Phylogeographic analyses of arctic organisms provide spatial and temporal frameworks for interpreting the role of climate change on biotic diversity in high-latitude ecosystems. Phylogenetic analyses based on 673 base pairs of the mitochondrial control region from 95 arctic hares (Lepus arcticus, L. othus, L. timidus) and 2 other Lepus species identified 6 strongly or moderately supported clades. The 3 arctic hare species are closely related, but phylogenetic discontinuities were found at the eastern and western boundaries of Beringia, the latter not previously identified as a species boundary. The locations of these discontinuities are congruent with previously described genetic breaks in Arctic plants, birds, and small mammals. Similarly, the finding of a Beringian clade corroborates previous studies identifying Beringia as a refugium. A coalescent view of a population on Seward Peninsula, Alaska (eastern Beringia), did not, however, provide a genetic signature of population expansion. In contrast, a Greenland population did show a signal of expansion.

Pleistocene glaciations had significant effects on the distribution and evolution of arctic species. We focus on these effects in Nearctic Beringia, a high-latitude ice-free refugium in northwest Canada and Alaska, by examining variation in mitochondrial cytochrome b (Cytb) sequences to elucidate phylogeographic relationships and identify times of evolutionary divergence in arctic ground squirrels (Spermophilus parryii). This arctic-adapted species provides an excellent model to examine the biogeographic history of the Nearctic due to its extensive subspecific variation and long evolutionary history in the region. Four geographically distinct clades are identified within this species and provide a framework for exploring patterns of biotic diversification and evolution within the region. Phylogeographic analysis and divergence estimates are consistent with a glacial vicariance hypothesis. Estimates of genetic and population divergence suggest that differentiation within Nearctic S. parryii occurred as early as the Kansan glaciation. Timing of these divergence events clusters around the onset of the Kansan, Illinoian, and Wisconsin glaciations, supporting glacial vicariance, and suggests that S. parryii survived multiple glacial periods in Nearctic Beringia. Across the Arctic, Beringia has been identified as an important regional refugium for a number of species. Within Nearctic Beringia, genetic differentiation across populations of arctic ground squirrels further reflects the effect of glacial patterns on a finer scale. The arctic ground squirrel has had a long evolutionary history in the Nearctic, with strong phylogeographic structure and stable clades persisting through multiple glacial cycles.

Feral horses (Equus caballus) in the Garfield Flat Herd Management Area in western Nevada exist as 2 subpopulations most of the year and as a single population once sufficient snow has accumulated to free them from dependence on their respective water sources. Populations were examined for genetic structure using 12 equine microsatellite markers. Microsatellite data also were generated from a distant population in the Granite Range Herd Management Area, in northwestern Nevada. Analyses of microsatellite allele frequencies supported the genetic individuality of the 3 groups. The Garfield Hills groups were marginally differentiated by virtue of low F_ST and low success in population assignment. Recent population bottlenecks and behavioral isolation are the likely mechanisms for the genetic differences between the 2 Garfield groups. Both Garfield groups were strongly differentiated from the Granite Range horses. Allele frequencies of both Garfield Flat subpopulations were within Hardy-Weinberg expectations, whereas the Granite Range frequencies were not, suggesting population structure beyond that previously identified.

One of the challenges in estimating grizzly bear (Ursus arctos) population size using DNA methods is heterogeneity of capture probabilities. This study developed general tools to explore heterogeneity variation using data from a DNA mark-recapture project in which a proportion of the bear population had GPS collars. The Huggins closed population mark-recapture model was used to determine if capture probability was influenced by sex or collar status. In addition, trap encounter rates were estimated by comparing the closest distance from traps where hair was snagged of bears that were captured, with bears for which we had radiolocations but were not captured. Results of the Huggins analysis suggested that sex, distance of bear DNA capture from grid edge, and whether a bear was radiocollared potentially affected capture probabilities. The encounter rate analysis estimated that 63% of bears that encountered traps were snagged, and that males encountered more traps than females. The following conclusions arise from this study. First, the distance of DNA capture of bears relative to the grid edge should be modeled as an individual covariate to ensure robust estimates of superpopulation size when closure violation is suspected. Second, sampling should be intensive to minimize heterogeneity and to ensure all bears encounter traps. Finally, estimators that are robust to heterogeneity variation should be used, given the various sources of heterogeneity variation.

Recent genetic data indicate that the eastern wolf is not a subspecies of the gray wolf (Canis lupus), but is a North American wolf more similar to the red wolf (C. rufus) and closely related to the coyote (C. latrans). The eastern wolf has been proposed as a separate species, C. lycaon. The largest protected area containing this wolf is Algonquin Provincial Park in Ontario, Canada, which is bounded to the south by areas containing the Tweed wolf or eastern coyote, a hybrid of the western coyote and eastern wolf. We assessed the relationships of animals in the park by using DNA profiles that comprised the genotype from 17 autosomal and 4 Y-linked microsatellite loci and the mitochondrial DNA control region. These profiles were used to establish maternity, paternity, and kin relationships for 102 wolves that were studied from 24 packs over a 12-year period. Genetic data do not support the hypothesis that a pack comprises an unrelated breeding pair and their offspring. There is evidence of frequent pack splitting, pack fusion, and adoption. Some unrelated individuals in the packs were identified as immigrants into the park. We found high levels of genetic structuring between the Tweed wolves to the southeast and the Algonquin Park wolves (R_ST = 0.114). Lower levels of genetic differentiation with animals to the north and west (R_ST = 0.057 and R_ST = 0.036) and high genetic diversity suggest that park animals are not an island population but the southern part of a larger metapopulation of C. lycaon.

American badgers (Taxidea taxus) are semifossorial carnivores present in many arid regions of central and western North America. Negative demographic trends have prompted recent discussion concerning their conservation status in the northwestern portion of their range. As such, further information regarding the metapopulation structure of this species and factors affecting dispersal is needed. To provide a preliminary assessment of genetic structure and variation, badgers from Alberta and British Columbia, Canada, and Montana were sampled and genotyped at 12 microsatellite loci, including individuals from 2 subspecific designations: T. t. taxus and T. t. jeffersonii. Relatively high levels of genetic variation were observed (average expected heterozygosity [H_E] = 77%). Gene flow between prairie populations of T. t. taxus did not seem to be restricted, nor did there seem to be a restriction of gene flow for populations within mountain ranges for T. t. jeffersonii. In contrast, minimal gene flow was observed between populations separated by mountain ranges. Our results support the current geographic delineation of the northwestern subspecies, T. t. taxus and T. t. jeffersonii, and have implications for their conservation by identifying genetically distinct units that may have independent population dynamics.

Evolutionary processes can be strongly affected by landscape features. In vagile carnivores that disperse widely, however, genetic structure has been found to be minimal. Using microsatellite DNA primers developed for other mustelids, we found that populations of a vagile forest carnivore, the fisher (Martes pennanti), exhibit high genetic structure (F_ST = 0.45, SE = 0.07) and limited gene flow (Nm < 1) within a >1,600-km narrow strip of forested habitat; that genetic diversity decreases from core to periphery; and that populations do not show an equilibrium pattern of isolation-by-distance. Genetic structure was greater at the periphery than at the core of the distribution and our data fit a 1-dimensional model of stepping-stone range expansion. Multiple lines of paleontological and genetic evidence suggest that the fisher recently (<5,000 years ago) expanded into the mountain forests of the Pacific coast. The reduced dimensionality of the distribution of the fisher in western coastal forests appears to have contributed to the high levels of structure and decreasing diversity from north to south. These effects were likely exacerbated by human-caused changes to the environment. The low genetic diversity and high genetic structure of populations in the southern Sierra Nevada suggest that populations in this part of the geographic range are vulnerable to extinction.

The fisher (Martes pennanti) is a forest mustelid that historically occurred in California from the mixed conifer forests of the north coast, east to the southern Cascades, and south throughout the Sierra Nevada. Today fishers in California occur only in 2 disjunct populations in the northwestern mountains and the southern Sierra Nevada. We studied the ecology of fishers in both populations (the north coast [Coastal] and southern Sierra Nevada [Sierra]) to characterize the size and composition of their home ranges, and to compare features between locations. Twenty-one (9 Coastal, 12 Sierra) of 46 radiocollared fishers were relocated frequently enough (>20 times) to estimate home ranges. The home ranges of males (X̄ = 3,934.5 ha) were significantly greater than those of females (980.5 ha), and the home ranges of females were significantly greater in the Coastal than in the Sierra area. The smaller home ranges in the Sierra were probably due to productive habitats rich in black oak (Quercus kelloggii). Midseral Douglas-fir (Pseudotsuga menziesii) and white fir (Abies concolor) types composed the greatest proportion (42.8%) of home ranges in the Coastal study area. The greatest proportion of home ranges in the Sierra study area were in the intermediate tree size class (60.7%), had dense canopy closure (66.3%), and were in the Sierran Mixed Conifer type (40.1%). These measures provide guidelines for managers who wish to influence landscape features to resemble occupied fisher habitat. The recovery of fishers in the Pacific States, however, will also require the consideration of microhabitat elements and characteristics of landscapes that might affect metapopulation dynamics.

Given the uneven and biased nature of present understanding of geographic distributions of mammal species, tools for extrapolating from what is known to a more general prediction would be most useful. We used the genetic algorithm for rule-set prediction (GARP) to generate ecological niche models that were then projected onto geography to predict potential geographic distributions for 17 mammal species of Insectivora, Chiroptera, Rodentia, and Artiodactyla in Oaxaca, Mexico. GARP depends on point occurrence localities from museum records of species, along with electronic maps describing features of climate, topography, and vegetation type. Point localities were divided in 2 sets: one of localities from museum records dated before 1960, which was used to generate the predicted distributions, and the other of localities of museum records resulting from recent inventories (post-1960), which was used to test model accuracy. Predicted distributions for 11 of 17 species were statistically significantly more coincident with independent test points than random expectations; tests for the remaining 6 species would have required larger numbers of test localities to establish significance. GARP is a robust tool for modeling species' geographic distributions, with excellent potential for applicability to strategies for conservation of mammals in Oaxaca and elsewhere.

We studied habitat relations of the Prince of Wales flying squirrel (Glaucomys sabrinus griseifrons), an endemic of the temperate, coniferous rainforest of southeastern Alaska, because of concerns over population viability from extensive clear-cut logging in the region. We used stepwise logistic regression to examine relationships between microhabitat use (i.e., captures among traps spaced at 40-m intervals) and 26 vegetative and structural habitat features measured in plots centered on trap stations. Seasonal (spring, autumn) models were created for two old-growth forest types: upland, western hemlock (Tsuga heterophylla)–Sitka spruce (Picea sitchensis) forests (upland-OG); and peatland-scrub–mixed-conifer forests (peatland-MC). Density of trees with diameter at breast height (dbh) >74 cm and abundance of Vaccinium were positively correlated with microhabitat use in peatland-MC during both seasons. During spring and autumn, the odds of capturing a flying squirrel increased by factors of 2.7 and 16.9, respectively, with an increase in mean density of 10 large trees/ha. Microhabitat use of upland-OG during autumn was positively correlated with density of snags with a dbh of 50–74 cm and negatively correlated with percentage cover of understory herbaceous vegetation; microhabitat use during spring was inversely correlated with percentage surface cover of water. At the macrohabitat (13-ha replicate of forest type) scale, large (>74-cm dbh) trees explained 65% of the variation in density between forest types; percent cover of moss and volume of down wood in decay classes I–IV explained 70% and 63–77% of the variation, respectively. Our findings corroborate general patterns reported for western coniferous forests, but suggest that G. sabrinus in temperate rainforests of southeastern Alaska differ ecologically from populations in the Pacific Northwest in important ways.

Roost use by bats is likely affected by their water balance and thermoregulatory abilities. To test this hypothesis, we explored the relationship between 4 traits of different species of bats (body size, general food habits, taxonomic group, and thermoregulatory pattern) and microclimates at roosts (temperature and humidity). We recorded roost variables and presence of bats in 18 caves from 5 contrasting biomes in central Mexico. There was little evidence of microclimatic specificity among the 23 species studied, but maternity colonies used warmer roosts and hibernating bats used cooler roosts. Heterothermic species (Vespertilionidae) used colder caves with the widest temperature range (1.6–29.8°C), whereas homeothermic species (Emballonuridae, Mormoopidae, Phyllostomidae, and Natalidae) occupied warmer roosts (14.5–37.5°C). Within these caves, precise (narrow body temperature range) homeotherms occupied slightly cooler roosts than more labile homeotherms. Body size alone was not associated with cave use patterns. However, when homeotherms and heterotherms were examined separately, body size and temperature were negatively correlated. The smallest homeothermic insectivorous species (<10 g) consistently occupied roosts with temperatures >20°C (more often >25°C), whereas only the largest homeothermic insectivores were found as low as 16°C. Frugivorous, nectarivorous, and sanguivorous bats were found in a wide range of temperatures (14.5–37°C), but often at <20°C. Humidity in roosts was highly variable for most species and we did not detect any trend regarding this factor. Our data suggest that the thermoregulatory ability resulting from the complex interaction of body size, type of food, and taxonomic affiliation constrains species with respect to types of roosts that they can successfully exploit. Our results support the hypothesis that temperature is the most important physical factor influencing roost selection in bats.

Understanding effects of habitat loss and fragmentation on populations or communities is critical to effective conservation and restoration. This is particularly important for bats because they provide vital services to ecosystems via pollination and seed dispersal, especially in tropical and subtropical habitats. Based on more than 1,000 h of survey during a 15-month period, we quantified species abundances and community structure of phyllostomid bats at 14 sites in a 3,000-km² region of eastern Paraguay. Abundance was highest for Artibeus lituratus in deforested landscapes and for Chrotopterus auritus in forested habitats. In contrast, Artibeus fimbriatus, Carollia perspicillata, Glossophaga soricina, Platyrrhinus lineatus, Pygoderma bilabiatum, and Sturnira lilium attained highest abundance in moderately fragmented forest landscapes. Forest cover, patch size, and patch density frequently were associated with abundance of species. At the community level, species richness was highest in partly deforested landscapes, whereas evenness was greatest in forested habitat. In general, the highest diversity of bats occurred in landscapes comprising moderately fragmented forest habitat. This underscores the importance of remnant habitat patches to conservation strategies.

Based on more than a year and a half of intensive fieldwork, we document the community structure of bats at 2 sites (Reserva Natural del Bosque Mbaracayú and Yaguareté Forests) in eastern Paraguay. Twenty-nine species from 17 genera and 3 families were documented based on more than 7,000 captures. In general, these communities share greatest affinities with either Atlantic rainforest or savanna-grassland sites of South America. Significant differences exist between these communities in terms of structure based on rank-abundance distributions and species composition. Moreover, Yaguareté exhibits significantly more species than does Mbaracayú even after removing the effects of differences due to high-flying insectivores. No significant differences existed between communities regarding other aspects of taxonomic diversity (e.g., evenness, diversity, or dominance of species) or any aspect of functional diversity. A higher degree of habitat heterogeneity at Yaguareté likely underlies these differences in community structure.

We describe and compare diets of 3 species of vampyrine bats based on analysis of food remains found in gastrointestinal tracts of preserved museum specimens. We also examined possible ontogenetic, intersexual, geographic, and seasonal variations in feeding habits of each species. Trachops cirrhosus fed mainly on insects (79% of prey items), whereas Chrotopterus auritus and Vampyrum spectrum primarily ate small vertebrates (61–73% of prey items for both species). Vertebrate prey most frequently eaten by C. auritus were murid rodents whereas V. spectrum consumed primarily passerine birds. The frequency of occurrence of food items did not differ significantly with age or sex, at least for T. cirrhosus and C. auritus. Significant seasonal variations in diet were observed only for C. auritus, which consumed more insects during the wet season. Our findings confirm the importance of insects in the diet of T. cirrhosus and present new information on a diversified diet for V. spectrum and opportunistic feeding for C. auritus.

We estimated nutritional condition for 96 female northern Yellowstone elk (Cervus elaphus nelsoni) during mid- to late winter 2000, 2001, and 2002. Neither year nor capture location significantly influenced any measure of condition (body fat, body mass, and longissimus dorsi thickness; P ≥ 0.14). Overall, age = 8.9 years ± 0.4 SE, body fat = 9.5% ± 0.4, body mass = 235.1 kg ± 2.2, and longissimus dorsi muscle thickness = 5.6 cm ± 0.1. Despite an age segregation pattern across the winter range (P = 0.016), we found no evidence of bias in our estimates of nutritional condition due to this pattern because condition was unrelated to age. Yearly pregnancy and lactation rates of all cows ranged from 78 to 84% and 8 to 16%, respectively, at the time of capture. Lactational status significantly influenced body condition (P = 0.003), with lactating cows having 50% less body fat than nonlactating cows. Probability of pregnancy observed for elk that we captured followed a logistic curve as a function of body fat levels. Based on mid- to late winter body fat levels, we would predict low mortality of adult cows during mild to normal winters. We suggest the possibility of nutritional limitations acting on this herd through summer–autumn forage conditions, in association with limitations during harsh winters.

Predation can provide both positive and negative effects on formation of social groups in rodents. On the basis of observational data of predation by the desert monitor lizard (Varanus griseus caspius) on the great gerbil (Rhombomys opimus), a social rodent of desert Central Asia, we predicted that in a year after a peak in prey density, when the abundance of terrestrial predators is still high, the group mode of life of a prey species might become disadvantageous. Social groups could advertise themselves and attract predators. We therefore hypothesized that the probability of predation would be higher for gerbils in outlying social groups than in groups closely associated with each other, in larger compared with smaller groups, and in groups with an active adult male compared with solitary females with no resident male. We also analyzed whether the survival of gerbils and the stress levels in adult and juvenile males were related to frequency of visits by monitor lizards at gerbil colonies (isolated systems of burrows used by gerbil groups of any size), distance between colonies, and size of social groups. We found that frequency of visits by the monitor lizard depended on distance to the nearest neighboring colony. The more distant the gerbil colony, the more visits by the lizard and the lower the survival of juveniles. We also found a positive correlation between concentration of fecal corticosterone in young males and frequency of monitor lizard visits at colonies. This pattern was not as pronounced in adult males. Results did not support the hypothesis that larger groups would have higher predation because frequency of predator visits, distances to the nearest occupied colonies, and survival of juveniles did not correlate significantly with the size of family groups. There was no difference in survival of juveniles in colonies occupied by single females compared with colonies in which an adult male was present. These results suggest that there is a possible trade-off between competing strategies of antipredator behavior and that factors other than predation are influencing gerbil survival.

I investigated the exploitation of pocket gophers (Thomomys talpoides) by grizzly bears (Ursus arctos horribilis) in the Yellowstone region of the United States with the use of data collected during a study of radiomarked bears in 1977–1992. My analysis focused on the importance of pocket gophers as a source of energy and nutrients, effects of weather and site features, and importance of pocket gophers to grizzly bears in the western contiguous United States prior to historical extirpations. Pocket gophers and their food caches were infrequent in grizzly bear feces, although foraging for pocket gophers accounted for about 20–25% of all grizzly bear feeding activity during April and May. Compared with roots individually excavated by bears, pocket gopher food caches were less digestible but more easily dug out. Exploitation of gopher food caches by grizzly bears was highly sensitive to site and weather conditions and peaked during and shortly after snowmelt. This peak coincided with maximum success by bears in finding pocket gopher food caches. Exploitation was most frequent and extensive on gently sloping nonforested sites with abundant spring beauty (Claytonia lanceolata) and yampah (Perdieridia gairdneri). Pocket gophers are rare in forests, and spring beauty and yampah roots are known to be important foods of both grizzly bears and burrowing rodents. Although grizzly bears commonly exploit pocket gophers only in the Yellowstone region, this behavior was probably widespread in mountainous areas of the western contiguous United States prior to extirpations of grizzly bears within the last 150 years.

Summer abundance of white-footed mice (Peromyscus leucopus) fluctuated periodically during 20 years (1983–2002) at the Holt Research Forest, Maine, USA, a pine-oak forest within 125 km of the northern edge of this species' range. The oscillation period of the series was 4.0 years, with fluctuations greater than in P. leucopus populations in Indiana, Virginia, Ohio, and Pennsylvania. Abundance always increased after a low population phase coupled with a large acorn (Quercus) crop, but in 3 summers population declines followed population peaks despite large acorn crops. We used linear autoregression to identify periodicity after accounting for the relationship between mice and acorn mast. Among 3 candidate models, a 2nd-order lagged abundance (AR[2]) model fit the data better and had greater predictive value (total r² = 0.69) than either a 1st-order (AR[1]) or an acorns-only model. The AR(2) term could represent unknown limiting factors, such as response of predators.

In order to ascertain the typical pattern and amount of parental care in the social vole (Microtus socialis guentheri) as well as the individual investment of the female, male, or both parents simultaneously, we studied ten primiparous females and their mates. Results revealed that out of seven parental behaviors, only crouching was correlated with litter size, suggesting that parental care was relatively independent of litter size—that is, duration of time spent with the young, licking them, retrieving them to the nest, having them attached to the female's nipples, and searching for a nipple on the male were not correlated with litter size. Individual investment of caretakers also varied, with no typical proportion of shared nurturing by the female and male. Accordingly, overall parental investment varied greatly among different sets of parents without correlation to the relative contribution of the female, the male, or both. Finally, duration and frequency of most parental behaviors declined over the course of postnatal development. Altogether, these data suggest a surplus parental investment that was probably not required for survival of offspring but might have evolved either for other purposes such as the formation of social bonds or was selected for in captivity.

In prey-rich environments, leopard survival is ensured by an energy-maximizing, prey-selective strategy through which the leopard obtains the maximum amount of energy as food for the minimum amount of energy expended in hunting. In prey-poor environments, like the southern Kalahari, this is impossible. These leopards must use other strategies for survival. One strategy is maximizing the number of prey without selection for species. Hunger motivates hunting in all leopards, but in the prey-poor southern Kalahari it is hypothesized that female leopards with cubs must develop additional strategies to increase their own survival and that of their cubs. This study shows that these females increase their hunting success and expend less energy in hunting than other leopards by moving shorter distances before making a kill and by regularly killing a high frequency of those types of smaller prey that are more easy to kill. Motherhood therefore motivates female leopards with cubs to hunt more efficiently than other leopards in the prey-poor southern Kalahari.

Resource dispersion influences mammalian mating systems by affecting space use by females and in turn the strategies employed by males. Other elements related to mating interactions, however, also may affect female decisions, and it usually becomes difficult to discriminate between them. Here we present the results of experimental food supplementation during rut in the red deer (Cervus elaphus hispanicus). We provided food at 2 levels of spatial dispersion in order to test whether changes in the distribution of food within a short period of time affect spatial behavior of females or other features of the mating system. Food clumping produced an increase in local density of females using an area and in the size of female groups. It also produced an increase in number of adult males, male–male interactions, and male harassment toward females. Despite the overall rate of harassment being higher with food clumping, females received a lower per capita rate of harassment because they gathered into much larger harems. Variance in harem size increased with higher levels of food clumping. Our data show that females were highly sensitive to food distribution when joining harems, which stresses the relative importance of direct benefits (food and sexual harassment avoidance) in molding the conditions under which selection operates during rut in Iberian red deer.

The theory of adaptive sex ratio variation assumes that parents can increase their fitness by investing in the offspring sex that will gain the greatest lifetime reproductive success. Many adaptive sex ratio hypotheses imply or predict a female-mediated physiological mechanism that facilitates parental control. However, the ability of females to control offspring sex ratio could be significantly affected if males provided X- or Y-chromosome-biased ejaculates, as was recently discovered in domestic artiodactyls. To determine whether this occurs in white-tailed deer (Odocoileus virginianus), we examined semen sex ratio of captive deer using DNA fluorescence flow cytometry. We also used microsatellite markers to assign paternity of fawns sired in previous years to determine if temporal patterns existed in fawn sex relative to conception date. The ratio of X- and Y-sperm did not differ from an expected 1:1 among deer or between collection periods. Median conception dates of male and female fawns sired in previous years were similar, and there were no apparent temporal trends in offspring sex. We find no evidence that skewed ejaculates occur in white-tailed deer.

Differential Global Positioning System technology can provide series of accurate locations of free-ranging animals with a short, fixed interval. The sum of straight-line distances between valid locations (y) plotted against number of attempted fixes per day (x) should fit a hyperbolic function (i.e., y = x/[ax − b]) after removing inaccurate fixes and inactive periods. Its asymptotic value (1/a) can provide an estimate of real travel distance. The ratio of 1/a and y is a correction factor to apply to perceived straight-line distance to estimate real distance traveled. We achieved a good model fit on free-ranging adult red deer (Cervus elaphus) from data obtained every 15 min for a male and a female in winter 1997–1998, with a narrow range of correction factors. To validate this model, we used independent datasets from 3 other adult red deer roaming in the same area in winter 2000. We applied the procedure to distances perceived with fixed intervals ranging from 30 to 240 min and found consistent results in estimated real distances. Application of various steps of this analytical method could further development of a general approach to assess real distance traveled by individuals, thus offering new ways of studying habitat use or energetic requirements.

We experimentally investigated effects of female immigrants on demography and social organization of prairie vole (Microtus ochrogaster) populations. We tested the hypothesis that increased immigrant pressure by unrelated adult females would decrease the survivorship of juveniles and indirectly decrease the proportion of communal groups in the populations. We established prairie vole populations in 8 enclosures (32 × 32 m). Four populations were supplemented with adult female immigrants, and the other 4 served as control populations in which no females were introduced. The results showed that adult female immigrants reduced the proportion of females and the proportion of juveniles in resident populations but did not change the social organization. We concluded that adult female immigrants did negatively affect resident populations. However, the direct numerical input and subsequent reproduction by immigrants would compensate for their negative effect on resident populations.

This study aims to elucidate the social system of the wild cavy (Cavia aperea), the feral ancestor of the domestic guinea pig, whose behavior under natural conditions is almost unstudied. Therefore, a population of C. aperea was investigated for a 6-month period in its natural habitat in southeastern Brazil. The animals' space use was examined via radiotelemetry, social interactions were recorded using direct observations, and genetic relationships were analyzed via DNA fingerprinting. Additionally, the distribution of plant cover, food resources, and predation risk was recorded to investigate the impact of different ecological factors on evolution of the social system. In the study period, a low population density was detected and a strong predation pressure existed, which resulted in a high mortality rate of C. aperea. Spatial distribution of wild cavies was strongly associated with areas of dense ground vegetation. Within these areas, small groups consisting of 1 male and 1–2 females occupied stable home ranges that overlapped only slightly with home ranges of adjacent groups. Social interactions were restricted mainly to individuals of the same group, and initial analyses of paternity indicate that the females' offspring were sired by the respective group male. The social system and spatial organization of C. aperea are regarded as adaptations to high predation pressure because in dense vegetation small group size reduces the risk of detection by predators. Moreover, habitat use, social interactions, and paternity point to a single-male system in this low-density population of wild cavies.

Despite much recent interest in the middle ear and hearing of subterranean mammals, there is very little information in the literature regarding the middle ear apparatus of tuco-tucos (Rodentia: Ctenomyidae). In this study, the middle ear apparatus of Ctenomys sociabilis was dissected and is described for the first time. The middle ear structures of this species proved to be very similar to those of other caviomorph rodents; for example, in the bullet-shaped malleus head and in the fusion of the malleus and incus. The caviomorphs represent a rather conservative group in this respect. The m. stapedius is not present in C. sociabilis—loss of middle ear muscles is a common trend among fossorial mammals, but this particular feature has been reported in many other members of the superfamily Octodontoidea. Although the middle ear apparatus of C. sociabilis includes features consistent with the fossorial paradigm, some of which might be interpreted as low-frequency adaptations, it is not obviously specialized relative to other caviomorphs in this respect.

We studied development of wings of Leschenault's rousette, Rousettus leschenaulti. Wingspan and wing area grows linearly until 45 days of age. Young bats begin to flutter at 45 days, manage sustained flight at 60 days, and achieve independent foraging flight at 75 days. Aspect ratio varies until 15 days, and adult proportions are attained at 2 months. Wing loading decreases linearly until 50 days and thereafter increases slowly, possibly because of completion of growth of wing area. Wingspan growth fits a logistic model, whereas wing area growth fits a Gompertz model. Minimum predicted flight power (P_mp) and maximum range power (P_mr) begin to increase linearly after remaining relatively constant for 30 days. At 150 days both are nearly equal to 65% of the power requirements of postpartum females. The predicted minimum power speed (V_mp), maximum range speed (V_mr), and minimum theoretical radius of a banked turn (r_min) decrease for 40 days, thereafter increase linearly, and at 150 days all are close to 90% of the respective values of the postpartum females.