Individuals of 1 species might obtain information by eavesdropping on calls produced by a syntopic species. Intercepting alarm calls allows the eavesdropper to respond with antipredator behavior without the need to produce its own call, which might attract the attention of a predator. We examined eavesdropping on heterospecific alarm calls by nonsocial eastern chipmunks (Tamias striatus) and woodchucks (Marmota monax), which live in the same community, share some predators, are solitary, and produce distinct alarm calls. If these 2 species recognize heterospecific alarm calls, we should see antipredator behaviors similar to those displayed upon hearing a conspecific's alarm call. We broadcast single alarm calls of woodchucks, eastern chipmunks, and American crows (Corvus brachyrhynchos) to individuals of the first 2 species, using the territorial song of the syntopic male black-capped chickadee (Poecile atricapillus) as a control. Woodchucks became more vigilant after hearing both conspecific and heterospecific alarm calls compared with controls; however, they spent more time vigilant in response to conspecific alarm calls compared to heterospecific alarm calls. Thus, woodchucks apparently can recognize heterospecific alarm calls, but they appear to process conspecific and heterospecific calls differently. Eastern chipmunks responded to heterospecific alarm calls, but sample sizes were small and the results not definitive. Our results suggest that nonsocial mammals might benefit from eavesdropping on heterospecifics.

Demographic structure is central to understanding the dynamics of animal populations. However, determining the age of free-ranging mammals is difficult, and currently impossible when sampling with noninvasive, genetic-based approaches. We present a method to estimate age class by combining measures of telomere lengths with other biologically meaningful covariates in a Bayesian network. We applied this approach to American and Pacific martens (Martes americana and M. caurina) and compared predicted age with that obtained from counts of cementum annuli. Using telomere length and the covariates sex, species, and estimates of population density obtained from commercial trapping records, we assigned martens to juvenile (<1 year) or adult (≥1 year) classes with 75–88% accuracy. In our analysis for live-captured martens, for which information on body size and whether animals were juveniles or adults would be available, we achieved 90–93% accuracy when assigning individuals to 5 discrete age classes (0–4 years). This general approach could be extended to other species for noninvasive estimation of age class, or in place of invasive aging methods, and enable demographically based population analyses that have heretofore been impossible.

Winter breeding under the snow is a critical ecological adaptation of lemmings and a key demographic process in their periodic multiannual fluctuations in abundance. However, logistic constraints limit our ability to quantify lemming winter reproduction. We evaluated a method to infer lemming reproduction based on the size distribution of feces found in their winter nests. We determined criteria allowing identification of reproduction from feces found in nests, using golden Syrian hamsters (Mesocricetus auratus) as a surrogate model. We found a large difference in individual mass of feces between juveniles at weaning and adults. Using bimodal distribution of feces size, mean size difference, and proportion of small feces, we showed that visual inspection of ≥30 feces was sufficient to infer hamster reproduction with an accuracy of >95%. We also applied the method to winter nests of collared lemmings (Dicrostonyx groenlandicus) and brown lemmings (Lemmus trimucronatus) found in the Canadian Arctic. Because characteristics of feces found in lemming winter nests matched those found in hamster nests, we suggest that the method can be used to detect winter reproductive activity of lemmings.

Demographic rates of animals (i.e., survival and breeding success) generally increase with experience early in life, but temporal variation in the effect of experience on demography is not well understood. The demographic difference between inexperienced versus experienced breeders can be accentuated during poor environmental conditions when food is scarce, or the difference can remain constant regardless of environmental fluctuation. I tested the hypothesis that environmental variation accentuates the difference between inexperienced and experienced breeders using 20 years of capture–mark–recapture data for northern elephant seals (Mirounga angustirostris) from the Farallon Islands, California. I estimated year-specific survival probabilities, breeding propensity (the probability that an individual will breed in year x), and breeding success of primiparous (inexperienced) and multiparous (experienced) females. Primiparous breeders did not suffer more than experienced breeders during years of environmental stress. The selection hypothesis (a decrease in heterogeneity in individual quality within cohorts over time, based on selection pressure) could explain the experience-related improvement in survival and breeding success. Lower variances in survival of multiparous breeders suggest that primiparous adults constitute a more heterogeneous portion of the population, and the 1st breeding event might act as a selective process leading to a more homogeneous pool of multiparous breeders.

Breeding success among male white-tailed deer (Odocoileus virginianus) has been correlated with numerous physical and physiological variables. We investigated the effect of relative body mass on breeding success in captive male deer from 21 breeding trials. Contrary to our prediction, larger males on average had identical levels of breeding success (59% of breeding opportunities) in the 1st and 2nd halves of the breeding season. The variability of breeding success increased with greater relative mass; thus deer with substantial mass disadvantages had only limited success, and males weighing ≥92% of the pen average had success ranging from 0% to 100% of potential breeding opportunities. Although constant proximity limited males primarily to a strategy of direct confrontation, some subordinate males evidently mated opportunistically when >1 female was receptive. We conclude that ≥1 uncontrolled variable, possibly related to aggressiveness or life-history strategy, remained influential and limited the ability of some males to compete successfully in spite of greater relative body mass.

A trade-off exists for migrating animals as to whether to migrate or remain residents. Few studies have documented relationships between landscape variables and deer migration strategies. From 2000 to 2007 we captured 267 adult female white-tailed deer (Odocoileus virginianus) at 7 study sites in Minnesota and South Dakota and monitored 149 individuals through ≥3 seasonal migration periods (585 deer-migration seasons). All deer classified as obligate migrators with ≥3 migrations (range 3–9 migration seasons) maintained their obligate status for the duration of the study. Multinomial logistic odds ratios from generalized estimating equations indicated that the odds of being a resident increased by 1.4 and 1.3 per 1-unit increase in forest patch density and mean area, respectively, compared to migrating deer. Odds of being an obligate migrator increased by 0.7 and 0.8 per 1-unit decrease in forest patch density and mean area, respectively, compared to resident or conditional migrating deer. Areas inhabited by resident deer were characterized by greater number of forest patches per 100 ha and larger mean forest patch area than conditional and obligate migrant areas. Odds of migrating increased by 1.1 per 1-unit increase in deer winter severity index. Migration behavior of white-tailed deer varied among regions, and land-cover and landscape characteristics provided predictive indicators of migration strategies for deer that could have important implications for conservation, metapopulation dynamics, and species management.

We investigated the association patterns of 48 identifiable Commerson's dolphins (Cephalorhynchus commersonii) photographed 2 or more times over a 2-year period in Bahía Engaño, Chubut, Argentina. The associations among them were not different from random for short time periods (7 days) but were significantly different from random for longer periods. Lagged identification rate and lagged association rate models show that dolphins remained in the area on average 15 days and then moved away as the original groups dissolved. Commerson's dolphins appear to have a fission–fusion society, and the observed strength of their associations is in concordance with the predictions regarding their body size and ranging patterns. The dolphins seem to rely on Bahía Engaño as a core area for most of their activities, but the aggregations are labile and some individuals remain associated in a more stable manner with only a few other individuals.

The marsh rice rat (Oryzomys palustris) is a semiaquatic rodent occurring in wetland habitats throughout the southeastern United States and along the Atlantic Coast. A lack of understanding of its ecology and distribution in inland parts of its range limits our ability to assess the species' status and needs. We trapped rice rats at random and previously occupied, wetland-dominated sites in 5 southern Illinois watersheds during 2007–2009 to determine key variables affecting habitat occupancy by the species. We detected rice rats within 3 of 5 watersheds, 16 of 48 sites, and at 5 new locations. Most rice rats were captured in permanent or semipermanent emergent wetlands (n  =  89; 46.3% of total captures) or roadside ditches in wetland patches (n  =  73; 38.0%). Habitat associations determined using logistic regression and occupancy modeling provided similar results. Percent herbaceous cover and percent visual obstruction (0.0–0.5 m) were the most important microhabitat variables positively influencing rice rat occurrence. In areas surrounding wetlands, the proportion composed of upland grass was the best predictive variable of rice rat occurrence among landcover models. Estimates of daily detection probability were high (0.44–0.87). The likelihood of occupancy increased with the proportion of upland grass cover adjacent to wetland complex and percent herbaceous cover at the microhabitat scale. Inland metapopulations of rice rats are clustered throughout the southeastern United States in appropriate wetland complexes. Construction, restoration, and protection of emergent wetlands, and consideration of connectivity and adjacent grasslands, should benefit rice rat populations.

Habitat fragmentation often separates and reduces populations of vertebrates, but the relative effects of habitat attributes within remnant patches versus the matrix surrounding the patches are less clear. For snowshoe hares (Lepus americanus) lower densities and disrupted cycles in their southern range have been ascribed to habitat fragmentation, although relevant scales of landscape influence remain unknown. In a fragmented forest in north-central Washington we counted fecal pellets of snowshoe hares to examine the extent to which relative snowshoe hare densities within stands of suitable habitat changed with the composition of surrounding habitats. Pellet densities were associated primarily with density of large shrubs and saplings and medium trees within a stand. Pellet densities also were correlated positively with the amount of moist forest (dominated by Engelmann spruce [Picea engelmannii] and subalpine fir [Abies lasiocarpa]) and correlated negatively with the amount of open-structured habitat within 300 m of the stand perimeter. These results suggest that forest managers will have positive impacts on hare densities by managing both focal stands and the surrounding stands for the higher densities of large shrubs and saplings and medium trees that hares select.

Large predators respond to land cover and physiography that maximize the likelihood of encountering prey. Using locations from global positioning system–collared wolves (Canis lupus), we examined whether land cover, vegetation productivity or change, or habitat-selection value for ungulate prey species themselves most influenced patterns of selection by wolves in a large, intact multiprey system of northern British Columbia. Selection models based on land cover, in combination with topographical features, consistently outperformed models based on indexes of vegetation quantity and quality (using normalized difference vegetation index) or on selection value to prey species (moose [Alces americanus], elk [Cervus elaphus], woodland caribou [Rangifer tarandus], and Stone's sheep [Ovis dalli stonei]). Wolves generally selected for shrub communities and high diversity of cover across seasons and avoided conifer stands and non-vegetated areas and west aspects year-round. Seasonal selection strategies were not always reflected in use patterns, which showed highest frequency of use in riparian, shrub, and conifer classes. Patterns of use and selection for individual wolf packs did not always conform to global models, and appeared related to the distribution of land cover and terrain within respective home ranges. Our findings corroborate the biological linkages between wolves and their habitat related to ease of movement and potential prey associations.

Food resources and predation can influence various aspects of the ecology of small mammals, including movement and space-use patterns. We used radiotelemetry to examine experimentally how supplemental feeding and mammalian predator exclusion affected size and exclusivity of hispid cotton rat (Sigmodon hispidus) home ranges. Supplemental feeding had no effect on home-range size, and exclusivity was not influenced by either treatment. However, predator exclusion was associated with increased home-range sizes, indicating a behavioral response to perceived predation risk. We suggest that this behavioral response reflects a trade-off between predation risk and space-use patterns.

The mesopredator release hypothesis (MRH) predicts that a reduced abundance of top-order predators results in an increase in the abundance of smaller predators due to the cessation of intraguild predation and competition. In turn, small prey preferred by mesopredators are predicted to benefit from the suppressive effects of top-order predators on mesopredators. In support of the MRH a growing body of evidence shows that Australia's largest terrestrial predator, the dingo (Canis lupus dingo, body mass of 15–25 kg), might suppress the abundance of the smaller invasive red fox (Vulpes vulpes, body mass of 3.5–7.5 kg). Foxes are implicated in the declines of native rodents and marsupials in arid Australia; where foxes are rare, native prey species are more likely to persist. However, the mechanism by which dingoes suppress fox populations and benefit native mammal species is not well understood. We used scat analysis and prey selectivity indexes to examine the potential for dietary competition between dingoes and foxes at 3 arid sites. Dietary overlap between dingoes and foxes was high (≥85%) at all sites. Dingoes and foxes preferentially selected identical prey types in greater proportion to their relative abundance at all sites, but foxes tended to consume smaller prey than dingoes. Dingoes consumed more large- (>999 g) and medium-sized (100–999 g) mammals, and foxes consumed greater numbers of smaller (<100 g) mammals. At 2 sites rabbits were the most frequently occurring prey for both predators and were consumed in greater proportion than their abundance. The extensive dietary overlap and preferential selection by the predators for the same prey suggest that considerable potential exists for dietary competition between these predators. Fox remains found in dingo scats provided evidence of intraguild predation. Our results support the notions that dingoes could suppress fox populations through both dietary competition and direct killing and that this suppression of foxes could benefit small prey.

Winter extremes of temperature and food shortage limit the distribution of arctic animals. North American porcupines (Erethizon dorsatum) are one of the most widely distributed mammals in North America and range from deserts to arctic tundra. In Alaska porcupines remain active at low winter temperatures (i.e., −39°C) while consuming woody plants that are low in nitrogen (N) and high in both fiber and plant secondary metabolites. Porcupines conserved lean body mass in winter by using fat stores. Fat mass declined from 50% ± 3% to 27% ± 7% of body mass over winter. Animals with small fat stores might be more reliant on food intake during winter, because proportional fat loss was correlated positively with total fat mass at the start of winter. Fat losses were minimized by lowering rates of energy expenditure. Field metabolic rate was 440 ± 18 kJ kg^−0.77 day⁻¹. Water turnovers were slow at 26.62 ml kg^−0.75 day⁻¹ in wild porcupines. Body temperatures were not reduced to save energy; core temperatures were maintained at 37.3°C ± 0.1°C despite variation in ambient air temperature from 7°C to −38°C in captivity. Persistence of porcupines at the northern limits of their range is due to plasticity of food intake and tolerance of low-quality diets and low ambient temperatures. Minimal expenditures of energy and N in winter are combined with the conservation of lean mass. Porcupines rely on abundant summer forages to replenish their stores of fat and protein for reproduction and survival in the subsequent winter.

In response to foraging for foods that fluctuate in availability, generalists often exhibit the ability to switch between different food sources. Many of the Carnivora on an omnivorous–frugivorous diet display temporal dietary switching and specialism, but the mechanisms underlying this are incompletely understood. Here we studied the diet of the opportunistically frugivorous yellow-throated marten (Martes flavigula) with regard to food-resource exploitation in a subtropical forest of central China. Diet was determined through scat analyses combined with surveys to estimate local food abundance. Peak fruit consumption and the lowest utilization of small mammals occurred when fruit abundance reached its temporal maximum in the environment in synchrony with a concomitant peak in small mammal abundance. When both fruits and small mammals were least abundant in the environment, the marten's diet shifted to the maximum utilization of small mammals with no fruit consumption. This dietary switching could not be explained by the fluctuation in the abundance of principal prey in the environment, that is, small mammals, but by the ease of procurement of fruit at peak fruiting season. The marten's diet thus does not simply reflect primary resource abundance but is a function of the relative abundance and inferred availability of alternative food types. This case study of the yellow-throated marten provides insight into foraging strategies that depend on the relative, temporal availability of food types, a phenomenon observed for other generalist omnivores (including several Carnivora).

Described in 2005, Laonastes aenigmamus is the only species of Diatomyidae. The known distribution of this rodent encompasses only the rugged mountains of the Khammouan karst in central Lao People's Democratic Republic. We used a sample of 52 specimens to survey population structure by sequencing 887 base pairs of the cytochrome-b gene. The overall haplotype diversity was low (0.789 ± 0.039 SD), with 14 haplotypes identified, whereas the nucleotide diversity was high (0.015 ± 0.008 SD). Phylogenetic and haplotypic network reconstructions revealed 3 well-supported and rather divergent lineages with mutational steps ranging from 28 to 32. Identified haplotype groups correspond to localities, suggesting that populations of L. aenigmamus are geographically structured. Mismatch distributions suggest population stability. An exact test for population differentiation confirms a significant level of differentiation. Taking into account human pressure increasingly threatening this ecosystem, we provide preliminary insights on the genetically discrete population structure of this enigmatic mammal species.

In the absence of obvious barriers to dispersal microsatellite studies of vagile mammalian carnivores frequently find panmictic-like genetic structure over wide scales, whereas high levels of differentiation at much finer scales are detected with mitochondrial DNA (mtDNA). Given the maternal inheritance of mtDNA, these differences are often attributed to male-biased dispersal, remnants of postglacial range expansion, or both. Based on such contrasting results, it is not always clear how to delineate contemporary populations. We investigated the genetic structure of American black bears (Ursus americanus) over a wide geographic area (>1,700 km) that has no obvious physiogeographic barriers to gene flow. We analyzed a 315-base pair fragment of the mtDNA control region from 660 individual bears from 23 regions of Ontario, Canada. Relative to black bear studies based on nuclear data, mitochondrial analyses revealed much stronger patterns of genetic structure among regions (0.09 < F_ST < 0.44), even at small-scale intervals (<150 km), which likely reflects strong female philopatry combined with male-biased dispersal. The patterns of genetic differentiation among regions were consistent with previously described historical patterns in black bears, specifically the division of the species into 2 phylogeographic clades (coastal and continental). We confirmed that further subdivision of the continental clade occurs in a region where obvious physiogeographic barriers do not exist. We postulate that this small-scale differentiation can be explained by residual patterns from postglacial recolonization routes on either side of the Great Lakes. We suggest that it was maintained through extreme female philopatry due to habitat saturation following the postglacial geographic expansion. Based on our results, we propose that a combination of several molecular markers can be more useful in defining population units for conservation and management decisions than biparentally inherited microsatellites.

A new species of Cerradomys is described from the sandy plains of the northeastern littoral of Rio de Janeiro State and the southern littoral of Espírito Santo State, southeastern Brazil. Morphological and karyological characters were used to distinguish the new taxon from the 3 closest related species: C. subflavus, C. vivoi, and C. langguthi. Skull differences include the relatively larger general size, pronounced crests, broader rostrum, broader lacrimals, and wider sphenopalatine vacuities. Canonical variate analyses based on craniometric data showed that the new species has little overlap with C. subflavus, C. vivoi, and C. langguthi in multivariate space. The pelage of the new species has a unique, sparser, and thinner aspect. The diploid number of 54 chromosomes and the autosomal fundamental number of 66 arms (the highest among the 3 related species), added to the morphology of both sexual chromosomes, are diagnostic for the new species. The new taxon is restricted to a particular section of the Brazilian littoral covered by a mosaic of open vegetation locally named restingas, where it is one of the most abundant terrestrial mammals. In the restingas of this region this species is associated more with shrub patches than more forested physiognomies, being captured both on ground and on tree branches, especially of Clusia trees, suggesting a degree of arboreality. The recognition of this species adds further biogeographic uniqueness to the restingas of the northeastern littoral of Rio de Janeiro and southern littoral of Espírito Santo.

Two morphological forms of black rats (Rattus cf. rattus) were found living in sympatry in high-altitude dense forests of the Nilgiri Mountains, South India. The 1st one, often brown- or gray-bellied, also is found commensal in lowland settlements and represents Rattus rattus cf. rufescens (Gray 1837), with a diploid number (2N) of 38 chromosomes. The 2nd form, which has most often a pure white belly, has 2N  =  42 chromosomes and is referable to Rattus r. satarae Hinton, 1918, based on morphological comparison with the holotype. A multidisciplinary study indicates that these 2 forms are characterized by clear-cut differences in biochemistry (electrophoresis of homologous isozymes), molecular sequences (mitochondrial and nuclear DNA), and chromosomes (detailed banding analysis). All these data, coupled to diagnostic morphological characteristics, support the hypothesis that Rattus satarae and Rattus rattus are separate, sympatric species, with no gene flow between them. Their similar external morphology is interpreted as the result of convergence through occupying the same ecological niche.

We present the most comprehensive study to date of species groups in Ctenomys (tuco-tucos), a species-rich genus of Neotropical rodents. To explore phylogenetic relationships among 38 species and 12 undescribed forms we sequenced the complete mitochondrial cytochrome-b genes of 34 specimens and incorporated 50 previously published sequences. Parsimony, likelihood, and Bayesian phylogenetic analyses were performed using additional hystricognath rodents as outgroup taxa. The basal dichotomy of Ctenomys splits C. sociabilis from the remaining tuco-tucos, within which 8 main species groups were identified: boliviensis, frater, mendocinus, opimus, magellanicus, talarum, torquatus, and tucumanus. Whereas most of these groups refer to previous clades proposed on the basis of chromosomes or morphology, the torquatus and magellanicus species groups are novel taxonomic hypotheses. However, relationships among species groups are poorly resolved. Furthmore, the positions of C. leucodon, C. maulinus, and C. tuconax are conflicting or unresolved, and they might represent additional independent lineages. On the basis of molecular dating, we estimate that most species groups originated approximately 3 million years ago.

Members of the genus Ctenomys (tuco-tuco; Rodentia: Caviomorpha: Octodontidae) are considered scratch diggers. We compared the forelimbs of adult C. azarae with those of 13 species within other genera of caviomorph rodents to identify morphofunctional variation in osseous elements related to fossorial habits. Eight measurements of the humerus and ulna were used to construct five functional indices that were subjected to principal components analysis and simple comparisons among means. Ctenomys has a general morphology similar to that of terrestrial caviomorph rodents but exhibits some features that reflect its specialized fossorial condition, such as its comparatively large epicondyles. These features indicate greater muscular development and capacity for force production in the pronators and supinators of the forelimb and manus and flexors of the manus. The deltoid complex is well developed, indicating a large moment arm for the deltoid and latissimus dorsi muscles, which increases the capacity for force production on humeral flexion. Humeral indices are the best for differentiating fossorial forms from diggers, occasional diggers, generalized, and cursorial forms. Limb bone segments are used differently by highly fossorial and scratch-digging forms.