2001 to 2003. Bats were tracked for an average of 9.6 days/bat ± 0.1 SE for a total of 240 roost-days. Bats used 118 roosts, 93% of which were in the crevices of rocks. Pregnant females chose horizontal crevices 58.8% of the time, whereas lactating (60.9%) and postlactating (75%) females selected vertical crevices more often. There was no difference in crevice length or crevice width among roosts in rocks used by pregnant, lactating, and postlactating females. Snags were used as roosts on only 6 occasions, and all were in ponderosa pines situated within a single watershed. The largest emergence count of fringed myotis that we recorded was 118 bats from a ponderosa pine snag. Snags used as roosts were larger in diameter, taller in height, and extended farther above the local canopy than random snags. Bats used the same roost for 1.8 consecutive days ± 0.12 SE and used an average of 5.5 roosts/bat ± 0.69 SE. Bats moved 1.6 km ± 0.34 SE between capture sites and roosts, with distance between successive roosts averaging 0.55 ± 0.12 km. Roosts were 1.4 km ± 0.36 SE from the closest perennial stream. Examination of these data indicates that snags are a less significant component of roosting habitat of fringed myotis in ponderosa pine forests on the east side of the Cascades than has been reported for the species in other regions of its distribution.

Little information has been published on selection of tree roosts by eastern pipistrelles (Perimyotis subflavus) in forested environments, and no radiotelemetry-based studies have been conducted on males in forested settings. Therefore, we used radiotelemetry to characterize summer roost selection by 21 male (33 roosts) and 7 female (14 roosts) eastern pipistrelles during 6 years in a forested region of the Ouachita Mountains of Arkansas. All roosts were located in the vegetation of tree canopies; 50% of roosts of females and 91% of roosts of males were in dead leaves of deciduous trees. Three (43%) of 7 maternity colonies were in dead needles of large live pines (Pinus echinata); this is the 1st documented use of pines by this species for roosting. Males selected tree sizes randomly but females selected trees that were larger (P < 0.05) than random. For males, 87% of roosts were in oaks (Quercus), and males roosted at sites with more midstory hardwoods, more large pines in the overstory, less canopy cover, and farther from the nearest trees than random locations. In a landscape offering a diversity of forest habitats, eastern pipistrelles during summer roosted mostly in leaves of oaks in mature (≥50-year-old) forest with a relatively complex structure and a hardwood component.

We used stage-structured matrix population models, derived from 3 years with disparate levels of precipitation, to assess the potential effects of climate change on annual population growth (λ) of deer mice (Peromyscus maniculatus). Populations of deer mice increased during a year of normal precipitation (λ = 1.69 ± 0.02 SE) and a wet year (λ = 1.03 ± 0.02), but declined in a dry year (λ = 0.34 ± 0.02). Life-table response experiment analyses indicated that reduced survival of adults in the dry year, and reduced survival of pups and juveniles in the wet year, exerted the greatest influence on variation in population growth. Stochastic models that projected populations of deer mice for a 50-year period predicted that populations would not be able to persist if mean annual precipitation was reduced ≥11% by increasing the frequency of dry years. Furthermore, the stochastic population growth rate declined more quickly when the probability of a normal year was reduced, simulating increased variability in rainfall, relative to other scenarios examined. Our stochastic models indicate that a relatively small reduction in mean precipitation could result in substantial population declines of P. maniculatus in the mixed-grass prairie of central North America.

Reports of geographic variation in behavior and morphology among prairie voles (Microtus ochrogaster) from Illinois, Kansas, and Tennessee have led to the belief that these animals vary in their mating strategies and the degree to which they are monogamous. Despite this, few studies have directly compared behavior between populations. Because the prairie vole is commonly discussed as a model for mammalian monogamy, understanding how aspects of social attachment and the mating system vary could provide further insight into the evolution of monogamy. We therefore conducted a series of experiments in the laboratory and field to assess morphological, behavioral, or genetic differences between 2 populations of this species. Voles from Illinois were morphologically similar to voles from Tennessee and exhibited comparable social and mating behavior under both laboratory and field conditions. Although genetically distinct, the 2 populations demonstrated similar levels of heterozygosity and allelic richness. Sexual dimorphism, a common indicator of mating strategy, was absent in voles from 7 widely distributed regions from across their geographic range. In the context of these results, we question the degree to which the previously described population differences are ecologically meaningful. If differences between prairie voles from Kansas and Illinois do indeed exist, examination of our data suggests that those from Kansas are atypical of prairie voles overall.

Knowledge of home-range sizes and the degree of spatial overlap between males and females can help elucidate mammalian mating systems and social organizations. To characterize the social system and mating strategies of an endangered species, the giant kangaroo rat (Dipodomys ingens), we compared home ranges of males and females during the breeding and nonbreeding seasons using radiotelemetry. Boundaries and sizes of home ranges varied seasonally for males, but not for females. During the nonbreeding season, both males and females remained in exclusive territories located in the core of each individual's home range. During the breeding season, home-range size of males increased significantly as mobility of males increased and home ranges expanded to overlap neighboring territories of females. Home ranges also were more uniformly distributed than in the nonbreeding season, and nearest neighbors were significantly more often opposite-sex individuals. Males likely increased home-range sizes to overlap with multiple females and to enhance their opportunities for mating, perhaps by becoming familiar with neighboring females and monitoring those females for signs of receptivity. Although home ranges of females remained similar in size throughout the year, females seemed able to adjust their home ranges in response to neighboring vacancies. We conclude that spacing of D. ingens is flexible in order to meet changing social and environmental conditions.

The subterranean ecotope, particularly in tropical regions, is almost free of daily fluctuations in environmental factors that may serve as zeitgebers. The question arises as to whether there is circadian periodicity in the activity of its permanent inhabitants and, if so, how it is induced and maintained. We used radiotelemetry to follow the activity of the silvery mole-rat, Heliophobius argenteocinereus (Bathyergidae), in its natural environment in Malawi during the dry season. Silvery mole-rats were found inside their nests during 63% ± 8% SD of radiofixes; the animals were inactive for 72% ± 8% of the within-nest fixes recorded. Activity tended to decrease over the course of the dry season. Although activity was detected at any time of day, most individuals showed a predictable (mostly unimodal, occasionally bimodal) pattern of activity that was associated with slight daily belowground temperature fluctuations (mostly less than 3°C). In the coldest part of the dry season, overall activity rose with daily temperature. At the beginning of the hot and dry season, the period of enhanced daily activity was shifted to earlier (colder) hours. Mole-rats in the field apparently respond to even slight temperature fluctuations and adjusted their activity accordingly. We propose that burrow temperature can work as zeitgeber of circadian activity in this species.

We used long-term (2- to 15-h) focal-animal sampling (“follows”) and supplementary behavioral observations of adult spotted hyenas (Crocuta crocuta) from 3 separate social groups within the Masai Mara National Reserve, Kenya, to investigate the degree to which sex, social rank, and human disturbance influenced hyena activity patterns, movement rates, and timing of den use. Hyenas followed for composite 24-h cycles were active during 31.5% ± 2.7% SE of the 24-h period. During hours of darkness (1900–0600 h) hyenas spent 53.0% ± 4.1% of their time active, and 96.2% ± 0.9% of all activity occurred from 1800 to 0900 h. Mean movement rate during this period was 928 m/h ± 104 SE, and was 584 ± 64 m/h throughout the 24-h period. Distance traveled during a 24-h period averaged 12.4 km. Male spotted hyenas tended to be more active than females, particularly during the morning (0700–1100 h), and also tended to exhibit higher movement rates. Neither rates of activity nor movement varied with social rank, but low-ranking females spent more time feeding than did high-ranking females. Finally, female hyenas in territories with daily livestock grazing and high tourist visitation rates showed lower activity and den use than hyenas in an undisturbed territory during the times of day when human activity coincided with potential hyena activity. Specific times of day when activity was reduced indicated that livestock grazing, not tourist activity, was probably responsible for observed shifts in activity. We discuss possible indirect costs associated with observed alterations in timing of den use and activity.

Although interspecific killing among carnivores can drive populations toward extinction, it is generally unknown how these intraguild interactions vary among populations, and whether the threat for vulnerable species can be mitigated. We studied imperiled populations of swift foxes (Vulpes velox) in Canada and kit foxes (Vulpes macrotis) in Mexico to determine potential differences in survival or predator-avoidance strategies. Survival rates were significantly lower in Canada than in Mexico because of mortality caused by coyotes (Canis latrans) and golden eagles (Aquila chrysaëtos), and the potential for population recovery is likely higher for the Mexican fox population. Differences in body size between coyotes and foxes, diet, group sizes, intraspecific home-range overlap, home-range sizes of coyotes, and movements of coyotes relative to foxes were similar among study areas. However, Canadian foxes had home ranges that were approximately 3 times larger than those in Mexico, and Canadian foxes were most frequently killed on their home-range peripheries. Home ranges of kit foxes decreased in size as the availability of black-tailed prairie dog (Cynomys ludovicianus) colonies increased and associated refuge holes, which foxes could use to escape predation, were significantly more abundant in Mexico than in Canada. Small home ranges of foxes probably reduced encounters with coyotes in Mexico, and a high availability of refuges likely allowed foxes to elude predators when such encounters did occur. Differences in survival of foxes relative to mortality caused by coyotes demonstrate that interactions between carnivores can vary greatly between populations and that, in some situations, vulnerable species may be able to coexist with dominant carnivores despite a lack of large-scale habitat partitioning.

An implicit assumption of the mesopredator release hypothesis (MRH) is that competition is occurring between the larger and smaller predator. When significant competition exists, the MRH predicts that larger species should affect population size, through direct predation or the elicitation of avoidance behavior, of smaller predators. However, there have been few manipulations designed to test these predictions, particularly regarding avoidance. To test whether striped skunks (Mephitis mephitis) avoid coyotes (Canis latrans), we intensively monitored 21 radiocollared skunks in a natural area in northeastern Illinois. We identified 2 spatially distinct groups and recorded 1,943 locations from September to November 2003. For each group, testing periods consisted of 4 weeks (2 weeks pretreatment, 1 week treatment, and 1 week posttreatment). We simulated coyote activity during the treatment week by playing taped recordings of coyote howls at 1-h intervals at 5 locations. Additionally, we liberally applied coyote urine to several areas within 20 randomly selected 100 × 100-m grid cells, and used the grid to classify cells as urine-treated, howling-treated, or control. We determined changes in home-range size and location, and intensity of cell use in response to treatment. We found no differences in home-range size related to treatment (P ≥ 0.248). Although weekly differences in home-range drift approached significance when individuals from both tests were pooled (P = 0.071), drift was highly correlated with mean weekly low temperatures (P = 0.004). Use of howling- and urine-treated cells did not vary among weeks (P ≥ 0.307), nor did proportions of locations within howling circles with assumed effective broadcast radii of 50–200 m (P ≥ 0.851). Examination of our data did not support the prediction that skunks avoid areas of coyote activity on our study site.

We tested the hypothesis that gravel roads, not paved roads, had the largest negative effect on habitat quality for a population of American black bears (Ursus americanus) that lived in a protected area, where vehicle collision was a relatively minimal source of mortality. We also evaluated whether road use by bears differed by sex or age and whether annual variation in hard mast productivity affected the way bears used areas near roads. In addition, we tested previous findings regarding the spatial extent to which roads affected bear behavior negatively. Using summer and fall home ranges for 118 black bears living in the Pisgah Bear Sanctuary in western North Carolina during 1981–2001, we estimated both home-range–scale (2nd-order) and within-home-range–scale (3rd-order) selection for areas within 250, 500, 800, and 1,600 m of paved and gravel roads. All bears avoided areas near gravel roads more than they avoided areas near paved roads during summer and fall for 2nd-order selection and during summer for 3rd-order selection. During fall, only adult females avoided areas near gravel roads more than they avoided areas near paved roads for 3rd-order selection. We found a positive relationship between use of roads by adults and annual variability in hard mast productivity. Overall, bears avoided areas within 800 m of gravel roads. Future research should determine whether avoidance of gravel roads by bears affects bear survival.

We evaluated selection of den sites by American black bears (Ursus americanus) in the Pisgah Bear Sanctuary, western North Carolina, by comparing characteristics of dens at 53 den sites with availability of habitat characteristics in annual home ranges of bears and in the study area. We also tested whether den-site selection differed by sex, age, and reproductive status of bears. In addition, we evaluated whether the den component of an existing habitat model for black bears predicted where bears would select den sites. We found bears selected den sites far from gravel roads, on steep slopes, and at high elevations relative to what was available in both annual home ranges and in the study area. Den-site selection did not differ by sex or age, but it differed by reproductive status. Adult females with cubs preferred to den in areas that were relatively far from gravel roads, but adult females without cubs did not. The habitat model overestimated the value of areas near gravel roads, underestimated the value of moderately steep areas, and did not include elevation as a predictor variable. Our results highlight the importance of evaluating den selection in terms of both use and availability of den characteristics.

Domestic cats (Felis catus) have been introduced on many islands in the world and are responsible for much damage to native insular faunas. The worldwide success and spread of this opportunistic predator is generally associated with its trophic adaptability. We examined the diet of a long-established feral cat population on a small Mediterranean island through the analysis of 1,219 scats collected during a 4-year period. Our results confirm that feral cats are generalist predators, able to feed on a wide range of prey. However, only a few prey species formed the major part of its diet. Two introduced mammals and a Mediterranean endemic seabird provided 93% of the yearly biomass consumed by cats (ship rats, 70%; wild rabbits, 7%; and yelkouan shearwaters, 6%). Ship rats remained by far the staple prey for cats throughout the year, but the diet of feral cats was more diversified in spring and early summer, frequently including insects, reptiles, and migrant birds. Endemic yelkouan shearwaters were preyed upon most frequently in autumn and winter, that is, during the shearwaters' prelaying period. Because rats provide the majority of the food of cats, they could help to maintain or inflate this alien predator population with deleterious consequences to the endemic shearwater. A cat eradication campaign would help protect the population of shearwaters on this island.

Seasonal habitat selection and foraging movements are important aspects of predator ecology, and individual movements can provide a method to link predator–prey dynamics to the spatial mosaic of the environment. Prairie Ridge State Natural Area in Jasper County, Illinois, is a highly fragmented reserve that provides critical habitat for many declining grassland-dependent birds. Nest predation in this area is likely to be substantial because of high mesopredator populations. We undertook a 2-year telemetry study to investigate raccoon (Procyon lotor) movements and habitat selection on the reserve. During the avian nesting season, raccoon pathways had significantly lower fractal dimension, indicating more linear movements and less searching behavior than for fall–winter pathways. Movement distances and rates did not differ between the sexes or seasons. Habitat selection was significantly different among seasons on 2 hierarchical levels. Raccoons generally avoided grasslands in spring and summer, and the shape of pathways indicated that raccoons apparently did not search for nests in grassland habitats. Consequently, nest predation likely occurred incidentally as raccoons moved across grasslands to richer food patches such as wetlands, streams, and residential areas.

We investigated habitat use by introduced raccoons (Procyon lotor) and native raccoon dogs (Nyctereutes procyonoides albus) in a northern deciduous forest of Japan to examine the relationship between the 2 species. Spatial and temporal habitat use in the forest was monitored using infrared-triggered cameras. We also surveyed environmental factors at 2 spatial scales: at the macrohabitat scale, we examined forest growth stage, forest fragmentation, and distance from a water source; at the microhabitat scale, we examined forest structure, understory vegetation, and beetle abundance. We then analyzed the relationship between environmental factors and habitat use by each species using generalized linear model. Except for fern coverage, most environmental factors at the micro- and macrohabitat scales had different effects on the habitat use of these species. Moreover, the degree of diurnal activity also differed between the species. These spatial and temporal differences in habitat use between raccoons and raccoon dogs provide further evidence that competition between these 2 species may be limited in this area.

To test how interindividual variation in response to resource availability might reveal mechanisms leading to interpopulation variation across the geographic range of a species, we investigated movement patterns and use of space by 18 radiocollared raccoon dogs (Nyctereutes procyonoides viverrinus) in a mixed landscape of agriculture and forestry that is widely distributed in Japan, and that is a typical landscape for raccoon dogs. We tested the idea that the behavior of raccoon dogs, as ecological generalists, is sufficiently plastic for individual movement patterns to match habitat variation in this landscape. Home ranges averaged 111 ha (95% kernel estimate), much larger than previously reported for this species in Japan, and varied greatly among individuals (23–228 ha). Home ranges were 62.5% larger in autumn than in other seasons, and 33.5% larger for subadults than for adults. Average movement rate tended to be higher in autumn (mean rate = 297 m/h), and lowest in winter (mean rate = 204 m/h). Within the population, some individuals occupied home ranges that were predominantly seminatural (we refer to these animals as “mountain type”), whereas those of others were dominated by heavily managed habitats (these we term “village type”). Within their home ranges, the types showed preferences for the habitats that were most prevalent there. Mountain-type individuals showed a preference for herbaceous habitat, whereas the village-type individuals used cropland disproportionately. Activity, as measured by the proportion of fixes designated active, tended to be lower in home ranges where cropland was predominant, and the magnitude of preference for cropland increased with its availability with the home range, suggesting a functional response to habitat availability. The fractal dimension of movement trails was more complex in seminatural areas than in agricultural land, possibly reflecting greater spatial regularity of agricultural habitat.