We examined the host selection of common vampire bats (Desmodus rotundus) with stable carbon isotopes in an area that offered 2 isotopically contrasting food sources, either introduced livestock living on C₄ plants or native rainforest mammals living on C₃ plants. We predicted that vampire bats would have carbon isotope ratios (δ¹³C) similar to those of livestock if they select exclusively cattle. The δ¹³C of vampire bats averaged −10.3 ± 2.6‰ (mean ± SD) and was almost identical to that of livestock (X̄ = −12.9 ± 1.6‰). Thus, both vampire bats and livestock are clearly members of the C₄ food web. Typical rainforest mammals such as the fruit-eating bat Carollia perspicillata had a δ¹³C of −24.4 ± 0.6‰, which identified them as members of the C₃ food web. The stable carbon isotope signature of local vampire bats implies a high degree of preference for cattle. We suggest that the population expansion of D. rotundus is only indirectly linked to increasing host densities and is more directly related to the bats' preference for livestock over native mammals, probably because fenced-in cattle are a more predictable resource than free-ranging natural hosts.

Food habits of the endangered gray myotis (Myotis grisescens) were ascertained from 10,736 fecal pellets collected from 1,225 bats of known sex, age, reproductive condition, and capture locations, including 5 maternity caves and 2 dispersal caves in Missouri. Diets were compared to availability of insects in 80 light-trap samples collected concomitantly with fecal samples. Proportional availability of insects varied among locations, over the season, between seasons, and between early-evening and late-night samples. Similarly, the diet varied among locations, over time, between early and late samples, and among sample groups by sex, age, and reproductive condition. Trichopterans, coleopterans, and lepidopterans were important in the diet and in light-trap samples, but there was poor correlation between corresponding diet and light-trap samples. Plecopterans, ephemeropterans, and dipterans were occasionally common in light-trap and dietary samples, although again there was poor correlation between corresponding diet and light-trap samples. Gray myotis forage individually over long distances along streams and wooded riparian habitats. Although this habitat produces a characteristic assemblage of insect prey, proportional availability varies temporally and spatially. Thus, although specific diet samples do not match corresponding insect samples, on a broader scale, diets and insect availability do correspond. On a microscale, the gray myotis exhibited some characteristics of an opportunistic forager, feeding on readily available prey, but on a macroscale was selective, feeding in aquatic-based habitats where specific types of insect prey were abundant. Juveniles foraged more in woodlands and ate more coleopterans, which may provide a greater energy reward per unit of capture effort, than did adults. Conservation efforts should include both aquatic and wooded riparian habitats.

We examined the diet of 2 island-dwelling phyllostomids, the brown flower bat (Erophylla sezekorni) and the Greater Antillean long-tongued bat (Monophyllus redmani), by analyzing fecal contents and pollen swabs from >100 individuals of each species. Although both bats are putative nectar-feeders, their feeding niches were differentiated. A greater proportion of M. redmani (91%) consumed nectar compared with E. sezekorni (50%), but the reverse was true for fruits (22% versus 85%, respectively); about 75% of both species included insects in their diets. However, insect consumption in E. sezekorni was dominated by coleopterans, whereas in M. redmani, diet was more diverse and included soft-bodied prey, such as lepidopterans and dipterans. Both species consumed fruits of Panama berry (Mutingia calabura) and elder (Piper aduncum), but E. sezekorni also included turkey berry (Solanum torvum). When consuming nectar, E. sezekorni often fed at flowers of guava (Psidium guajava), whereas M. redmani visited flowers of guava, woman's tongue (Albizia lebbek), myrtle (Eugenia), and wild tamarind (Leucaena leucocephala). Interspecific differences in diet are consistent with published differences in craniodental and wing (flight) characteristics. The more diverse diet of M. redmani and its lesser reliance on fruit may allow it to survive stochastic events, such as hurricanes, and recover more quickly than populations of E. sezekorni.

African elephants (Loxodonta africana) are mixed feeders, incorporating varying proportions of grass and browse into their diets. Disagreement persists as to whether elephants preferentially graze or browse, and the degree to which the consumption of these foods is a reflection of their local availability. We used stable carbon isotope analysis of feces to investigate seasonal and spatial variation in the diets of elephants from Kruger National Park (KNP), South Africa. Elephant diets (overall average ∼35% grass) are shown to be distinct from those of grazers (>90% grass), browsers (<5% grass), and another mixed-feeder, the impala (Aepyceros melampus; ∼50% grass). Fecal δ¹³C values suggest that elephant populations from northern KNP eat more grass (∼40%) during the dry season than do their southern counterparts (∼10%). The wet-season diets of elephants from northern and southern KNP include similar amounts of grass (∼50%), because elephants in the south, but not in the north, ate significantly more grass during this time. Although habitat differences in KNP appear to account partially for variations in elephant diets, the specific influence of each habitat type on diet selectivity is not clear. The homogeneity of woody vegetation in the north (dominated by Colophospermum mopane “shrubveld”) may deter browsing and force elephants in this area to opt for alternative food sources (grass) throughout the seasonal cycle.

Social organization seems to determine the occurrence of male infanticide in equids. Although, no information concerning social organization of the maneless zebra (Equus burchelli borensis) has been available, we presumed that the occurrence of infanticide would be the same across all subspecies of plains zebra. We examined the occurrence of this phenomenon in 9 herds of 4 subspecies: the maneless zebra, Grant's zebra (E. burchelli boehmi), Chapmann's zebra (E. b. chapmanni), and the Damara zebra (E. b. antiquorum) at 4 zoos. The probability of a foal's death was affected by the presence of a new male and subspecies. Except for the maneless zebra, all subspecies showed existence of male infanticide. We found no occurrence of male infanticide in maneless zebras, which suggests a different social system. This would also support the subspecific status of the maneless zebra.

One behavioral tactic that juvenile mammals can use to resolve conflict with adults is the reversion to behaviors of an earlier developmental stage. Therefore, we examined the appearance, body posture, and ontogenetic differences of submissive crouch behavior between juvenile male and female guanacos from birth to 9 months of age in Torres del Paine National Park, Chile. On average, submissive crouches appeared 73 days after birth, and juvenile males displayed them more frequently than did juvenile females. Juvenile males also displayed more extreme body postures during submissive crouches than did juvenile females. Sex, group size, and season significantly influenced a juvenile's likelihood of displaying a submissive crouch.

We studied a system in which 2 desert rodent species coexist through temporal partitioning. Previous research suggests that the common spiny mouse (Acomys cahirinus) competitively forces the golden spiny mouse (A. russatus) into diurnal activity, but the mechanism driving this separation is not entirely understood. To test whether aggression is the driving force in this exclusion, we analyzed interactions between pairs of these 2 species. In contrast with our working hypothesis, the golden spiny mouse was more aggressive as reflected in its significantly more frequent chasing and biting behaviors. These results suggest that aggressive interference does not explain the temporal partitioning between these species. Other factors such as foraging efficiency, antipredator avoidance, water conservation, or productivity may account for the shift of golden spiny mice into diurnal activity.

Animals adapted to extreme environmental conditions often show rhythmic activity with stable periodicity. We studied the daily activity pattern of European ground squirrels (Spermophilus citellus) to determine effects of environmental factors on this pattern. Activity was evaluated by counting the number of squirrels visible above ground in 3 manipulated groups. To test the hypothesis that midday air temperature contributes to the bimodal activity pattern, we manipulated ambient temperature perception by altering the coloration of their head fur. Significantly fewer dark-headed squirrels were visible on the surface in midday on sunny days than were light-headed animals. Because ambient temperature perception is strongly affected by the darkness of the top of the head, we concluded that extremely high midday ambient temperatures play a central role in contributing to the observed midday rest phase in ground squirrels.

Little is known about the ovulation patterns in ground squirrels, even though the timing of ovulation could influence mate-order effects and sperm competition, which have been documented in a number of species. The Cape ground squirrel (Xerus inauris) is a social, nonhibernating, semifossorial rodent with aseasonal reproduction. Evidence suggests that sperm competition is an important aspect of male reproductive success in this species. We examined whether the Cape ground squirrel is an induced or spontaneous ovulator. Fifteen reproductive adult females were removed from natal colonies and housed individually. Females were subjected to 1 of 3 trials: no male contact, chemical and visual contact but no physical contact with intact males, or direct contact with epididymectomized males. Females from each of the 3 experimental treatments exhibited similar urinary progesterone metabolite concentrations and qualitative ovarian histology. Neither the presence of males nor copulation appear necessary for ovulation to occur, and ovulation in this social African ground squirrel appears to be spontaneous.

Very little is known about the reproductive biology of the Namaqua rock mouse (Aethomys namaquensis), despite its wide distribution and its being a major component of small mammal communities in southern Africa. Consequently, body mass, reproductive-tract morphometrics, gonadal histology, and plasma progesterone and 17β-estradiol concentrations in females, and plasma testosterone concentration in males were studied over 12 consecutive months in wild-caught A. namaquensis from a population in northeastern South Africa in an attempt to gain insight on the pattern of reproduction in the species. The number of graafian follicles and corpora lutea, and plasma progesterone and 17β-estradiol concentrations in 102 females increased significantly between September and early March relative to between April and August. Gravid and lactating females were observed between October and early March, whereas no lactating females were recorded between April and September. Although testicular mass relative to body mass, testicular volume, seminiferous tubule diameter, and circulating plasma testosterone concentration increased significantly between September and February relative to between March and August, little or no spermatogenesis or presence of sperm in the epididymis were observed between March and September. Examination of these data suggests that the Namaqua rock mouse in northeastern South Africa is a seasonal breeder, with reproduction confined to the rainy summer months of the Southern Hemisphere when nutritional supplies are abundant.

We studied reproduction of 56 female wolverines (Gulo gulo) in 2 areas of northern Scandinavia. Minimum average age at 1st reproduction was 3.4 years. Mean proportion of females (≥3 years old) reproducing was 0.53 (95% confidence interval [CI] = 0.43–0.63, n = 94), and the annual mean was 0.58 (95% CI = 0.35–0.80, n = 83). Mean annual birth rate was 0.74 (95% CI = 0.33–1.14, n = 83) young per female (≥ 3 years old). Mean size of 74 litters was 1.88 (95% CI = 1.68–2.07, range = 1–4). Examination of our data suggests that female wolverines have low productivity and low capacity to compensate for increased mortality. Therefore, wildlife managers should consider wolverine demographics, especially mortality of adult female wolverines, when developing and implementing conservation policies and harvest regulations.

Based on 65 free-ranging gray wolves (Canis lupus) of known age and 25 of estimated age examined during summers of 1970–2004 in northeastern Minnesota, body mass of both males and females peaked at 5 or 6 years of age, with mean masses of 40.8 kg and 31.2 kg, respectively. Testis size varied as a function of age and month through at least 8 years of age, with length plus width ranging from 1.9 to 7.8 cm. Most females aged 4–9 years bred based on assessment of nipple sizes; those that had not bred had average lower body mass than those that had. This is the 1st report of such data from known-aged wolves.

We document the accuracy, efficacy, and safety of ultrasound in estimating reproductive characteristics of gray wolves (Canis lupus) in central Alaska. We examined 68 adult female wolves with ultrasound during late March and early April to diagnose pregnancy and litter size. Seventy-two percent were pregnant. We compared ultrasound diagnoses with postmortem embryo or placental scar counts in 14 females that died within 10 months of being examined by ultrasound; all ultrasound and postmortem examinations agreed in the diagnoses of pregnancy. Among 12 pregnant females, 6 agreed exactly in fetal count, 11 were within 1 fetus, and all were within 2 fetuses. In the postmortem sample we detected a decline in average placental scar color density between mid-September and mid-February. Radiocollared females were monitored from the air to estimate denning rates. Distance from the den declined as parturition approached, but few females localized near dens before parturition. Among 46 pregnant females diagnosed by ultrasound, 80.4% entered and remained at dens, 15.2% failed to enter dens, and 4.4% denned but abandoned the den within 1 week. None of the females diagnosed as nonpregnant entered dens. We present models of fetal growth from ultrasound measurements of embryonic vesicle diameters (EVD) or crown–rump length (CRL) of in utero fetuses. CRL was a better predictor of gestational age (r² = 0.92) than was EVD (r² = 0.79). We found no evidence that capture of females during the 2nd trimester of pregnancy affected denning or productivity.

We studied age-related variation in body mass and epididymal distension in male Daubenton's bats. Examination of data on epididymal distension in young of the year indicates that some reach sexual maturity by the year of birth, whereas others do so in their 2nd summer. Body mass and epididymal distension were positively correlated in young of the year and adults, suggesting that early sexual maturation and reproductive condition during later life are dependent on body condition. Older males tended to be heavier and in better reproductive condition than younger ones. Examination of our data suggests that physical and reproductive condition of males increase after the initial onset of fertility until 3 years of age. This late physical maturation is in line with other life-history traits characterizing long-lived bats as K-strategists among small mammals.

To minimize impact on small mammals while preventing invasion of woody vegetation, we mowed alternating 15-m strips on our area. We then compared numbers and movements of 5 species of rodents on mowed and unmowed strips. Numbers of hispid cotton rats (Sigmodon hispidus) and prairie voles (Microtus ochrogaster) were reduced temporarily in the mowed strips, whereas numbers of white-footed mice (Peromyscus leucopus), deer mice (P. maniculatus), and western harvest mice (Reithrodontomys megalotis) did not change significantly. Movements of cotton rats, prairie voles, and harvest mice across mowed strips were reduced, whereas movements within unmowed strips were relatively unaffected, decreasing only for white-footed and harvest mice in 1 of 2 temporal replicates. Changes in numbers and movements were of short duration, and hence mowing narrow strips when vegetation could recover rapidly had little sustained impact on this rodent community.

Many studies have examined coexistence among similar small mammal species. Most investigations have tended to focus on interactions such as predation and competition, with less emphasis on use of habitat space, plant cover stratification, and food resource partitioning. We investigated 2 similar small mammal species, the white-footed mouse (Peromyscus leucopus) and the golden mouse (Ochrotomys nuttalli) to determine how differences in 3-dimensional habitat use, vegetative cover, and food resources allow for similar species to coexist. P. leucopus was removed from 4 of 8 experimental grids within a forested riparian peninsula to assess the effect of competitive removal on population dynamics of O. nuttalli. After removal of P. leucopus, the relative abundance of O. nuttalli in removal grids did not change significantly from abundance in control grids. However, differences in use of 3-dimensional habitat appeared to provide enough niche segregation to allow these 2 species to coexist in the same habitat. Abundant resources (acorn mast crop of Quercus nigra and heavy vegetative cover of Ligustrum sinense) also appeared to dampen competition between these 2 species.

Effective population size (N_e) is a fundamental concept that links population structure to the evolutionary processes that shape genetic variation. Demographic estimates of N_e may be influenced by a number of factors, including adult sex ratio and variance in individual reproductive success. Genetic estimates of N_e are influenced not only by these variables but also by neighborhood size, degree of population substructure, and historical changes in population size. Hence, comparisons of demographic and genetic estimates of N_e may yield important insights into the parameters that determine effective size. To explore interactions between demography and N_e, we compared estimates of effective population size/census size (N_e/N) for 2 demographically distinct populations of the talar tuco-tuco (Ctenomys talarum), a subterranean rodent from Buenos Aires Province, Argentina. Examination of data on adult sex ratios and reproductive success obtained from long-term field studies of C. talarum at Mar de Cobo and Necochea led us to predict that N_e/N should be smaller for Mar de Cobo. Demographic and genetic estimates of N_e/N were consistent with this prediction. However, interpopulation variation in N_e/N was greater for the genetic data set. Based on analyses of microsatellite variation, we suggest that this result is due primarily to differences in current demography, rather than historical reductions in population size. The observed differences in N_e/N imply that the strength of genetic drift differs between Mar de Cobo and Necochea, thereby potentially affecting patterns and rates of diversification among populations of C. talarum.

The effects of fragmentation may be variable for species that have seasonal patterns of density and reproduction. We tested whether the effects of fragment size and habitat on reproduction and density varied over the course of the breeding season for the white-footed mouse (Peromyscus leucopus). The relative density of mice changed; in small fragments densities were lower in spring, similar during the midsummer lull, and higher in autumn than in large fragments. Large fragments displayed the bimodal pattern of litter production previously reported for P. leucopus, but small fragments showed a relatively constant number of litters among spring, lull, and autumn reproductive periods. Although no differences were found between edge and interior habitats in density, litter production, and reproductive effort during spring and lull periods, all were higher in edge than interior habitats during autumn. Changes in effects of fragment size and habitat may be mediated by the influence of fragmentation on seasonally important abiotic and biotic factors.

Little is known about the behavior of mammals moving on unfamiliar ground, yet this information could be critical to assessing and enhancing landscape connectivity. I investigated the movements of adult red squirrels (Tamiasciurus hudsonicus) on unfamiliar ground to determine if squirrels selected specific microhabitat features and if manipulations of preferred features influenced movement choices. Rather than selecting for cover from predators or territorial conspecifics, 25 squirrels released outside their home ranges used microhabitat features that appeared to allow rapid, efficient, and inconspicuous travel (logs, open vegetation, low slopes, and high shrub cover per stem) while maintaining proximity to arboreal escape routes. Similarly, in 73 trials with 55 individuals, squirrels released in experimental plots moved preferentially through areas of greater log cover and cover per stem. Manipulating microhabitat features in plots within forested habitat enhanced red squirrel movements, underscoring the possibility of altering microhabitats in 2nd-growth forests or corridors to increase landscape connectivity for forest-associated mammals.

We examined den-site selection patterns for western spotted skunks (Spilogale gracilis) and striped skunks (Mephitis mephitis) co-occurring in mesquite brushland of Tom Green County, Texas. Sixteen S. gracilis and 14 M. mephitis were radiocollared to locate den sites from October 2001 through June 2003. Characteristics of dens were assessed using 23 habitat variables. S. gracilis favored den sites with dense mesquite (Prosopis glandulosa), shrubs, and cacti (Opuntia), whereas M. mephitis used these areas but also more open habitats. Den habitats of S. gracilis were more uniform than were those of M. mephitis, implying that S. gracilis is more specialized in den-site selection. Both species used multiple den sites, both above and below ground, rather than a primary den. Aboveground denning occurred year-round for both species. For S. gracilis, 56% (n = 60) of dens were above ground, but denning was more common above ground in the spring and summer. Aboveground denning was more common than belowground denning for M. mephitis in all seasons, representing 64% (n = 50) of all dens. Den habitat analysis suggests that S. gracilis, unlike M. mephitis, may be limited to areas with sufficient cover, including prickly pear cactus, for denning.

Nine sewellel (Aplodontia rufa) bone specimens are identified in the Duncan's Point Cave vertebrate archaeofauna. At least 3 individuals are represented and 3 specimens exhibit evidence of deposition in the cave as carnivore prey. The extralimital presence of A. rufa near the mouth of the Russian River demonstrates their occurrence over a wider area during the mid-Holocene and raises the possibility of the existence or recent extirpation of a 3rd isolated coastal Californian population of the species. Based on the presence of bones of A. rufa in the Duncan's Point Cave archaeofauna and the availability of suitable habitat in the region, a detailed survey of the area surrounding the mouth of the Russian River is warranted.

Fossil remains of bats have been recovered from caves and fissures in Bermuda dating from middle Pleistocene to late Holocene. Three bones from 2 different localities are identified as eastern pipistrelle (Pipistrellus subflavus), which was not recorded from Bermuda until 2004. Remains of an individual eastern red bat (Lasiurus borealis), from a 400,000-year-old beach deposit, imply that the migratory pattern in this species, a regular transient in Bermuda today, may have been established by the middle Pleistocene. Fairly common remains of Lasiurus, either L. borealis or L. seminolus, were found in 5 cave deposits. In 1 finely stratified sequence, this bat does not appear until the onset of the last glacial period, suggesting that a resident population may have become established at that time. A strong taphonomic bias, indicated by the preponderance of large wing bones, probably of females, may be the result of hawk predation.

Mitochondrial cytochrome-b (Cytb) and control region (CR) sequence data were used to investigate the phylogeography of the disjunct population of southern flying squirrels (Glaucomys volans) from Nova Scotia. Consistent with previous studies, there is little differentiation in Cytb sequences (0–1.3% sequence divergence) across the entire range of G. volans in North America. Nested clade phylogeographic analysis of CR sequences (which exhibited 0.5–5.7% sequence divergence) provided a finer scale of differentiation and allowed for inferences to be made regarding the phylogeographic history of the population from Nova Scotia. We propose that G. volans rapidly expanded its range from a southern refugium after the Wisconsin glaciation (∼12,000 years ago) and was then isolated in southwestern Nova Scotia during subsequent climactic fluctuations. More specifically, the population from Nova Scotia was isolated from extant populations in Ontario by the loss of intermediate populations. Although the population of G. volans in Nova Scotia would not be considered an evolutionarily significant unit under some definitions, examination of CR sequence data suggests that this population may nevertheless be diverging from other populations.

In recent years many cryptic bat species have been unmasked by differences in their echolocation calls. The yellow house bat (Scotophilus dinganii) is 1 of 3 species of Scotophilus currently described in southern Africa and is distinguished from the other 2 species by its size and yellow venter. Here we use genetic, morphological, and echolocation call data to show the existence of a cryptic species. We found that S. dinganii consists of 2 forms, one that uses a peak echolocation frequency of 44 kHz and the other a peak frequency of 33 kHz. Both forms have yellow venters. The 44-kHz phonic type is up to 15% smaller than the 33-kHz phonic type and differed genetically by an average cytochrome-b (Cytb) sequence divergence of 3.3%. Furthermore, combined phylogenetic analyses of Cytb and control region sequences indicate that the 2 phonic types are reciprocally monophyletic, suggesting that they are sibling species.

Ecomorphological analysis was used to evaluate ecological relationships between 2 species of bats, Myotis auriculus and M. evotis. We imaged jaws and skulls of 242 specimens from 20 localities within the range of both taxa, emphasizing their southwestern regional area of sympatry. Using traditional morphometric and geometric morphometric methods, values for characters taken from dentaries of both species were analyzed in detail. Both methods detected character displacement and allowed us to detect differences in jaw size and shape within both species. The morphological difference in jaw shape is more emphasized within sympatric populations of M. evotis than in M. auriculus. This may indicate that competitive selection acts more on M. evotis. At sympatric localities, M. evotis displayed a shift to a more specialized trophic state with a trophic architecture (more highly placed articular process and robust molars) likely better at capturing beetles, whereas M. auriculus may have a greater advantage for capturing soft-bodied prey such as moths. On the other hand, the articular process is located lower relative to the toothrow of the dentary in M. auriculus. Also the shape of the jaw in this species suggests a weaker bite, more shearing force, and wider gape. All shape differences in jaw morphology are emphasized in sympatry, confirming active competitive interactions between these 2 species.